To reduce seismic vulnerability and the economic impact of seismic structural damage, it is important to protect structures using supplemental energy dissipation devices. Several types of supplemental damping systems can limit loads transferred to structures and absorb significant response energy without sacrificial structural damage. Lead extrusion dampers are one type of supplemental energy dissipation devices. A smaller volumetric size with high force capacities, called high force to volume (HF2V) devices, have been employed in a large series of scaled and full-scaled experiments, as well as in three new structures in Christchurch and San Francisco. HF2V devices have previously been designed using very simple models with limited precision. They are then manufactured, and tested to ensure force capacities match design goals, potentially necessitating reassembly or redesign if there is large error. In particular, devices with a force capacity well above or below a design range can require more testing and redesign, leading to increased economic and time cost. Thus, there is a major need for a modelling methodology to accurately estimate the range of possible device force capacity values in the design phase – upper and lower bounds. Upper and lower bound force capacity estimates are developed from equations in the metal extrusion literature. These equations consider both friction and extrusion forces between the lead and the bulged shaft in HF2V devices. The equations for the lower and upper bounds are strictly functions of device design parameters ensuring easy use in the design phase. Two different sets of estimates are created, leading to estimates for the lower and upper bounds denoted FLB,1, FUB,1, FUB,2, respectively. The models are validated by comparing the bounds with experimental force capacity data from 15 experimental HF2V device tests. All lower bound estimates are below or almost equal to the experimental device forces, and all upper bound estimates are above. Per the derivation, the (FLB,1, FUB,1) pair provide narrower bounds. The (FLB,1, FUB,1) pair also had a mean lower bound gap of -34%, meaning the lower bound was 74% of device force on average, while the mean upper bound gap for FUB,1 was +23%. These are relatively tight bounds, within ~±2 SE of device manufacture, and can be used as a guide to ensure device forces are in range for the actual design use when manufactured. Therefore, they provide a useful design tool.
Supplemental energy dissipation devices are increasingly used to protect structures, limit loads transferred to structural elements and absorbing significant response energy without sacrificial structural damage. Lead extrusion dampers are supplemental energy dissipation devices, where recent development of smaller volumetric size with high force capacities, called high force to volume (HF2V) devices, has seen deployment in a large series of scaled and full-scaled experiments, as well as in three new structures in Christchurch, NZ and San Francisco, USA. HF2V devices have previously been designed using limited precision models, so there is variation in force prediction capability. Further, while the overall resistive force is predicted, the knowledge of the relative contributions of the different internal reaction mechanisms to these overall resistive forces is lacking, limiting insight and predictive accuracy in device design. There is thus a major need for detailed design models to better understand force generation, and to aid precision device design. These outcomes would speed the overall design and implementation process for uptake and use, reducing the need for iterative experimental testing. Design parameters from 17 experimental HF2V device tests are used to create finite element models using ABAQUS. The analysis is run using ABAQUS Explicit, in multiple step times of 1 second with automatic increments, to balance higher accuracy and computational time. The output is obtained from the time- history output of the contact pressure forces including the normal and friction forces on the lead along the shaft. These values are used to calculate the resistive force on the shaft as it moves through the lead, and thus the device force. Results of these highly nonlinear, high strain analyses are compared to experimental device force results. Model errors compared to experimental results for all 17 devices ranged from 0% to 20% with a mean absolute error of 6.4%, indicating most errors were small. In particular, the standard error in manufacturing is SE = ±14%. In this case, 15 of 17 devices (88%) are within ±1SE (±14%) and 2 of 17 devices (12%) are within ±2SE (±28). These results show low errors and a distribution of errors compared to experimental results that are within experimental device construction variability. The overall modelling methodology is objective and repeatable, and thus generalizable. The exact same modelling approach is applied to all devices with only the device geometry changing. The results validate the overall approach with relatively low error, providing a general modelling methodology for accurate design of HF2V devices.
In recent years, significant research has been undertaken into the development of lead-extrusion damping technology. The high force-to-volume (HF2V) devices developed at the University of Canterbury have been the subject of much of this research. However, while these devices have undergone a limited range of velocity testing, limitations in test equipment has meant that they have never been tested at representative earthquake velocities. Such testing is important as the peak resistive force provided by the dampers under large velocity spikes is an important design input that must be known for structural applications. This manuscript presents the high-speed testing of HF2V devices with quasi-static force capacities of 250-300kN. These devices have been subjected to peak input velocities of approximately 200mm/s, producing peak resistive forces of approximately 350kN. The devices show stable hysteretic performance, with slight force reduction during high-speed testing due to heat build-up and softening of the lead working material. This force reduction is recovered following cyclic loading as heat is dissipated and the lead hardens again. The devices are shown to be only weakly velocity dependent, an advantage in that they do not deliver large forces to the connecting elements and surrounding structure if larger than expected response velocities occur. This high-speed testing is an important step towards uptake as it provides important information to designers.
In recent years, significant research has been undertaken into the development of lead-extrusion damping technology. The high force-to-volume (HF2V) devices developed at the University of Canterbury have been the subject of much of this research. However, while these devices have undergone a limited range of velocity testing, limitations in test equipment has meant that they have never been tested at representative earthquake velocities. Such testing is important as the peak resistive force provided by the dampers under large velocity spikes is an important design input that must be known for structural applications. This manuscript presents the high-speed testing of HF2V devices with quasi-static force capacities of 250-300kN. These devices have been subjected to peak input velocities of approximately 200mm/s, producing peak resistive forces of approximately 350kN. The devices show stable hysteretic performance, with slight force reduction during high-speed testing due to heat build-up and softening of the lead working material. This force reduction is recovered following cyclic loading as heat is dissipated and the lead hardens again. The devices are shown to be only weakly velocity dependent, an advantage in that they do not deliver large forces to the connecting elements and surrounding structure if larger than expected response velocities occur. This high-speed testing is an important step towards uptake as it provides important information to designers.
Earthquakes cause significant damage to buildings due to strong vibration of the ground. Levitating houses using magnets and electromagnets would provide a complete isolation of ground motion for protecting buildings from seismic damage. Two types of initial configuration for the electromagnet system were proposed with the same air gap (10mm) between the electromagnet and reluctance plate. Both active and passive controller are modelled to investigate the feasibility of using a vibration control system for stabilizing the magnetic system within the designed air gap (10mm) in the vertical direction. A nonlinear model for the magnetic system is derived to implement numerical simulation of structural response under the earthquake record in Christchurch Botanic Gardens on 21 February 2011. The performance of the uncontrolled and the controlled systems are compared and the optimal combination of control gains are determined for the PID active controller. Simulation results show both active PID controller with constant and nonlinear attracting force are able to provide an effective displacement control within the required air gap (+/-5mm). The maximum control force demand for the PID controller in the presence of nonlinear attracting force is 4.1kN, while the attracting force in equilibrium position is 10kN provided by the electromagnet. These results show the feasibility of levitating a house using the current electromagnet and PID controller. Finally, initial results of passive control using two permanent magnets or dampers show the structural responses can be effectively reduced and centralized to +/-1mm using a nonlinear centring barrier function.
High-Force-to-Volume lead dampers (HF2V) have been recently developed through an experimental research program at University of Canterbury – New Zealand. Testing of the device and applications on beam column joints have demonstrated stable hysteretic behaviour with almost no damage. This paper reports testing of HF2V devices with straight, bulged and constricted shaft configurations subjected to velocities of 0.15 - 5.0mm/s. The effect of the shaft configuration on the hysteresis loop shape, design relationships and the effect of the velocity on the resistive force of the device are described. Results show that hysteresis loop shape of the device is almost square regardless of the shaft configuration, and that devices are characterized by noticeable velocity dependence in the range of 0.15-1.0mm/s.
This thesis studies the behaviour of diaphragms in multi-storey timber buildings by providing methods for the estimation of the diaphragm force demand, developing an Equivalent Truss Method for the analysis of timber diaphragms, and experimentally investigating the effects of displacement incompatibilities between the diaphragm and the lateral load resisting system and developing methods for their mitigation. The need to better understand the behaviour of diaphragms in timber buildings was highlighted by the recent 2010-2011 Canterbury Earthquake series, where a number of diaphragms in traditional concrete buildings performed poorly, compromising the lateral load resistance of the structure. Although shortcomings in the estimation of force demand, and in the analysis and design of concrete floor diaphragms have already been partially addressed by other researchers, the behaviour of diaphragms in modern multi-storey timber buildings in general, and in low damage Pres-Lam buildings (consisting of post-tensioned timber members) in particular is still unknown. The recent demand of mid-rise commercial timber buildings of ten storeys and beyond has further highlighted the lack of appropriate methods to analyse timber diaphragms with irregular floor geometries and large spans made of both light timber framing and massive timber panels. Due to the lower stiffness of timber lateral load resisting systems, compared with traditional construction materials, and the addition of in-plane flexible diaphragms, the effect of higher modes on the global dynamic behaviour of a structure becomes more critical. The results from a parametric non-linear time-history analysis on a series of timber frame and wall structures showed increased storey shear and moment demands even for four storey structures when compared to simplistic equivalent static analysis. This effect could successfully be predicted with methods available in literature. The presence of diaphragm flexibility increased diaphragm inter-storey drifts and the peak diaphragm demand in stiff wall structures, but had less influence on the storey shears and moments. Diaphragm force demands proved to be significantly higher than the forces derived from equivalent static analysis, leading to potentially unsafe designs. It is suggested to design all diaphragms for the same peak demand; a simplified approach to estimate these diaphragm forces is proposed for both frame and wall structures. Modern architecture often requires complex floor geometries with long spans leading to stress concentrations, high force demands and potentially large deformations in the diaphragms. There is a lack of guidance and regulation regarding the analysis and design of timber diaphragms and a practical alternative to the simplistic equivalent deep beam analysis or costly finite element modelling is required. An Equivalent Truss Method for the analysis of both light timber framed and massive timber diaphragms is proposed, based on analytical formulations and verified against finite element models. With this method the panel unit shear forces (shear flow) and therefore the fastener demand, chord forces and reaction forces can be evaluated. Because the panel stiffness and fastener stiffness are accounted for, diaphragm deflection, torsional effects and transfer forces can also be assessed. The proposed analysis method is intuitive and can be used with basic analysis software. If required, it can easily be adapted for the use with diaphragms working in the non-linear range. Damage to floor diaphragms resulting from displacement incompatibilities due to frame elongation or out-of plane deformation of walls can compromise the transfer of inertial forces to the lateral load resisting system as well as the stability of other structural elements. Two post-tensioned timber frame structures under quasi-static cyclic and dynamic load, respectively, were tested with different diaphragm panel layouts and connections investigating their ability to accommodate frame elongations. Additionally, a post-tensioned timber wall was loaded under horizontal cyclic loads through two pairs of collector beams. Several different connection details between the wall and the beams were tested, and no damage to the collector beams or connections was observed in any of the tests. To evaluate the increased strength and stiffness due to the wall-beam interaction an analytical procedure is presented. Finally, a timber staircase core was tested under bi-directional loading. Different connection details were used to study the effect of displacement incompatibilities between the orthogonal collector beams. These experiments showed that floor damage due to displacement incompatibilities can be prevented, even with high levels of lateral drift, by the flexibility of well-designed connections and the flexibility of the timber elements. It can be concluded that the flexibility of timber members and the flexibility of their connections play a major role in the behaviour of timber buildings in general and of diaphragms specifically under seismic loads. The increased flexibility enhances higher mode effects and alters the diaphragm force demand. Simple methods are provided to account for this effect on the storey shear, moment and drift demands as well as the diaphragm force demands. The analysis of light timber framing and massive timber diaphragms can be successfully analysed with an Equivalent Truss Method, which is calibrated by accounting for the panel shear and fastener stiffnesses. Finally, displacement incompatibilities in frame and wall structures can be accommodated by the flexibilities of the diaphragm panels and relative connections. A design recommendations chapter summarizes all findings and allows a designer to estimate diaphragm forces, to analyse the force path in timber diaphragms and to detail the connections to allow for displacement incompatibilities in multi-storey timber buildings.
On 22 February 2011, the second day of the first semester, a devastating magnitude 6.2 earthquake struck the city of Christchurch forcing the campus of the University of Canterbury to close for several weeks. Here, we report on the sudden curriculum and assessment overhaul that needed to be implemented using two large, first-year introductory courses as case studies. We discuss the reasoning and justifications behind these changes, as well as the logistics of this process. We draw conclusions based on student feedback and assessments and formulate lessons learnt.
Currently there is a worldwide renaissance in timber building design. At the University of Canterbury, new structural systems for commercial multistorey timber buildings have been under development since 2005. These systems incorporate large timber sections connected by high strength post-tensioning tendons, and timber-concrete composite floor systems, and aim to compete with existing structural systems in terms of cost, constructability, operational and seismic performance. The development of post-tensioned timber systems has created a need for improved lateral force design approaches for timber buildings. Current code provisions for seismic design are based on the strength of the structure, and do not adequately account for its deformation. Because timber buildings are often governed by deflection, rather than strength, this can lead to the exceedence of design displacement limitations imposed by New Zealand codes. Therefore, accurate modeling approaches which define both the strength and deformation of post-tensioned timber buildings are required. Furthermore, experimental testing is required to verify the accuracy of these models. This thesis focuses on the development and experimental verification of modeling approaches for the lateral force design of post-tensioned timber frame and wall buildings. The experimentation consisted of uni-direcitonal and bi-directional quasi-static earthquake simulation on a two-thirds scale, two-storey post-tensioned timber frame and wall building with timber-concrete composite floors. The building was subjected to lateral drifts of up to 3% and demonstrated excellent seismic performance, exhibiting little damage. The building was instrumented and analyzed, providing data for the calibration of analytical and numerical models. Analytical and numerical models were developed for frame, wall and floor systems that account for significant deformation components. The models predicted the strength of the structural systems for a given design performance level. The static responses predicted by the models were compared with both experimental data and finite element models to evaluate their accuracy. The frame, wall and floor models were then incorporated into an existing lateral force design procedure known as displacement-based design and used to design several frame and wall structural systems. Predictions of key engineering demand parameters, such as displacement, drift, interstorey shear, interstorey moment and floor accelerations, were compared with the results of dynamic time-history analysis. It was concluded that the numerical and analytical models, presented in this thesis, are a sound basis for determining the lateral response of post-tensioned timber buildings. However, future research is required to further verify and improve these prediction models.
Rock mass defect controlled deep-seated landslides are widespread within the deeply incised landscapes formed in Tertiary soft rock terrain in New Zealand. The basal failure surfaces of deep-seated slope failures are defined by thin, comparatively weak and laterally continuous bedding parallel layers termed critical stratigraphic horizons. These horizons have a sedimentary origin and have typically experienced some prior tectonically induced shear displacement at the time of slope failure. The key controls on the occurrence and form of deep-seated landslides are considered in terms of rock mass defect properties and tectonic and climatic forcing. The selection of two representative catchments (in southern Hawke's Bay and North Canterbury) affected by tectonic and climatic forcing has shown that the spatial and temporal initiation of deep-seated bedrock landslides in New Zealand Tertiary soft rock terrain is a predictable rather than a stochastic process; and that deep-seated landslides as a mass wasting process have a controlling role in landscape evolution in many catchments formed in Tertiary soft rock terrain. The Ella Landslide in North Canterbury is a deep-seated (~85 m) translational block slide that has failed on a 5 - 10 mm thick, kaolinite-rich, pre-sheared critical stratigraphic horizon. The residual strength of this sedimentary horizon, (C'R 2.6 - 2.7 kPa, and Ѳ'R = 16 - 21°), compared to the peak strength of the dominant lithology (C' = 176 kPa, and Ѳ' = 37°) defines a high strength contrast in the succession, and therefore a critical location for the basal failure surface of deep-seated slope failures. The (early to mid Holocene) Ella Landslide debris formed a large landslide dam in the Kate Stream catchment and this has significantly retarded rates of mass wasting in the middle catchment. Numerical stability analysis shows that this slope failure would have most likely required the influence of earthquake induced strong ground motion and the event is tentatively correlated to a Holocene event on the Omihi Fault. The influence of this slope failure is likely to affect the geomorphic development of the catchment on a scale of 10⁴ - 10⁵ years. In deeply incised catchments at the southeastern margin of the Maraetotara Plateau, southern Hawke's Bay, numerous widespread deep-seated landslides have basal failure surfaces defined by critical stratigraphic horizons in the form of thin « 20 mm) tuffaceous beds in the Makara Formation flysch (alternating sandstone and mudstone units). The geometry of deep-seated slope failures is controlled by these regularly spaced (~70 m), very weak critical stratigraphic horizons (C'R 3.8 - 14.2 kPa, and Ѳ'R = 2 - 5°), and regularly spaced (~45 m) and steeply dipping (-50°) critical conjugate joint/fault sets, which act as slide block release surfaces. Numerical stability analysis and historical precedent show that the temporal initiation of deep-seated landslides is directly controlled by short term tectonic forcing in the form of periodic large magnitude earthquakes. Published seismic hazard data shows the recurrence interval of earthquakes producing strong ground motions of 0.35g at the study site is every 150 yrs, however, if subduction thrust events are considered the level of strong ground motion may be much higher. Multiple occurrences of deep-seated slope failure are correlated to failure on the same critical stratigraphic horizon, in some cases in three adjacent catchments. Failure on multiple critical stratigraphic horizons leads to the development of a "stepped" landscape morphology. This slope form will be maintained during successive accelerated stream incision events (controlled by long term tectonic and climatic forcing) for as long as catchments are developing in this specific succession. Rock mass defect controlled deep seated landslides are controlling catchment head progression, landscape evolution and hillslope morphology in the Hawke's Bay study area and this has significant implications for the development of numerical landscape evolution models of landscapes formed in similar strata. Whereas the only known numerical model to consider deep seated landslides as an erosion process (ZSCAPE) considers them as stochastic in time and space, this study shows that this could not be applied to a landscape where the widespread spatial occurrence of deep-seated landslides is controlled by rock mass defects. In both of the study areas for this project, and by implication in many catchments in Tertiary soft rock terrain, deep-seated landslides controlled by rock mass defect strength, spacing and orientation, and tectonic and climatic forcing have an underlying control on landscape evolution. This study quantifies parameters for the development of numerical landscape evolution models that would assess the role of specific parameters, such as uplift rates, incision rates and earthquake recurrence in catchment evolution in Tertiary soft rock terrain.
This thesis looks at the protocols museums and galleries adopt for the safeguarding of art, artefacts and cultural heritage. In particular, it analyses these procedures in relation to the 2010 and 2011 earthquakes in Christchurch, and considers how these events shaped the preventative conservation measures in place in museum and gallery institutions. Through gathering, assessing, and comparing this information about Christchurch’s institutions to disaster management best practices in national and international organisations, this thesis gauges the extent to which disaster management was changed in response to the events in Christchurch. This thesis first considers the growth in disaster management as a field, before examining what are considered best practices within this sector. Finally, it looks at specific institutions in Christchurch, including the Christchurch Art Gallery Te Puna o Waiwhetu, Canterbury Museum, and the Air Force Museum of New Zealand.
Following the 2010/2011 Canterbury earthquakes, approximately 60% of multi-story buildings with reinforced concrete walls required demolition. Both practitioners and researchers have increasingly realized that low-damage structural systems could be an alternative to improve the seismic behaviour of concrete buildings and to reduce the economic and social impact of structural damage in future earthquakes. To verify the seismic response of a low-damage concrete wall building representing state-of-art design practice, a shake table test on a two-story concrete building was recently conducted as part of an ILEE-QuakeCoRE collaborative research program. The building utilized flexible wall-to-floor connections in the long span direction and isolating wall-to-floor devices in the short span direction to provide a comparison of their respective behaviour. Additionally, the wall-to-floor interaction such as effects of wall uplift on the link slab, and force transfer mechanism from floor to the wall will be discussed in this paper.
Extended Direct Analysis (EDA), developed at the University of Canterbury, is an advance on the AISC Direct Analysis method for the analysis of frames subjected to static forces. EDA provides a faster, simple and more rational way to properly consider the second-order effects, initial residual stresses (IRS) and the initial imperfections or steel structures under one directional loading than conventional analysis methods. This research applied the EDA method to quantify the effect of member overstrength on frame behaviour for a single storey frame. Also, the effects of IRS, which were included in the EDA static analysis, but which are not considered explicitly in non-linear seismic analysis, were evaluated in two ways. Firstly, they were considered for simple structures subject to increasing cyclic displacement in different directions. Secondly, incremental dynamic analysis with realistic ground motion was used to quantify the likely effect of IRS in earthquakes. It was found that, contrary to traditional wisdom and practice, greater member strengths can result in lower frame strengths for frames under monotonic lateral loading. The structural lateral capacity of the overstrength case was reduced by 6% compared to the case using the dependable member strengths. Also, it resulted significantly different in member demands. Therefore, it is recommended that when either plastic analysis or EDA is used, that both upper and lower bounds on the likely member strength should be considered to determine the total frame strength and the member demands. Results of push-pull analysis under displacement control showed that for IRS ratio, gamma < 0.5 and axial compressive force ratio, N*/Ns, up to 0.5, IRS did affect the structural behaviour in the first half cycle. However, the behavior in the later cycles was not significantly affected. It also showed that the effect of initial residual stresses in the frame was less significant than for the column alone when the column was subjected to similar axial compressive force. The incremental dynamic analysis results from both cantilever column and the three-storey steel frame showed that by increasing gamma = 0 to 0.5, the effect of IRS on seismic responses, based on the 50% confidence level, was less than 3% for N*/Ns, up to 0.5.
The recent Canterbury earthquake sequence in 2010-2011 highlighted a uniquely severe level of structural damage to modern buildings, while confirming the high vulnerability and life threatening of unreinforced masonry and inadequately detailed reinforced concrete buildings. Although the level of damage of most buildings met the expected life-safety and collapse prevention criteria, the structural damage to those building was beyond economic repair. The difficulty in the post-event assessment of a concrete or steel structure and the uneconomical repairing costs are the big drivers of the adoption of low damage design. Among several low-damage technologies, post-tensioned rocking systems were developed in the 1990s with applications to precast concrete members and later extended to structural steel members. More recently the technology was extended to timber buildings (Pres-Lam system). This doctoral dissertation focuses on the experimental investigation and analytical and numerical prediction of the lateral load response of dissipative post-tensioned rocking timber wall systems. The first experimental stages of this research consisted of component testing on both external replaceable devices and internal bars. The component testing was aimed to further investigate the response of these devices and to provide significant design parameters. Post-tensioned wall subassembly testing was then carried out. Firstly, quasi-static cyclic testing of two-thirds scale post-tensioned single wall specimens with several reinforcement layouts was carried out. Then, an alternative wall configuration to limit displacement incompatibilities in the diaphragm was developed and tested. The system consisted of a Column-Wall-Column configuration, where the boundary columns can provide the support to the diaphragm with minimal uplifting and also provide dissipation through the coupling to the post-tensioned wall panel with dissipation devices. Both single wall and column-wall-column specimens were subjected to drifts up to 2% showing excellent performance, limiting the damage to the dissipating devices. One of the objectives of the experimental program was to assess the influence of construction detailing, and the dissipater connection in particular proved to have a significant influence on the wall’s response. The experimental programs on dissipaters and wall subassemblies provided exhaustive data for the validation and refinement of current analytical and numerical models. The current moment-rotation iterative procedure was refined accounting for detailed response parameters identified in the initial experimental stage. The refined analytical model proved capable of fitting the experimental result with good accuracy. A further stage in this research was the validation and refinement of numerical modelling approaches, which consisted in rotational spring and multi-spring models. Both the modelling approaches were calibrated versus the experimental results on post-tensioned walls subassemblies. In particular, the multi-spring model was further refined and implemented in OpenSEES to account for the full range of behavioural aspects of the systems. The multi-spring model was used in the final part of the dissertation to validate and refine current lateral force design procedures. Firstly, seismic performance factors in accordance to a Force-Based Design procedure were developed in accordance to the FEMA P-695 procedure through extensive numerical analyses. This procedure aims to determine the seismic reduction factor and over-strength factor accounting for the collapse probability of the building. The outcomes of this numerical analysis were also extended to other significant design codes. Alternatively, Displacement-Based Design can be used for the determination of the lateral load demand on a post-tensioned multi-storey timber building. The current DBD procedure was used for the development of a further numerical analysis which aimed to validate the procedure and identify the necessary refinements. It was concluded that the analytical and numerical models developed throughout this dissertation provided comprehensive and accurate tools for the determination of the lateral load response of post-tensioned wall systems, also allowing the provision of design parameters in accordance to the current standards and lateral force design procedures.
The aim of this report is to investigate the ductile performance of concrete tilt-up panels reinforced with cold-drawn mesh to improve the current seismic assessment procedure. The commercial impact of the project was also investigated. Engineering Advisory Group (EAG) guidelines state that a crack in a panel under face loading may be sufficient to fracture the mesh. The comments made by EAG regarding the performance of cold-drawn mesh may be interpreted as suggesting that assessment of such panels be conducted with a ductility of 1.0. Observations of tilt-up panel performance following the Christchurch earthquakes suggest that a ductility higher than μ=1.0 is likely to be appropriate for the response of panels to out-of-plane loading. An experimental test frame was designed to subject ten tilt-panel specimens to a cyclic quasi-static loading protocol. Rotation ductility, calculated from the force-displacement response from the test specimens, was found to range between 2.9 and 5.8. Correlation between tensile tests on 663L mesh, and data collected from instrumentation during testing confirmed that the mesh behaves as un-bonded over the pitch length of 150mm. Recommendation: Based on a moment-rotation assessment approach with an un-bonded length equal to the pitch of the mesh, a rotation ductility of μ=2.5 appears to be appropriate for the seismic assessment of panels reinforced with cold-drawn mesh.
Despite their good performance in terms of their design objectives, many modern code-prescriptive buildings built in Christchurch, New Zealand had to be razed after the 2010-2011 Canterbury earthquakes because repairs were deemed too costly due to widespread sacrificial damage. Clearly a more effective design paradigm is needed to create more resilient structures. Rocking, post-tensioned connections with supplemental energy dissipation can contribute to a damage avoidance designs (DAD). However, few have achieved all three key design objectives of damage-resistant rocking, inherent recentering ability, and repeatable, damage-free energy dissipation for all cycles, which together offer a response which is independent of loading history. Results of experimental tests are presented for a near full-scale rocking beam-column sub-assemblage. A matrix of test results is presented for the system under varying levels of posttensioning, with and without supplemental dampers. Importantly, this parametric study delineates each contribution to response. Practical limitations on posttensioning are identified: a minimum to ensure static structural re-centering, and a maximum to ensure deformability without threadbar yielding. Good agreement between a mechanistic model and experimental results over all parameters and inputs indicates the model is robust and accurate for design. The overall results indicate that it is possible to create a DAD connection where the non-linear force-deformation response is loading history independent and repeatable over numerous loading cycles, without damage, creating the opportunity for the design and implementation of highly resilient structures.
Base isolation is arguably the most reliable method for providing enhanced protection of buildings against earthquake-induced actions, by virtue of a physical separation between the structure and the ground through elements/devices with controlled force capacity, significant lateral deformation capacity and (often) enhanced energy dissipation. Such a design solution has shown its effectiveness in protecting both structural and non-structural components, hence preserving their functionality even in the aftermath of a major seismic event. Despite lead rubber bearings being invented in New Zealand almost forty years ago, the Christchurch Women's hospital was the only isolated building in Christchurch when the Canterbury earthquake sequence struck in 2010/11. Furthermore, a reference code for designing base-isolated buildings in New Zealand is still missing. The absence of a design standard or at least of a consensus on design guidelines is a potential source for a lack of uniformity in terms of performance criteria and compliance design approaches. It may also limit more widespread use of the technology in New Zealand. The present paper provides an overview of the major international codes (American, Japanese and European) for the design of base-isolated buildings. The design performance requirements, the analysis procedures, the design review process and approval/quality control of devices outlined in each code are discussed and their respective pros and cons are compared through a design application on a benchmark building in New Zealand. The results gathered from this comparison are intended to set the basis for the development of guidelines specific for the New Zealand environment.
An extensive research program is on-going at the University of Canterbury, New Zealand to develop new technologies to permit the construction of multi-storey timber buildings in earthquake prone areas. The system combines engineered timber beams, columns and walls with ductile moment resisting connections using post-tensioned tendons and eventually energy dissipaters. The extensive experimental testing on post-tensioned timber building systems has proved a remarkable lateral response of the proposed solutions. A wide number of post-tensioned timber subassemblies, including beam-column connections, single or coupled walls and column-foundation connections, have been analysed in static or quasi-static tests. This contribution presents the results of the first dynamic tests carried out with a shake-table. Model frame buildings (3-storey and 5-storey) on one-quarter scale were tested on the shake-table to quantify the response of post-tensioned timber frames during real-time earthquake loading. Equivalent viscous damping values were computed for post-tensioned timber frames in order to properly predict their response using numerical models. The dynamic tests were then complemented with quasi-static push and pull tests performed to a 3-storey post-tensioned timber frame. Numerical models were included to compare empirical estimations versus dynamic and quasi-static experimental results. Different techniques to model the dynamic behaviour of post-tensioned timber frames were explored. A sensitivity analysis of alternative damping models and an examination of the influence of designer choices for the post-tensioning force and utilization of column armouring were made. The design procedure for post-tensioned timber frames was summarized and it was applied to two examples. Inter-storey drift, base shear and overturning moments were compared between numerical modelling and predicted/targeted design values.
Non-structural elements (NSEs) have frequently proven to contribute to significant losses sustained from earthquakes in the form of damage, downtime, injury and death. In New Zealand (NZ), the 2010 and 2011 Canterbury Earthquake Sequence (CES), the 2013 Seddon and Cook Strait earthquake sequence and the 2016 Kaikoura earthquake were major milestones in this regard as significant damage to building NSEs both highlighted and further reinforced the importance of NSE seismic performance to the resilience of urban centres. Extensive damage in suspended ceilings, partition walls, façades and building services following the CES was reported to be partly due to erroneous seismic design or installation or caused by intervening elements. Moreover, the low-damage solutions developed for structural systems sometimes allow for relatively large inter-story drifts -compared to conventional designs- which may not have been considered in the seismic design of NSEs. Having observed these shortcomings, this study on suspended ceilings was carried out with five main goals: i) Understanding the seismic performance of the system commonly used in NZ; ii) Understanding the transfer of seismic design actions through different suspended ceiling components, iii) Investigating potential low-damage solutions; iii) Evaluating the compatibility of the current ceiling system with other low-damage NSEs; and iv) Investigating the application of numerical analysis to simulate the response of ceiling systems. The first phase of the study followed a joint research work between the University of Canterbury (UC) in NZ, and the Politecnico Di Milano, in Italy. The experimental ceiling component fragility curves obtained in this existing study were employed to produce analytical fragility curves for a perimeter-fixed ceiling of a given size and weight, with grid acceleration as the intensity measure. The validity of the method was proven through comparisons between this proposed analytical approach with the recommended procedures in proprietary products design guidelines, as well as experimental fragility curves from other studies. For application to engineering design practice, and using fragility curves for a range of ceiling lengths and weights, design curves were produced for estimating the allowable grid lengths for a given demand level. In the second phase of this study, three specimens of perimeter-fixed ceilings were tested on a shake table under both sinusoidal and random floor motion input. The experiments considered the relationship between the floor acceleration, acceleration of the ceiling grid, the axial force induced in the grid members, and the effect of boundary conditions on the transfer of these axial forces. A direct correlation was observed between the axial force (recorded via load cells) and the horizontal acceleration measured on the ceiling grid. Moreover, the amplification of floor acceleration, as transferred through ceiling components, was examined and found (in several tests) to be greater than the recommended factor for the design of ceilings provided in the NZ earthquake loadings standard NZS1170.5. However, this amplification was found to be influenced by the pounding interactions between the ceiling grid members and the tiles, and this amplification diminished considerably when the high frequency content was filtered out from the output time histories. The experiments ended with damage in the ceiling grid connection at an axial force similar to the capacity of these joints previously measured through static tests in phase one. The observation of common forms of damage in ceilings in earthquakes triggered the monotonic experiments carried out in the third phase of this research with the objective of investigating a simple and easily applicable mitigation strategy for existing or new suspended ceilings. The tests focused on the possibility of using proprietary cross-shaped clip elements ordinarily used to provide seismic gap as a strengthening solution for the weak components of a ceiling. The results showed that the solution was effective under both tension and compression loads through increasing load bearing capacity and ductility in grid connections. The feasibility of a novel type of suspended ceiling called fully-floating ceiling system was investigated through shaking table tests in the next phase of this study with the main goal of isolating the ceiling from the surrounding structure; thereby arresting the transfer of associated seismic forces from the structure to the ceiling. The fully-floating ceiling specimen was freely hung from the floor above lacking any lateral bracing and connections with the perimeter. Throughout different tests, a satisfactory agreement between the fully-floating ceiling response and simple pendulum theory was demonstrated. The addition of isolation material in perimeter gaps was found effective in inducing extra damping and protecting the ceiling from pounding impact; resulting in much reduced ceiling displacements and accelerations. The only form of damage observed throughout the random floor motion tests and the sinusoidal tests was a panel dislodgement observed in a test due to successive poundings between the ceiling specimen and the surrounding beams at resonant frequencies. Partition walls as the first effective NSE in direct interaction with ceilings were the topic of the final experimental phase. Low-damage drywall partitions proposed in a previous study in the UC were tested with two common forms of suspended ceiling: braced and perimeter-fixed. The experiments investigated the in-plane and out-of-plane performance of the low-damage drywall partitions, as well as displacement compatibility between these walls and the suspended ceilings. In the braced ceiling experiment, where no connection was made between ceiling grids and surrounding walls no damage in the grid system or partitions was observed. However, at high drift values panel dislodgement was observed on corners of the ceiling where the free ends of grids were not restrained against spreading. This could be prevented by framing the grid ends using a perimeter angle that is riveted only to the grid members while keeping sufficient clearance from the perimeter walls. In the next set of tests with the perimeter-fixed ceiling, no damage was observed in the ceiling system or the drywalls. Based on the results of the experiments it was concluded that the tested ceiling had enough flexibility to accommodate the relative displacement between two perpendicular walls up to the inter-storey drifts achieved. The experiments on perimeter-fixed ceilings were followed by numerical simulations of the performance of these ceilings in a finite element model developed in the structural analysis software, SAP2000. This model was relatively simple and easy to develop and was able to replicate the experimental results to a reasonable degree. Filtering was applied to the experimental output to exclude the effect of high frequency noise and tile-grid impact. The developed model generally simulated the acceleration responses well but underestimated the peak ceiling grid accelerations. This was possibly because the peak values in time histories were affected by impact occurring at very short periods. The model overestimated the axial forces in ceiling grids which was assumed to be caused by the initial assumptions made about the tributary area or constant acceleration associated with each grid line in the direction of excitation. Otherwise, the overall success of the numerical modelling in replicating the experimental results implies that numerical modelling using conventional structural analysis software could be used in engineering practice to analyse alternative ceiling geometries proposed for application to varying structural systems. This however, needs to be confirmed through similar analyses on other ceiling examples from existing instrumented buildings during real earthquakes. As the concluding part of this research the final phase addressed the issues raised following the review of existing ceiling standards and guidelines. The applicability of the research findings to current practice and their implications were discussed. Finally, an example was provided for the design of a suspended ceiling utilising the new knowledge acquired in this research.
The effects of soil-foundation-structure interaction (SFSI) have been a topic of discussion amongst the structural and geotechnical community for many decades. The complexity of the mechanisms, as well as the need for inter-disciplinary knowledge of geotechnical and structural dynamics has plagued the advancement and the consequent inclusion of SFSI effects in design. A rigorous performance-based design methodology should not just consider the performance of the superstructure but the supporting foundation system as well. Case studies throughout history (eg. Kobe 1995, Kocaeli 1999 and Christchurch earthquakes 2010-2011) have demonstrated that a poor performance at the foundation level can result in a full demolition of the structure and, in general terms, that the extent of damage to, and repairability of, the building system as a whole, is given by the combination of the damage to the soil, foundation and superstructure. The lack of consideration of the modifying factors of SFSI and an absence of intuitive performance levels for controlling foundation and soil behaviour under seismic loads has resulted in inadequate designs for buildings sited on soft soil. For engineers to be satisfied that their designs meet the given performance levels they must first, understand how SFSI affects the overall system performance and secondly have tools available to adequately account for it in their design/assessment. This dissertation presents an integrated performance-based design procedure for buildingfoundation systems that considers all of the major mechanisms of SFSI. A new soil-foundation macro-element model was implemented into a nonlinear finite element software and validated against several experimental tests. The numerical model was used to provide insights in to the mechanisms of SFSI and statistical analysis on the results yielded simple expressions that allow the behaviour to be quantified. Particular attention was paid to the effects of shear force on the foundation response and the quantification of the rocking mode of response. The residual deformations of the superstructure and distribution of forces up the structure were also investigated. All of the major SFSI mechanisms are discussed in detail and targeted numerical studies are used to explain and demonstrate concepts. The design procedure was validated through the design and assessment of a series of concrete buildings that were designed to account for the effects of SFSI.
The nonlinear dynamic soil-foundation-structure interaction (SFSI) can signifi cantly affect the seismic response of buildings, causing additional deformation modes, damage and repair costs. Because of nonlinear foundation behaviour and interactions, the seismic demand on the superstructure may considerably change, and also permanent deformations at the foundation level may occur. Although SFSI effects may be benefi cial to the superstructure performance, any advantage would be of little structural value unless the phenomenon can be reliably controlled and exploited. Detrimental SFSI effects may also occur, including acceleration and displacement response ampli cation and differential settlements, which would be unconservative to neglect. The lack of proper understanding of the phenomenon and the limited available simpli ed tools accounting for SFSI have been major obstacles to the implementation of integrated design and assessment procedures into the everyday practice. In this study concepts, ideas and practical tools (inelastic spectra) for the seismic design and assessment of integrated foundation-superstructure systems are presented, with the aim to explicitly consider the impact of nonlinearities occurring at the soil-foundation interface on the building response within an integrated approach, where the foundation soil and superstructure are considered as part of an integrated system when evaluating the seismic response, working synergically for the achievement of a target global performance. A conceptual performance-based framework for the seismic design and assessment of integrated foundation-superstructure systems is developed. The framework is based on the use of peak and residual response parameters for both the superstructure and the foundation, which are then combined to produce the system performance matrix. Each performance matrix allows for worsening of the performance when different contributions are combined. An attempt is made to test the framework by using case histories from the 2011 Christchurch earthquake, which are previously shown to have been severely affected by nonlinear SFSI. The application highlights the framework sensitivity to the adopted performance limit states, which must be realistic for a reliable evaluation of the system performance. Constant ductility and constant strength inelastic spectra are generated for nonlinear SFSI systems (SDOF nonlinear superstructure and 3DOF foundation allowing for uplift and soil yielding), representing multistorey RC buildings with shallow rigid foundations supported by cohesive soils. Different ductilities/strengths, hysteretic rules (Bi-linear, Takeda and Flag-Shape), soil stiffness and strength and bearing capacity factors are considered. Footings and raft foundations are investigated, characterized respectively by constant (3 and 8) and typically large bearing capacity factors. It is confi rmed that when SFSI is considered, the superstructure yielding force needed to satisfy a target ductility for a new building changes, and that similarly, for an existing building, the ductility demand on a building of a given strength varies. The extent of change of seismic response with respect to xed-base (FB) conditions depends on the class of soils considered, and on the bearing capacity factor (SF). For SF equal to 3, the stiffer soils enhance the nonlinear rotational foundation behaviour and are associated with reduced settlement, while the softer ones are associated with increased settlement response but not signi ficant rotational behaviour. On average terms, for the simplifi ed models considered, SFSI is found to be bene cial to the superstructure performance in terms of acceleration and superstructure displacement demand, although exceptions are recorded due to ground motion variability. Conversely, in terms of total displacement, a signi cant response increase is observed. The larger the bearing capacity factor, the more the SFSI response approaches the FB system. For raft foundation buildings, characterized by large bearing capacity factors, the impact of foundation response is mostly elastic, and the system on average approaches FB conditions. Well de fined displacement participation factors to the peak total lateral displacement are observed for the different contributions (i.e. peak foundation rotation and translation and superstructure displacement). While the superstructure and foundation rotation show compensating trends, the foundation translation contribution varies as a function of the moment-to-shear ratio, becoming negligible in the medium-to-long periods. The longer the superstructure FB period, the less the foundation response is signifi cant. The larger the excitation level and the less ductile the superstructure, the larger the foundation contribution to the total lateral displacement, and the less the superstructure contribution. In terms of hysteretic behaviour, its impact is larger when the superstructure response is more signifi cant, i.e. for the softer/weaker soils and larger ductilities. Particularly, for the Flag Shape rule, larger superstructure displacement participation factors and smaller foundation contributions are recorded. In terms of residual displacements, the total residual-to-maximum ratios are similar in amplitudes and trends to the corresponding FB system responses, with the foundation and superstructure contributions showing complementary trends. The impact of nonlinear SFSI is especially important for the Flag Shape hysteresis rule, which would not otherwise suffer of any permanent deformations. By using the generated peak and residual inelastic spectra (i.e. inelastic acceleration/ displacement modifi cation factor spectra, and/or participation factor and residual spectra), conceptual simplifi ed procedures for the seismic design and assessment of integrated foundation-superstructure systems are presented. The residual displacements at both the superstructure and foundation levels are explicitly considered. Both the force- and displacement-based approaches are explored. The procedures are de fined to be complementary to the previously proposed integrated performance-based framework. The use of participation factor spectra allows the designer to easily visualize the response of the system components, and could assist the decision making process of both the design and assessment of SFSI systems. The presented numerical results have been obtained using simpli ed models, assuming rigid foundation behaviour and neglecting P-Delta effects. The consideration of more complex systems including asymmetry in stiffness, mass, axial load and ground conditions with a exible foundation layout would highlight detrimental SFSI effects as related to induced differential settlements, while accounting for PDelta effects would further amplify the displacement response. Also, the adopted acceleration records were selected and scaled to match conventional design spectra, thus not representing any response ampli cation in the medium-to-long period range which could as well cause detrimental SFSI effects. While these limitations should be the subject of further research, this study makes a step forward to the understanding of SFSI phenomenon and its incorporation into performance-based design/assessment considerations.
To this extent, modern buildings generally demonstrated good resistance to collapse during the recent earthquakes in New Zealand. However, damage to non-structural elements (NSE) has been persistent during these events. NSEs include secondary systems or components attached to the floors, roofs, and walls of a building or industrial facility that are not explicitly designed to participate in the main vertical or lateral load-bearing mechanism of the structure. They play a major role in the operational and functional aspects of buildings and contribute a major portion of the building’s overall cost. Therefore, they are expected to accommodate the effects of seismic actions such as drifts and accelerations. Typical examples of NSEs include internal non-loadbearing partitions, suspended ceilings, sprinkler piping systems, architectural claddings, building contents, mechanical/electrical equipment, and furnishings. The main focus of this thesis is the drift sensitive NSEs: precast concrete cladding panels and internal partition walls. Even though most precast concrete cladding panels performed well from a life-safety point of view during recent earthquakes in NZ, some collapsed panels posed a significant threat to life safety. It is, therefore, important that the design and detailing of the panel-to-structure connections ensure that their strength and displacement capacity are adequate to meet the corresponding seismic demands, at least during design level earthquakes. In contrast, the partition wall is likely to get damaged and lose serviceability at a low inter-story drift unless designed to accommodate the relative deformations between them and the structure. Partition walls suffered wide-ranging damage such as screw failures, diagonal cracking, detachments to the gypsum linings, and anchorage failures during the 2011 Canterbury Earthquake Sequence in NZ. Therefore, the thesis is divided into two parts. Part I of the thesis focuses on developing novel low-damage precast concrete cladding panel connections, i.e. “rocking” connection details comprising vertically slotted steel embeds and weld plates. The low-damage seismic performance of novel “rocking” connection details is verified through experimental tests comprising uni-directional, bi-directional, and multi-storey scaled quasi-static cyclic tests. Comparison with the seismic performance of traditional panel connections reported in the literature demonstrated the system’s significantly improved seismic resilience. Furthermore, the finite element models of panel connections and sealants are developed in ABAQUS. The force-drift responses of the “rocking” panel system modelled in SAP2000 is compared with the experimental results to evaluate their accuracy and validity. Part II of the thesis focuses on a) understanding the seismic performance of traditional rigid timber-framed partition wall, b) development and verification of low-damage connections (i.e. “rocking” connection details comprising of dual-slot tracks), and c) seismic evaluation of partition walls with a novel “bracketed and slotted” connections (comprising of innovative fastener and plastic bracket named Flexibracket) under uni-directional and bidirectional quasi-static cyclic loadings. Moreover, parametric investigation of the partition walls was conducted through several experimental tests to understand better the pros and cons of the rocking connection details. The experimental results have confirmed that the implementation of the proposed low damage solutions of precast cladding panels and internal partition walls can significantly reduce their damage in a building.
The assessment of damage and remaining capacity after an earthquake is an immediate measure to determine whether a reinforced concrete (RC) building is usable and safe for occupants. The recent Christchurch earthquake (22 February 2011) caused a uniquely severe level of structural damage to modern buildings, resulting in extensive damage to the building stock. About 60% of damaged multistorey concrete buildings (3 storeys and up) were demolished after the earthquake, and the cost of reconstruction amounted to 40 billion NZD. The aftermath disclosed issues of great complexities regarding the future of the RC buildings damaged by the earthquakes. This highlighted the importance of post-event decision-making, as the outcome will allow the appropriate course of action—demolition, repair or acceptance of the existing building—to be considered. To adopt the proper strategy, accurate assessment of the residual capacity and the level of damage is required. This doctoral dissertation aims to assess the damage and remaining capacity at constituent material and member level (i.e., concrete material and beams) through a systematic approach in an attempt to address part of an existing gap in the available literature. Since the residual capacity of RC members is not unique and depends on previously applied loading history, post-event residual capacity in this study was assessed in terms of fraction of fatigue life (i.e., the number of cycles required to failure). This research comprises three main parts: (1) residual capacity and damage assessment at material level (i.e., concrete), (2) post-yield bond deterioration and damage assessment at the interface of steel and concrete, and, finally, (3) residual capacity and damage assessment at member level (i.e., RC beam). The first part of this research focused on damage assessment and the remaining capacity of concrete from a material point of view. It aimed to employ appropriate and reliable durability-based testing and image-detection techniques to quantify deterioration in the mechanical properties of concrete on the basis that stress-induced damage occurred in the microstructural system of the concrete material. To this end, in the first phase, a feasibility study was conducted in which a combination of oxygen permeability, electrical resistivity and porosity tests were assessed to determine if they were robust and reliable enough to reveal damage which occurred in the microstructural system of concrete. The results, in terms of change in permeability, electrical resistivity and porosity features of disk samples taken from the middle third of damaged concrete cylinders (200 mm × 100 mm) monotonically pre-loaded to 50%, 70%, 90% and 95% of the ultimate strength (f′c), showed the permeability test is a reliable tool to identify the degree of damage, due to its high sensitivity to the load-induced microcracking. In parallel, to determine the residual capacity, the companion damaged concrete cylinders already loaded to the same level of compressive strength were reloaded up to failure. Comparing the stress–strain relationship of damaged concrete with intact material, it was also found that the strain capacity of the reloaded pre-damaged concrete cylinders decreases while strength remained virtually unchanged. In the second phase of the first part, a fluorescent microscopy technique was used to assess the damage and develop a correlation between material degradation, by virtue of the geometrical features, and damage to the concrete. To account for the effect of confinement and cyclic loading, in the third phase, the residual capacity and damage assessment of unconfined and GFRP confined concrete cylinders subjected to low-cycle fatigue loading, was investigated. Similar to the first phase, permeability testing technique was used to provide an indirect evaluation of fatigue damage. Finally, in the fourth phase of the first part, the suitability of permeability testing technique to assess damage was evaluated for cored concrete taken from three types of RC members: columns, beams and a beam-column joint. In view of the fact that the composite action of an RC member is highly dependent on the bond between reinforcement and surrounding concrete, understanding the deterioration of the bond in the post-yield range of strain in steel was crucial to assess damage at member level. Therefore, in the second phase of this research, a state-of-the- art distributed fibre optic strain sensor system (DFOSSS) system was used to evaluate bond deterioration in a cantilever RC beam subjected to monotonic lateral loading. The technology allowed the continuous capture of strain, every 2.6 mm along the length, in both reinforcing bars and cover concrete. The strain profile provided a basis by which the slip, axial stress and bond stress distributions were then established. In the third part, the study focused on the damage assessment and residual capacity of seven half-scale RC beams subjected to a constant-amplitude cyclic loading protocol. In the first stage, the structural performances of three specimens under constant-amplitude fatigue at 1%, 2% and 4% chord rotation (drift) were examined. In parallel, the number of cycles to failure, degradation in strength, stiffness and energy dissipation were characterized. In the second stage, four RC beams were subjected to loading up to 70% and 90% of their fatigue life, at 2% and 4% drift, and then monotonically pulled up to failure. To determine the residual flexural capacity, the lateral force–displacement results of pre-damaged specimens were compared with an undamaged specimen subjected to only monotonic loading. The study showed significant losses in strength, deformability, stiffness and energy dissipation capacity. A nonlinear finite element analysis (FEA) using concrete damage plasticity (CDP) model was also conducted in ABAQUS to numerically investigate the behaviour of the tested specimen. The results of the FE simulations indicated a reasonable response compared with the behaviour of the test specimen in terms of force–displacement and cracking pattern. During the Christchurch earthquake it was observed that the loading history has a significant influence on structural responses. While in conventional pseudo-static loading protocol, internal forces can be redistributed along the plastic length: there is little chance for structures undergoing high initial loading amplitude to redistribute pertinent stresses. As a result, in the third phase of this part, the effect of high rate of loading on the behaviour of seismically designed RC beams was investigated. Two half-scale cantilever RC beams were subjected to similar constant-amplitude cyclic loading at 2% and 4% drifts, but at a rate of 500 mm/s. Due to the incapability of conventional measuring techniques, a motion-tracking system was employed for data acquisition with the high-speed tests. The effect of rate of loading on the fatigue life of specimens (i.e., the number of cycles required to failure), secant stiffness, failure mode, cracking pattern, beam elongations and bar fracture surface were analysed. Integrating the results of all parts of this research has resulted in a better understanding of residual capacity and the development of damage at both the material and member level by using a low-cycle fatigue approach.
This report presents the simplified seismic assessment of a case study reinforced concrete (RC) building following the newly developed and refined NZSEE/MBIE guidelines on seismic assessment (NZSEE/MBIE, semi-final draft 26 October 2016). After an overview of the step-by-step ‘diagnostic’ process, including an holistic and qualitative description of the expected vulnerabilities and of the assessment strategy/methodology, focus is given, whilst not limited, to the implementation of a Detailed Seismic Assessment (DSA) (NZSEE/MBIE, 2016c). The DSA is intended to provide a more reliable and consistent outcome than what can be provided by an initial seismic assessment (ISA). In fact, while the Initial Seismic Assessment (ISA), of which the Initial Evaluation Procedure is only a part of, is the more natural and still recommended first step in the overall assessment process, it is mostly intended to be a coarse evaluation involving as few resources as reasonably possible. It is thus expected that an ISA will be followed by a Detailed Seismic Assessment (DSA) not only where the threshold of 33%NBS is not achieved but also where important decisions are intended that are reliant on the seismic status of the building. The use of %NBS (% New Building Standard) as a capacity/demand ratio to describe the result of the seismic assessment at all levels of assessment procedure (ISA through to DSA) is deliberate by the NZSEE/MBIE guidelines (Part A) (NZSEE/MBIE 2016a). The rating for the building needs only be based on the lowest level of assessment that is warranted for the particular circumstances. Discussion on how the %NBS rating is to be determined can be found in Section A3.3 (NZSEE/MBIE 2016a), and, more specifically, in Part B for the ISA (NZSEE/MBIE 2016b) and Part C for the DSA (NZSEE/MBIE 2016c). As per other international approaches, the DSA can be based on several analysis procedures to assess the structural behaviour (linear, nonlinear, static or dynamic, force or displacement-based). The significantly revamped NZSEE 2016 Seismic Assessment Guidelines strongly recommend the use of an analytical (basically ‘by hand’) method, referred to the Simple Lateral Mechanism Analysis (SLaMA) as a first phase of any other numerically-based analysis method. Significant effort has thus been dedicated to provide within the NZSEE 2016 guidelines (NZSEE/MBIE 2016c) a step-by-step description of the procedure, either in general terms (Chapter 2) or with specific reference to Reinforced Concrete Buildings (Chapter 5). More specifically, extract from the guidelines, NZSEE “recommend using the Simple Lateral Mechanism Analysis (SLaMA) procedure as a first step in any assessment. While SLaMA is essentially an analysis technique, it enables assessors to investigate (and present in a simple form) the potential contribution and interaction of a number of structural elements and their likely effect on the building’s global capacity. In some cases, the results of a SLaMA will only be indicative. However, it is expected that its use should help assessors achieve a more reliable outcome than if they only carried out a detailed analysis, especially if that analysis is limited to the elastic range For complex structural systems, a 3D dynamic analysis may be necessary to supplement the simplified nonlinear Simple Lateral Mechanism Analysis (SLaMA).” This report presents the development of a full design example for the the implementation of the SLaMA method on a case study buildings and a validation/comparison with a non-linear static (pushover) analysis. The step-by-step-procedure, summarized in Figure 1, will be herein demonstrated from a component level (beams, columns, wall elements) to a subassembly level (hierarchy of strength in a beam-column joint) and to a system level (frame, C-Wall) assuming initially a 2D behaviour of the key structural system, and then incorporating a by-hand 3D behaviour (torsional effects).
Previous earthquakes demonstrated destructive effects of soil-structure interaction on structural response. For example, in the 1970 Gediz earthquake in Turkey, part of a factory was demolished in a town 135 km from the epicentre, while no other buildings in the town were damaged. Subsequent investigations revealed that the fundamental period of vibration of the factory was approximately equal to that of the underlying soil. This alignment provided a resonance effect and led to collapse of the structure. Another dramatic example took place in Adapazari, during the 1999 Kocaeli earthquake where several foundations failed due to either bearing capacity exceedance or foundation uplifting, consequently, damaging the structure. Finally, the Christchurch 2012 earthquakes have shown that significant nonlinear action in the soil and soil-foundation interface can be expected due to high levels of seismic excitation and spectral acceleration. This nonlinearity, in turn, significantly influenced the response of the structure interacting with the soil-foundation underneath. Extensive research over more than 35 years has focused on the subject of seismic soil-structure interaction. However, since the response of soil-structure systems to seismic forces is extremely complex, burdened by uncertainties in system parameters and variability in ground motions, the role of soil-structure interaction on the structural response is still controversial. Conventional design procedures suggest that soil-structure interaction effects on the structural response can be conservatively ignored. However, more recent studies show that soil-structure interaction can be either beneficial or detrimental, depending on the soil-structure-earthquake scenarios considered. In view of the above mentioned issues, this research aims to utilise a comprehensive and systematic probabilistic methodology, as the most rational way, to quantify the effects of soil-structure interaction on the structural response considering both aleatory and epistemic uncertainties. The goal is achieved by examining the response of established rheological single-degree-of-freedom systems located on shallow-foundation and excited by ground motions with different spectral characteristics. In this regard, four main phases are followed. First, the effects of seismic soil-structure interaction on the response of structures with linear behaviour are investigated using a robust stochastic approach. Herein, the soil-foundation interface is modelled by an equivalent linear cone model. This phase is mainly considered to examine the influence of soil-structure interaction on the approach that has been adopted in the building codes for developing design spectrum and defining the seismic forces acting on the structure. Second, the effects of structural nonlinearity on the role of soil-structure interaction in modifying seismic structural response are studied. The same stochastic approach as phase 1 is followed, while three different types of structural force-deflection behaviour are examined. Third, a systematic fashion is carried out to look for any possible correlation between soil, structural, and system parameters and the degree of soil-structure interaction effects on the structural response. An attempt is made to identify the key parameters whose variation significantly affects the structural response. In addition, it is tried to define the critical range of variation of parameters of consequent. Finally, the impact of soil-foundation interface nonlinearity on the soil-structure interaction analysis is examined. In this regard, a newly developed macro-element covering both material and geometrical soil-foundation interface nonlinearity is implemented in a finite-element program Raumoko 3D. This model is then used in an extensive probabilistic simulation to compare the effects of linear and nonlinear soil-structure interaction on the structural response. This research is concluded by reviewing the current design guidelines incorporating soil-structure interaction effects in their design procedures. A discussion is then followed on the inadequacies of current procedures based on the outcomes of this study.
Following the 22 February 2011, MW 6.2 earthquake located on a fault beneath the Port Hills of Christchurch, fissuring of up to several hundred metres in length was observed in the loess and loess-colluvium of foot-slope positions in north-facing valleys of the Port Hills. The fissuring was observed in all major valleys, occurred at similar low altitudes, showing a contour-parallel orientation and often accompanied by both lateral compression/extension features and spring formation in the valley floor below. Fissuring locations studied in depth included Bowenvale Valley, Hillsborough Valley, Huntlywood Terrace–Lucas Lane, Bridle Path Road, and Maffeys Road–La Costa Lane. Investigations into loess soil, its properties and mannerisms, as well as international examples of its failure were undertaken, including study of the Loess Plateau of China, the Teton Dam, and palaeo-fissuring on Banks Peninsula. These investigations lead to the conclusion that loess has the propensity to fail, often due to the infiltration of water, the presence of which can lead to its instantaneous disaggregation. Literature study and laboratory analysis of Port Hills loess concluded that is has the ability to be stable in steep, sub-vertical escarpments, and often has a sub-vertically jointed internal structure and has a peak shear strength when dry. Values for cohesion, c (kPa) and the internal friction angle, ϕ (degrees) of Port Hills loess were established. The c values for the 40 Rapaki Road, 3 Glenview Terrace loess samples were 13.4 kPa and 19.7 kPa, respectively. The corresponding ϕ values were thought unusually high, at 42.0° and 43.4°.The analysed loess behaved very plastically, with little or no peak strength visible in the plots as the test went almost directly to residual strength. A geophysics resistivity survey showed an area of low resistivity which likely corresponds to a zone of saturated clayey loess/loess colluvium, indicating a high water table in the area. This is consistent with the appearances of local springs which are located towards the northern end of each distinct section of fissure trace and chemical analysis shows that they are sourced from the Port Hills volcanics. Port Hills fissuring may be sub-divided into three categories, Category A, Category B, and Category C, each characterised by distinctive features of the fissures. Category A includes fissures which display evidence of, spring formation, tunnel-gullying, and lateral spreading-like behaviour or quasi-toppling. These fissures are several metres down-slope of the loess-bedrock interface, and are in valleys containing a loess-colluvium fill. Category B fissures are in wider valleys than those in Category A, and the valleys contain estuarine silty sediments which liquefied during the earthquake. Category C fissures occurred at higher elevations than the fissures in the preceding categories, being almost coincident with bedrock outcropping. It is believed that the mechanism responsible for causing the fissuring is a complex combination of three mechanisms: the trampoline effect, bedrock fracturing, and lateral spreading. These three mechanisms can be applied in varying degrees to each of the fissuring sites in categories A, B, and C, in order to provide explanation for the observations made at each. Toppling failure can describe the soil movement as a consequence of the a three causative mechanisms, and provides insight into the movement of the loess. Intra-loess water coursing and tunnel gullying is thought to have encouraged and exacerbated the fissuring, while not being the driving force per se. Incipient landsliding is considered to be the least likely of the possible fissuring interpretations.
Geologic phenomena produced by earthquake shaking, including rockfalls and liquefaction features, provide important information on the intensity and spatiotemporal distribution of earthquake ground motions. The study of rockfall and liquefaction features produced in contemporary well- instrumented earthquakes increases our knowledge of how natural and anthropogenic environments respond to earthquakes and improves our ability to deduce seismologic information from analogous pre-contemporary (paleo-) geologic features. The study of contemporary and paleo- rockfall and liquefaction features enables improved forecasting of environmental responses to future earthquakes. In this thesis I utilize a combination of field and imagery-based mapping, trenching, stratigraphy, and numerical dating techniques to understand the nature and timing of rockfalls (and hillslope sedimentation) and liquefaction in the eastern South Island of New Zealand, and to examine the influence that anthropogenic activity has had on the geologic expressions of earthquake phenomena. At Rapaki (Banks Peninsula, NZ), field and imagery-based mapping, statistical analysis and numerical modeling was conducted on rockfall boulders triggered by the fatal 2011 Christchurch earthquakes (n=285) and compared with newly identified prehistoric (Holocene and Pleistocene) boulders (n=1049) deposited on the same hillslope. A significant population of modern boulders (n=26) travelled farther downslope (>150 m) than their most-travelled prehistoric counterparts, causing extensive damage to residential dwellings at the foot of the hillslope. Replication of prehistoric boulder distributions using 3-dimensional rigid body numerical models requires the application of a drag-coefficient, attributed to moderate to dense slope vegetation, to account for their spatial distribution. Radiocarbon dating provides evidence for 17th to early 20th century deforestation at the study site during Polynesian and European colonization and after emplacement of prehistoric rockfalls. Anthropocene deforestation enabled modern rockfalls to exceed the limits of their prehistoric predecessors, highlighting a shift in the geologic expression of rockfalls due to anthropogenic activity. Optical and radiocarbon dating of loessic hillslope sediments in New Zealand’s South Island is used to constrain the timing of prehistoric rockfalls and associated seismic events, and quantify spatial and temporal patterns of hillslope sedimentation including responses to seismic and anthropogenic forcing. Luminescence ages from loessic sediments constrain timing of boulder emplacement to between ~3.0 and ~12.5 ka, well before the arrival of Polynesians (ca AD 1280) and Europeans (ca AD 1800) in New Zealand, and suggest loess accumulation was continuing at the study site until 12-13 ka. Large (>5 m3) prehistoric rockfall boulders preserve an important record of Holocene hillslope sedimentation by creating local traps for sediment aggradation and upbuilding soil formation. Sediment accumulation rates increased considerably (>~10 factor increase) following human arrival and associated anthropogenic burning of hillslope vegetation. New numerical ages are presented to place the evolution of loess-mantled hillslopes in New Zealand’s South Island into a longer temporal framework and highlight the roles of earthquakes and humans on hillslope surface process. Extensive field mapping and characterization for 1733 individual prehistoric rockfall boulders was conducted at Rapaki and another Banks Peninsula site, Purau, to understand their origin, frequency, and spatial and volumetric distributions. Boulder characteristics and distributions were compared to 421 boulders deposited at the same sites during the 2010-2011 Canterbury earthquake sequence. Prehistoric boulders at Rapaki and Purau are comprised of two dominant lithofacies types: volcanic breccia and massive (coherent) lava basalt. Volcanic breccia boulders are found in greatest abundance (64-73% of total mapped rockfall) and volume (~90-96% of total rockfall) at both locations and exclusively comprise the largest boulders with the longest runout distances that pose the greatest hazard to life and property. This study highlights the primary influence that volcanic lithofacies architecture has on rockfall hazard. The influence of anthropogenic modifications on the surface and subsurface geologic expression of contemporary liquefaction created during the 2010-2011 Canterbury earthquake sequence (CES) in eastern Christchurch is examined. Trench observations indicate that anthropogenic fill layer boundaries and the composition/texture of discretely placed fill layers play an important role in absorbing fluidized sand/silt and controlling the subsurface architecture of preserved liquefaction features. Surface liquefaction morphologies (i.e. sand blows and linear sand blow arrays) display alignment with existing utility lines and utility excavations (and perforated pipes) provided conduits for liquefaction ejecta during the CES. No evidence of pre-CES liquefaction was identified within the anthropogenic fill layers or underlying native sediment. Radiocarbon dating of charcoal within the youngest native sediment suggests liquefaction has not occurred at the study site for at least the past 750-800 years. The importance of systematically examining the impact of buried infrastructure on channelizing and influencing surface and subsurface liquefaction morphologies is demonstrated. This thesis highlights the importance of using a multi-technique approach for understanding prehistoric and contemporary earthquake phenomena and emphasizes the critical role that humans play in shaping the geologic record and Earth’s surface processes.
Deformational properties of soil, in terms of modulus and damping, exert a great influence on seismic response of soil sites. However, these properties for sands containing some portion of fines particles have not been systematically addressed. In addition, simultaneous modelling of the modulus and damping behaviour of soils during cyclic loading is desirable. This study presents an experimental and computational investigation into the deformational properties of sands containing fines content in the context of site response analysis. The experimental investigation is carried on sandy soils sourced from Christchurch, New Zealand using a dynamic triaxial apparatus while the computational aspect is based on the framework of total-stress one-dimensional (1D) cyclic behaviour of soil. The experimental investigation focused on a systematic study on the deformational behaviour of sand with different amounts of fines content (particle diameter ≤ 75µm) under drained conditions. The silty sands were prepared by mixing clean sand with three different percentages of fines content. A series of bender element tests at small-strain range and stress-controlled dynamic triaxial tests at medium to high-strain ranges were conducted on samples of clean sand and silty sand. This allowed measurements of linear and nonlinear deformational properties of the same specimen for a wide strain range. The testing program was designed to quantify the effects of void ratio and fines content on the low-strain stiffness of the silty sand as well as on the nonlinear stress-strain relationship and corresponding shear modulus and damping properties as a function of cyclic shear strains. Shear wave velocity, Vs, and maximum shear modulus, Gmax, of silty sand was shown to be significantly smaller than the respective values for clean sands measured at the same void ratio, e, or same relative density, Dr. However, the test results showed that the difference in the level of nonlinearity between clean sand and silty sands was small. For loose samples prepared at an identical relative density, the behaviour of clean sand was slightly less nonlinear as compared to sandy soils with higher fines content. This difference in the nonlinear behaviour of clean sand and sandy soils was negligible for dense soils. Furthermore, no systematic influence of fines content on the material damping curve was observed for sands with fines content FC = 0 to 30%. In order to normalize the effects of fines on moduli of sands, equivalent granular void ratio, e*, was employed. This was done through quantifying the participation of fines content in the force transfer chain of the sand matrix. As such, a unified framework for modelling of the variability of shear wave velocity, Vs, (or shear modulus, Gmax) with void ratio was achieved for clean sands and sands with fines, irrespective of their fines content. Furthermore, modelling of the cyclic stress-strain behaviour based on this experimental program was investigated. The modelling effort focused on developing a simple constitutive model which simultaneously models the soil modulus and damping relationships with shear strains observed in laboratory tests. The backbone curve of the cyclic model was adopted based on a modified version of Kondner and Zelasko (MKZ) hyperbolic function, with a curvature coefficient, a. In order to simulate the hysteretic cycles, the conventional Masing rules (Pyke 1979) were revised. The parameter n, in the Masing’s criteria was assumed to be a function of material damping, h, measured in the laboratory. As such the modulus and damping produced by the numerical model could match the stress-strain behaviour observed in the laboratory over the course of this study. It was shown that the Masing parameter n, is strain-dependent and generally takes values of n ≤ 2. The model was then verified through element test simulations under different cyclic loadings. It was shown that the model could accurately simulate the modulus and the damping simultaneously. The model was then incorporated within the OpenSees computational platform and was used to scrutinize the effects of damping on one-dimensional seismic site response analysis. For this purpose, several strong motion stations which recorded the Canterbury earthquake sequence were selected. The soil profiles were modelled as semi-infinite horizontally layered deposits overlying a uniform half-space subjected to vertically propagating shear waves. The advantages and limitations of the nonlinear model in terms of simulating soil nonlinearity and associated material damping were further scrutinized. It was shown that generally, the conventional Masing criteria unconservatively may underestimate some response parameters such as spectral accelerations. This was shown to be due to larger hysteretic damping modelled by using conventional Masing criteria. In addition, maximum shear strains within the soil profiles were also computed smaller in comparison to the values calculated by the proposed model. Further analyses were performed to study the simulation of backbone curve beyond the strain ranges addressed in the experimental phase of this study. A key issue that was identified was that relying only on the modulus reduction curves to simulate the stress-strain behaviour of soil may not capture the actual soil strength at larger strains. Hence, strength properties of the soil layer should also be incorporated to accurately simulate the backbone curve.
In major seismic events, a number of plan-asymmetric buildings which experienced element failure or structural collapse had twisted significantly about their vertical axis during the earthquake shaking. This twist, known as “building torsion”, results in greater demands on one side of a structure than on the other side. The Canterbury Earthquakes Royal Commission’s reports describe the response of a number of buildings in the February 2011 Christchurch earthquakes. As a result of the catastrophic collapse of one multi-storey building with significant torsional irregularity, and significant torsional effects also in other buildings, the Royal Commission recommended that further studies be undertaken to develop improved simple and effective guides to consider torsional effects in buildings which respond inelastically during earthquake shaking. Separately from this, as building owners, the government, and other stakeholders, are planning for possible earthquake scenarios, they need good estimates of the likely performance of both new and existing buildings. These estimates, often made using performance based earthquake engineering considerations and loss estimation techniques, inform decision making. Since all buildings may experience torsion to some extent, and torsional effects can influence demands on building structural and non-structural elements, it is crucial that demand estimates consider torsion. Building seismic response considering torsion can be evaluated with nonlinear time history analysis. However, such analysis involves significant computational effort, expertise and cost. Therefore, from an engineers’ point of view, simpler analysis methods, with reasonable accuracy, are beneficial. The consideration of torsion in simple analysis methods has been investigated by many researchers. However, many studies are theoretical without direct relevance to structural design/assessment. Some existing methods also have limited applicability, or they are difficult to use in routine design office practice. In addition, there has been no consensus about which method is best. As a result, there is a notable lack of recommendations in current building design codes for torsion of buildings that respond inelastically. There is a need for building torsion to be considered in yielding structures, and for simple guidance to be developed and adopted into building design standards. This study aims to undertaken to address this need for plan-asymmetric structures which are regular over their height. Time history analyses are first conducted to quantify the effects of building plan irregularity, that lead to torsional response, on the seismic response of building structures. Effects of some key structural and ground motion characteristics (e.g. hysteretic model, ground motion duration, etc.) are considered. Mass eccentricity is found to result in rather smaller torsional response compared to stiffness/strength eccentricity. Mass rotational inertia generally decreases the torsional response; however, the trend is not clearly defined for torsionally restrained systems (i.e. large λty). Systems with EPP and bilinear models have close displacements and systems with Takeda, SINA, and flag-shaped models yield almost the same displacements. Damping has no specific effect on the torsional response for the single-storey systems with the unidirectional eccentricity and excitation. Displacements of the single-storey systems subject to long duration ground motion records are smaller than those for short duration records. A method to consider torsional response of ductile building structures under earthquake shaking is then developed based on structural dynamics for a wide range of structural systems and configurations, including those with low and high torsional restraint. The method is then simplified for use in engineering practice. A novel method is also proposed to simply account for the effects of strength eccentricity on response of highly inelastic systems. A comparison of the accuracy of some existing methods (including code-base equivalent static method and model response spectrum analysis method), and the proposed method, is conducted for single-storey structures. It is shown that the proposed method generally provides better accuracy over a wide range of parameters. In general, the equivalent static method is not adequate in capturing the torsional effects and the elastic modal response spectrum analysis method is generally adequate for some common parameters. Record-to-record variation in maximum displacement demand on the structures with different degrees of torsional response is considered in a simple way. Bidirectional torsional response is then considered. Bidirectional eccentricity and excitation has varying effects on the torsional response; however, it generally increases the weak and strong edges displacements. The proposed method is then generalized to consider the bidirectional torsion due to bidirectional stiffness/strength eccentricity and bidirectional seismic excitation. The method is shown to predict displacements conservatively; however, the conservatism decreases slightly for cases with bidirectional excitation compared to those subject to unidirectional excitation. In is shown that the roof displacement of multi-storey structures with torsional response can be predicted by considering the first mode of vibration. The method is then further generalized to estimate torsional effects on multi-storey structure displacement demands. The proposed procedure is tested multi-storey structures and shown to predict the displacements with a good accuracy and conservatively. For buildings which twist in plan during earthquake shaking, the effect of P-Δλ action is evaluated and recommendations for design are made. P-Δλ has more significant effects on systems with small post- yield stiffness. Therefore, system stability coefficient is shown not to be the best indicator of the importance of P-Δλ and it is recommended to use post-yield stiffness of system computed with allowance for P-Δλ effects. For systems with torsional response, the global system stability coefficient and post- yield stiffness ration do not reflect the significance of P-Δλ effects properly. Therefore, for torsional systems individual seismic force resisting systems should be considered. Accuracy of MRSA is investigated and it is found that the MRSA is not always conservative for estimating the centre of mass and strong edge displacements as well as displacements of ductile systems with strength eccentricity larger than stiffness eccentricity. Some modifications are proposed to get the MRSA yields a conservative estimation of displacement demands for all cases.
Field surveys and experimental studies have shown that light steel or timber framed plasterboard partition walls are particularly vulnerable to earthquake damage prompting the overarching objective of this research, which is to further the development of low damage seismic systems for non-structural partition walls in order to facilitate their adoption by industry to assist with reducing the losses associated with the maintenance and repair cost of buildings across their design life. In particular, this study focused on the behaviour of steel-framed partition walls systems with novel detailing that aim to be “low-damage” designed according to common practice for walls used in commercial and institutional buildings in New Zealand. This objective was investigated by (1) investigating the performance of a flexible track system proposed by researchers and industry by experimental testing of full-scale specimens; (2) investigating the performance of the seismic gap partition wall systems proposed in a number of studies, further developed in this study with input from industry, by experimental testing of full-scale specimens; and (3) investigating the potential implications of using these systems compared with traditionally detailed partition wall systems within multi-storey buildings using the Performance Based Earthquake Engineering loss assessment methodology. Three full-scale testing frames were designed in order to replicate, under controlled laboratory conditions, the effects of seismic shaking on partition walls within multi-storey buildings by the application of quasi-static uni-directional cyclic loading imposing an inter-storey drift. The typical configuration for test specimens was selected to be a unique “y-shape”, including one angled return wall, with typical dimensions of approximately 2400 mm along the main wall and 600 mm along (approximately) the returns walls with a height of 2405 mm from floor to ceiling. The specimens were aligned within test frames at an oblique angle to the direction of loading in order to investigate bi- directional effects. Three wall specimens with flexible track detailing, two identical plane specimens and the third including a doorway, were tested. The detailing involved removing top track anchors within the proximity of wall intersections, thus allowing the tracks to ‘bow’ out at these locations. Although the top track anchors were specified to be removed the proximity of wall intersections, a construction error was made whereby a single top track slab to concrete anchor was left in at the three-way wall junction. Despite this error, the experimental testing was deemed worthwhile since such errors will also occur in practice and because the behaviour of the wall can be examined with this fixing in mind. The specimens also included an acoustic/fire sealant at the top lining to floor boundary. In addition to providing drift capacities, the force-displacement behaviour is also reported, the dissipated energy was computed, and the parameters of the Wayne-Stewart hysteretic model were fitted to the results. The specimen with the door opening behaved significantly different to the plane specimens: damage to the doorway specimen began as cracking of the wallboard propagating from the corners of the doorway following which the L- and Y- shaped junctions behaved independently, whereas damage to the plane specimens began as cracking of the wallboard at the top of the L-junction and wall system deformed as a single unit. The results suggest that bi-directional behaviour is important even if its impact cannot be directly quantified by the experiments conducted. Damage to sealant implies that the bond between plasterboard and sealant is important for its seismic performance. Careful quality control is advised as defects in the bond may significantly impact its ability to withstand seismic movement. Two specimens with seismic gap detailing were tested: a steel stud specimen and a timber stud specimen. Observed drift capacities were significantly greater than traditional plasterboard partition systems. Equations were used to predict the drift at which damage state 1 (DS1) and damage state 2 (DS2) would initiate. The equation used to estimate the drift at the onset of DS1 accurately predicted the onset of plaster cracking but overestimated the drift at which the gap filling material was damaged. The equation used to predict the onset of DS2 provided a lower bound for both specimens and also when used to predict results of previous experimental tests on seismic gap systems. The gap-filling material reduced the drift at the onset of DS1, however, it had a beneficial effect on the re-centring behaviour of the linings. Out-of-plane displacements and return wall configuration did not appear to significantly impact the onset of plaster cracking in the specimens. A loss assessment according to the PBEE methodology was conducted on four steel MRF case study buildings: (1) a 4-storey building designed for the Christchurch region, (2) a 4-storey building designed for the Wellington region, (3) a 12-storey building designed for the Christchurch region, and (4) a 12- storey building designed for the Wellington region. The fragility parameters for a traditional partition system, the flexible track partition system, and the seismic gap steel stud and timber stud partition systems were included within the loss assessment. The order (lowest to highest) of each system in terms of the expected annual losses of each building when incorporating the system was, (1) the seismic gap timber stud system, (2) the seismic gap steel stud system, (3) the traditional/baseline system, and (4) the flexible track system. For the seismic gap timber stud system, which incurred the greatest reduction in expected annual losses for each case study building, the reduction in expected annual losses in comparison to the losses found when using the traditional system ranged from a 5% to a 30% reduction. This reinforces the fact that while there is a benefit to the using low damage partition systems in each building the extent of reduction in expected annual losses is significantly dependent on the particular building design and its location. The flexible track specimens had larger repair costs at small hazard levels compared to the traditional system but smaller repair costs at larger hazard levels. However, the resulting expected annual losses for the flexible track system was higher than the traditional system which reinforces findings from past studies which observed that the greatest contribution to expected annual losses arises from low to moderate intensity shaking seismic events (low hazard levels).
