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Research papers, University of Canterbury Library

Light timber framed (LTF) structures provide a cost-effective and structurally efficient solution for low-rise residential buildings. This paper studies seismic performance of single-storey LTF buildings sheathed by gypsum-plasterboards (GPBs) that are a typical lining product in New Zealand houses. Compared with wood-based structural panels, GPBs tend to be more susceptible to damage when they are used in bracing walls to resist earthquake loads. This study aims to provide insights on how the bracing wall irregularity allowed by the current New Zealand standard NZS 3604 and the in-plane rigidity of ceiling diaphragms affect the overall seismic performance of these GPB-braced LTF buildings. Nonlinear time-history analyses were conducted on a series of single-storey baseline buildings with different levels of bracing wall irregularities and ceiling diaphragm rigidity. The results showed significant torsional effect caused by the eccentric bracing wall layout with semi-rigid/rigid ceiling diaphragms. On average, bracing wall drift demand caused by the extreme bracing wall irregularities was three times of that in the regular bracing wall layout under the rigid diaphragm assumption. This finding agreed well with the house survey after the 2011 Canterbury Earthquake in which significantly more damage was observed in the houses with irregular bracing wall layouts and relatively rigid diaphragms. Therefore, it is recommended to limit the level of bracing wall eccentricity and ensure the sufficiently rigid diaphragms to avoid excessive damage in these LTF buildings in future events.

Images, UC QuakeStudies

A view of the Cranmer Court building on the corner of Kilmore and Montreal Streets, showing damage from the 4 September 2010 earthquake. Masonry has fallen away from the apexes of several of the building's gables, which have been reinforced with timber bracing. A green cord has been used to tie bracing to the octagonal section on the corner of the building. This corner section is the part that housed Plato Creative from March 2008 to November 2009.

Videos, UC QuakeStudies

A video of interviews with members of the public about which option they prefer for the restoration of the ChristChurch Cathedral. The options considered are those unveiled by the Anglican Church: the restoration option which would restore the current cathedral; the traditional option which would reinterpret the original cathedral in modern materials; and the contemporary option which would create a new building featuring a lightweight timber frame, more glazing, and modern interiors.

Research papers, University of Canterbury Library

Based on the recent developments on alternative jointed ductile dry connections for concrete multistorey buildings, the paper aims to extend and propose similar innovative seismic connections for laminated veneer lumber (LVL) timber buildings. The dry connections herein proposed are characterised by a sort of rocking occurring at the section interface of the structural elements when an earthquake occurs; unbonded post-tensioned techniques and dissipative devices respectively provide self-centring and dissipation capacities. The paper illustrates some experimental investigations of an extensive campaign, still undergoing at the University of Canterbury Christchurch, NZ) are herein presented and critically discussed. In particular, results of cyclic quasi-static testing on exterior beam-column subassemblies and wall-to-foundation systems are herein presented; preliminary results of pseudo-dynamic testing on wall-to-foundation specimens are also illustrated. The research investigations confirmed the enhanced seismic performance of these systems/connections; three key aspects , as the no-damageability in the structural elements, typical “flag-shape” cyclic behaviour (with self-centring and dissipation capacity), negligible residual deformations, i.e. limited costs of repair, joined with low mass, flexibility of design and rapidity of construction LVL timber, all create the potential for an increased use in low-rise multistorey buildings.

Research papers, University of Canterbury Library

This paper describes part of an extensive experimental programme in progress at the University of Canterbury to develop Laminated Veneer Lumber (LVL) structural systems and connections for multistorey timber buildings in earthquake-prone areas. The higher mechanical properties of LVL, when compared to sawn timber, in addition to its low mass, flexibility of design and rapidity of construction, create the potential for increased use of LVL in multi-storey buildings. The development of these innovative ductile connections in LVL, proposed here for frame systems, have been based on the successful implementation of jointed ductile connections for precast concrete systems, started in the early 1990s with the PRESSS Program at the University of California, San Diego, further developed in Italy and currently under further refinement at the University of Canterbury. This paper investigates the seismic behaviour of the so-called “hybrid” connection, characterised by the combination of unbonded post-tensioned tendons and either external or internal energy dissipaters passing through the critical contact surface between the structural elements. Experimental results on hybrid exterior beam-to-column and column-to-foundation subassemblies under cyclic quasi-static unidirectional loading are presented. The proposed innovative solutions exhibit a very satisfactory seismic performance characterised by an appreciable energy dissipation capacity (provided by the dissipaters) combined with self-centring properties (provided by the unbonded tendons) and negligible damage of the LVL structural elements.

Research papers, University of Canterbury Library

The ultimate goal of this study is to develop a model representing the in-plane behaviour of plasterboard ceiling diaphragms, as part of the efforts towards performance-based seismic engineering of low-rise light timber-framed (LTF) residential buildings in New Zealand (NZ). LTF residential buildings in NZ are constructed according to a prescriptive standard – NZS 3604 Timberframed buildings [1]. With regards to seismic resisting systems, LTF buildings constructed to NZS3604 often have irregular bracing arrangements within a floor plane. A damage survey of LTF buildings after the Canterbury earthquake revealed that structural irregularity (irregular bracing arrangement within a plane) significantly exacerbated the earthquake damage to LTF buildings. When a building has irregular bracing arrangements, the building will have not only translational deflections but also a torsional response in earthquakes. How effectively the induced torsion can be resolved depends on the stiffness of the floors/roof diaphragms. Ceiling and floor diaphragms in LTF buildings in NZ have different construction details from the rest of the world and there appears to be no information available on timber diaphragms typical of NZ practice. This paper presents experimental studies undertaken on plasterboard ceiling diaphragms as typical of NZ residential practice. Based on the test results, a mathematical model simulating the in-plane stiffness of plasterboard ceiling diaphragms was developed, and the developed model has a similar format to that of plasterboard bracing wall elements presented in an accompany paper by Liu [2]. With these two models, three-dimensional non-linear push-over studies of LTF buildings can be undertaken to calculate seismic performance of irregular LTF buildings.

Research papers, University of Canterbury Library

Seismic isolation is an effective technology for significantly reducing damage to buildings and building contents. However, its application to light-frame wood buildings has so far been unable to overcome cost and technical barriers such as susceptibility of light-weight buildings to movement under high-wind loading. The 1994 Northridge Earthquake (6.7 MW) in the United States, 1995 Kobe Earthquake (6.9 MW) in Japan and 2011 Christchurch Earthquake (6.7 Mw) all highlighted significant loss to light-frame wood buildings with over half of earthquake recovery costs allocated to their repair and reconstruction. This poster presents a value case to highlight the benefits of seismically isolated residential buildings compared to the standard fixed-base dwellings for the Wellington region. Loss data generated by insurance claim information from the 2011 Christchurch Earthquake has been used to determine vulnerability functions for the current light-frame wood building stock. By using a simplified single degree of freedom (SDOF) building model, methods for determining vulnerability functions for seismic isolated buildings are developed. Vulnerability functions are then applied directly in a loss assessment to determine the Expected Annual Loss. Vulnerability was shown to dramatically reduce for isolated buildings compared to an equivalent fixed-base building resulting in significant monetary savings, justifying the value case. A state-of-the-art timber modelling software, Timber3D, is then used to model a typical residential building with and without seismic isolation to assess the performance of a proposed seismic isolation system which addresses the technical and cost issues.

Research papers, University of Canterbury Library

New Zealand has a long tradition of using light timber frame for construction of its domestic dwellings. After the most recent earthquakes (e.g. Canterbury earthquakes sequence), wooden residential houses showed satisfactory life safety performance which aligns with New Zealand design codes requirements. However, poor performance was reported in terms of their seismic resilience that can be generally associated with community demands. Future expectations of the seismic performance of wooden-framed houses by homeowners were assessed in this research. Homeowners in the Wellington region were asked in a survey about the levels of safety and expected possible damage in their houses after a seismic event. Findings bring questions about whether New Zealand code requirements are good enough to satisfy community demands. Also, questions whether available information of strengthening techniques to structurally prepare wooden-framed houses to face future major earthquakes can help to make homeowners feel safer at home during major seismic events.

Research papers, University of Canterbury Library

The Canterbury Earthquakes of 2010-2011, in particular the 4th September 2010 Darfield earthquake and the 22nd February 2011 Christchurch earthquake, produced severe and widespread liquefaction in Christchurch and surrounding areas. The scale of the liquefaction was unprecedented, and caused extensive damage to a variety of man-made structures, including residential houses. Around 20,000 residential houses suffered serious damage as a direct result of the effects of liquefaction, and this resulted in approximately 7000 houses in the worst-hit areas being abandoned. Despite the good performance of light timber-framed houses under the inertial loads of the earthquake, these structures could not withstand the large loads and deformations associated with liquefaction, resulting in significant damage. The key structural component of houses subjected to liquefaction effects was found to be their foundations, as these are in direct contact with the ground. The performance of house foundations directly influenced the performance of the structure as a whole. Because of this, and due to the lack of research in this area, it was decided to investigate the performance of houses and in particular their foundations when subjected to the effects of liquefaction. The data from the inspections of approximately 500 houses conducted by a University of Canterbury summer research team following the 4th September 2010 earthquake in the worst-hit areas of Christchurch were analysed to determine the general performance of residential houses when subjected to high liquefaction loads. This was followed by the detailed inspection of around 170 houses with four different foundation types common to Christchurch and New Zealand: Concrete perimeter with short piers constructed to NZS3604, concrete slab-on-grade also to NZS3604, RibRaft slabs designed by Firth Industries and driven pile foundations. With a focus on foundations, floor levels and slopes were measured, and the damage to all areas of the house and property were recorded. Seven invasive inspections were also conducted on houses being demolished, to examine in more detail the deformation modes and the causes of damage in severely affected houses. The simplified modelling of concrete perimeter sections subjected to a variety of liquefaction-related scenarios was also performed, to examine the comparative performance of foundations built in different periods, and the loads generated under various bearing loss and lateral spreading cases. It was found that the level of foundation damage is directly related to the level of liquefaction experienced, and that foundation damage and liquefaction severity in turn influence the performance of the superstructure. Concrete perimeter foundations were found to have performed most poorly, suffering high local floor slopes and being likely to require foundation repairs even when liquefaction was low enough that no surface ejecta was seen. This was due to their weak, flexible foundation structure, which cannot withstand liquefaction loads without deforming. The vulnerability of concrete perimeter foundations was confirmed through modelling. Slab-on-grade foundations performed better, and were unlikely to require repairs at low levels of liquefaction. Ribraft and piled foundations performed the best, with repairs unlikely up to moderate levels of liquefaction. However, all foundation types were susceptible to significant damage at higher levels of liquefaction, with maximum differential settlements of 474mm, 202mm, 182mm and 250mm found for concrete perimeter, slab-on-grade, ribraft and piled foundations respectively when subjected to significant lateral spreading, the most severe loading scenario caused by liquefaction. It was found through the analysis of the data that the type of exterior wall cladding, either heavy or light, and the number of storeys, did not affect the performance of foundations. This was also shown through modelling for concrete perimeter foundations, and is due to the increased foundation strengths provided for heavily cladded and two-storey houses. Heavy roof claddings were found to increase the demands on foundations, worsening their performance. Pre-1930 concrete perimeter foundations were also found to be very vulnerable to damage under liquefaction loads, due to their weak and brittle construction.

Research papers, University of Canterbury Library

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).

Audio, Radio New Zealand

It was so nearly lost. As the Christ Church Anglican Cathedral is being rebuilt, historian Edmund Bohan is releasing a history of the distinctive Gothic building. It shows it was controversial even before work started on designing it, let alone building in. From the laying of the foundations to the official opening, it took 40 years, after squabbles over pretty much every aspect of its construction - not to mention the huge problems raising the money to build it in the City Centre. In Heart of the City: The Story of Christchurch's Controversial Cathedral, Edmund is critical of the former Anglican Bishop Victoria Matthews' determination to demolish the badly-damaged cathedral after the Canterbury earthquakes, to replace it with a modern church. And he tells Lynn Freeman he's very much looking forward to seeing the Cathedral restored to its former glory after a lengthy and pricey rebuild. But first he sets the scene. Back in the 1860s, there was controversy over where the cathedral should go, its design, whether it should be in stone or timber - even if there should be a cathedral built at all! Heart of the City: The Story of Christchurch's Controversial Cathedral, by Edmund Bohan is published by Quentin Wilson Publishing.

Research papers, University of Canterbury Library

In most design codes, infill walls are considered as non-structural elements and thus are typically neglected in the design process. The observations made after major earthquakes (Duzce 1999, L’Aquila 2009, Christchurch 2011) have shown that even though infill walls are considered to be non-structural elements, they interact with the structural system during seismic actions. In the case of heavy infill walls (i.e. clay brick infill walls), the whole behaviour of the structure may be affected by this interaction (i.e. local or global structural failures such as soft storey mechanism). In the case of light infill walls (i.e. non-structural drywalls), this may cause significant economical losses. To consider the interaction of the structural system with the ‘non-structural ’infill walls at design stage may not be a practical approach due to the complexity of the infill wall behaviour. Therefore, the purpose of the reported research is to develop innovative technological solutions and design recommendations for low damage non-structural wall systems for seismic actions by making use of alternative approaches. Light (steel/timber framed drywalls) and heavy (unreinforced clay brick) non-structural infill wall systems were studied by following an experimental/numerical research programme. Quasi-static reverse cyclic tests were carried out by utilizing a specially designed full scale reinforced concrete frame, which can be used as a re-usable bare frame. In this frame, two RC beams and two RC columns were connected by two un-bonded post tensioning bars, emulating a jointed ductile frame system (PRESSS technology). Due to the rocking behaviour at the beam-column joint interfaces, this frame was typically a low damage structural solution, with the post-tensioning guaranteeing a linear elastic behaviour. Therefore, this frame could be repeatedly used in all of the tests carried out by changing only the infill walls within this frame. Due to the linear elastic behaviour of this structural bare frame, it was possible to extract the exact behaviour of the infill walls from the global results. In other words, the only parameter that affected the global results was given by the infill walls. For the test specimens, the existing practice of construction (as built) for both light and heavy non-structural walls was implemented. In the light of the observations taken during these tests, modified low damage construction practices were proposed and tested. In total, seven tests were carried out: 1) Bare frame , in order to confirm its linear elastic behaviour. 2) As built steel framed drywall specimen FIF1-STFD (Light) 3) As built timber framed drywall specimen FIF2-TBFD (Light) 4) As built unreinforced clay brick infill wall specimen FIF3-UCBI (Heavy) 5) Low damage steel framed drywall specimen MIF1-STFD (Light) 6) Low damage timber framed drywall specimen MIF2-TBFD (Light) 7) Low damage unreinforced clay brick infill wall specimen MIF5-UCBI (Heavy) The tests of the as built practices showed that both drywalls and unreinforced clay brick infill walls have a low serviceability inter-storey drift limit (0.2-0.3%). Based on the observations, simple modifications and details were proposed for the low damage specimens. The details proved to be working effectively in lowering the damage and increasing the serviceability drift limits. For drywalls, the proposed low damage solutions do not introduce additional cost, material or labour and they are easily applicable in real buildings. For unreinforced clay brick infill walls, a light steel sub-frame system was suggested that divides the infill panel zone into smaller individual panels, which requires additional labour and some cost. However, both systems can be engineered for seismic actions and their behaviour can be controlled by implementing the proposed details. The performance of the developed details were also confirmed by the numerical case study analyses carried out using Ruaumoko 2D on a reinforced concrete building model designed according to the NZ codes/standards. The results have confirmed that the implementation of the proposed low damage solutions is expected to significantly reduce the non-structural infill wall damage throughout a building.

Research papers, University of Canterbury Library

Drywalls are the typical infill or partitions used in new structures. They are usually located within structural frames and/or between upper and lower floor slabs in buildings. Due to the materials used in their construction, unlike masonry blocks, they can be considered as light non-structural infill/partition walls. These types of walls are especially popular in New Zealand and the USA. In spite of their popularity, little is known about their in-plane cyclic behaviour when infilled within a structural frame. The cause of this lack of knowledge can be attributed to the typical assumption that they are weak non-structural elements and are not expected to interact with the surrounding structural system significantly. However, recent earthquakes have repeatedly shown that drywalls interact with the structure and suffer severe damage at very low drift levels. In this paper, experimental test results of two typical drywall types (steel and timber framed) are reported in order to gather further information on; i) their reverse cyclic behaviour, ii) inter-storey drift levels at which they suffer different levels of damage, iii) the level of interaction with the surrounding structural frame system. The drywall specimens were tested using quasi-static reverse cyclic testing protocols within a full scale precast RC frame at the Structures Laboratory of the University of Canterbury.

Research papers, Victoria University of Wellington

Construction and Demolition (C&D) waste contributes to over 50% of New Zealand’s overall waste. Materials such as timber, plasterboard, and concrete make up 81% of the C&D waste that goes into landfills each year. Alongside this, more than 235 heritage-listed buildings have been demolished in Christchurch since the 2011 earthquakes. This research portfolio aims to find a solution to decrease C&D waste produced by demolishing heritage buildings. With the recent announcement of The Cathedral of the Blessed Sacrament’s demolition, this will be another building added to the list of lost heritage in Christchurch. This research portfolio aims to bridge the relationship between heritage and waste through the recycling and reuse of the demolished materials, exploring the idea that history and heritage are preserved through building material reuse. This research portfolio mainly focuses on reducing construction and demolition waste in New Zealand, using the design of a new Catholic Cathedral as a vessel. This thesis will challenge how the construction and design industry deals with the demolition of heritage buildings and their contribution to New Zealand’s waste. It aims to explore the idea of building material reuse not only to reduce waste but also to retain the history and heritage of the demolished building within the materials.

Research papers, University of Canterbury Library

Surface rupture of the previously unrecognised Greendale Fault extended west-east for ~30 km across alluvial plains west of Christchurch, New Zealand, during the Mw 7.1 Darfield (Canterbury) earthquake of September 2010. Surface rupture displacement was predominantly dextral strike-slip, averaging ~2.5 m, with maxima of ~5 m. Vertical displacement was generally less than 0.75 m. The surface rupture deformation zone ranged in width from ~30 to 300 m, and comprised discrete shears, localised bulges and, primarily, horizontal dextral flexure. About a dozen buildings, mainly single-storey houses and farm sheds, were affected by surface rupture, but none collapsed, largely because most of the buildings were relatively flexible and resilient timber-framed structures and also because deformation was distributed over a relatively wide zone. There were, however, notable differences in the respective performances of the buildings. Houses with only lightly-reinforced concrete slab foundations suffered moderate to severe structural and non-structural damage. Three other buildings performed more favourably: one had a robust concrete slab foundation, another had a shallow-seated pile foundation that isolated ground deformation from the superstructure, and the third had a structural system that enabled the house to tilt and rotate as a rigid body. Roads, power lines, underground pipes, and fences were also deformed by surface fault rupture and suffered damage commensurate with the type of feature, its orientation to the fault, and the amount, sense and width of surface rupture deformation.

Research papers, University of Canterbury Library

Earthquake Engineering is facing an extraordinarily challenging era, the ultimate target being set at increasingly higher levels by the demanding expectations of our modern society. The renewed challenge is to be able to provide low-cost, thus more widely affordable, high-seismic-performance structures capable of sustaining a design level earthquake with limited or negligible damage, minimum disruption of business (downtime) or, in more general terms, controllable socio-economical losses. The Canterbury earthquakes sequence in 2010-2011 has represented a tough reality check, confirming the current mismatch between societal expectations over the reality of seismic performance of modern buildings. In general, albeit with some unfortunate exceptions, modern multi-storey buildings performed as expected from a technical point of view, in particular when considering the intensity of the shaking (higher than new code design) they were subjected to. As per capacity design principles, plastic hinges formed in discrete regions, allowing the buildings to sway and stand and people to evacuate. Nevertheless, in many cases, these buildings were deemed too expensive to be repaired and were consequently demolished. Targeting life-safety is arguably not enough for our modern society, at least when dealing with new building construction. A paradigm shift towards damage-control design philosophy and technologies is urgently required. This paper and the associated presentation will discuss motivations, issues and, more importantly, cost-effective engineering solutions to design buildings capable of sustaining low-level of damage and thus limited business interruption after a design level earthquake. Focus will be given to the extensive research and developments in jointed ductile connections based upon controlled rocking & dissipating mechanisms for either reinforced concrete and, more recently, laminated timber structures. An overview of recent on-site applications of such systems, featuring some of the latest technical solutions developed in the laboratory and including proposals for the rebuild of Christchurch, will be provided as successful examples of practical implementation of performance-based seismic design theory and technology.

Research papers, University of Canterbury Library

Base isolation is an incredibly effective technology used in seismic regions throughout the world to limit structural damage and maintain building function, even after severe earthquakes. However, it has so far been underutilised in light-frame wood construction due to perceived cost issues and technical problems, such as a susceptibility to movement under strong wind loads. Light-frame wood buildings make up the majority of residential construction in New Zealand and sustained significant damage during the 2010-2011 Canterbury earthquake sequence, yet the design philosophy has remained largely unchanged for years due to proven life-safety performance. Recently however, with the advent of performance based earthquake engineering, there has been a renewed focus on performance factors such as monetary loss that has driven a want for higher performing residential buildings. This research develops a low-cost approach for the base isolation of light-frame wood buildings using a flat-sliding friction base isolation system, which addresses the perceived cost and technical issues, and verifies the seismic performance through physical testing on the shake table at the University of Canterbury. Results demonstrate excellent seismic performance with no structural damage reported despite a large number of high-intensity earthquake simulations. Numerical models are subsequently developed and calibrated to New Zealand light-frame wood building construction approaches using state-of-the-art wood modelling software, Timber3D. The model is used to accurately predict both superstructure drift and acceleration demand parameters of fixed-base testing undertaken after the base isolation testing programme is completed. The model development allows detailed cost analyses to be undertaken within the performance based earthquake engineering framework that highlights the monetary benefits of using base isolation. Cost assessments indicate the base isolation system is only 6.4% more compared to the traditional fixed-base system. Finally, a design procedure is recommended for base isolated light-frame wood buildings that is founded on the displacement based design (DBD) approach used in the United States and New Zealand. Nonlinear analyses are used to verify the DBD method which indicate its suitability.

Research papers, University of Canterbury Library

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.