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Research papers, University of Canterbury Library

Beam-column joints are addressed in the context of current design procedures and performance criteria for reinforced concrete ductile frames subjected to large earthquake motions. Attention is drawn to the significant differences between the pertinent requirements of concrete design codes of New Zealand and the United States for such joints. The difference between codes stimulated researchers and structural engineers of the United States, New Zealand, Japan and China to undertake an international collaborative research project. The major investigators of the project selected issues and set guidelines for co-ordinated testing of joint specimens designed according to the codes of the countries. The tests conducted at the University of Canterbury, New Zealand, are reported. Three full-scale beam-column-slab joint assemblies were designed according to existing code requirements of NZS 3101:1982, representing an interior joint of a one-way frame, an interior joint of a two-way frame, and an exterior joint of a two-way frame. Quasistatic cyclic loading simulating severe earthquake actions was applied. The overall performance of each test assembly was found to be satisfactory in terms of stiffness, strength and ductility. The joint and column remained essentially undamaged while plastic hinges formed in the beams. The weak beam-strong column behaviour sought in the design, desirable in tall ductile frames designed for earthquake resistance, was therefore achieved. Using the laws of statics and test observations, the action and flow of forces from the slabs, beams and column to the joint cores are explored. The effects of bond performance and the seismic shear resistance of the joints, based on some postulated mechanisms, are examined. Implications of the test results on code specifications are discussed and design recomendations are made.

Research papers, University of Canterbury Library

On the second day of teaching for 2011, the University of Canterbury (UC) faced the most significant crisis of its 138-year history. After being shaken severely by a magnitude 7.1 earthquake on 4 September 2010, UC felt it was well along the pathway to getting back to ‘normal’. That all changed at 12:51pm on 22 February 2011, when Christchurch city was hit by an even more devastating event. A magnitude 6.3 (Modified Mercalli intensity ten – MM X) earthquake, just 13km south-east of the Christchurch city centre, caused vertical peak ground accelerations amongst the highest ever recorded in an urban environment, in some places more than twice the acceleration due to gravity. The earthquake caused immediate evacuation of the UC campus and resulted in significant damage to many buildings. Thankfully there were no serious injuries or fatalities on campus, but 185 people died in the city and many more suffered serious injuries. At the time of writing, eighteen months after the first earthquake in September, Christchurch is still experiencing regular earthquakes. Seismologists warn that the region may experience heightened seismicity for a decade or more. While writing this report we have talked with many different people from across the University. People’s experiences are different and we have not managed to talk with everyone, but we hope that by drawing together many different perspectives from across the campus that this report will serve two purposes; to retain our institutional memory of what we have learnt over the past eighteen months, and also to share our learnings with other organisations in New Zealand and around the world who, we hope, will benefit from learning about our experience.

Research papers, University of Canterbury Library

In order to provide information related to seismic vulnerability of non-ductile reinforced concrete (RC) frame buildings, and as a complementary investigation on innovative feasible retrofit solutions developed in the past six years at the University of Canterbury on pre-19170 reinforced concrete buildings, a frame building representative of older construction practice was tested on the shake table. The specimen, 1/2.5 scale, consists of two 3-storey 2-bay asymmetric frames in parallel, one interior and one exterior, jointed together by transverse beams and floor slabs. The as-built (benchmark) specimen was first tested under increasing ground motion amplitudes using records from Loma Prieta Earthquake (California, 1989) and suffered significant damage at the upper floor, most of it due to lap splices failure. As a consequence, in a second stage, the specimen was repaired and modified by removing the concrete in the lap splice region, welding the column longitudinal bars, replacing the removed concrete with structural mortar, and injecting cracks with epoxy resin. The modified as-built specimen was then tested using data recorded during Darfield (New Zealand, 2010) and Maule (Chile, 2010) Earthquakes, with whom the specimen showed remarkably different responses attributed to the main variation in frequency content and duration. In this contribution, the seismic performance of the three series of experiments are presented and compared.

Research papers, University of Canterbury Library

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.

Research papers, The University of Auckland Library

Test results are presented for wall-diaphragm plate anchor connections that were axially loaded to rupture. These connection samples were extracted post-earthquake by sorting through the demolition debris from unreinforced masonry (URM) buildings damaged in the Christchurch earthquakes. Unfortunately the number of samples available for testing was small due to the difficulties associated with sample collection in an environment of continuing aftershocks and extensive demolition activity, when personal safety combined with commercial activity involving large demolition machinery were imperatives that inhibited more extensive sample collection for research purposes. Nevertheless, the presented data is expected to be of assistance to structural engineers undertaking seismic assessment of URM buildings that have existing wall-diaphragm anchor plate connections installed, where it may be necessary to estimate the capacity of the existing connection as an important parameter linked with determining the current seismic capacity of the building and therefore influencing the decision regarding whether supplementary connections should be installed.

Research papers, University of Canterbury Library

Pumice materials, which are problematic from an engineering viewpoint, are widespread in the central part of the North Island. Considering the impacts of the 2010-2011 Christchurch earthquakes, a clear understanding of their properties under earthquake loading is necessary. For example, the 1987 Edgecumbe earthquake showed evidence of localised liquefaction of sands of volcanic origin. To elucidate on this, research was undertaken to investigate whether existing empirical field-based methods to evaluate the liquefaction potential of sands, which were originally developed for hard-grained soils, are applicable to crushable pumice-rich deposits. For this purpose, two sites, one in Whakatane and another in Edgecumbe, were selected where the occurrence of liquefaction was reported following the Edgecumbe earthquake. Manifestations of soil liquefaction, such as sand boils and ejected materials, have been reported at both sites. Field tests, including cone penetration tests (CPT), shear-wave velocity profiling, and screw driving sounding (SDS) tests were performed at the sites. Then, considering estimated peak ground accelerations (PGAs) at the sites based on recorded motions and possible range of ground water table locations, liquefaction analysis was conducted at the sites using available empirical approaches. To clarify the results of the analysis, undisturbed soil samples were obtained at both sites to investigate the laboratory-derived cyclic resistance ratios and to compare with the field-estimated values. Research results clearly showed that these pumice-rich soils do not fit existing liquefaction assessment frameworks and alternate methods are necessary to characterise them.

Research papers, University of Canterbury Library

A one story, two bays, approximately half scaled, perimeter moment frame containing precastprestressed floor units was built and tested at the University of Canterbury to investigate the effect of precastprestressed floor units on the seismic performance of reinforced concrete moment resisting frame. This paper gives an overview of the experimental set up and summarizes the results obtained from the test. The results show that elongation in the beam plastic hinges is partially restrained by the prestressed floor, which increases the strength of the beams much more than that being specified in the codes around the world.

Research papers, University of Canterbury Library

During the past two decades, the focus has been on the need to provide communities with structures that undergo minimal damage after an earthquake event while still being cost competitive. This has led to the development of high performance seismic resisting systems, and advances in design methodologies, in order respect this demand efficiently. This paper presents the experimental response of four pre-cast, post-tensioned rocking wall systems tested on the shake-table at the University of Canterbury. The wall systems were designed as a retrofit solution for an existing frame building, but are equally applicable for use in new design. Design of the wall followed a performance-based retrofit strategy in which structural limit states appropriate to both the post-tensioned wall and the existing building were considered. Dissipation for each of the four post-tensioned walls was provided via externally mounted devices, located in parallel to post-tensioned tendons for re-centring. This allowed the dissipation devices to be easily replaced or inspected following a major earthquake. Each wall was installed with viscous fluid dampers, tension-compression yielding steel dampers, a combination of both or no devices at all – thus relying on contact damping alone. The effectiveness of both velocity and displacement dependant dissipation are investigated for protection against far-field and velocity-pulse ground motion characteristics. The experimental results validate the behaviour of ‘Advanced Flag-Shape’ rocking, dissipating solutions which have been recently proposed and numerically tested. Maximum displacements and material strains were well controlled and within acceptable bounds, and residual deformations were minimal due to the re-centring contribution from the post-tensioned tendons. Damage was confined to inelastic yielding (or fluid damping) of the external dampers.

Research papers, University of Canterbury Library

A three dimensional approximately half scale experimental subassemblage is currently being tested at the University of Canterbury to investigate the effect of precast-prestressed floor units, which do not span past the internal columns, on the seismic performance of reinforced concrete moment resisting frames. This paper reports the preliminary results from the test, with the focus on elongation within the plastic hinges and strength enhancement in the frames. The preliminary results have shown that elongation between the external and internal plastic hinges varies by more than two fold. With the addition of the prestressed floor units, the strength of the moment resisting frame used in the test was found to be 25% higher than the current code specified value. In other situations, particularly where there are more than 2 bays in a moment resisting frame, greater strength enhancement may be expected. Any underestimation of beam strength is undesirable as it may result in the development of nonductile failure modes in a major earthquake.

Research papers, University of Canterbury Library

This presentation summarizes the development of high-resolution surficial soil velocity models in the Canterbury, New Zealand basin. Shallow (<30m) shear wave velocities were primarily computed based on a combination of a large database of over 15,000 cone penetration test (CPT) logs in and around Christchurch, and a recently-developed Christchurch-specific empirical correlation between soil shear wave velocity and CPT. Large active-source testing at 22 locations and ambient-wavefield surface wave and H/V testing at over 80 locations were utilized in combination with 1700 water well logs to constrain the inter-bedded stratigraphy and velocity of Quaternary sediments up to depths of several hundred meters. Finally, seismic reflection profiles and the ambient-wavefield surface wave data provide constraint on velocities from several hundred meters to several kilometres. At all depths, the high resolution data illustrates the complexity of the soil conditions in the region, and the developed 3D models are presently being used in broadband ground motion simulations to further interpret the observed strong ground motions in the 2010-2011 Canterbury earthquake sequence.

Research papers, University of Canterbury Library

Recent severe earthquakes, such as Christchurch earthquake series, worldwide have put emphasis on building resilience. In resilient systems, not only life is protected, but also undesirable economic effects of building repair or replacement are minimized following a severe earthquake. Friction connections are one way of providing structure resilience. These include the sliding hinge joint with asymmetric friction connections (SHJAFCs) in beam-to-column connections of the moment resisting steel frames (MRSFs), and the symmetric friction connections (SFCs) in braces of the braced frames. Experimental and numerical studies on components have been conducted internationally. However, actual building performance depends on the many interactions, occurring within a whole building system, which may be difficult to determine accurately by numerical modelling or testing of structural components alone. Dynamic inelastic testing of a full-scale multi-storey composite floor building with full range of non-structural elements (NSEs) has not yet been performed, so it is unclear if surprises are likely to occur in such a system. A 9 m tall three-storey configurable steel framed composite floor building incorporating friction-based connections is to be tested using two linked bi-directional shake tables at the International joint research Laboratory of Earthquake Engineering (ILEE) facilities, Shanghai, China. Beams and columns are designed to remain elastic during an earthquake event, with all non-linear behaviour occurring through stable sliding frictional behaviour, dissipating energy by SHJAFCs used in MRFs and SFCs in braced frames, with and without Belleville springs. Structural systems are configurable, allowing different moment and braced frame structural systems to be tested in two horizontal directions. In some cases, these systems interact with rocking frame or rocking column system in orthogonal directions subjected to unidirectional and bidirectional horizontal shaking. The structure is designed and detailed to undergo, at worst, minor damage under series of severe earthquakes. NSEs applied include precast-concrete panels, glass curtain walling, internal partitions, suspended ceilings, fire sprinkler piping as well as some other common contents. Some of the key design considerations are presented and discussed herein

Research papers, University of Canterbury Library

This thesis addresses the topic of local bond behaviour in RC structures. The mechanism of bond refers to the composite action between deformed steel reinforcing bars and the surrounding concrete. Bond behaviour is an open research topic with a wide scope, particularly because bond it is such a fundamental concept to structural engineers. However, despite many bond-related research findings having wide applications, the primary contribution of this research is an experimental evaluation of the prominent features of local bond behaviour and the associated implications for the seismic performance of RC structures. The findings presented in this thesis attempt to address some structural engineering recommendations made by the Canterbury Earthquakes Royal Commission following the 2010-2011 Canterbury (New Zealand) earthquake sequence. A chapter of this thesis discusses the structural behaviour of flexure-dominated RC wall structures with an insufficient quantity of longitudinal reinforcement, among other in situ conditions, that causes material damage to predominantly occur at a single crack plane. In this particular case, the extent of concrete damage and bond deterioration adjacent to the crack plane will influence the ductility capacity that is effectively provided by the reinforcing steel. As a consequence of these in situ conditions, some lightly reinforced wall buildings in Christchurch lost their structural integrity due to brittle fracture of the longitudinal reinforcement. With these concerning post-earthquake observations in mind, there is the underlying intention that this thesis presents experimental evidence of bond behaviour that allows structural engineers to re-assess their confidence levels for the ability of lightly reinforced concrete structures to achieve the life-safety seismic performance objective the ultimate limit state. Three chapters of this thesis are devoted to the experimental work that was conducted as the main contribution of this research. Critical details of the experimental design, bond testing method and test programme are reported. The bond stress-slip relationship was studied through 75 bond pull-out tests. In order to measure the maximum local bond strength, all bond tests were carried out on deformed reinforcing bars that did not yield as the embedded bond length was relatively short. Bond test results have been presented in two separate chapters in which 48 monotonic bond tests and 27 cyclic bond tests are presented. Permutations of the experiments include the loading rate, cyclic loading history, concrete strength (25 to 70 MPa), concrete age, cover thickness, bar diameter (16 and 20 mm), embedded length, and position of the embedded bond region within the specimen (close or far away to the free surface). The parametric study showed that the concrete strength significantly influences the maximum bond strength and that it is reasonable to normalise the bond stress by the square-root of the concrete compressive strength, √(f'c). The generalised monotonic bond behaviour is described within. An important outcome of the research is that the measured bond strength and stiffness was higher than stated by the bond stress-slip relationship in the fib Model Code 2010. To account for these observed differences, an alternative model is proposed for the local monotonic bond stress-slip relationship. Cyclic bond tests showed a significant proportion of the total bond degradation occurs after the loading cycle in the peak bond strength range, which is when bond slip has exceeded 0.5 mm. Subsequent loading to constant slip values showed a linear relationship between the amount of bond strength degradation and the log of the number of cycles that were applied. To a greater extent, the cyclic bond deterioration depends on the bond slip range, regardless of whether the applied load cycling is half- or fully-reversed. The observed bond deterioration and hysteretic energy dissipated during cyclic loading was found to agree reasonably well between these cyclic tests with different loading protocols. The cyclic bond deterioration was also found to be reasonably consistent exponential damage models found in the literature. This research concluded that the deformed reinforcing bars used in NZ construction, embedded in moderate to high strength concrete, are able to develop high local bond stresses that are mobilised by a small amount of local bond slip. Although the relative rib geometry was not varied within this experimental programme, a general conclusion of this thesis is that deformed bars currently available in NZ have a relative rib bearing area that is comparatively higher than the test bars used in previous international research. From the parametric study it was found that the maximum monotonic bond strength is significant enhanced by dynamic loading rates. Experimental evidence of high bond strength and initial bond stiffness generally suggests that only a small amount of local bond slip that can occur when the deformed test bar was subjected to large tension forces. Minimal bond slip and bond damage limits the effective yielding length that is available for the reinforcing steel to distribute inelastic material strains. Consequently, the potential for brittle fracture of the reinforcement may be a more problematic and widespread issue than is apparent to structural engineers. This research has provided information that improve the reliability of engineering predictions (with respect to ductility capacity) of maximum crack widths and the extent of bond deterioration that might occur in RC structures during seismic actions.

Research papers, University of Canterbury Library

It is fast becoming common practice for civil engineering infrastructure and building structures to be designed to achieve a set of performance objectives. To do so, consideration is now being given to systems capable of sustaining minimal damage after an earthquake while still being cost competitive. This has led to the development of high performance seismic resisting systems, followed by advances in design methodologies. The paper presents the experimental response of four pre-cast, post-tensioned rocking walls with high-performing dissipating solutions tested on the shake-table at the University of Canterbury. The wall systems were designed as a retrofit solution for an existing frame building however, can also be used for the design of new, high-performance structures. The use of externally mounted dampers allowed numerous dissipation schemes to be explored including mild-steel dampers (hysteretic dampers), viscous dampers, a combination of both or no dampers. The advantages of both velocity and displacement dependant dissipation was investigated for protection against strong ground motions with differing rupture characteristics i.e. far-field and near-field events. The experimental results are used to verify a proposed design procedure for post-tensioned rocking systems with supplementary hysteretic and viscous dissipation. The predicted response compared well with the measured shake-table response.

Research papers, University of Canterbury Library

An as-built reinforced concrete (RC) frame building designed and constructed according to pre-1970s code design construction practice has been recently tested on the shake table at the University of Canterbury. The specimen, 1/2.5 scaled version of the original prototype, consists of two 3-storey 2-bay asymmetric frames in parallel, one interior and one exterior, jointed together by transverse beams and floor slabs. Following the benchmark test, a retrofit intervention has been proposed to rehabilitate the tested specimen. In this paper, detailed information on the assessment and design of the seismic retrofit procedure using GFRP (glass fibre reinforced polymer) materials is given for the whole frame. Hierarchy of strength and sequence of events (damage mechanisms) in the panel zone region are evaluated using a moment-axial load (M-N) interaction performance domain, according to a performance-based retrofit philosophy. Specific limit states or design objectives are targeted with attention given to both strength and deformation limits. In addition, an innovative retrofit solution using FRP anchor dowels for the corner beam-column joints with slabs is proposed. Finally, in order to provide a practical tool for engineering practice, the retrofit procedure is provided in a step-by step flowchart fashion.

Research papers, University of Canterbury Library

This paper summarizes the development of a region-wide surficial shear wave velocity model based on the combination of the large high-spatial-density database of cone penetration test (CPT) logs in and around Christchurch, New Zealand and a recently-developed Christchurch-specific empirical correlation between soil shear wave velocity and CPT. The ongoing development of this near-surface shear wave velocity model has applications for site characterization efforts via the development of maps of time-averaged shear wave velocities over specific depths, and the identification of regional similarities and differences in soil shear stiffness.

Research papers, University of Canterbury Library

Describes an extensive experimental program at the University of Canterbury, for the development of new structural systems and connections for multi-storey laminated veneer lumber (LVL) timber buildings in earthquake-prone areas. The proposed innovative ductile timber connections are conceptually similar to recent seismic solutions successfully developed for precast concrete multi- storey buildings. The paper gives an overview of the research program, and the results of quasi-static cyclic tests on frame subassemblies, including exterior beam-column joints and cantilever columns, as well as pseudo-dynamic tests on cantilever columns. The experimental results showed significant dissipation of hysteretic energy, good self-centering capacity and no appreciable damage of the structural elements, confirming the expected enhanced performance of the proposed structural systems.

Research papers, University of Canterbury Library

Post-tensioned timber technology was originally developed and researched at the University of Canterbury (UC) in New Zealand in 2005. It can provide a low-damage seismic design solution for multi-storey mass timber buildings. Since mass timber products, such as cross-laminated timber (CLT), have high in-plane stiffness, a post-tensioned timber shear wall will deform mainly in a rocking mechanism. The moment capacity of the wall at the base is commonly determined using the elastic form of the Modified Monolithic Beam Analogy (MMBA). In the calculation of the moment capacity at the wall base, it is critical to accurately predict the location of the neutral axis and the timber compressive stress distribution. Three 2/3 scale 8.6m tall post-tensioned CLT walls were experimentally tested under quasi-static cyclic loading – both uni-directional and bi-directional- in this study. These specimens included a single wall, a coupled wall, and a C-shaped core-wall. The main objective was to develop post-tensioned C-shaped timber core-walls for tall timber buildings with enhanced lateral strength and stiffness. To better understand the timber compressive stress distributions at the wall base, particle tracking technology (PTT) technology was applied for the first time to investigate the behaviour of the compression toe. Previous post-tensioned timber testing primarily used the displacement measurements to determine the timber compressive behavior at the wall base or rocking interfaces. However, by using PTT technology, the timber strain measurements in the compression zone can be much more accurate as PTT is able to track the movement of many particles on the timber surface. This paper presents experimental testing results of post-tensioned CLT walls with a focus on capturing timber compressive behavior using PTT. The PTT measurements were able to better capture small base rotations which occurred at the onset of gap opening and capture unexpected phenomena in core-wall tests. The single wall test result herein presented indicates that while the MMBA could predict the moment rotation behavior with reasonable accuracy, the peak strain response was under predicted in the compression toe. Further detailed study is required to better understand the complex strain fields generated reflective of the inherent cross-thickness inhomogeneity and material variability of CLT.

Research papers, University of Canterbury Library

Liquefaction of sandy soil has been observed to cause significant damage to infrastructure during major earthquakes. Historical cases of liquefaction have typically occurred in sands containing some portion of fines particles, which are defined as 75μm or smaller in diameter. The effects of fines on the undrained behaviour of sand are not however fully understood, and this study therefore attempts to quantify these effects through the undrained testing of sand mixed with non-plastic fines sourced from Christchurch, New Zealand. The experimental program carried out during this study consisted of undrained monotonic and cyclic triaxial tests performed on three different mixtures of sand and fines: the Fitzgerald Bridge mixture (FBM), and two Pinnacles Sand mixtures (PSM1 and PSM2). The fines content of each host sand was systematically varied up to a maximum of 30%, with all test specimens being reconstituted using moist tamping deposition. The undrained test results from the FBM soils were interpreted using a range of different measures of initial state. When using void ratio and relative density, the addition of fines to the FBM sand caused more contractive behaviour for both monotonic and cyclic loadings. This resulted in lower strengths at the steady state of deformation, and lower liquefaction resistances. When the intergranular void ratio was used for the interpretation, the effect of additional fines was to cause less contractive response in the sand. The state parameter and state index were also used to interpret the undrained cyclic test results – these measures suggested that additional fines caused less contractive sand behaviour, the opposite to that observed when using the void ratio. This highlighted the dependency on the parameter chosen as a basis for the response comparison when determining the effects of fines, and pointed out a need to identify a measure that normalizes such effects. Based on the FBM undrained test results and interpretations, the equivalent granular void ratio, e*, was identified from the literature as a measure of initial state that normalizes the effects of fines on the undrained behaviour of sand up to a fines content of 30%. This is done through a parameter within the e* definition termed the fines influence factor, b, which quantifies the effects of fines from a value of zero (no effect) to one (same effect as sand particles). The value of b was also determined to be different when interpreting the steady state lines (bSSL) and cyclic resistance curves (bCR) respectively for a given mixture of sand and fines. The steady state lines and cyclic resistance curves of the FBM soils and a number of other sand-fines mixtures sourced from the literature were subsequently interpreted using the equivalent granular void ratio concept, with bSSL and bCR values being back-calculated from the respective test data sets. Based on these interpretations, it was concluded that e* was conceptually a useful parameter for characterizing and quantifying the effects of fines on the undrained behaviour of sand, assuming the fines influence factor value could be derived. To allow prediction of the fines influence factor values, bSSL and bCR were correlated with material and depositional properties of the presented sand-fines mixtures. It was found that as the size of the fines particles relative to the sand particles became smaller, the values of bSSL and bCR reduced, indicating lower effect of fines. The same trend was also observed as the angularity of the sand particles increased. The depositional method was found to influence the value of bCR, due to the sensitivity of cyclic loading to initial soil fabric. This led to bSSL being used as a reference for the effect of fines, with specimens prepared by moist tamping having bCR > bSSL, and specimens prepared by slurry deposition having bCR < bSSL. Finally the correlations of the fines influence factor values with material and depositional properties were used to define the simplified estimation method – a procedure capable of predicting the approximate steady state lines and cyclic resistance curves of a sand as the non-plastic fines content is increased up to 30%. The method was critically reviewed based on the undrained test results of the PSM1 and PSM2 soils. This review suggested the method could accurately predict undrained response curves as the fines content was raised, based on the PSM1 test results. It also however identified some key issues with the method, such as the inability to accurately predict the responses of highly non-uniform soils, a lack of consideration for the entire particle size distribution of a soil, and the fact the errors in the prediction of bSSL carry through into the prediction of bCR. Lastly some areas of further investigation relating to the method were highlighted, including the need to verify the method through testing of sandy soils sourced from outside the Christchurch area, and the need to correlate the value of bCR with additional soil fabrics / depositional methods.

Research papers, University of Canterbury Library

The 2010 Darfield and 2011 Christchurch Earthquakes triggered extensive liquefaction-induced lateral spreading proximate to streams and rivers in the Christchurch area, causing significant damage to structures and lifelines. A case study in central Christchurch is presented and compares field observations with predicted displacements from the widely adopted empirical model of Youd et al. (2002). Cone penetration testing (CPT), with measured soil gradation indices (fines content and median grain size) on typical fluvial deposits along the Avon River were used to determine the required geotechnical parameters for the model input. The method presented attempts to enable the adoption of the extensive post-quake CPT test records in place of the lower quality and less available Standard Penetration Test (SPT) data required by the original Youd model. The results indicate some agreement between the Youd model predictions and the field observations, while the majority of computed displacements error on the side of over-prediction by more than a factor of two. A sensitivity analysis was performed with respect to the uncertainties used as model input, illustrating the model’s high sensitivity to the input parameters, with median grain size and fines content among the most influential, and suggesting that the use of CPT data to quantify these parameters may lead to variable results.

Research papers, University of Canterbury Library

Following a major earthquake event, essential public amenities such as medical facilities and transport networks need to remain functional - not only to fulfil their ongoing role in serving the community but also to cope with the added and immediate demand of a population affected by a natural disaster. Furthermore, the economic implications of wide spread damage to housing and commercial facilities should not be discounted. A shift in design approach is required that is consistent with current trends towards performance based building design. The present aim is to achieve seismic energy dissipation during the earthquake event, without the aftermath of damage to structural elements, whilst maintaining design economies. Structures permitted to rock on their foundations and provide recoverable rotations at the beam-column interfaces offer significant advantages over those using conventional ductile detailing. A jointed construction philosophy can be applied whereby structural elements are connected with unbonded prestressing tendons. Supplemental damping is provided by replaceable flexural steel components designed to deform inelastically. For this research a multi-storey test building of one quarter scale has been constructed and tested on an earthquake simulator at the University of Canterbury. A computer model has been developed and a set ofpreliminary design procedures proposed.

Research papers, University of Canterbury Library

Recent severe earthquakes, such as the 2010-2011 Christchurch earthquake series, have put emphasis on building resilience all over the world. To achieve such resilience, procedures for low damage seismic design have been developed to satisfy both life safety requirements and the need to minimize undesirable economic effects of required building repair or structural member replacement following a major earthquake. Seismic resisting systems following this concept are expected to withstand severe earthquakes without requiring major post-earthquake repairs, using isolating mechanisms or sacrificial systems that either do not need repair or are readily repairable or replaceable. These include the sliding hinge joint with asymmetric friction connections (SHJAFCs) in beam-to-column connections of the moment resisting steel frames (MRSFs) and symmetric friction connections (SFCs) in braces of the braced frames. A 9 m tall, configurable three-storey steel framed composite floor building incorporating frictionbased connections is to be tested using two linked bi-directional shake tables at the International joint research Laboratory of Earthquake Engineering (ILEE) facilities, Shanghai, China. The structural systems are configurable, allowing different moment and braced frame structural systems tested in two horizontal directions. The structure is designed and detailed to undergo, at worst, minor damage under a planned series of severe earthquakes.

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.