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Research papers, University of Canterbury Library

A multi-disciplinary geo-structural-environmental engineering project funded by the Ministry of Business Innovation and Employment (MBIE) is being carried out at the University of Canterbury. The project aims at developing an eco-friendly seismic isolation foundation system which will improve the seismic performance of medium-density low-rise buildings. Such system is characterized by two main elements: 1) granulated scrap rubber mixed with gravelly soils to be placed beneath the structure, with the goal damping part of the seismic energy before it reaches the superstructure; and 2) a basement raft made of steel-fibre reinforced rubberised concrete (SFRRuC) to enhance the flexibility and toughness of the foundation, looking at better accommodating the displacement demand. In this paper, the main objectives, scope and methodology of the project will be briefly described. A literature review of the engineering properties of steel-fibre reinforced rubberised concrete (RuC) will be presented. Then, preliminary results on concrete mixes with different rubber and steel fibres content will be exhibited.

Research papers, University of Canterbury Library

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.

Images, UC QuakeStudies

A close up of the damaged stonework of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the wall to limit further damage.

Images, UC QuakeStudies

A close up of the front of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the front wall to limit further damage.

Images, UC QuakeStudies

A close up of the damaged stonework of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the wall to limit further damage.

Images, UC QuakeStudies

The damaged cathedral is supported with steel bracing and cordoned off with fencing and barriers. Taken on a day when a walkway was opened up between Re:Start Mall and Cathedral Square to allow temporary public access.

Images, UC QuakeStudies

A close up of the front of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the wall to limit further damage.

Images, UC QuakeStudies

The damaged cathedral is supported with steel bracing and cordoned off with fencing and barriers. Taken on a day when a walkway was opened up between Re:Start Mall and Cathedral Square to allow temporary public access.

Images, UC QuakeStudies

The damaged cathedral is supported with steel bracing and cordoned off with fencing and barriers. Taken on a day when a walkway was opened up between Re:Start Mall and Cathedral Square to allow temporary public access.

Images, UC QuakeStudies

The damaged cathedral is supported with steel bracing and cordoned off with fencing and barriers. Taken on a day when a walkway was opened up between Re:Start Mall and Cathedral Square to allow temporary public access.

Images, UC QuakeStudies

The damaged cathedral is supported with steel bracing and cordoned off with fencing and barriers. Taken on a day when a walkway was opened up between Re:Start Mall and Cathedral Square to allow temporary public access.

Images, UC QuakeStudies

The damaged cathedral is supported with steel bracing and cordoned off with fencing and barriers. Taken on a day when a walkway was opened up between Re:Start Mall and Cathedral Square to allow temporary public access.

Research papers, University of Canterbury Library

In recent years, rocking isolation has become an effective approach to improve seismic performance of steel and reinforced concrete structures. These systems can mitigate structural damage through rigid body displacement and thus relatively low requirements for structural ductility, which can significantly improve seismic resilience of structures and reduce repairing costs after strong earthquakes. A number of base rocking structural systems with only a single rocking interface have been proposed. However, these systems can have significant high mode effect for high rise structures due to the single rocking interface. This RObust BUilding SysTem (ROBUST) project is a collaborative China-New Zealand project sponsored by the International Joint Research Laboratory of Earthquake Engineering (ILEE), Tongji University, and a number of agencies and universities within New Zealand including the BRANZ, Comflor, Earthquake Commission, HERA, QuakeCoRE, QuakeCentre, University of Auckland, and the University of Canterbury. A number of structural configurations will be tested [1, 2], and non-structural elements including ceilings, infilling walls, glazed curtain walls, precast concrete panels, piping system will also be tested in this project [3]. Within this study, a multiple rocking column steel structural system was proposed and investigated mainly by Tongji team with assistance of NZ members. The concept of rocking column system initiates from the structure of Chinese ancient wooden pagoda. In some of Chinese wooden pagodas, there are continuous core columns hanged only at the top of each pagoda, which is not connected to each stories. This core column can effectively avoid collapse of the whole structure under large storey drifts. Likewise, there are also central continuous columns in the newly proposed steel rocking column system, which can avoid weak story failure mechanism and make story drifts more uniform. In the proposed rocking column system, the structure can switch between an elastic rigidly connected moment resisting frame and a controlled rocking column system when subjected to strong ground motion excitations. The main seismic energy can be dissipated by asymmetric friction beam–column connections, thereby effectively reducing residual displacement of the structure under seismic loading without causing excessive damage to structural members. Re–centering of the structure is provided not only by gravity load carried by rocking columns, but also by mould coil springs. To investigate dynamic properties of the proposed system under different levels of ground excitations, a full-scale threestory steel rocking column structural system with central continuous columns is to be tested using the International joint research Laboratory of Earthquake Engineering (ILEE) facilities, Shanghai, China and an analytical model is established. A finite element model is also developed using ABAQUS to simulate the structural dynamic responses. The rocking column system proposed in this paper is shown to produce resilient design with quick repair or replacement.

Research papers, University of Canterbury Library

Shaking table testing of a full-scale three storey resilient and reparable complete composite steel framed building system is being conducted. The building incorporates a number of interchangeable seismic resisting systems of New Zealand and Chinese origin. The building has a steel frame and cold formed steel-concrete composite deck. Energy is dissipated by means of friction connections. These connections are arranged in a number of structural configurations. Typical building nonskeletal elements (NSEs) are also included. Testing is performed on the Jiading Campus shaking table at Tongji University, Shanghai, China. This RObust BUilding SysTem (ROBUST) project is a collaborative China-New Zealand project sponsored by the International Joint Research Laboratory of Earthquake Engineering (ILEE), Tongji University, and a number of agencies and universities within New Zealand including BRANZ, Comflor, Earthquake Commission, HERA, QuakeCoRE, QuakeCentre, University of Auckland, and the University of Canterbury. This paper provides a general overview of the project describing a number of issues encountered in the planning of this programme including issues related to international collaboration, the test plan, and technical issues.

Images, UC QuakeStudies

The front of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the wall to limit further damage. The Citizens' Memorial statue stands to the left.

Images, UC QuakeStudies

The front of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the front wall to limit further damage. The Citizens' Memorial statue stands to the left.

Images, UC QuakeStudies

A security fence stands behind fallen rubble and the charred remains of the McKenzie & Willis building on High Street. A portable toilet has been placed on the road next to a steel beam which is supporting the building.

Audio, Radio New Zealand

A momentous day in Christchurch as a huge steel frame was installed as part of the stabilisation work for Christ Church Cathedral. Karyn speaks with project director Keith Paterson about the plans to return the famed rose window extensively damage in the 2011 earthquake.

Images, UC QuakeStudies

The Octagon Live Restaurant (formerly Trinity Church) on Worcester Street. Steel bracing has been placed on the tower to limit further damage from aftershocks. Sculptures of a cyclist, bungee jumper, rock climber and kayaker can be seen on the bracing posts.

Research papers, University of Canterbury Library

Recently developed performance-based earthquake engineering framework, such as one provided by PEER (Deierlein et al. 2003), assist in the quantification in terms of performance such as casualty, monetary losses and downtime. This opens up the opportunity to identify cost-effective retrofit/rehabilitation strategies by comparing upfront costs associated with retrofit with the repair costs that can be expected over time. This loss assessment can be strengthened by learning from recent earthquakes, such as the 2010 Canterbury and 2016 Kaikoura earthquakes. In order to investigate which types of retrofit/rehabilitation strategies may be most cost-effective, a case study building was chosen for this research. The Pacific Tower, a 22-storey EBF apartment located within the Christchurch central business district (CBD), was damaged and repaired during the 2010 Canterbury earthquake series. As such, by taking hazard levels accordingly (i.e. to correspond to the Christchurch CBD), modelling and analysing the structure, and considering the vulnerability and repair costs of its different components, it is possible to predict the expected losses of the aforementioned building. Using this information, cost-effective retrofit/rehabilitation strategy can be determined. This research found that more often than not, it would be beneficial to improve the performance of valuable non-structural components, such as partitions. Although it is true that improving such elements will increase the initial costs, over time, the benefits gained from reduced losses should be expected to overcome the initial costs. Aftershocks do increase the predicted losses of a building even in lower intensities due to the fact that non-structural components can get damaged at such low intensities. By comparing losses computed with and without consideration of aftershocks for a range of historical earthquakes, it was found that the ratio between losses due to main shock with aftershocks to the losses due to the main shock only tended to increase with increasing main shock magnitude. This may be due to the fact that larger magnitude earthquakes tend to generate larger magnitude aftershocks and as those aftershocks happen within a region around the main shock, they are more likely to cause intense shaking and additional damage. In addition to this observation, it was observed that the most significant component of loss of the case study building was the non-structural partition walls.

Images, UC QuakeStudies

A photograph of the entrance to Gap Filler's temporary outdoor cinema on the corner of Madras and St Asaph Streets. The entranceway is made of lights on a steel frame, and leads to a painted "red carpet".

Images, UC QuakeStudies

A digitally manipulated photograph of twisted reinforcing rods amongst the rubble from the demolition of QEII. The photographer comments, "These rarely seen worms live in the pressurised earth under the foundations of buildings. They need a damp soil and be under at least 100 pounds of pressure per square inch. After the destructive force of an earthquake they swiftly rise to the surface through gaps in the rubble. Unfortunately they quickly die and then crystallise as hard as iron in the dry low pressure air".

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.