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Research papers, The University of Auckland Library

A non-destructive hardness testing method has been developed to investigate the amount of plastic strain demand in steel elements subjected to cyclic loading. The focus of this research is on application to the active links of eccentrically braced frames (EBFs), which are a commonly used seismic-resisting system in modern steel framed buildings. The 2010/2011 Christchurch earthquake series, especially the very intense February 22 shaking, which was the first earthquake worldwide to push complete EBF systems fully into their inelastic state, generating a moderate to high level of plastic strain in EBF active links, for a range of buildings from 3 to 23 storeys in height. This raised two important questions: 1) what was the extent of plastic deformation in active links; and 2) what effect does that have to post-earthquake steel properties? This project comprised determining a robust relationship between hardness and plastic strain in order to be able to answer the first question and provide the necessary input into answering the second question. A non-destructive Leeb (portable) hardness tester (model TH170) has been used to measure the hardness, in order to determine the plastic strain, in hot rolled steel universal sections and steel plates. A bench top Rockwell B was used to compare and validated the hardness measured by the portable hardness tester. Hardness was measured from monotonically strained tensile test specimens to identify the relationship between hardness and plastic strain demand. Test results confirmed a good relationship between hardness and the amount of monotonically induced plastic strain. Surface roughness was identified as an important parameter in obtaining reliable hardness readings from a portable hardness reader. A proper surface preparation method was established by using three different cleaning methods, finished with hand sanding to achieve surface roughness coefficients sufficiently low not to distort the results. This work showed that a test surface roughness (Ra) is not more than 1.6 micron meter (μm) is required for accurate readings from the TH170 tester. A case study on an earthquake affected building was carried out to identify the relationship between hardness and amount of plastic strain demand in cyclically deformed active links. Hardness was carried out from active links shown visually to have been the most affected during one of the major earthquake events. Onsite hardness test results were then compared with laboratory hardness test results. A good relationship between hardness from onsite and laboratory was observed between the test methods; Rockwell B bench top and portable Leeb tester TH170. Manufacturing induced plastic strain in the top and bottom of the webs of hot rolled sections were discovered from this research, an important result which explains why visual effects of earthquake induced active link yielding (eg cracked or flaking paint) was typically more prevalent over the middle half depth of the active link. The extent of this was quantified. It was also evident that the hardness readings from the portable hardness tester are influenced by geometry, mass effects and rigidity of the links. The final experimental stage was application of the method to full scale cyclic inelastic tested nominally identical active links subjected to loading regimes comprising constant and variable plastic strain demands. The links were cyclically loaded to achieve different plastic strain level. A novel Digital Image Correlation (DIC) technique was incorporated during the tests of this scale, to confirm the level of plastic strain achieved. Tensile test specimens were water jet cut from cyclically deformed webs to analyse the level of plastic strain. Test results show clear evidence that cyclically deformed structural steel elements show good correlation between hardness and the amount of plastic strain demand. DIC method was found to be reliable and accurate to check the level of plastic strain within cyclically deformed structural steel elements

Images, UC QuakeStudies

The old Railway Station clock tower on Moorhouse Avenue with plywood and steel reinforcement covering two sides, and a crane hanging over top. The brickwork suffered extensive cracking during the earthquake making it in need of reinforcement. The clock has stopped at around 16:35, the time of the earthquake.

Images, UC QuakeStudies

The old Railway Station clock tower on Moorhouse Avenue with plywood and steel reinforcement covering two sides, and a crane hanging over top. The brickwork suffered extensive cracking during the earthquake making it in need of reinforcement. The clock has stopped at around 16:35, the time of the earthquake.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Registry Building on the corner of Montreal and Worcester Streets. Masonry around the gable has collapsed onto the footpath below. Steel bracing has been used to hold up the remaining masonry. Wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Registry Building on the corner of Montreal and Worcester Streets. Masonry around the gable has collapsed onto the footpath below. Steel bracing has been used to hold up the remaining masonry. Wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

Damage to the front gable of the Durham Street Methodist Church. Masonry has fallen from the top of the gable, and the resulting gap has been weather proofed with plywood, tarpaulins and metal tiles. The steel bracing propping the whole front wall can be seen at the bottom of the photograph.

Images, UC QuakeStudies

A photograph of the Christchurch Arts Centre taken from Rolleston Avenue. A spire has been removed from one of the towers and braced on the footpath in front of the building. Wire fencing and road cones have been used to cordon off one side of the road.

Images, UC QuakeStudies

A view across London Street in Lyttelton showing damage to the Four Square supermarket and Lyttelton Coffee Company buildings. The Four Square's windows have been boarded up with plywood. and cracks are visible in the masonry of the Lyttelton Coffee Company building. Steel rods have been installed to support its sagging awning.

Images, UC QuakeStudies

Steel bracing on the front of the Worcester Street face of the Octagon Live Restaurant (formerly Trinity Church), which is being repaired. The scaffolding has been decorated with sculptures of people kayaking, cycling, climbing and bungee jumping. Some of the figures are wearing santa hats. A fence has been constructed at the base of the building.

Images, UC QuakeStudies

Steel bracing on the front of the Worcester Street face of the Octagon Live Restaurant (formerly Trinity Church), which is being repaired. The scaffolding has been decorated with sculptures of people kayaking, cycling, climbing and bungee jumping. Some of the figures are wearing santa hats. A fence has been constructed at the base of the building.

Images, UC QuakeStudies

Steel bracing on the front of the Worcester Street face of the Octagon Live Restaurant (formerly Trinity Church), which is being repaired. The scaffolding has been decorated with sculptures of people kayaking, cycling, climbing and bungee jumping. Some of the figures are wearing santa hats. A fence has been constructed at the base of the building.

Images, UC QuakeStudies

Steel bracing on the front of the Worcester Street face of the Octagon Live Restaurant (formerly Trinity Church), which is being repaired. The scaffolding has been decorated with sculptures of people kayaking, cycling, climbing and bungee jumping. Some of the figures are wearing santa hats. A fence has been constructed at the base of the building.

Images, UC QuakeStudies

Steel bracing on the front of the Worcester Street face of the Octagon Live Restaurant (formerly Trinity Church), which is being repaired. The scaffolding has been decorated with sculptures of people kayaking, cycling, climbing and bungee jumping. Some of the figures are wearing santa hats. A fence has been constructed at the base of the building.

Images, UC QuakeStudies

Steel bracing on the front of the Worcester Street face of the Octagon Live Restaurant (formerly Trinity Church), which is being repaired. The scaffolding has been decorated with sculptures of people kayaking, cycling, climbing and bungee jumping. Some of the figures are wearing santa hats. A fence has been constructed at the base of the building.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Piko Wholefoods Building on the corner of Kilmore and Barbadoes Street. Sections of the top storey of the building have collapsed and the bricks and other rubble have spilled onto the footpath below. Steel fences have been placed around the building as a cordon.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Kenton Chambers Building on Hereford Street. Large cracks have formed in the columns between the building's windows. A section on the bottom storey has collapsed and the bricks have spilled onto the footpath in front. Steel fences have been placed across the street as a cordon.

Images, UC QuakeStudies

A photograph of a piece of plywood sitting on top of a pile of bricks from the Carlton Hotel. USAR codes have been spray-painted on the wood. In the foreground, metal fencing, cordon tape and a road cone have been used to cordon off the building.

Images, UC QuakeStudies

A photograph of a building on the corner of Victoria Street and Bealey Avenue. Large sections of the building have collapsed and the bricks have spilled onto the footpath below. Scaffolding has been constructed around the rest of the building, blocking it from view. In the foreground steel fencing and road cones have been placed across Victoria Street as a cordon.

Images, UC QuakeStudies

A photograph of emergency management personnel walking down Manchester Street towards the intersection of High and Lichfield Streets. Many of the buildings on the left side of the road have been damaged by the earthquakes. In the distance rubble from the earthquake-damaged buildings has spilled onto the road. Steel fences have been placed along the footpath to the left.

Images, UC QuakeStudies

A poem written on Gap Filler and Poetica's "Instant Poetry" wall on Colombo Street. The poem reads, "Amidst the shards of glass and twisted steel, beside the fallen brick and scattered concrete, we began to understand that there is beauty in the broken. Strangers do not live here anymore". This poem was picked by the public as the favourite poem written on the wall. It was then painted permanently onto the mural.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Kenton Chambers Building on Hereford Street. Large cracks have formed in the columns between the building's windows. A section of the bottom storey has collapsed and the bricks have spilled onto the footpath in front. Steel fences have been placed on the street as a cordon. In the distance there are many other earthquake-damaged buildings.

Images, UC QuakeStudies

A photograph of the north side of the ChristChurch Cathedral in Cathedral Square. The front of the building has been propped up with steel bracing but further earthquakes have caused more damage, leaving a gap between the bracing and the wall. The tower has been partially demolished, but the lower section is still visible. Wire fencing has been placed around the entire building. In the background, a crane is rising high above the square.

Images, UC QuakeStudies

A photograph of the north side of the ChristChurch Cathedral in Cathedral Square. The front of the building has been propped up with steel bracing but further earthquakes have caused more damage, leaving a gap between the bracing and the wall. The tower has been partially demolished, but the lower section is still visible. Wire fencing has been placed around the entire building. In the background, a crane is rising high above the square.

Images, UC QuakeStudies

The ruins of the historic Durham Street Methodist Church in the aftermath of the 22 February 2011 earthquake. The only parts of the building still upright are those supported by steel braces placed there after the 4 September 2010 earthquake to strengthen the building as it awaited repairs. Rubble has spilled out onto the street, knocking over the safety fences that were also erected after September. Silt from liquefaction has covered the road around the church.

Images, UC QuakeStudies

A photograph of the north side of the ChristChurch Cathedral in Cathedral Square. The front of the building has been propped up with steel bracing but further earthquakes have caused more damage, leaving a gap between the bracing and the wall. The tower has been partially demolished, but the lower section is still visible. Wire fencing has been placed around the entire building. In the background, a crane is rising high above the square.

Research papers, University of Canterbury Library

Since the mid 1990s, the Christchurch inventory of substation buildings was seismically retrofitted as part of the Risk and Realities improvement programme. • The substation buildings were retrofitted using a system of simple and cost-effective steel elements. • The 2010/2011 Canterbury earthquakes caused significant immediate disruption to power distribution network in Christchurch. • It took a single day in September 2010 and ten days in February 2011 to restore power to 90% customers. Tostudytheseismicperformanceofmasonrysubstationbuildingsfromamulti-disciplinary perspective on structural,economic and social aspects.

Research papers, The University of Auckland Library

Reinforced concrete (RC) frame buildings designed according to modern design standards achieved life-safety objectives during the Canterbury earthquakes in 2010-11 and the Kaikōura earthquake in 2016. These buildings formed ductile plastic hinges as intended and partial or total building collapse was prevented. However, despite the fact that the damage level of these buildings was relatively low to moderate, over 60% of multi-storey RC buildings in the Christchurch central business district were demolished due to insufficient insurance coverage and significant uncertainty in the residual capacity and repairability of those buildings. This observation emphasized an imperative need to improve understanding in evaluating the post-earthquake performance of earthquake-damaged buildings and to develop relevant post-earthquake assessment guidelines. This thesis focuses on improving the understanding of the residual capacity and repairability of RC frame buildings. A large-scale five-storey RC moment-resisting frame building was tested to investigate the behaviour of earthquake-damaged and repaired buildings. The original test building was tested with four ground motions, including two repeated design-level ground motions. Subsequently, the test building was repaired using epoxy injection and mortar patching and re-tested with three ground motions. The test building was assessed using key concepts of the ATC-145 post-earthquake assessment guideline to validate its assessment procedures and highlight potential limitations. Numerical models were developed to simulate the peak storey drift demand and identify damage locations. Additionally, fatigue assessment of steel reinforcement was conducted using methodologies as per ATC-145. The residual capacity of earthquake-strained steel reinforcement was experimentally investigated in terms of the residual fatigue capacity and the residual ultimate strain capacity. In addition to studying the fatigue capacity of steel reinforcement, the fatigue damage demand was estimated using 972 ground motion records. The deformation limit of RC beams and columns for damage control was explored to achieve a low likelihood of requiring performance-critical repair. A frame component test database was developed, and the deformation capacity at the initiation of lateral strength loss was examined in terms of the chord rotation, plastic rotation and curvature ductility capacity. Furthermore, the proposed curvature ductility capacity was discussed with the current design curvature ductility limits as per NZS 3101:2006

Images, UC QuakeStudies

Personnel from the USAID Disaster Assistance Response Team (DART) standing in Firefighters Reserve, in preparation for the two minutes of silence to honour the people who lost their lives in the 22 February 2011 earthquake. Just out of the picture is a sculpture fashioned from 5 tonnes of structural steel salvaged from the site of the World Trade Centre following their collapse on 11 September 2001 in terrorist attacks on New York City. The sculpture is now used as a tribute to firefighters in New Zealand.

Research papers, University of Canterbury Library

Research following the 2010-2011 Canterbury earthquakes investigated the minimum vertical reinforcement required in RC walls to generate well distributed cracking in the plastic hinge region. However, the influence of the loading sequence and rate has not been fully addressed. The new minimum vertical reinforcement limits in NZS 3101:2006 (Amendment 3) include consideration of the material strengths under dynamic load rates, but these provisions have not been validated at a member or system level. A series of tests were conducted on RC prisms to investigate the effect of loading rate and sequence on the local behaviour of RC members. Fifteen axially loaded RC prisms with the designs representing the end region of RC walls were tested under various loading rates to cover the range of pseudo-static and earthquake loading scenarios. These tests will provide substantial data for understanding the local behaviour of RC members, including hysteretic load-deformation behaviour, crack patterns, failure mode, steel strain, strain rate and ductility. Recommendations will be made regarding the effect of loading rate and reinforcement content on the cracking behaviour and ductility of RC members.

Research papers, The University of Auckland Library

High demolition rates were observed in New Zealand after the 2010-2011 Canterbury Earthquake Sequence despite the success of modern seismic design standards to achieve required performance objectives such as life safety and collapse prevention. Approximately 60% of the multi-storey reinforced concrete (RC) buildings in the Christchurch Central Business District were demolished after these earthquakes, even when only minor structural damage was present. Several factors influenced the decision of demolition instead of repair, one of them being the uncertainty of the seismic capacity of a damaged structure. To provide more insight into this topic, the investigation conducted in this thesis evaluated the residual capacity of moderately damaged RC walls and the effectiveness of repair techniques to restore the seismic performance of heavily damaged RC walls. The research outcome provided insights for developing guidelines for post-earthquake assessment of earthquake-damaged RC structures. The methodology used to conduct the investigation was through an experimental program divided into two phases. During the first phase, two walls were subjected to different types of pre-cyclic loading to represent the damaged condition from a prior earthquake, and a third wall represented a repair scenario with the damaged wall being repaired using epoxy injection and repair mortar after the pre-cyclic loading. Comparisons of these test walls to a control undamaged wall identified significant reductions in the stiffness of the damaged walls and a partial recovery in the wall stiffness achieved following epoxy injection. Visual damage that included distributed horizontal and diagonal cracks and spalling of the cover concrete did not affect the residual strength or displacement capacity of the walls. However, evidence of buckling of the longitudinal reinforcement during the pre-cyclic loading resulted in a slight reduction in strength recovery and a significant reduction in the displacement capacity of the damaged walls. Additional experimental programs from the literature were used to provide recommendations for modelling the response of moderately damaged RC walls and to identify a threshold that represented a potential reduction in the residual strength and displacement capacity of damaged RC walls in future earthquakes. The second phase of the experimental program conducted in this thesis addressed the replacement of concrete and reinforcing steel as repair techniques for heavily damaged RC walls. Two walls were repaired by replacing the damaged concrete and using welded connections to connect new reinforcing bars with existing bars. Different locations of the welded connections were investigated in the repaired walls to study the impact of these discontinuities at the critical section. No significant changes were observed in the stiffness, strength, and displacement capacity of the repaired walls compared to the benchmark undamaged wall. Differences in the local behaviour at the critical section were observed in one of the walls but did not impact the global response. The results of these two repaired walls were combined with other experimental programs found in the literature to assemble a database of repaired RC walls. Qualitative and quantitative analyses identified trends across various parameters, including wall types, damage before repair, and repair techniques implemented. The primary outcome of the database analysis was recommendations for concrete and reinforcing steel replacement to restore the strength and displacement capacity of heavily damaged RC walls