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Research papers, The University of Auckland Library

This thesis describes the strategies for earthquake strengthening vintage clay bricks unreinforced masonry (URM) buildings. URM buildings are well known to be vulnerable to damage from earthquake-induced lateral forces that may result in partial or full building collapse. The 2010/2011 Canterbury earthquakes are the most recent destructive natural disaster that resulted in the deaths of 185 people. The earthquake events had drawn people’s attention when URM failure and collapse caused about 39 of the fatality. Despite the poor performance of URM buildings during the 2010/2011 Canterbury earthquakes, a number of successful case study buildings were identified and their details research in-depth. In order to discover the successful seismic retrofitting techniques, two case studies of retrofitted historical buildings located in Christchurch, New Zealand i.e. Orion’s URM substations and an iconic Heritage Hotel (aka Old Government Building) was conducted by investigating and evaluating the earthquake performance of the seismic retrofitting technique applied on the buildings prior to the 2010/2011 Canterbury earthquakes and their performance after the earthquakes sequence. The second part of the research reported in this thesis was directed with the primary aim of developing a cost-effective seismic retrofitting technique with minimal interference to the vintage clay-bricks URM buildings. Two retrofitting techniques, (i) near-surface mounted steel wire rope (NSM-SWR) with further investigation on URM wallettes to get deeper understanding the URM in-plane behaviour, and (ii) FRP anchor are reported in this research thesis.

Research papers, The University of Auckland Library

Following the 2010–2011 Canterbury earthquakes, a renewed focus has been directed across New Zealand to the hazard posed by the country‘s earthquake-vulnerable buildings, namely unreinforced masonry (URM) and reinforced concrete (RC) buildings with potentially nonductile components that have historically performed poorly in large earthquakes. The research reported herein was pursued with the intention of addressing several recommendations made by the Canterbury Earthquakes Royal Commission of Inquiry which were classified into the following general categories:  Identification and provisional vulnerability assessment of URM and RC buildings and building components;  Testing, assessment, and retrofitting of URM walls loaded out-of-plane, with a particular focus on highly vulnerable URM cavity walls;  Testing and assessment of RC frame components, especially those with presumably non-ductile reinforcement detailing;  Portfolio management considering risks, regulations, and potential costs for a portfolio that includes several potentially earthquake-vulnerable buildings; and  Ongoing investigations and proposed research needs. While the findings from the reported research have implications for seismic assessments of buildings across New Zealand and elsewhere, an emphasis was placed on Auckland given this research program‘s partnership with the Auckland Council, the Auckland region accounting for about a third each of the country‘s population and economic production, and the number and variety of buildings within the Auckland building stock. An additional evaluation of a historic building stock was carried out for select buildings located in Hawke‘s Bay, and additional experimental testing was carried out for select buildings located in Hawke‘s Bay and Christchurch.

Research papers, The University of Auckland Library

The performance of retrofitted unreinforced masonry (URM) bearing wall buildings in Christchurch is examined, considering ground motion recordings from multiple events. Suggestions for how the experiences in Christchurch might be relevant to retrofit practices common to New Zealand, U.S. and Canada are also provided. Whilst the poor performance of unretrofitted URM buildings in earthquakes is well known, much less is known about how retrofitted URM buildings perform when subjected to strong ground shaking.

Research papers, The University of Auckland Library

Seismic retrofitting of unreinforced masonry buildings using posttensioning has been the topic of many recent experimental research projects. However, the performance of such retrofit designs in actual design level earthquakes has previously been poorly documented. In 1984 two stone masonry buildings within The Arts Centre of Christchurch received posttensioned seismic retrofits, which were subsequently subjected to design level seismic loads during the 2010/2011 Canterbury earthquake sequence. These 26 year old retrofits were part of a global scheme to strengthen and secure the historic building complex and were subject to considerable budgetary constraints. Given the limited resources available at the time of construction and the current degraded state of the steel posttension tendons, the posttensioned retrofits performed well in preventing major damage to the overall structure of the two buildings in the Canterbury earthquakes. When compared to other similar unretrofitted structures within The Arts Centre, it is demonstrated that the posttensioning significantly improved the in-plane and out-of-plane wall strength and the ability to limit residual wall displacements. The history of The Arts Centre buildings and the details of the Canterbury earthquakes is discussed, followed by examination of the performance of the posttension retrofits and the suitability of this technique for future retrofitting of other historic unreinforced masonry buildings. http://www.aees.org.au/downloads/conference-papers/2013-2/

Images, UC QuakeStudies

A view across Norwich Quay in Lyttelton showing the historic Post Office building and Forbes' Store. Masonry has fallen from the walls of both buildings and the awning of Forbes' Store has collapsed.

Images, UC QuakeStudies

A photograph of the Durham Street Methodist Church which collapsed during the 22 February 2011 earthquake. All that is left is a small section of the front wall. A large pile of masonry sits in front. To the left, scaffolding indicates the height of the building before it collapsed.

Images, UC QuakeStudies

A view across Lincoln Road from Bernard Street to the former Spice 'N' Things building. Masonry from the building's upper section have collapsed onto the road. A sign painted beside the building reads, "Spice 'N' Things moved to 208 Lincoln Rd".

Images, UC QuakeStudies

Three buildings on Norwich Quay in Lyttelton, enclosed by safety fences. From left to right, the buildings are: Shadbolt House, Lyttelton Hotel and The Stand Gourmet Takeout and Cafe. Masonry from the Lyttelton Hotel building and The Stand has collapsed onto the road.

Research papers, The University of Auckland Library

Following the 22 February 2011 Christchurch earthquake a comprehensive damage survey of the unreinforced masonry (URM) building stock of Christchurch city, New Zealand was undertaken. Because of the large number of aftershocks associated with both the 2011 Christchurch earthquake and the earlier 4 September 2010 Darfield earthquake, and the close proximity of their epicentres to Christchurch city, this earthquake sequence presented a unique opportunity to assess the performance of URM buildings and the various strengthening methods used in New Zealand to increase the performance of these buildings in earthquakes. Because of the extent of data that was collected, a decision was made to initially focus exclusively on the earthquake performance of URM buildings located in the central business district (CBD) of Christchurch city. The main objectives of the data collection exercise were to document building characteristics and any seismic strengthening methods encountered, and correlate these attributes with observed earthquake damage. In total 370 URM buildings in the CBD were surveyed. Of the surveyed buildings, 62% of all URM buildings had received some form of earthquake strengthening and there was clear evidence that installed earthquake strengthening techniques in general had led to reduced damage levels. The procedure used to collect and process information associated with earthquake damage, general analysis and interpretation of the available survey data for the 370 URM buildings, the performance of earthquake strengthening techniques, and the influence of earthquake strengthening levels on observed damage are reported within. http://15ibmac.com/home/

Research papers, The University of Auckland Library

It is well known that buildings constructed using unreinforced masonry (URM) are susceptible to damage from earthquake induced lateral forces that may result in partial or full building collapse. The 2010/2011 Canterbury earthquakes are the most recent New Zealand example of destructive earthquakes, which have drawn people's attention to the inherent seismic weaknesses of URM buildings and anchored masonry veneer systems in New Zealand. A brief review of the data collected following the 2010 Darfield earthquake and more comprehensive documentation of data that was collected following the 2011 Christchurch earthquake is presented, along with the findings from subsequent data interrogation. Large stocks of earthquake prone vintage URM buildings that remain in New Zealand and in other seismically active parts of the world result in the need for minimally invasive and cost effective seismic retrofit techniques. The principal objective of the doctoral research reported herein was to investigate the applicability of near surface mounted (NSM) carbon fibre reinforced polymer (CFRP) strips as a seismic improvement technique. A comprehensive experimental program consisting of 53 pull tests is presented and is used to assess the accuracy of existing FRP-to-masonry bond models, with a modified model being proposed. The strength characteristics of vintage clay brick URM wall panels from two existing URM buildings was established and used as a benchmark when manufacturing replica clay brick test assemblages. The applicability of using NSM CFRP strips as a retrofitting technique for improving the shear strength and the ductility capacity of multi-leaf URM walls constructed using solid clay brick masonry is investigated by varying CFRP reinforcement ratios. Lastly, an experimental program was undertaken to validate the proposed design methodology for improving the strength capacity of URM walls. The program involved testing full-scale walls in a laboratory setting and testing full-scale walls in-situ in existing vintage URM buildings. Experimental test results illustrated that the NSM CFRP technique is an effective method to seismically strengthen URM buildings.

Images, UC QuakeStudies

A view across Cambridge Terrace to the former Canterbury Public Library. Masonry from the building's corners and end gable has fallen onto the footpath below. Wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

A view across Stanmore Road to several badly damaged buildings, including Marcel's Picnic, Chalet Hair Fashion and Stanmore Road Dairy. Masonry and structural components from the buildings have collapsed onto the footpath and the buildings have been cordoned off by a safety fence.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Canterbury Provincial Chambers on Durham Street. The top of one of the chambers has crumbled and the masonry has fallen onto the footpath. Scaffolding which was erected after the 4 September 2010 earthquake has also fallen. Wire fences have been placed around the building as a cordon.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Canterbury Provincial Chambers on Durham Street. The top of one of the chambers has crumbled and the masonry has fallen onto the footpath. Scaffolding which was erected after the 4 September 2010 earthquake has also fallen. Wire fences have been placed around the building as a cordon.

Images, UC QuakeStudies

A view across Hereford Street to the former Canterbury Public Library. Masonry from the building's corners and end gable has fallen onto the footpath and wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

A photograph of St Luke's Church on the corner of Manchester Street and Kilmore Street. Large sections of the church have collapsed and the masonry and other rubble have spilled onto the car park. Wire fences have been placed around the side of the building as a cordon.

Images, UC QuakeStudies

A view down Sumner Road in Lyttelton with the former Lyttelton Public Library building to the left and the former Lyttelton Fire Station building to the right. Masonry has collapsed from both buildings and wire fencing has been placed around their bases as cordons.

Images, UC QuakeStudies

A view across Cambridge Terrace to the former Canterbury Public Library. Masonry from the building's corners and end gable has fallen onto the footpath and the base of the building has been cordoned off with wire fencing.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Canterbury Provincial Chambers. The top section of the building has crumbled, the masonry spilling onto the footpath. Wire fencing has been placed around the building as a cordon.