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Research papers, The University of Auckland Library

Reinforced concrete buildings that satisfied modern seismic design criteria generally behaved as expected during the recent Canterbury and Kaikoura earthquakes in New Zealand, forming plastic hinges in intended locations. While this meant that life-safety performance objectives were met, widespread demolition and heavy economic losses took place in the aftermath of the earthquakes.The Christchurch central business district was particularly hard hit, with over 60% of the multistorey reinforced concrete buildings being demolished. A lack of knowledge on the post-earthquake residual capacity of reinforced concrete buildings was a contributing factor to the mass demolition.Many aspects related to the assessment of earthquake-damaged reinforced concrete buildings require further research. This thesis focusses on improving the state of knowledge on the post earthquakeresidual capacity and reparability of moderately damaged plastic hinges, with an emphasis on plastic hinges typical of modern moment frame structures. The repair method focussed on is epoxy injection of cracks and patching of spalled concrete. A targeted test program on seventeen nominally identical large-scale ductile reinforced concrete beams, three of which were repaired by epoxy injection following initial damaging loadings, was conducted to support these objectives. Test variables included the loading protocol, the loading rate, and the level of restraint to axial elongation.The information that can be gleaned from post-earthquake damage surveys is investigated. It is shown that residual crack widths are dependent on residual deformations, and are not necessarily indicative of the maximum rotation demands or the plastic hinge residual capacity. The implications of various other types of damage typical of beam and column plastic hinges are also discussed.Experimental data are used to demonstrate that the strength and deformation capacity of plastic hinges with modern seismic detailing are often unreduced as a result of moderate earthquake induced damage, albeit with certain exceptions. Special attention is given to the effects of prior yielding of the longitudinal reinforcement, accounting for the low-cycle fatigue and strain ageing phenomena. A material-level testing program on the low-cycle fatigue behaviour of grade 300E reinforcing steel was conducted to supplement the data available in the literature.A reduction in stiffness, relative to the initial secant stiffness to yield, occurs due to moderate plastic hinging damage. This reduction in stiffness is shown to be correlated with the ductility demand,and a proposed model gives a conservative lower-bound estimate of the residual stiffness following an arbitrary earthquake-type loading. Repair by epoxy injection is shown to be effective in restoring the majority of stiffness to plastic hinges in beams. Epoxy injection is also shown to have implications for the residual strength and elongation characteristics of repaired plastic hinges.

Images, UC QuakeStudies

A photograph of the earthquake damage to the former St Albans Library on Colombo Street. Parts of the walls have crumbled, the bricks spilling onto the pavement. Wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

A photograph of the Wellington Emergency Management Office, taking photos of St Paul's Church in Dallington. The church was severely damaged after the 4 September earthquake. Police emergency tape can be seen around the building, keeping people away.

Images, UC QuakeStudies

A photograph of the former site of Westende Jewellers and Alva Rados, on the corner of Manchester Street and Worcester Street. The building was badly-damaged in the 4 September earthquake and was demolished soon afterwards. A two-storey building was built on the site and completed in July 2012. The building then had to be removed when the decision was made to widen Manchester Street as part of the draft transport plan for central Christchurch. The photograph was modelled after an image taken by Ian McGregor from Fairfax Media in September 2010.

Images, UC QuakeStudies

A photograph of the former site of Westende Jewellers and Alva Rados, on the corner of Manchester Street and Worcester Street. The building was badly-damaged in the 4 September earthquake and was demolished soon afterwards. A two-storey building was built on the site and completed in July 2012. The building then had to be removed when the decision was made to widen Manchester Street as part of the draft transport plan for central Christchurch. The photograph was modelled after an image taken by Ian McGregor from Fairfax Media in September 2010.

Images, UC QuakeStudies

A photograph of the earthquake damage to Poplar Street taken from Tuam Street shortly after the 22 February 2011 earthquake. The road is completely covered by loose bricks and a car has been crushed. To the left, the corner of a building has collapsed, rubble falling into the street.

Images, UC QuakeStudies

A photograph of the badly-damaged Octagon Live Restaurant on the corner of Worcester and Manchester Streets. The masonry around the gable has crumbled, falling onto the footpath in front. Wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

Damaged shops on Manchester Street. The front wall of the top storey of these buildings has crumbled onto the street, crushing vehicles. Emergency personnel have spray painted the word "Clear" on the cars to indicate that they have been checked for trapped or injured people.

Images, UC QuakeStudies

Damaged shops on Manchester Street. The front wall of the top storey of these buildings has crumbled onto the street, crushing vehicles. Emergency personnel have spray painted the word "Clear" on the cars to indicate that they have been checked for trapped or injured people.

Images, UC QuakeStudies

Damaged shops on Manchester Street. The front wall of the top storey of these buildings has crumbled onto the street, crushing vehicles. Emergency personnel have spray painted the word "Clear" on the cars to indicate that they have been checked for trapped or injured people.

Images, UC QuakeStudies

A photograph of the Arts Centre taken from Rolleston Avenue near the Botanic Gardens. The building has been cordoned off by wire fencing and a wooden structure has been secured to the tower with tie-downs to help reduce damage from further aftershocks.

Images, UC QuakeStudies

A photograph looking north up Colombo Street across the intersection of Kilmore Street. The buildings on either side of the street have been severely damaged by the earthquakes. The rubble and other debris has since been cleared from the street and footpaths.

Images, UC QuakeStudies

A house on Avonside Drive showing damage from the 4 September 2010 earthquake. Numerous cracks in the masonry can be seen, and several sections of brick have fallen off the walls. The building's porch has also collapsed. A pile of dried liquefaction is visible in the driveway.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Christchurch Chinese Methodist Church on Papanui Road. The wall of the gable has crumbled, the bricks spilling onto the lawn below. Wire fencing has been placed around the building as a cordon.

Images, UC QuakeStudies

A photograph of the earthquake damage to the Christchurch Chinese Methodist Church on Papanui Road. The gable wall has crumbled, the bricks and window frame falling onto the ground. Wire fencing has been placed around the building as a cordon.