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Research papers, The University of Auckland Library

New Zealand’s stock of unreinforced masonry (URM) bearing wall buildings was principally constructed between 1880 and 1935, using fired clay bricks and lime or cement mortar. These buildings are particularly vulnerable to horizontal loadings such as those induced by seismic accelerations, due to a lack of tensile force-resisting elements in their construction. The poor seismic performance of URM buildings was recently demonstrated in the 2011 Christchurch earthquake, where a large number of URM buildings suffered irreparable damage and resulted in a significant number of fatalities and casualties. One of the predominant failure modes that occurs in URM buildings is diagonal shear cracking of masonry piers. This diagonal cracking is caused by earthquake loading orientated parallel to the wall surface and typically generates an “X” shaped crack pattern due to the reversed cyclic nature of earthquake accelerations. Engineered Cementitious Composite (ECC) is a class of fiber reinforced cement composite that exhibits a strain-hardening characteristic when loaded in tension. The tensile characteristics of ECC make it an ideal material for seismic strengthening of clay brick unreinforced masonry walls. Testing was conducted on 25 clay brick URM wallettes to investigate the increase in shear strength for a range of ECC thicknesses applied to the masonry wallettes as externally bonded shotcrete reinforcement. The results indicated that there is a diminishing return between thickness of the applied ECC overlay and the shear strength increase obtained. It was also shown that, the effectiveness of the externally bonded reinforcement remained constant for one and two leaf wallettes, but decreased rapidly for wall thicknesses greater than two leafs. The average pseudo-ductility of the strengthened wallettes was equal to 220% of that of the as-built wallettes, demonstrating that ECC shotcrete is effective at enhancing both the in-plane strength and the pseudo-ductility of URM wallettes. AM - Accepted Manuscript

Images, UC QuakeStudies

A photograph of an earthquake-damaged building on the corner of Colombo Street and St Asaph Street. The walls of the top storey of the building have crumbled, and bricks and other rubble have fallen onto the footpath and road below. In the background are many other earthquake-damaged buildings. Wire fencing and police tape have been placed across the street as a cordon.

Images, UC QuakeStudies

The corner of Colombo Street and Kilmore Street in the aftermath of the 22 February 2011 earthquake. The walls of several buildings along Colombo Street have collapsed, including Sala Thai Restaurant, which has spilled bricks onto the road. A bus has stopped alongside the building and police officers can be seen walking along the road.

Images, UC QuakeStudies

A photograph of the earthquake damage to a group of shops on Westminster Street in St Albans. Bricks and other rubble from the buildings have been piled on the footpath. Wire fencing, road cones and police tape have been placed around the buildings as a cordon.

Images, UC QuakeStudies

Damage to The Bone Dude's Bone Carving Studio and Cultured Gallery on Fitzgerald Avenue. The brick wall is cracked, and the guttering has fallen. The photographer comments, "This building was damaged in the September earthquake in Christchurch. It was the Bone dude's bone carving studio. The motto on the wall was 'Carve your own' and it looks like the earthquakes did just that".

Images, UC QuakeStudies

A photograph of the earthquake damage to the Iconic bar on the corner of Manchester and Gloucester Streets. Large sections of the outer walls have collapsed, the bricks and masonry spilling onto the footpath below, crushing several cars. USAR codes have been spray-painted near the door and a red sticker has been taped above. The red sticker indicates that the building is unsafe to enter.

Images, UC QuakeStudies

A photograph of a member of the Wellington Emergency Management Office Emergency Response Team climbing a ladder up the back of a house on Gloucester Street. The ladder has been placed against the house so that the ERT members can enter the building through the open window. To the right a section of the house next door has collapsed and the bricks have spilled onto the shed below.

Images, UC QuakeStudies

A photograph looking south down Manchester Street taken shortly after the 22 February 2011 earthquake. A crowd of people have gathered on the road. A brick building to the right has partially collapsed, rubble spilling onto the street.

Images, UC QuakeStudies

A photograph of a earthquake damaged building on Tuam Street taken shortly after the 22 February 2011 earthquake. Bricks from the top of the façade have crumbled, falling into the street below and crushing some parked cars.

Images, UC QuakeStudies

A photograph of earthquake damage to the Crown Masonic Lodge on Wordsworth Street, also known as the Freemasons Centre. Sections of the brick wall at the front of the building have collapsed. The entranceway is supported with wooden bracing.

Images, UC QuakeStudies

A photograph of earthquake damage to the Crown Masonic Lodge on Wordsworth Street, also known as the Freemasons Centre. Sections of the brick wall at the front of the building have collapsed. The entranceway is supported with wooden bracing.