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Images, UC QuakeStudies

Large cracks between concrete slabs in a pathway beside the Southern Region Coastguard Waimakariri-Ashley boathouse on Charles Street in Kaiapoi show how the land has slumped towards the river.

Images, UC QuakeStudies

A group of people inspect the damaged rowing club buildings at Kerrs Reach. A large gap has appeared between two concrete slabs beside the building, where the land has slumped towards the river.

Research papers, University of Canterbury Library

Research Report No.2010-03Ground motion prediction equations (GMPEs) for geometric-mean pseudo-spectral acceleration amplitudes from New Zealand (NZ) earthquakes are developed. A database of 2437 three-component ground motion records is developed by applying stringent quality criteria to the historically recorded events in NZ. Despite the large number of records, the database is deficient in empirical records from large magnitude events recorded at close distances to the fault rupture plane. As a result, the basis for the NZ-specific GMPE development is to examine the applicability of foreign GMPEs for similar tectonic regions and then modify the most applicable GMPEs based on both theoretical and statistically significant empirically-driven arguments. For active shallow crustal events, five different GMPEs are considered. It was found that the McVerry et al. (2006) model, which is the current model upon which seismic design guidelines and site-specific seismic hazard analyses in NZ are based, provided the worst fit to the NZ database, and that the Chiou et al. (2010) (C10) modification of the Chiou and Youngs (2008) model was the most applicable. Discrepancies between the C10 model and the NZ database that were empirically identified and theoretically justified were used to modify the C10 model for: (i) small magnitude scaling; (ii) scaling of short period ground motion from normal faulting events in volcanic crust; (iii) scaling of ground motions on very hard rock sites; (iv) anelastic attenuation in the NZ crust; and (v) consideration of the increased anelastic attenuation in the Taupo Volcanic Zone (TVZ). For subduction slab events, initially three models were considered. It was found that all of the models had some significant biases with respect to applicability for NZ. The Zhao et al. (2006) (Z06) model was selected because of the rigorous database upon which it was developed and modified by: (i) NZ-specific scaling at small magnitudes; (ii) path scaling at large distances; (iii) consideration of the increased TVZ attenuation; and (iv) revision of the standard deviation model. Based on these modifications the developed model showed no bias of the inter- and intra-event residuals as a function of various predictor variables. The standard deviation of the residuals using the revised standard deviation model also indicated that the model has an adequate precision. Three GMPEs were considered for subduction interface events. The Zhao et al. (2006) (Z06) model was the best performing model with only bias exhibited in the site response model, and possible over-prediction of large magnitude events. The Z06 interface model was modified to account for site response and magnitude scaling using the same functional forms as those of the developed active shallow crustal and subduction slab models. The developed model showed no bias of the inter- and intra-event residuals as a function of various predictor variables. The developed GMPEs include specific features as evident in the NZ database; consistent scaling for parameters not well constrained by the NZ database; and pseudo-spectral amplitudes for vibration periods from 0.01 to 10 seconds. Hence, these models represent a significant advance in the state-of-the art for empirical ground motion prediction in NZ.

Research papers, University of Canterbury Library

This report describes in-plane experimental testing and numerical modelling of timberconcrete floor diaphragms. The experimental tests investigated the in-plane stiffness of the diaphragm and the stiffness and strength of different connections between the diaphragm and the lateral load resisting system. The test model was 1/3 scale and three meters square in plan. Seven tests with a different kind of connection between the floor and the rigid lateral supports (which simulated a timber lateral load resisting system) have been performed. The results of the experimental testing are used to calibrate numerical models which are used to investigate the effects of the floor flexibility on the seismic behaviour of post-tensioned timber buildings. For the experimental tests, screw and nail fasteners were used to connected to floor unit to the lateral supports. These fasteners were embedded into the concrete slab or timber edge joints at different orientations. The stiffness of the diaphragm connections was vastly different for each detail. Screws installed at a 45? angle (inclined) to the lateral supports were four times stiffer than the screws installed orthogonal to the lateral supports. The initial stiffness of the inclined fasteners was similar for timber-to-timber and concrete-to-timber connections. For the timberto- timber connections the orientation did not seem to influence the strength of the connection. The tested diaphragm had an uncracked stiffness of 4000 kN/mm and a cracked stiffness of 300 kN/mm. For the tested floor unit it was concluded that the influence of the diaphragm flexibility was negligible compared to the connector flexibility. The floor flexibility can be idealized as three different parts, the deformation of the connectors, the shear deformation of the diaphragm and the flexural deformation of the diaphragm. The numerical analyses showed that in most perceivable situations the connection deformation will govern the in-plane seismic response of the floor. Hence, it is justified to model it as a single-degree-of-freedom (SDOF) element. The influence of the floor flexibility on the seismic response of post-tensioned timber buildings is small. In most cases neglecting the floor flexibility is a conservative approach for the structural design of the building. However, structures with stiff walls and long floor spans there can be a significant amplification of the seismic response. For that case, a simple SDOF representation is proposed. Code-based recommendations for predicting the peak floor accelerations are found to be inadequate. A methodology is proposed to more accurately predict the expected peak floor accelerations for design