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Research papers, University of Canterbury Library

A linear and non-linear model are developed to analyze the structural impact and response of two single degree of freedom structures, representing adjacent buildings or bridge sections. Different impact coefficients of restitution, normalized distances between structures and a range of different structural periods are considered. The probability of impact and the displacement changes that can result from these collisions are computed. The likelihood of an increase in displacement is quantified in a probabilistic sense. A full matrix of response simulations are performed to individually investigate and delineate the effects of inter-structure gap-ratio, period ratios, structural non-linearity and impact elasticity. Column inelasticity is incorporated through the use of a Ramberg-Osgood type hysteresis rule. The minimum normalized distance, or gap-ratio, required between two structures to ensure that the likelihood of increased displacement of more than 10% for either structure for 90% of the given earthquake ground motions is assessed as one of many possible design risk bounds. Increased gap ratio, defined as a percentage of spectral displacement, is shown to reduce the likelihood of impact, as well as close structural periods. Larger differences in the relative periods of the two structures were seen to significantly increase the likelihood of impact. Inclusion of column inelasticity and higher plasticity of impact reduce displacement increases from impact and thus possible further damage to the structures. Such information can be used as a guideline to manage undesirable effects of impact in design - a factor that has been observed to be very important during the recent Canterbury, New Zealand Earthquakes.

Research papers, University of Canterbury Library

Previous earthquakes demonstrated destructive effects of soil-structure interaction on structural response. For example, in the 1970 Gediz earthquake in Turkey, part of a factory was demolished in a town 135 km from the epicentre, while no other buildings in the town were damaged. Subsequent investigations revealed that the fundamental period of vibration of the factory was approximately equal to that of the underlying soil. This alignment provided a resonance effect and led to collapse of the structure. Another dramatic example took place in Adapazari, during the 1999 Kocaeli earthquake where several foundations failed due to either bearing capacity exceedance or foundation uplifting, consequently, damaging the structure. Finally, the Christchurch 2012 earthquakes have shown that significant nonlinear action in the soil and soil-foundation interface can be expected due to high levels of seismic excitation and spectral acceleration. This nonlinearity, in turn, significantly influenced the response of the structure interacting with the soil-foundation underneath. Extensive research over more than 35 years has focused on the subject of seismic soil-structure interaction. However, since the response of soil-structure systems to seismic forces is extremely complex, burdened by uncertainties in system parameters and variability in ground motions, the role of soil-structure interaction on the structural response is still controversial. Conventional design procedures suggest that soil-structure interaction effects on the structural response can be conservatively ignored. However, more recent studies show that soil-structure interaction can be either beneficial or detrimental, depending on the soil-structure-earthquake scenarios considered. In view of the above mentioned issues, this research aims to utilise a comprehensive and systematic probabilistic methodology, as the most rational way, to quantify the effects of soil-structure interaction on the structural response considering both aleatory and epistemic uncertainties. The goal is achieved by examining the response of established rheological single-degree-of-freedom systems located on shallow-foundation and excited by ground motions with different spectral characteristics. In this regard, four main phases are followed. First, the effects of seismic soil-structure interaction on the response of structures with linear behaviour are investigated using a robust stochastic approach. Herein, the soil-foundation interface is modelled by an equivalent linear cone model. This phase is mainly considered to examine the influence of soil-structure interaction on the approach that has been adopted in the building codes for developing design spectrum and defining the seismic forces acting on the structure. Second, the effects of structural nonlinearity on the role of soil-structure interaction in modifying seismic structural response are studied. The same stochastic approach as phase 1 is followed, while three different types of structural force-deflection behaviour are examined. Third, a systematic fashion is carried out to look for any possible correlation between soil, structural, and system parameters and the degree of soil-structure interaction effects on the structural response. An attempt is made to identify the key parameters whose variation significantly affects the structural response. In addition, it is tried to define the critical range of variation of parameters of consequent. Finally, the impact of soil-foundation interface nonlinearity on the soil-structure interaction analysis is examined. In this regard, a newly developed macro-element covering both material and geometrical soil-foundation interface nonlinearity is implemented in a finite-element program Raumoko 3D. This model is then used in an extensive probabilistic simulation to compare the effects of linear and nonlinear soil-structure interaction on the structural response. This research is concluded by reviewing the current design guidelines incorporating soil-structure interaction effects in their design procedures. A discussion is then followed on the inadequacies of current procedures based on the outcomes of this study.

Research papers, University of Canterbury Library

A preliminary case study assessing the seismic sustainability of two reinforced concrete structures, a frame structure and a wall structure, was conducted to determine which structural system is more seismically sustainable. The two structures were designed to the same standards and were assumed to be located in Christchurch, New Zealand. A component-based probabilistic seismic loss assessment, considering direct losses only, was conducted for two ground motion records, regarded to approximately represent a 1 in 500 year earthquake event and a 1 in 2500 year earthquake event, respectively. It is shown that the wall structure results in lower direct losses than the frame structure in the less severe ground motion scenario. However, in the more severe ground motion scenario, the frame structure results in lower direct losses. Hence, this study demonstrates that which structural system has the lower direct losses depends on the ground motion intensity level.

Research papers, University of Canterbury Library

This document reviews research-based understandings of the concept of resilience. A conceptual model is developed which identifies a number of the factors that influence individual and household resilience. Guided by the model, a series of recommendations are developed for practices that will support individual and household resilience in Canterbury in the aftermath of the 2010-2011 earthquakes.

Images, eqnz.chch.2010

Shipping containers against the cliff on the road to Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_012.JPG From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Container Love: shipping container decorated with knitted and crocheted squares. Sumner, Christchurch. File reference: CCL-2012-05-12-Around-Sumner-May-2012 DSC_034.JPG From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Shirley Road, Christchurch. File reference: CCL-2012-05-10-Around-Shirley-May-2012 DSC_02852.JPG From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

The Cranmer Court demolition started today in Christchurch. The 1876 building was originally a Normal School and was in a derelict state in the early 1980s when it was rescued and converted into apartments. The heritage-listed building was red-stickered after the February 2011 earthquake.

Images, eqnz.chch.2010

Canterbury Brewery, St Asaph Street, Christchurch. File reference: CCL-2012-02-20-CanterburyBrewery-February-2012 DSC_144.JPG From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Canterbury Brewery, St Asaph Street, Christchurch. File reference: CCL-2012-02-20-CanterburyBrewery-February-2012 DSC_147.JPG From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Demolition work on Brannigans building, Gloucester Street. File reference: CCL-2012-02-07-IMG_9204 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Canterbury Brewery, St Asaph Street, Christchurch. File reference: CCL-2012-02-20-CanterburyBrewery-February-2012 DSC_142.JPG From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Demolition work on Brannigans building, Gloucester Street. File reference: CCL-2012-02-07--IMG_9194 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Canterbury Brewery, St Asaph Street, Christchurch. File reference: CCL-2012-02-20-CanterburyBrewery-February-2012 DSC_146.JPG From the collection of Christchurch City Libraries.