Keynote Address Learning from Hawke's Bay 1931 Earthquake Performance Assessment and Retrofit Decision Making for Risk Mitigation Behaviour of Walls and Piers Understanding Reinforced Concrete Behaviour Modelling Earthquake Performance Earthquake Performance Poster Papers Design and Development 

Three Dimensional Pile Finite Element Modelling using OpenSees

Liam Wotherspoon

This paper details the computer analysis of a pile embedded in a homogenous soil deposit loaded at its tip with both monotonic and cyclic loads. Analysis was undertaken using OpenSees, a three dimensional non-linear finite element analysis program developed for the seismic simulation of geotechnical and structural systems.

Initial analysis focused on simple models where elastic material models were adopted for both the pile and soil material. Modelling output was compared to closed form solutions for the loading of elastic piles in an elastic soil medium.

Paper P26: [Read]

Shallow Foundation Stiffness: Continuous Soil and Discrete Spring Models Compared

Mick Pender, Liam Wotherspoon, Jason Ingham and Athol Carr

In this paper we compare two ways of modelling shallow foundation stiffness. One method assumes that the soil beneath the foundation can be idealised as an elastic continuum and the other that the soil can be represented as a bed of independent springs. The essential difference is that the elastic material is continuous so that a displacement or load at one location induces changes elsewhere, while in the case of springs there is no interaction so that what happens at one spring has no effect on other springs. Modelling with springs is simpler than using a continuous medium and also leads to a simple method for handling progressive uplift of the foundation under moment loading. The question addressed in the paper is how appropriate is the spring model.

Paper P27: [Read]

Probabilistic Formulation of a Performance-based Matrix Combining Maximum and Residual Deformations

S.R. Uma, Stefano Pampanin and Constantin Christopoulos

Reports from past earthquake reconnaissance observations as well as results from analytical studies indicate that most structures designed according to current codes will sustain residual (permanent) deformations in the event of a design-level earthquake, even if they perform exactly as expected. Despite this reality, little consideration is currently given to residual displacements unlike the maximum transient response during seismic design or performance assessment of structures. The concept of a performance-based matrix, where maximum and residual displacements are combined as complementary damage indicators has been recently introduced by the authors, is a viable tool to identify performance levels. In this paper, a probabilistic formulation of the performance based matrix concept is presented, within a refined framework for performance based seismic design and assessment of structures. Extensive non-linear time history analyses have been performed on equivalent SDOF systems designed using the Displacement Based Design (DBD) approach and modelled with different hysteresis rules to represent multi-storey reinforced concrete or steel buildings. Fragility curves representing the probabilities of exceedence of different joined maximum-residual performance levels are derived using bivariate probability distributions. Valuable observations are derived with regard to the contributions from the response parameters to the total probability of exceedence based on the hysteretic behaviour. As part of the proposed formulation for performance-based seismic design and assessment, performance objectives can be defined and associated with targeted probability of achieving them.

Paper P28: [Read]

Column Axial Shortening Effects in Steel Frames

Greg MacRae, Karissa Hyde, Warren Walpole, Peter Moss, Clark Hyland, Charles Clifton and Nandor Mago

Steel members subject to constant axial compression and inelastic cyclic displacements exhibit axial shortening. This column axial shortening, which may occur during an earthquake, can cause undesirable effects in the building, especially if it occurs to different extents in different columns of a seismic-resisting system. This paper summarizes experiments, and finite-element analyses, used to model the axial shortening in a steel column. A method to minimize column axial shortening is then proposed and investigated with finite-element analyses. Future frame modelling to include axial shortening effects is described.

Paper P29: [Read]

Riskscape New Zealand - A Multihazard Loss Modelling Tool

Andrew King and Rob Bell

RiskScape New Zealand is a national multi-hazard impact model that presents relative risks and community exposure to a range of natural hazards. The prototype currently under development will consider the impact of five of the most commonly encountered natural hazard (including earthquakes and tsunami) on three representative New Zealand communities. The model evolution recognizes the conflict between the GIS presentational environment expected by typically non-technical end users (such as emergency management officials and community planners) and the need for a computationally efficient environment that will ensure processing time for large inventory datasets remains acceptably short.

The desire to maintain a consistent probabilistic approach between the various hazards, often with a dearth of quality input data, is an issue that is being worked through. The expansion of the model to enable real-time event impacts to be assessed and RiskScape to be used for response implementation is recognized, particularly with reference to the ongoing upgrade that is underway to New Zealand’s seismograph and strong motion network through the Geonet programme. The possible expansion of this network to include tidal and flood simulation is also being incorporated into RiskScape NZ

Paper P30: [Read]

Earthquake Risk Buildings

Rob Jury

The publishing, in late 2005, of the draft NZSEE Study Group recommendations for the assessment and improvement of the structural performance of buildings in earthquakes signalled the end of another step towards the publishing of the final guidelines.This paper briefly outlines the contents of the guideline document, the approaches adopted (particularly the interpretations made of the new Building Act legislation) and the expected roadmap to achieve the publication of the final guideline document.

Paper P52: [Read]

Keynote Address Learning from Hawke's Bay 1931 Earthquake Performance Assessment and Retrofit Decision Making for Risk Mitigation Behaviour of Walls and Piers Understanding Reinforced Concrete Behaviour Modelling Earthquake Performance Earthquake Performance Poster Papers Design and Development