Keynote Address Session 1 Session 2 Session 3 Session 4 Session 5 Session 6 Poster Session Session 8 

Seismic Loss Estimation for Efficient Decision Making

Brendon Bradley, Rajesh Dhakal, Misko Cubrinovski, Greg MacRae and Dominic Lee

In order to incorporate seismic risk of facilities into a decision making framework, procedures are needed to quantify such risk for stakeholders. Seismic loss estimation methods combine seismic hazard, structural response, damage fragility, and damage consequences to allow quantification of seismic risk. This paper presents a loss estimation methodology which allows various means of quantifying seismic risk of a specific facility. The methodology is component-based and can therefore distinguish between different structural configurations or different facility contents and is consistent with state-of-the-art loss assessment procedures. Loss is measured in the forms of direct structural and non-structural repair costs, and although not considered in the example, business disruption and occupant casualties can also be considered. This framework has been packaged in a computer code available for future dissemination in the public domain so that users need only to have a basic understanding of the methodology and the input data that is required. Discussion is given to the flexibility of the framework in terms of the rigour which can be employed at each of the main steps in the procedure. Via a case study of a high-rise office building, the use of the methodology in decision-making is illustrated. Methodological requirements and further research directions are discussed.

Paper P32: [Read] [Presentation]

The Challenges of Reconstruction after the October 2005 Kashmir Earthquake

Hamid Mumtaz, Habib Mughal, Maggie Stephenson and Jitendra Bothara

The 8th October 2005 Kashmir Earthquake was one the largest earthquakes in Northern Pakistan in its recorded history. It caused an unprecedented level of damage and destruction in Pakistan Administered Kashmir (PAK) and the North Western Frontier Province (NWFP). It damaged or collapsed more than 0.6 million buildings - leaving 3.5 million people shelter less as winter approached. A large part of the earthquake-affected area is difficult to access and highly snow-prone, with rugged terrain and scattered settlements. It posed unique challenges and efforts on a massive-scale for reconstruction. For residential buildings, the Pakistan government adopted a house-owner driven approach. The reconstruction policy stated that the government and other agencies would provide equal technical assistance and subsidy to each family, without differentiating between who lost what. To increase capacity in earthquake-resistant construction, there was large-scale training of artisans, technicians, engineers, and community mobilisers. Campaigns to “build back better” have raised awareness in the communities. Local Housing Reconstruction Centres have been established for training, advice, and dissemination of earthquake-resistant technology. This decentralised approach has helped in achieving reconstruction smoothly. This paper will present the authors’ first-hand experience in the reconstruction effort, and the opportunities and unique challenges faced.

Paper P34: [Read] [Presentation]

Appropriateness of Seismic Strengthening Interventions in Heritage Buildings: A Framework for Appraisal

Alistair Cattanach, Gareth Alley and Adam Thornton

New Zealand is entering a critical era in the preservation of its heritage buildings, resulting from the Earthquake-Prone Building provisions of the Building Act 2004. Structural Engineers are often given the task of designing what they believe to be the most appropriate intervention for the building, often without necessarily having the “heritage” skills or external review specialists to aid their decisions.

The following paper suggests a framework under which the appropriateness of structural interventions may be measured. The level of performance of primary and secondary elements are discussed, as well as criteria to judge the appropriateness of each intervention into the historic fabric.

The recent upgrade of Shed 13 on Wellington Waterfront, recipient of a NZIA (Heritage) Architecture Award, is discussed as a case in point. The strengthening utilises a combination of un-bonded post-tensioning of the existing brickwork and hysteretic energy dissipaters as primary load-resisting elements.

Paper P30: [Read] [Presentation]

Performance Assessment of Existing Buildings in New Zealand

S.R. Uma, Jitendra Bothara, Rob Jury and Andrew King

Earthquake risk assessment of the New Zealand building inventory requires assessing the physical vulnerability of building assets to the required level of hazard. The lateral strength and deformation capacity of building categories differ due to various reasons including the construction vintage, material of construction and other structural characteristics. One of the biggest challenges in deriving the physical vulnerability model is to acquire an appropriate building inventory model. In this paper, the types of building structures in New Zealand are reviewed and a suitable classification scheme is proposed. The implications of code recommendations on the existing building stock are discussed to underline the inherent building characteristics with respect to the building system and the vintage of the code. Further, to obtain the lateral strength and deformation profiles of the buildings, a rational procedure is developed based on the lines suggested for Initial and Detailed Assessment Procedures recommended by a study group of the New Zealand Society for Earthquake Engineering. In this paper, fragility functions are developed for typical wooden houses, reinforced-concrete moment resisting frames and shear-wall structures, which predominantly comprise the New Zealand inventory.

Paper P45: [Read] [Presentation]

Seismic design of bridge structures with allowance for large relative girder movements to avoid pounding

Nawawi Chouw and Hong Hao

Pounding between bridge girders has been observed in almost all previous major earthquakes. This is because conventional bridge expansion joint gaps are usually only a few centimetres, which is insufficient to avoid pounding. There are often large relative displacements between bridge girders, caused by differing vibration properties of adjacent bridge spans, varying ground motions at bridge supports and varying soil-structure interaction (SSI). A new bridge expansion joint design method is introduced in this paper. Instead of tolerating pounding and providing possible mitigating measures, the proposed design approach provides for large movement between bridge girders, which entirely avoids pounding. The new expansion joint is called a Modular Expansion Joint (MEJ). Large movements are obtained by providing a number of small gaps within the joint. This study investigates the MEJ gap size required to completely avoid girder pounding. The most significant influence factors, namely the varying vibration properties of adjacent bridge spans, the effect of SSI and ground motion spatial variation on expansion joint size required to preclude pounding, are calculated. The relative importances of the various structural and ground motion properties that generate relative displacements of adjacent bridge girders are discussed.

Paper P10: [Read] [Presentation]

Effect of bearing characteristics on the response of friction pendulum base-isolated buildings under three components of earthquake excitation

Montazar Rabiei

This investigation has been conducted to examine the effect of bearing characteristics on the response of friction pendulum base-isolated buildings under three components of earthquake excitation. The structure is idealized as a three-dimensional single-story building resting on a friction pendulum bearing. The coupled differential equations of motion for the isolated system are derived and solved in the incremental form using Newmark’s step-by-step method of integration. The response of this system subjected to three components (including vertical component), two components (excluding vertical component) and single component (excluding vertical component and no interaction between orthogonal directions) of Tabas 1940 and two records of Northridge 1994 earthquakes are investigated. The effect that the vertical component of the earthquake has on the peak values of both the bearing displacement and the base shear of the isolated structure is investigated. This includes variation of the bearing characteristics, such as the isolation period and friction coefficient of the sliding surface. It is demonstrated that bearing characteristics could significantly influence the response of friction pendulum base-isolated structure subjected to three components of earthquake excitation.

Paper P17: [Read] [Presentation]

Keynote Address Session 1 Session 2 Session 3 Session 4 Session 5 Session 6 Poster Session Session 8