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Keynote Presentations

Problems with Seismic Design Based on Elastic Stiffness

M.J.N. Priestley

ABSTRACT: Compared to its small population, New Zealand has had a disproportionate influence internationally on seismic design philosophy. It will be shown that many of the contributions of different New Zealanders to understanding seismic performance have been at least related to problems perceived in the consequences of designing structures based on elastic stiffness estimates.

[Paper 243]

Chile 27 F: Lessons and Future Challenges

E. Ríos

ABSTRACT: The earthquake and tsunami that affected the mid-south of Chile on 27 February 2010, along with the deep economical and social impact, left evidence of the fragility of the protection systems to face this kind of natural catastrophe and a series of imperfections in the functioning of the insurance market, that when summed up tend to position Chile at a relatively low level of development in this matter. This presentation reviews, in a brief manner, the principal lessons that this tragic event left us, the measures that, up to this date, this authority has taken to deal with some of the observed problems and the options that are being evaluated to strengthen the administration and protection system for this kind of catastrophic risk. Although the problems are faced from the experience and vision of the insurance regulator, focusing on the problems and improvements that this industry requires, it also lays out topics that go further beyond this sector and that we hope represent an agenda to be studied in Chile in the near future.

[Paper 242]

Performance-Based Seismic Design in the United States

Robin K. McGuire

ABSTRACT: Performance-based seismic design is being used in the United States as a way to determine and justify seismic ground motion levels for design. Applications for the seismic design of nuclear power plants indicate that current design requirements lead to seismic core damage frequencies that are lower (safer) than those of existing plants by a substantial margin. Applications for the seismic design of commercial buildings indicate that a target collapse probability of 1% in 50 years is met. However, probabilities of lower levels of seismic damage to commercial buildings may be relatively high and would benefit from explicit evaluation and management in the design process.

[Paper 240]

Human Casualties in Earthquakes: Modelling and Mitigation

R.J.S. Spence & E.K.M. So

ABSTRACT: Earthquake risk modelling is needed for the planning of post-event emergency operations, for the development of insurance schemes, for the planning of mitigation measures in the existing building stock and for the development of appropriate building regulations; in all these applications estimates of casualty numbers are essential. But there are many questions about casualty estimation which are still poorly understood. These questions relate to the causes and nature of the injuries and deaths, and the extent to which they can be quantified. This paper looks at the evidence on these questions from recent studies. It then reviews casualty estimation models available, and finally compares the performance of some casualty models in making rapid post-event casualty estimates in recent earthquakes.

[Paper 224]

The AISC 2010 Seismic Provisions for Composite Structures: Towards an Application of PBD Principles for Connection Design

R.T. Leon & J.W. Hu

ABSTRACT: The 2010 AISC Seismic Design provisions represent a major change for composite structures for at least two reasons. First, the provisions for composite structures have been folded into a single document with those for steel; the net result, at least superficially, is that composite construction is considered equivalent to steel in quality and performance. Second, the provisions for composite members and structural systems have become more prescriptive in an attempt to ensure a minimum level of performance. An unintended consequence of this latter item is that some freedom in the introduction of innovative composite connections has been removed. In this paper, a short review of the AISC composite provisions will be given, and a case study on the development of an innovative connection will be described. A refined finite element model was developed to conduct numerical experiments on the proposed joints to obtain the global behaviour of the connection and develop simplified models. Very good agreement was found between the simple and sophisticated models for strength, stiffness and energy dissipation capacity, verifying the robustness of the approach. The paper argues that careful analytical studies can replace the requirement for physical testing present in current steel codes.

[Paper 241]