DESIGN CRITERIA AND LOADS
Graham L. Hutchinson, Nelson T. K. Lam and John L. Wilson
This paper has provided an overview of both the philosophy and methods used in the design and analysis of building structures to earthquake ground shaking. In particular, the following topics and issues were discussed : (a) seismic hazard and soil response modelling, (b) aseismic design methods, (c) design and detailing of structural systems and (d) future directions for seismic design.
seismic hazard, soil response modelling, aseismic design methods, structural systems, passive damping, ductility, earthquake engineering, tall buildings.
In seismically active areas of the world design engineers are faced with a dilemma of being required to design for an earthquake event which has a high probability of not occurring during the life of the facility. The engineer has many choices between the bounds of designing the structure to remain elastic during a rare event and totally ignoring the hazard thus possibly leaving themselves open to charges of negligence.
To overcome this problem the concept of a dual design philosophy was introduced. This philosophy involved designing for a damageability limit state (an event that has, say, a 50% chance of being exceeded during the design life of the structure) and an ultimate limit state event (where there is a 10% chance of exceedance). The design philosophy associated with the ultimate event is based on the preservation of life. Following a number of significant earthquakes in the past 15 years which caused extensive damage and costly dislocations to the function of large cities this philosophy has been revised. A new philosophy incorporating performance based design concepts has been developed and is gaining acceptance for inclusion in modern building standards (SEAOC, 2000; FEMA273, 1997).