Seismic Performance of Tall Steel Framed Buildings Built Between 1960-1994

The 1994 Northridge, California earthquake demonstrated the potential vulnerability of older tall steel-framed buildings to large earthquakes. This paper will focus on the seismic performance of many tall steel framed structures in San Francisco designed between 1960 and 1990. The paper will discuss how the structural design and detailing of these buildings evolved due to changes in construction technology, architectural considerations, engineering design techniques, and analysis software. Detailed modeling techniques used to simulate the potential for fracture of both the welded beam-to-column connections and the partial joint penetration column splices will also be presented. Evaluation of the results clearly demonstrated that it is difficult, if not impossible, to draw broad conclusions about the seismic performance of this entire class of buildings. However, these detailed evaluations allowed for comparison between the different seismic performance features and provide the ability to make some observations about individual building performance characteristics.