Overview

Charles W. Roeder, Ph.D., P.E.

Professor of Civil Engineering
University of Washington
Seattle, Washington

Design of buildings for lateral forces requires a greater understanding of the load mechanism than many other aspects of structural design. To fulfill this need, this section provides a basic overview of current practice in seismic and wind design. It also discusses recent changes in design provisions and recent developments that will have an impact on future design.

There are fundamental differences between design methods for wind and earthquake loading. Wind-loading design is concerned with safety, but occupant comfort and serviceability is a dominant concern. Wind loading does not require any greater understanding of structural behavior beyond that required for gravity and other loading, although it is noted that complex, large, or aerodynamically sensitive structures frequently require wind-tunnel testing or more sophisticated dynamic analysis to assure occupant comfort during wind storms. As a result, the primary emphasis of the treatment of wind loading in this chapter is on the loading and the distribution of loading.

Design for seismic loading also is primarily concerned with structural safety during major earthquakes, but increasing emphasis is placed on economic loss and serviceability through performance-based design. These different design goals are achieved by permitting a range of different structural performance levels. During large infrequent seismic events, collapse prevention and life-safety performance limits are economically achieved by permitting large but controlled inelastic deformations of the structure. Inelastic deformation of the structure during severe earthquakes results in more detailed structural design...