When creating a commercial building, designers have the option of designing a structure to behave elastically or inelastically (a ductile response). Elastically designed structures are stiffer and return to their original position with close to no damage following a design-level earthquake. Ductile structures have the ability to plastically deform within limits set by the Building Code. They may not necessarily return to their original position following a large earthquake.
One option is to design an elastic structure that, when subjected to seismic forces, its deflection will be small enough that non-structural components of the building envelope are not damaged. However, in practice, it can be impractical to build a structure with this degree of stiffness, so designers usually turn to a ductile response as a more feasible solution.
However, ductile structures can undergo significant lateral deflection during an earthquake, and the connections between the frame and building envelope typically require more careful detailing to accommodate the differences in horizontal deflection.
In this section: