Question

List two ways that performance-based design fundamentally varies from the capacity-based design approach.

Answer 1

Performance-based design is a major shift from traditional structural design concepts and represents the future of earthquake engineering. Rather than focusing on strength and stress, this approach addresses how to accommodate the displacement demands imposed by earthquake motions so that bridge structures can remain operational or repairable after a major seismic event. Capacity design concepts using energy dissipation and ductility are used to determine and control acceptable levels of earthquake damage. Pre-planned yielding of certain members of a structure during an earthquake does not necessarily constitute failure but can actually help to save the rest of the structure. Special devices, such as dampers and sliders, can also be used to dissipate energy and allow larger displacements with smaller forces.