Principles of earthquake-resistant design

This chapter articulates general principles relied upon in the design of earthquake-resistant structures. The linear elastic oscillator subjected to the ground motion has a complicated response over time that includes many cycles of response. Inelastic response is expected in most buildings located in higher seismic zones. The distribution of strength to the components of the structural system determines whether a single mechanism is dominant over a large suite of possible ground motions, or whether different mechanisms may develop under different excitations. The load path should be viewed from both force and deformation perspectives. Load paths that require complicated deformation patterns to mobilize the forces required for static equilibrium are associated with more complex dynamic response and may not work as envisaged. Capacity design principles are used to determine the strengths of the ductile, yielding portions of the structure as it deforms in a mechanism, typically associated with a quasi-first-mode deformation pattern.