Analysis to Light-Frame Wood Residential Buildings
Seismic design of buildings has its basis in a combination of (1) empirical knowledge (observational and measured data) and (2) engineering analysis. The experience accumulated from seismic events and large-scale tests provides confidence in engineering models and serves to establish acceptable levels of risk for code compliance.
The design philosophy underpinning the current seismic building code requirements is focused on the objective of life safety at the Maximum Considered Earthquake (MCE) ground motion level which corresponds to a 2% probability of exceedance in 50 years. It is expected that an MCE event will cause inelastic deformations in the seismic force-resisting system, but the structure will remain stable with a low probability of collapse. The inelastic deformations cause damage to the seismic force-resisting system but also provide a mechanism for the structure to control seismic forces – an engineering strategy for economical earthquake-resistant systems.
This design philosophy is implemented in engineering standards through the use of seismic performance factors (SPFs) which modify the elastic forces and deformations determined in accordance with Newton‘s second law of motion. These modified forces and deformations are intended to represent the nonlinear response of a building system. The SPFs established in ASCE/SEI 7-10 (ASCE 7) Minimum Design Loads for Buildings and Other Structures are based on performance observations and engineering knowledge and judgment.
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