ASCE/SEI 41 assessment of reinforced concrete buildings: Benchmarking linear procedures and FEMA P-2018 with empirical damage observations

Abstract

The US consensus standard for seismic evaluation and retrofit of existing buildings, ASCE/SEI 41, establishes provisions for seismic analysis procedures that vary in complexity and fidelity. Although ASCE/SEI 41 provides detailed nonlinear dynamic procedures, most engineers rely on simpler methods to evaluate building seismic performance and retrofit, particularly the ASCE/SEI 41 linear procedures and, more recently, the FEMA P-2018 methodology for evaluating collapse potential. Under ideal conditions, these procedures identify similar structural deficiencies. However, evaluation outcomes in practice may differ due to the complexity of real building response, approximations used in modeling and analysis, and level of intentional conservativism that reflects the limitations of the procedures. To quantify these differences, this study considers six reinforced concrete buildings that sustained damage in real earthquakes or in shake table tests and compares the performance assessed by the ASCE/SEI 41 linear and nonlinear dynamic procedures, as well as the FEMA P-2018 seismic evaluation methodology. The results show that for these highly damaged buildings, the overall performance level estimated from the ASCE/SEI 41 linear procedures is consistent with observed damage. In general, the procedures also correctly identify the story with the most damage and the component failure mode. However, the ASCE/SEI 41 linear procedure generally underpredicts drift response and greatly overpredicts peak floor accelerations. Though these are not directly used to evaluate structural performance, they are related to component deformation and force demands, respectively. Moreover, the linear procedures predict damage in components that would be precluded by yielding or failure of other components in the load path. Results from the FEMA P-2018 methodology for the six buildings provide more distinction between buildings than the ASCE/SEI 41 Collapse Prevention performance level. The results also suggest the FEMA P-2018 limit-state mechanism analysis can provide supplemental information to support and improve the ASCE/SEI 41 linear procedures.