Seismic vulnerability of moment-resisting frame buildings accounting for the variability of the mechanical properties of concrete and steel

Abstract

Moment-resisting frames are one of the most widely used structural systems in building construction. This system is popular due to its ability to withstand lateral loads, such as winds and earthquakes, and because they have shown suitable performance in past earthquakes. Errors in concrete mixing, or improper handling of the material can adversely affect the structure’s ability to withstand forces, thus it becomes important to investigate how the variability of the mechanical properties of the material affects the safety of the building. This research analyzes the effect of epistemic uncertainty of the properties of concrete and steel on the seismic response of a 14-story building located in Colombia. The probability of the maximum inter-story drift exceeding limits varying between slight damage and collapse was quantified using 300 different nonlinear models in OpenSeesPy subjected to the far-field ground motion suite of FEMA P-695. The material properties for each model were obtained using a probability density function, whose mean value corresponds to the design values of f’c and fy, and the dispersion was obtained from experimental data available for the country. The results show that the collapse probability can be up to 4.5%, depending on the material characteristics, with the steel yielding strength exerting a greater influence. In contrast, the compressive concrete strength had a greater influence on the probability of slight damage, varying between 22% and 36%. Overall, the results demonstrate that the variability of the mechanical properties of concrete and steel exerts a significant influence on the seismic vulnerability of the structure.