Seismic behavior of modular buildings with reinforced concrete (RC) structural walls as seismic force resisting system

Modular construction is becoming more popular worldwide due to its reduced construction time, lower construction waste, decreased on-site labor requirements, among other benefits. However, the unique structural characteristics of modular buildings, such as discrete floor diaphragms, limited connections between modules, may result in different behavior during earthquakes compared to conventional buildings. However, the seismic response of modular buildings is not well understood, and the force demand in seismic collectors (i.e., connections between modules and seismic force resisting elements) is not quantified. To address this problem, a 9-story prototype building with reinforced concrete (RC) walls was used to investigate the structural properties and responses of modular buildings. Firstly, a nonlinear numerical model was created to accurately model the RC walls, modular frames, inter-module connections, seismic collectors, and other key structural elements. Elastic modal analysis and nonlinear response history analyses were conducted to assess the building's behavior under seismic loads. Subsequently, a simplified numerical model was developed to investigate the effect of three key parameters: the stiffness of seismic collectors, RC wall strength, and earthquake intensity. It was found that modular buildings with RC walls in the center are torsional flexible. Reducing the seismic collector's rigidity can lead to greater force response in the collector. The maximum forces experienced by seismic collectors at the first floor are sensitive to earthquake intensity but not significantly affected by the RC wall strength. Both an increase in the of RC wall strength and earthquake intensity can lead to an increase in the maximum forces experienced by seismic collectors. The method in ASCE 7–16 substantially underestimated the maximum acceleration coefficients at stories below 80 % of the structural height.