An Optimization Methodology For Modular Structural Systems

The work proposes an optimization methodology for the design of bracing systems in modular buildings located in seismic areas. According to this, modular building components should be designed to ensure that the assembled building delivers targeted performance levels across diverse operational scenarios. The methodology is formulated as a constrained mathematical optimization problem, where the independent variables are the in-plane stiffnesses of the bracing systems’ modular components. The objective function, called Working Index (WI), quantifies the number of scenarios in which both inter-story drift and base shear limits are simultaneously satisfied. These threshold values are defined a priori in the problem setup to guarantee adequate structural performance and foundation cost control. The two performance indicators are evaluated through explicit functions: inter-story drift is estimated using a simplified expression based on the displacement response of a single degree of freedom (SDOF) oscillator representing the building, while base shear is computed from the pseudo-acceleration response spectrum, considering the seismic mass of the system. Scenarios are defined by combining different geometric configurations of modular buildings with various levels of seismic action, represented by combinations of PGA values and soil coefficients. For each set of independent variables, inter-story drift and base shear are calculated, and the corresponding WI is evaluated. The optimization process is solved using a random search technique implemented in a MATLAB script. Several case studies are finally considered, to show the effectiveness of the proposed approach. In fact, the results confirm that optimized components allow for higher WI values compared to non-optimized ones.