Application of reliability-based robustness assessment of steel moment resisting frame structures under post-mainshock cascading events

This paper proposes a reliability-based framework for quantifying structural robustness considering the occurrence of a major earthquake (mainshock) and subsequent cascading hazard events, such as aftershocks that are triggered by the mainshock. These events can significantly increase the probability of failure of buildings, especially for structures that are damaged during the mainshock. The application of the proposed framework is exemplified through three numerical case studies. The case studies correspond to three SAC steel moment frame buildings of three, nine, and 20 stories, which were designed to pre-Northridge codes and standards. Two-dimensional nonlinear finite-element models of the buildings are developed with the Open System for Earthquake Engineering Simulation framework (OpenSees), using a finite length plastic hinge beam model and a bilinear constitutive law with deterioration, and are subjected to multiple mainshock-aftershock seismic sequences. For the three buildings analyzed herein, it is shown that the structural reliability under a single seismic event can be significantly different from that under a sequence of seismic events. The reliability based robustness indicator shows that the structural robustness is influenced by the extent to which a structure can distribute damage

Topology design of optimizing material arrangements of beam-to-column connection frames with maximal stiffness

AbstractThis study presents conceptually effective layouts of materials, i.e. steel or fiber, optimally positioned into building frames. The design information of the material layout may be helpful in dealing with large-scale safety design issues in civil or architectural engineering fields, against natural phenomena, such as winds and earthquakes. The material topology optimization method evaluates an optimal layout reinforcing or arranging material of a specified volume in a given design space that maximizes stiffness for a given set of loads and boundary conditions. Generating the optimal distribution of material is similar to the so-called strut-and-tie method using truss members of straight lines, and it leads to the stiffest structures. Numerical applications verify that the present material topology optimization method is an applicable concept design tool to create effective layout designs of material in given structural frames in civil and building industries