Influence of Ground Rotations on the Seismic Response of Building Structures
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Authors
Aryal, Rajan
Issue Date
2023
Type
Thesis
Language
Keywords
Alternative Title
Abstract
Despite being studied for over four decades, seismic design codes still fail to incorporate ground rotations in analysis and design. The primary reason is the currently installed accelerometers' inability to measure ground rotation. In addition, installing sensors to measure ground rotations on a large scale is not feasible anytime soon. So, researchers have relied on indirect methods to derive rotational motions from translational records such as single station, multiple station procedures, and so on. However, these methods are unreliable during near-field events where the instruments can themselves rotate. This paper utilizes the application of high-performance computing (HPC) to extract ground rotations in light of these shortcomings. Due to recent advancements in HPC, the simulation of strong near-field events with high accuracy and high-frequency resolution is possible. This paper implements the newly developed Earthquake Simulation (EQSIM) fault-to-structure framework that uses an emerging GPU-based exascale computer platform. The simulation workflow consists of two steps. Initially, a 3D geophysical model representing a large domain of earth is developed, and the model is analyzed in SW4 fourth-order wave propagation code for two earthquake scenarios, Strike-slip and Reverse-thrust. Then, the ground motions extracted from the first step, including the rotational motion, are used to drive the engineering model of fixed-base and soil-structure interaction systems (SSI) through Domain Reduction Method (DRM). For this purpose, four canonical steel moment frame structures of 3-, 9-,20-, and 40-story are modeled in OpenSees. Finally, nonlinear time history analyses are performed to study the effect of ground rotation on the response of the considered structures. Results indicate that the ground rotations can significantly increase the buildings' inter-story drifts, producing additional amplification when SSI is included. The impact of ground rotation is dictated by the fundamental natural frequency of the building along with the frequency and phase content of input motions.