Virtual Shake Robot: Dynamics Simulation of Precariously Balanced Rocks for Hazard Analysis

Zhiang Chen, Devin Keating, Jnaneshwar Das, Christine Wittich, & Ramon Arrowsmith

Submitted August 11, 2021, SCEC Contribution #11255, 2021 SCEC Annual Meeting Poster #021

Physical shake tables have been used to study fragility of Precariously Balanced Rocks (PBRs) and other structures. These analyses are critical to reduce uncertainties in probabilistic seismic hazard analysis (PSHA) models. With recent developments in robotics, simulation tools with high-accuracy particle dynamics have been developed for industrial and aerospace testing. By utilizing these simulation tools, we constructed a virtual shake robot to rapidly prototype PBR-pedestal models and study PBR dynamics. The virtual shake robot was modeled in Gazebo simulator with Bullet physics engine and manipulated by the Robot Operating System (ROS). Bullet provides high-accuracy dynamics computation for arbitrarily shaped rigid bodies with elastic interactions and frictional contacts. The integrated ROS-Gazebo ecosystem brings advantages for conveniently configuring physics parameters, controlling the ground motion, and monitoring the pedestal and PBR states. We tested the virtual shake robot with a PBR instance at Double Rock, CA. A 3D mesh model of the PBR and site was produced by structure from motion using unpiloted aircraft imagery. The 3D mesh mode of the PBR was isolated and imported to the virtual shake robot. Repeated simulations were automated to investigate the PBR responses with respect to a set of unidirectional, sinusoidal ground motions (a linear mesh of PGV/PGA and PGA sets). We were also able to conduct parallel simulations with different initial PBR orientations to study anisotropy of fragility using OpenUAV cloud containers. Apart from PBR fragility, the virtual shake robot also enables the studies of PBR large displacements by monitoring the toppling PBR trajectory. Large displacement of PBRs, which has not been considered in PSHA models, should be able to better refine the model validation by examining longer term PBR fate.

Citation
Chen, Z., Keating, D., Das, J., Wittich, C., & Arrowsmith, R. (2021, 08). Virtual Shake Robot: Dynamics Simulation of Precariously Balanced Rocks for Hazard Analysis . Poster Presentation at 2021 SCEC Annual Meeting.


Related Projects & Working Groups
Computational Science (CS)