Development of a Reduced-order Simulation Model for the Nonlinear Response Analysis of a Large-scale Laminar Soil Box Experimental System
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Authors
Ghimire, Pratibha
Issue Date
2024
Type
Thesis
Language
Keywords
Acceleration Response Spectrum , Laminar Soil Box , Nonlinear Response Analysis , Reduced Order Model , Shake Table , Soil Structure Interaction
Alternative Title
Abstract
The stability of major structures is influenced by the properties of the soil on which the structure is founded. During earthquake shaking, soil deforms and transfers the vibrations to the supported structure. Consequently, the structure is displaced, and induced forces are transferred back into the soil through the foundation. These forces will affect the displacement of the soil, which will, in turn, modify the structure's vibration. This two-way relationship between soil and structure is referred to as Soil-Structure Interaction (SSI) and is not comprehensively addressed by most structural design codes. However, past earthquakes have demonstrated that SSI effects can influence structural damage. Critical infrastructures such as nuclear plants, large buildings, bridges, underground pipes, and tunnels are more vulnerable, and SSI should be considered for their design. A comprehensive understanding of SSI effects must be informed by observations of actual system performance. However, field installations of sensors along with their data acquisition systems to obtain detailed data on SSI during extreme events is challenging. To overcome this challenge, researchers have been using shake tables to conduct SSI tests. This type of tests provides a method for investigating the coupled soil and structure system using representative earthquake ground motions under carefully controlled conditions. Shake table testing can provide substantial data to analyze the soil and structure behavior in the laboratory, which can inform future design methodologies. The University of Nevada, Reno, has recently developed a unique experimental capability by designing and commissioning the largest soil box in the nation along with its dedicated shake table. This experimental apparatus is capable of fully controlled large-scale experiments that can be used to study SSI in the laboratory under various soil conditions, structure types, and ground motions. The study described herein focuses on developing a reduced-order computational model and comparing its output to the experimentally collected data for the same laminar soil box experiment. A 1-D soil column was developed in SAP2000. The compacted soil in the soil box was represented as a 1-D Timoshenko beam model. This model can provide an essential and efficient tool for capturing the response of the soil box. The model was developed to represent the nonlinear response behavior of the soil box system through continuous updating of the model shear modulus and damping ratios based on the effective strain of the soil. Through comparison with soil box response data from carefully controlled soil box system commissioning tests, the reduced order model was demonstrated to be capable of capturing the dynamic behavior of the overall soil box, including both low-amplitude linear vibrations and high-amplitude nonlinear response.