| Our understanding of dynamic soil-foundation-structure-interaction (SFSI) in relation to the earthquake response of structural systems is lacking. Though many numerical models are available, the case histories and physical models required to assess these numerical models are few. Typically, case histories from earthquakes lack the detailed instrumentation required to develop a full understanding of the SFSI behavior. Physical modeling has generally focused on very small-scale centrifuge models, making it difficult to scale the results up to the prototype, particularly with regard to nonlinear behavior of structure. To overcome these deficiencies in our physical modeling, this research aimed at the development and validation of the use of a large laminar container for use on a shake table to better model dynamic SFSI.; The 4m long by 2m wide by 2m high laminar container was first tested on the shake table with dry Nevada sand alone, in order to verify the container could accurately model free-field conditions. The results of this first phase of testing showed that the boundary effects were limited to a zone within approximately 25% of the container height from the end-walls. The middle 3m of the container showed relatively uniform motions that could be predicted with either a simple 1-D site response analysis utilizing sand properties under low confining stress, as well as 2-D finite element analyses utilizing a more sophisticated multi-yield surface constitutive model.; A series of tests were then performed to study SFSI using a 1/9-scale model of a pile group supporting a reinforced concrete bridge column excited by a variety of motions. The piles were modeled using aluminum, whereas the column was constructed of reinforced concrete. The test results showed that the horizontal stiffness of the foundation decreased with increasing levels of excitation, while the rotational stiffness remained constant, indicating the effect of gapping around the pile cap on the horizontal stiffness. The response of the soil, foundation, and structure were then modeled successfully using the finite element method, showing that the laminar container developed as part of this study was a viable means of physically modeling SFSI at large scale. |
