Dynamic Soil-Structure-Interaction Analysis of Structures in Dense Urban Environments

A series of centrifuge experiments were performed at which examined aspects of soil-structure interaction (SSI) or structure-soil-structure interaction (SSSI) through the use of nonlinear structural model buildings situated on different foundations that were supported on deep sand deposits. The centrifuge experiments created a suite of small-scale physical model "case histories" that provided "data" and insight that could be extended through calibrated numerical simulations. The results of the first three centrifuge experiments in the test series (i.e., Test-1, Test-2, and Test-3) were utilized in this dissertation.;Test-1 and Test-2 examined SSI and SSSI effects of two moment-resisting frames (MRFs). Test-1 employed a solitary 3-story (prototype) MRF founded on shallow spread footings and a solitary 9-story (prototype) MRF founded on a deep basement (equivalent to 3-stories, prototype) to investigate SSI effects. In Test-2, the 3-story (prototype) and 9-story (prototype) MRFs were placed immediately adjacent to one another to examine SSSI effects. Kinematic interaction effects were primarily observed in these tests. Hence, Test-3 was designed to investigate inertial interaction effects. Three structures were included in Test-3: two MRFs founded on shallow spread footings and one elastic shear-wall structure on a mat foundation. Each of these structures was designed to maximize inertial interaction by: (1) matching the flexible base period of each structure to the soil column to induce resonance, and (2) optimizing structural properties to increase inertial interaction effects. One MRF was positioned alone at one end of the centrifuge model, a SSI condition, and the other MRF and the elastic shear-wall structure were positioned immediately adjacent to each other in the other end of the centrifuge model, a SSSI condition.;The rich data set developed through the centrifuge experiments formed the basis of the initial FLAC analyses. A critical aspect of any seismic analysis is the constitutive model used to capture the soil response to cyclic loading. Several soil models were examined during an initial seismic site response analysis. Free-field data from sensors located within the centrifuge soil column were used to quantify the vertical propagation of ground motions through the soil profile. T.;After successfully capturing the free-field seismic site responses of Test-1 and Test-2, the dynamic responses of the structural models were examined. Each structure was modeled satisfactorily with a two-dimensional, plane-strain numerical model. Engineering design parameters (EDPs) were computed for key structural responses, including (1) transient peak roof drift, (2) residual roof drift, (3) transient peak displacement and (4) peak acceleration at the center of mass of the structure. Additionally, the acceleration time histories and pseudo-acceleration response spectra at the center of mass of the structure for each motion were examined. These metrics were used to compare the numerically estimated dynamic responses with those recorded in the centrifuge experiments. The dynamic response of the 3-story (prototype) MRF estimated with the numerical model was in close agreement with the observed experimental data for both the SSI (Test-1) and SSSI (Test-2) configurations. The more complicated 9-story (prototype) model exhibited greater sensitivity to numerical system inputs, including fixed-base fundamental period and applied structural Rayleigh damping.;Finally, two prototypical structures were examined. The first, a 3-story MRF, was the model upon which the centrifuge 3-story (prototype) model was based (Ganuza, 2006). Both solitary (SSI) and adjacent (SSSI) configurations were considered for this prototypical 3-story MRF founded on a dense sand soil column. The dynamic responses of the MRF for the solitary (SSI) condition paralleled those observed in the centrifuge experiments. For the considered configurations of adjacent low-rise structures, SSSI effects were found to be either negligible or only slightly beneficial or detrimental for the five ground motions utilized for dynamic analysis. The other prototypical MRF, a 5-story structure, was a simplified version of a typical, medium-rise structure (Ganuza, 2006). The 5-story MRF exhibited dynamic responses consistent with previous work. Amplification was observed at (1) the first and second modes of vibration of the structure, (2) the site period, and (3) the mean period of the motion. Further research is needed to study and more fully quantify SSSI effects for a wider set of structures, adjacent configurations, and ground motions. (Abstract shortened by UMI.).