Search

This paper presents the earthquake response of three low-rise frame-wall-foundation centrifuge building models, including a structural hinging-dominated, foundation rocking-dominated, and balanced design model. The models were designed such that the capacities of the dominant inelastic elements varied; however, each was subjected to a similar sequence of earthquake shaking in a 30-g centrifuge environment to facilitate comparison. Experimental results reveal that the traditional frame-wall building with a strong foundation (i.e., a hinging-dominated system) has the least potential to recover from displacements induced during earthquake shaking. As a result, this system suffered the most significant residual deformation. In contrast, systems with rocking foundations sustained a smaller peak roof acceleration, residual drift, and peak base shear despite the relatively larger peak transient drift demand. Consistent with slow cyclic test results, dissipated hysteretic energy was reasonably distributed amongst superstructure and substructure inelastic components in the balanced model during moderate and high intensity shaking. [ABSTRACT FROM AUTHOR]

The mechanism of foundation rocking has received much attention recently due to its appealing seismic resistant features, namely, self-centering tendency and energy dissipation capability. It is well recognized, however, that other inelastic mechanisms will contribute to a system's seismic resistance. Considering the strength difference between a rocking footing and a shear wall structural fuse, and the system symmetry, six different two-story-two-bay frame-wall-foundation building models were constructed and tested in a geotechnical centrifuge. In this paper, the test program and experimental results when the models were subjected to slow cyclic loading are presented. A companion paper presents results from the dynamic phase of testing. Results indicate that, with the aid of foundation rocking, the system behaves in a ductile and stable manner with no strength degradation, even when the model is pushed to a drift of more than 2.5%. Importantly, when structural and foundation component strengths are approximately equal, the hysteretic energy is reasonably distributed among the superstructure inelastic components and the rocking foundations. Finally, numerical analyses predictions demonstrate comparable local and global response to measurements obtained during the experiments. [ABSTRACT FROM AUTHOR]

Two geotechnical centrifuge tests were designed to elicit the influence of soil-foundation-structure interaction (SFSI) and structure-soil-structure interaction (SSSI) effects on the seismic demands of an inelastic frame structure founded on individual spread footings. Four experimental cases were considered: (1) SFSI of an individual inelastic frame structure (baseline case); (2) in-plane SSSI between the frame structure and a large elastic wall structure designed to respond predominately in a rocking mode; (3) anti-plane SSSI between the frame and wall structures; and (4) combined in-plane and anti-plane SSSI between the frame structure and two wall structures. Results from Cases 1, 2, and 4 are analyzed considering 13 demand parameters. The peak seismic demands from the baseline case are compared to the peak demands from the SSSI cases to elicit the impacts of building adjacency. The number of earthquake motions that resulted in increases or decreases in the seismic demands in the frame structure are tracked for the SSSI cases. For these tests, SSSI consistently results in increased peak foundation moment and foundation base shear demands, regardless of the geometric layout of the structures. These increases propagate throughout the superstructure, resulting in increases in moment, shear and curvature ductility demands in the structural components. SSSI effects are observed to be most significant for low-to-moderate intensity earthquake motions, suggesting that particular consideration should be given to the likelihood of SSSI for highly probable earthquakes. [ABSTRACT FROM AUTHOR]