Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
The research in this dissertation was conducted with the primary aim of understanding the seismic response of unbonded post-tensioned precast concrete rocking walls both with and without additional hysteretic energy dissipaters. These wall systems dissipate the seismic input energy mainly through impacts of the wall on top of the foundation during rocking as well as the external hysteretic damping. The behavior of these walls are largely investigated based on experimental tests using quasi-static loading and few numerical studies. A systematic seismic design approach for their application in high seismic regions is still lacking. To date, there are limited large-scale studies that have evaluated the lateral response of these rocking walls using earthquake ground motions of different intensities and there is little published data on quantification of their different energy dissipation components.
To address the main objective of overcoming the aforementioned limitations, a series of large-scale experimental shake table tests were conducted on four unbonded post-tensioned precast Single Rocking Walls (SRWs) and four Precast Wall with End Columns (PreWEC) systems by subjecting them to a set of earthquake excitations with varying intensities. These walls were designed by varying key design parameters such as: (i) the initial prestress force, Pi, (ii) base moment to base shear ratio, and (iii) the number and location of additional hysteretic dampers in PreWECs, namely O-connectors.
Minimal wall base damage was observed as these wall systems were subjected to the design-level ground motions. As intended, all walls provided the self-centering behavior during ground motions of different intensities and the additional O-connectors started to yield and dissipate the seismic energy at 0.6% wall drifts. The rocking wall tests generally indicated the satisfactorily seismic performance of SRWs and PreWECs in terms of the lateral drift, absolute acceleration, and residual drift during design-level and greater earthquakes; however it was found that walls with reduced resistance responded beyond the allowable limits during such strong ground motions. Further studies were experimentally conducted to evaluate equivalent viscous damping ratios of SRWs and PreWECs and apply them to achieve desirable seismic design forces that ensure their promising seismic response. Participation of different damping components of the walls with and without external hysteretic dampers in energy dissipation of the system was also evaluated. The results revealed the potential of SRWs to remove a part of the seismic energy and dissipate the rest relying on their limited damping capacity. It was highlighted that the additional hysteretic damping provided in PreWECs reduced the maximum drift and decay of the response.
An investigation was performed using a simplified single degree of freedom analytical model to emulate the seismic response of SRWs and PreWECs. The nonlinear dynamic analysis results calculated from this model were then verified using the shake table test results.
Lastly, the seismic forces recommended for the design of rocking walls with different damping ratios, as prescribed in the preliminary stages of this research, were validated by conducting an extensive numerically based case-study. For this purpose, six, nine, and twelve story buildings were designed using SRWs and PreWECs and the responses were evaluated during a set of near-field and far-field ground motions scaled to represent design-level and maximum considered events. In addition to an excellent performance of both systems designed following the recommendations of this dissertation, PreWECs were shown to be the most economical rocking wall solution for the design of these seismic-resilient buildings.
Nazari, Maryam, "Seismic performance of unbonded post-tensioned precast wall systems subjected to shake table testing" (2016). Graduate Theses and Dissertations. 15778.