Browsing by Author "Phillips, Adam Richard"

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    Large-Scale Cyclic Testing and Development of Ring Shaped - Steel Plate Shear Walls for Improved Seismic Performance of Buildings
    Phillips, Adam Richard (Virginia Tech, 2016-11-28)
    A novel shear wall system for building structures has been developed that improves upon the performance of conventional steel plate shear walls by mitigating buckling. The new structural system, called the Ring Shaped - Steel Plate Shear Wall, was investigated and developed through experimental and computational methods. First, the plastic mechanism of the system was numerically derived and then analytically validated with finite element analyses. Next, five large-scale, quasi-static, cyclic experimental tests were conducted in the Thomas M. Murray Structures Laboratory at Virginia Tech. The large-scale experiments validated the system performance and provided data on the boundary frame forces, infill panel shear deformation modes, buckling mode shapes, and buckling magnitudes. Multiple computational modeling techniques were employed to reproduce different facets of the system behavior. First, detailed finite element models were constructed to accurately reproduce the cyclic performance, yielding pattern, and buckling mode shapes. The refined finite element models were utilized to further study the boundary element forces and ultra-low cycle fatigue behavior of the system. Second, reduced-order computational models were constructed that can accurately reproduce the hysteretic performance of the web plates. The reduced-order models were then utilized to study the nonlinear response history behavior of four prototype building structures using Ring Shaped - Steel Plate Shear Walls and conventional steel plate shear walls. The nonlinear response history analyses investigated the application of the system to a short period and a long period building configuration. In total 176 nonlinear response history analyses were conducted and statistically analyzed. Lastly, a practical design methodology for the Ring Shaped - Steel Plate Shear Wall web plates was presented. The experimental tests and computational simulations reported in this dissertation demonstrate that Ring Shaped - Steel Plate Shear Walls are capable of improving seismic performance of buildings by drastically reducing buckling and improving cyclic energy dissipation.
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    Seismic Performance and Damage Risk of Modular CLT Housing Using Nonlinear Time History Analysis
    Chininin, Javier Andres (Virginia Tech, 2025-01-10)
    The United States (U.S.) faces significant housing challenges, including a shortage of affordable housing and high rates of homelessness. This, combined with the pursuit of sustainable and resilient communities, has positioned Cross-Laminated Timber (CLT) modular structures as a promising alternative due to their environmental, mechanical, and prefabrication advantages. However, a comprehensive study of their seismic performance and risk across the U.S. is needed to establish CLT modular construction as a resilient housing option. Therefore, this thesis assesses the seismic risk and performance of five modular CLT houses, studying (i) the variability of their collapse fragility curves across the U.S., (ii) the conditional probability of collapse under Maximum Considered Earthquake (MCE) intensities, and (iii) the unconditional probabilities of experiencing non-structural damage and collapse within 50 years for ten representative locations. The houses use the latest platform-constructed CLT shear wall lateral-force resisting system included in ASCE 7-22 (2022) and were designed using prescriptive code-based methods to represent a feasible construction alternative. The analyses were conducted under the performance-based earthquake engineering framework. Ground motion data sets were established for three seismic regions: (1) Western U.S. with forward-directivity pulses, (2) Western U.S. without forward-directivity pulses, and (3) Central and Eastern U.S. Numerical models for each house were developed and calibrated using OpenSees to perform nonlinear static and time history analyses. The Multiple Stripe Analysis procedure was used to derive the conditional probability of collapse fragility curves and interstory drift distributions, which, along with generic damage fragilities and seismic hazard curves, estimated the probabilities of non-structural damage and collapse within 50 years at representative locations. The results indicate that differences in ground motion characteristics, including pulse-like motions, do not significantly impact the collapse fragility curves. All houses satisfy the ASCE 7-22 (2022) target of a 10% conditional probability of collapse at MCE intensity. Expected non-structural damage is within acceptable limits compared to common performance objectives. Increasing house strength does not significantly enhance performance in non-structural damage states, as performance is primarily influenced by the hazard curve of the location. The unconditional probability of collapse within 50 years remains conservatively low, satisfying the ASCE 7-22 (2022) performance objective of a 1% probability of collapse within 50 years. In summary, the consistent behavior, low collapse risk, acceptable non-structural damage levels, and potential improvements through performance-based design make modular CLT houses a reliable, resilient, and high-performance seismic housing alternative in the U.S.