Poster Presentations:
PhD Student Oregon State University
Project Overview and Finite-Element modeling of a Full-Scale Six-Story Hybrid Mass Timber and Steel Building Subjected to Shake Table Motions
Co-Authors: Andre Barbosa (Oregon State University), Arijit Sinha (Oregon State University), Steve Pryor (Simpson Strong-Tie), Patricio Uarac (StructureCraft), John W. van de Lindt (Colorado State University), and Barbara Simpson (Stanford University)
Abstract: The Natural Hazards Engineering Research Infrastructure (NHERI) Converging Design project is a multi-objective, multi-phase collaboration between Oregon State University, Colorado State University, Stanford University, and Penn State University with the goal of developing a new design paradigm in structural engineering. As part of the Converging Design project a full-scale, six-story mass timber building was constructed and tested in three phases at the University of California, San Diego Large High-Performance Outdoor Shake Table. Phase One tested mass timber self-centering rocking walls with cross-laminated timber and mass-ply panels (MPP), distributed energy dissipation provided using U-shaped flexural plates, and post-tensioned threaded steel rods for re-centering. Phase Two replaced the distributed energy dissipation MPP walls with an MPP wall with buckling-restrained boundary elements for providing energy dissipation concentrated across the first story. Phase Three removed the MPP walls again and replaced it with a steel moment frame/concentrically braced frame with yield-link brace connections for energy dissipation and a frame system including yield-link moment connections designed to provide restoring forces.
Besides providing an overview of the project, this presentation will focus on the development of a post-test three-dimensional OpenSeesPy numerical model of Phase Three, which was updated using particle swarm optimization to minimize the error between the comprehensive set of experimental time series obtained during shake table testing and numerical time series of the OpenSees model. Uncertain model parameters were selected for updating to improve global and component-level response. The presented framework enables calibrated simulation of system behavior under unseen seismic loading and supports future applications in areas such as the development of digital twins and performance-based seismic design.
Masters Student Stanford University
Application of Multi-Stripe Analysis to Reinforced Concrete Frames with Implications for the FEMA P-695 Spectral Shape Factor Adjustment
Co-Authors: Kuanshi Zhong (University of Cincinnati), Jack Baker (Stanford University), and Gregory Deierlein (Stanford University)
Abstract: Multi-Stripe Analysis (MSA) is a method used in Performance-based Earthquake Engineering (PBE) that selects and scales ground motions to match site-specific ground motion hazard characteristics. This study applies MSA to examine the collapse safety of reinforced concrete (RC) frame archetypes at sites in Los Angeles (LA) and San Francisco (SF), which have comparable MCER intensity levels but distinct hazard characteristics, i.e., characteristic earthquake magnitude and distance. Site-specific hazards are characterized using conditional spectra (CS) conditioned at the fundamental period of the RC frames. In addition, matching the CS, ground motion records are selected to be consistent with the significant duration of the characteristic earthquakes at each site. The MSA ‘stripes’ correspond to return periods ranging from 224 to 9950 years. The target hazard characterization and ground motion selection are performed using a tool designed for integration with the SimCenter EE-UQ platform. The resulting collapse fragility curves reveal significant sensitivity to differences in the characteristic spectral shapes and durations between the LA and SF sites, with ground motions in SF being more damaging. The MSA-based collapse fragility curves contribute to an ongoing effort to update the Spectral Shape Factor (SSF) adjustment in FEMA P-695 using the SaRatio, aiming to more accurately reflect spectral-shape variations across sites and hazard intensity levels. Results to date indicate that the SaRatio-based adjustment provides closer agreement with the MSA-derived fragility curves than the epsilon-based adjustment in the current FEMA P-695 procedure.
Postdoctoral Scholar Sharif University of Technology
Incremental Seismic Retrofit: A Cost-Benefit Procedure for Decision Making Procedure
Abstract: This study presents a risk-informed decision-making methodology for partial seismic retrofitting of buildings. The approach aims to optimize budget allocation while minimizing monetary seismic risk. A 10-story nonductile steel special moment-resisting frame building, representative of typical U.S. construction prior to 1994, is employed as a case study building. The recent earthquakes exposed the high vulnerability of such structures. To assess the performance of different retrofit techniques, the connections were strengthened at varying numbers of stories along the building’s height. Both retrofitted and unretrofitted configurations were subjected to three suites of ground motions from the FEMA/SAC project, corresponding to 20%, 10%, and 2% probabilities of exceedance in 50 years. Inter-story drift ratio and peak floor acceleration were opted as engineering demand parameters, estimated through multi-stripe analysis. A rigorous seismic loss assessment was then performed following the FEMA P-58 framework. Results were presented and discussed in terms of expected annual loss, the net present value of benefit, and marginal benefit for each retrofit scenario. According to the findings, recommendations are proposed to support the cost-effective retrofit decision-making procedure.
PhD Student Oregon State University
Experimental Dynamic Characterization of Scaled Light Wood Framing Structures Subjected to Storm Surge Loading
Co-Authors: Andre Barbosa (Oregon State Univerisity), Dan Cox (Oregon State Univeristy), Pedro Lomonaco (Oregon State University), and Aaron Anton (Oregon State University)
Abstract: Understanding the dynamic response of coastal residential buildings under storm surge loading is critical for improving the performance of structures exposed to extreme wave hazards. While post-event damage observations are widely reported, experimental evidence linking storm surge demands and its effects on changes in the dynamic properties of a structure and progressive damage remain limited. This study analyzes the damage progression of two 1:3 scaled light wood framing structures tested in the directional wave basin at the Hinsdale NHERI Wave Research Laboratory at Oregon State University. Baseline testing consisted of snap tests, in which a lateral load was applied to each structure and then rapidly released while displacements and accelerations at each level were recorded. In addition to snap tests, ambient vibration measurements and forced vibration tests using an eccentric mass electric motor were performed to further characterize the dynamic response of the structures. Hydrodynamic testing was conducted by subjecting the structures to storm surge loading with progressively increasing water levels. The dynamic properties of each structure were evaluated throughout the wave loading trials and between successive storm surge stages. Progressive damage was assessed by tracking changes in the identified natural frequencies of each specimen over the duration of testing. Results show that storm surge level relative to the first floor elevation strongly influences structural response and damage development. The structure with lower floor elevation experienced higher hydrodynamic demand at earlier stages, leading to earlier damage onset and pronounced elongation of natural periods, while the specimen with the larger first floor elevation exhibited delayed damage progression and smaller shifts in dynamic properties.