Instrumentation and Data Post-Processing of Soft-Story Woodframe Buildings for Full-Scale Testing
Author:Mary Faith Silva
Mentor:John van de Lindt, George T. Abell Professor in Infrastructure, Civil and Environmental Engineering, Colorado State University
A soft-story is classified as a building level with a 70% or less lateral stiffness of the upper story or 80% less stiffness compared to the three stories located above it. This significantly reduced stiffness decreases the building’s ability to resist lateral forces due to earthquakes. The purpose of the NEES-Soft four-story woodframe test program was to validate four retrofit techniques under FEMA P-807 guidelines and performance-based seismic retrofit (PBSR) methodology using cross-laminated timber, steel special moment frames, and toggle brace viscous dampers (with plywood structural panels on the upper stories for PBSR design). The purpose of this undergraduate research project under NEES-Soft was to validate full-scale testing methods so that other undergraduate researchers could use the data to analyze different behaviors of the building. Instrumentation methodology involved an understanding of how to instrument the building with accelerometers, strain gauges, linear potentiometers, and string potentiometers. Quantities including, but not limited to, inter-story drift, shear wall deformation, translational and torsional diaphragm displacement, and forces at hold-downs were obtained from these sensors after each testing sequence. Furthermore, this project describes how post-processed data was roughly verified against expected quantities by cross-referencing measurements against different sensors located near the sensors of interest. Proper instrumentation and post-processing yielded data that could be used by other undergraduates to analyze diaphragm rigidity, the natural period of the building, and cost-benefit correlation between inter-story drift and damage. A well-designed instrumentation methodology is crucial knowledge that adds to the growing area of research in full-scale seismic testing of woodframe structures within the fields of earthquake and structural engineering.