Development of rapid visual screening tool for seismic evaluation of wood-frame dwellings

Graduation date: 2012During the past several decades, earthquakes have caused extensive damage to\ud buildings, including wood-frame, single-family dwellings, in the United States. In\ud order to mitigate future losses, existing buildings in earthquake prone areas should be\ud evaluated for their seismic safety. This is also an important issue for buildings in\ud Oregon due to the Cascadia subduction zone along its west coast.\ud \ud One seismically vulnerable element observed in wood-frame, single-family dwellings\ud is the shear walls. In general, assessment of shear wall seismic performance can be\ud accomplished by a building-specific engineering calculation. Extra effort is required if\ud the effects of plan irregularity are a concern. This project aims to facilitate seismic\ud evaluation of wood-frame dwellings by proposing a new engineering-based rapid\ud visual screening method to examine the expected performance level of the structure's\ud exterior shear walls to resist lateral forces from ground motions, including torsional\ud forces induced from plan irregularity.\ud \ud In order to achieve the objective, SAPWood software was used to perform a series of\ud nonlinear time-history analyses for 480 representative models, covering different\ud combinations of shape parameters and shear wall opening-related parameters. The evolutionary parameter hysteresis model was used to represent the load-displacement\ud relationship of structural panel-sheathed shear walls and a ten parameter CUREE\ud hysteresis model for gypsum wallboard sheathed walls. The calculated maximum\ud lateral drifts were used as basic information for the development of the new method.\ud \ud Through the development process, the significance of both plan configuration and\ud shear wall openings were emphasized as they affect the overall seismic performance\ud of a building through building mass, lateral stiffnesses, and eccentricities. Within the\ud study range, single-family dwellings with two stories, a larger percentage of openings,\ud and having a garage door were shown to be more vulnerable to seismic events. Plan\ud configuration and shear wall openings were important features especially in houses\ud located in high 1 (0.5g ≤ S[subscript a] < 1.0g) and high 2 (1.0g ≤ S[subscript a] < 1.5g) seismicity regions, as\ud they could potentially lead to severe damage. For low and moderate seismicity, the\ud performance ranges from satisfying the collapse prevention limit to the immediate\ud occupancy limit.\ud \ud The developed piRVS (plan irregularity Rapid Visual Screening) takes into\ud consideration the shape of the floor plan, number of stories, base rectangular area,\ud percent cutoff, and openings from doors/windows and garage doors, and supports\ud evaluation at the immediate occupancy (IO), life safety (LS), and collapse prevention\ud (CP) performance levels. The piRVS provides relatively more conservative\ud assessment results than FEMA 154 and ASCE 31 Tier 1. Its prediction for the two\ud applicable Northridge earthquake damage samples is reasonable. This method will\ud help architects, engineers, building officials, and trained inspectors in examining the\ud expected seismic performance of shear walls, considering the effects of plan\ud irregularity in wood-frame, single-family dwelling