Joint Seismic and Scour Fragility Assessment of a Steel Building Incorporating Soil-Structure Interaction

This paper focuses on the development of joint seismic and scour fragility function of a three-story existing steel moment resisting frame structure in the Central United States. The structure dimensions with beam and column details were obtained from the design plan from the building owner. With all the information, a three-dimensional (3D) model of the structure with soil springs reflecting the soil-structure interaction behaviors during an earthquake was created through commercially available finite element software. To account for joint seismic and scour risk, a total of forty eight synthetic ground motions having different spectral accelerations (Sa) were used, and the soil springs were progressively removed. Numerous nonlinear time history analyses reflecting the effects of scour effects by adjusting the removed soil spring number was conducted to determine peak inter-story drifts of the structure simultaneously subjected to the ground motions. Federal Emergency Management Agency (FEMA)-based three performance levels (i.e., immediate occurrence, life safety, and collapse prevention) were considered for the creation of joint seismic and scour fragility functions. Significant findings show that the joint seismic and scour vulnerability of the structure increased as they become more damaged due to the reduced resistant forces from the removal of soil springs over a broad spectrum of Sa.