The California building inventory includes many different building types. Two common building types in this inventory are tilt-up buildings and reinforced concrete buildings with embedded steel frames (sometimes referred to as steel reinforced concrete, or SRC, buildings). Many of these buildings were built before the implementation of modern provisions for seismic design and may be susceptible to significant damage in moderate-to-strong earthquake ground motions. Given this potential vulnerability, a study was undertaken to assess modeling and evaluation approaches for each building type.
For tilt-up buildings, a nonlinear analysis methodology was developed using a series of simple 2-D models to evaluate connection forces and deformations, as well as demand in the roof diaphragm, for a given ground motion. Data from the response of an instrumented building (CSMIP Station 47391) were used to validate the model. The correlation studies showed that the model was capable of representing the overall measured response of the building reasonably well. Sensitivity studies were performed to assess the influence of various parameters on tilt-up response, including soil-foundation-structure interaction (SFSI). The sensitivity studies indicate that diaphragm stiffness has a considerable impact on response and behavior and that near-field earthquakes with forward directivity increased connection and diaphragm forces from 10 to 25%. Soil-foundation-structure interaction did not have a significant impact on building response.
Due to the nature of the dynamic response of SRC buildings, which is dominated by out-of-plane “breathing” of the walls and roof, linear dynamic analysis methods were employed. The Linear Dynamic Procedure (LDP) described in FEMA 273 was used to assess critical structural elements of the lateral and gravity force-resisting systems. The evaluation indicated that the system was both strong and stiff, and thus, remained essentially elastic for the spectrum provided (10%/50 yr). Soil-foundation-structure interaction did not have a significant impact due to the dynamic response characteristics of the building.
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