Seismic risk assessment of code-conforming reinforced concrete moment resisting frame buildings : consideration of unreinforced masonry infill wall and soil-structure interactions
Creators: name: Mohammad Noh, Nurbaiah
Publisher: name: University of British Columbia
Year: 2023

description: The seismic vulnerability of reinforced concrete (RC) frames with unreinforced masonry (URM) infill walls has been a concern in areas with high seismic activity. The seismic response of this structural system is usually modelled in the form of global building analysis using simplified procedures without considering the aspects resulting from the response between the infill walls and the frame. Another factor usually ignored is the soil-structure interactions (SSI), which can considerably impact the actual structure's behaviour. Current design standards do not provide adequate instructions or transparent methodologies for assessing the risk of the infilled RC building systems with consideration of the SSI effect. This research aims to provide a conceptual framework and benchmark data for assessing building risk, particularly for code-conforming RC frames with URM infill walls incorporating SSI in Vancouver, British Columbia. The study starts by selecting a simple and reliable analytical model for the infill wall response. A systematic guideline was developed to evaluate various parameters to define the monotonic and hysteretic response of infill walls modelled by equivalent struts. Different strut formulations and hysteretic models have been analyzed in detail and used to reproduce several experimental tests available in the literature. The numerical analyses are performed using the OpenSees computer program. Subsequently, this study assesses the seismic risk of the three- and six-storey regular RC moment-resisting frame (MRF) building systems, with and without URM infill walls, representing low- to mid-rise structures through incremental dynamic analyses (IDA). These structures are designed per the National Building Code of Canada 2010 and detailed based on the 2014 Canadian Standards Association A23.3 standard provision for seismically active regions. Two different ductility classes of seismic building design, namely ductile and moderately ductile, are considered to identify the capability, equality, and/or difference in the seismic performance of these designed buildings. Finally, a parametric study was conducted to determine the performance of the building with the consideration of the SSI. The goal was pursued through a parametric study in which the structure type and shallow foundation embedment depth were varied. Overall, the study's findings suggest that bare RC frame buildings are prone to collapse during earthquakes as the number of stories increases. The presence of URM infill walls greatly affects the collapse behaviour of the frame structure. Ductile RC MRF buildings outperform moderately ductile RC MRF buildings in terms of collapse performance, with the capacity of the building system being a significant factor. Additionally, the results indicate that the SSI effect significantly impacts the structural performance and vulnerability, particularly for low-rise buildings with surface foundations. It was discovered that implementing a realistic model with a wide range of parameters in the analysis is evident and now practicable.