Seismic fragility and loss assessment of standard/sub-standard RC frames of Pakistan retrofitted with steel bracing schemes

• Published in: Bulletin of earthquake engineering Vol. 22; no. 9; pp. 4581 - 4608
• Main Authors: Khan, Muhammad Shoaib, Rizwan, Muhammad
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.07.2024; Springer Nature B.V
• Subjects: Beam-columns; Building codes; Civil Engineering; Concrete; Decision making; Developing countries; Earth and Environmental Science; Earth Sciences; Earthquake damage; Earthquakes; Environmental Engineering/Biotechnology; Fragility; Frames; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hydrogeology; Joints (junctions); LDCs; Mathematical models; Numerical models; Original Article; Public awareness; Reinforced concrete; Reinforcing steels; Retrofitting; Risk assessment; Seismic activity; Seismic hazard; Steel; Steel structures; Structural Geology; Pakistan; RC frames; Diagonal braces; Eccentric braces; Joint detailing; Retrofitting; Concentric braces; Hysteretic response
• ISSN: 1570-761X; 1573-1456
• DOI: 10.1007/s10518-024-01947-4

Building code implementation in developing countries is a serious concern due to poorly regulated construction practices. Deficiencies in terms of material strength and structural detailing are found the most in reinforced concrete frames in Pakistan. This paper presents the results of quasi-static cyclic tests performed on reduced-scale RC frames with and without beam-column joint detailing and considering normal and low-strength concrete respectively. Fragility functions and loss curves for the standard/sub-standard frames were derived using an experimentally validated numerical model. Furthermore, the existing RC frames building stock was rehabilitated with various configurations of steel bracing i.e. one way diagonal, one way eccentric, two way diagonal, two way eccentric and concentric. The developed fragility and loss curves for the rehabilitated frames confirmed that the two way diagonal steel bracing system outclasses the other types. Moreover, inter-story drift limits for as-built and rehabilitated frames were proposed under design base earthquakes and maximum considered earthquakes. Maximum considered earthquakes pushed the ductile as-built frame further than the moderate damage state, thus rehabilitation after such an event will be required for the structure. The presented results will help in seismic risk assessment, decision-making and public awareness.