Utilizing Steel Brace for Seismic Retrofitting of Old School Buildings with Open Ground Storey

Abstract

This paper investigates the seismic performance of an old school building with open ground storey. The building was designed according to an old Egyptian design code that did not consider the earthquake load; thus, the building is vulnerable to sudden lack of stiffness in the open ground storey (soft storey effect). The first check showed that the building is unable to resist the loads from earthquakes in both longitudinal and transverse directions. Therefore, two retrofitting options were suggested and investigated: using steel bracings; and changing the thickness of some ground floor infill walls. Pushover analyses were conducted to evaluate the building seismic performance. For these analyses, the FEA was applied considering both material and geometric nonlinearities. Both retrofitting methods helped to make the building capable to resist the earthquake loads according to the current Egyptian codes. In particular, retrofitting increased the lateral resistance by up to 55% and 25% in longitudinal and transverse directions, respectively. The research findings facilitate an economical and practical upgrading of many old school buildings without violating their function. Based on authors’ expe-rience, there are hundreds of such school buildings in Egypt alone.

Keywords

• Reinforced Concrete School
• Soft Storey
• Seismic Analysis
• Retrofitting by Steel Bracing
• Finite Element Analysis