Performance assessment of RC frame buildings with open ground storey

Buildings with open ground storey (OGS) evidenced catastrophic failure in past earthquakes. Building code provisions usually: (i) avoid designing such buildings (e.g., ASCE 7-16), (ii) provide structural walls up to 2% plan density (e.g., IS 1893-1) and (iii) design by amplifying the demand at ground storey using modification factor (e.g., Eurocode 8) or reducing the response reduction factor using an irregularity factor (e.g., NTE-E030). Hence applicability of these provisions is checked with a set of 2D RC frame buildings; it includes (i) a simple OGS building (OGS1), (ii) OGS building with structural wall at ground storey, IS 1893-1 (OGS2), (iii) OGS buildings designed as per NTE-E030 (OGS3) and Eurocode 8 (OGS4). Their inelastic behaviour is obtained using nonlinear static and dynamic analysis, including infill walls as an equivalent strut. OGS2 suffered the least (damage in struts), and OGS3 sustained more damage (in struts, beams and columns). It is mandatory to provide structural walls at the ground storey rather than designing for amplified force demands. A parametric study is conducted (for OGS using IS 1893-1): (a) by varying the height of the building, and (b) including structural walls in 1, 3 and 5 bays. Increasing height or providing structural walls in more bays increases damage in struts and no damage in other elements. The response reduction factor (R) for OGS3 is more than OGS1, OGS2 and OGS4, as it shows more damage; it is necessary to avoid damage in OGS buildings. Also, the R-value reduces with building height and increases with structural walls in more bays; thus, a single R-value is not applicable to all buildings.