SEISMIC EVALUATION AND RETROFIT ON AN EXISTING HOSPITAL BUILDING

Abstract

The nonlinear pushover analysis was used to evaluate an existing 8-storey reinforced concrete framed hospital building under seismic force and presented in this manuscript. The ‘Guru Teg Bahadur Hospital' is one of the important hospitals at Delhi-India, it was selected for this research. The three-dimensional frame model was used to model the building with a fixed base. The beams and columns were modeled by using three-dimension line frame elements with the centre lines joined at nodes. Diagonal strut elements were used to model the brick masonry infills. The slabs were considered as rigid diaphragms. The plastic hinge rotation capacities as per Federal Emergency Management Agency 356 (FEMA 356) with Performance Levels were adopted in this study, considering the axial force-moment and shear force-moment interactions. The nonlinear pushover analysis of the selected building was done with infills and it was observed that the infills (due to their small number in the considered building) do not make any appreciable effect on the performance level, except their failure at an early stage. The Capacity Spectrum Method (CSM) and Displacement Coefficient Method (DCM) were used to estimate the performance point of the building. The values of various coefficients as per Federal Emergency Management Agency 440 (FEMA 440) were adopted. The DCM was observed to give slightly higher target displacements, as compared to CSM. It was observed in the nonlinear pushover analysis that the unreinforced masonry (URM) infills collapse before the performance point of the building for the Maximum Considered Earthquake (MCE). As the intervention inside the functioning hospital is extremely difficult, it was explored whether it is possible to safeguard the infills by stiffening the building by providing external buttresses. Two cases of retrofitting schemes with 1.2m wide and 3m wide buttresses in transverse direction were used and analysed. It was found that this is not a practicable approach, as the infills collapse even with 3m wide buttresses.