Performance based earthquake design

Abstract

Every Civil Engineering structure or building is unique in nature unlike other engineering products which are produced in a massive scale using the same technique again and again. The present Project is an effort to understand Performance Based Design Approach. In this Work an four storey office building is designed using STAAD.Pro and a nonlinear static analysis is carried out using point plastic hinge model. After the building is designed it is imported to SAP platform in order to model point plastic hinges and carry out Pushover Analysis. The designed building was modeled and the hinges or possible failure locations were assigned. The stiffness of the building was increased due to the slab present and this was incorporated in the model using diaphragm. The Floor Centre of Mass was calculated and an incremental Inverted triangular loading was applied to this central load and the base shear along with displacement of this building was recorded until the building reached a state of collapse. The Displacement controlled Pushover Analysis was carried out and the Pushover Curve were obtained for the building in both the direction i.e. X and Y. The Pushover curve is analyzed for various percentage of displacement. As per FEMA 356 typical values of roof drifts for the three performance levels are as follows.
i) Immediate Occupancy: Transient drift is about 1% with negligible permanent drift.
ii) Life Safety: Transient drift is about 2% with 1% permanent drift.
iii) Collapse Prevention: 4% inelastic drift, transient or permanent.
The Capacity Spectrum, Demand Spectrum and Performance point of the building was found in both the direction using the analysis carried out in SAP 2000 (v14). From the Performance point it was found that the Base Shear carried by the building is well above the design base shear and the building can take a lateral force up to 10% of the seismic weight of the building. The Displacement obtain was less than 1% and hence the chances of crossing the elastic state for the building was very less. Very Rare chances are there for the building to cross Life safety performance level. In the collapse state the failure was due to the collapse of ground floor Columns which is a serious issue and should be looked for further research. The Building designed as per Indian standards was found to be well above Life safety performance level considering Designed Based Earthquake .