Non-Linear Static Pushover Analysis of Real Life Reinforced Concrete Frame with ATENA 3-D Program

Abstract

The non-linear static analysis (push over analysis) provides good understanding of seismic behavior of structures. Pushover analysis produces pushover curve which consists of capacity spectrum. In the current paper, the non-linear response of four storeyed RC frame under the pushover loading (monotonically incremental load) has been obtained to study the response and load-carrying capacity of RC frame using non-linear finite element analysis. An analysis model for four storeyed RC frame using software ATENA, a computer program using stress analysis with finite element method, is presented. The results obtained from FE analysis are compared with the experimental data for four storeyed RC frame, at the same location as used in experimental test. The correctness of the finite element model is assessed by the comparison with experimental results which are to be in good agreement. The pushover curves (base shear versus displacement curves) obtained from finite element analysis agree with the experimental results in linear and non- linear range. The concrete has been the most preferred construction material for many decades due to its wonderful properties There are a variety of factors which are responsible for the degradation of RC structures such as increasing load, deterioration of steel due to corrosion, seismic forces, environmental degradations and accidental impacts on the structure. The increase in height of modern structures is intimately related with the extent and impact of disaster in terms of human and economical loss in the occurrence of structural failure. The existing structures can also become seismically deficient since design code requirements are constantly upgraded due to advancement in engineering knowledge. In India most of the buildings constructed over past two decades are seismically inadequate due to lack of knowledge regarding seismic behavior of structures. Hence a careful and systematic structural safety analysis becomes compulsory. To evaluate RC structures against failure an accurate estimation of the ultimate load is necessary and the prediction of the load-deformation behavior of the structure throughout the range of linear and non-linear response is advantageous. To obtain a global mechanism for the structure with a ductile behavior the non-linear analysis is required to be carried out. Nowadays the statically nonlinear method called pushover method, is becoming a popular tool for seismic performance evaluation of new and existing structures. The pushover analysis is a nonlinear static analysis for a reinforced concrete framed structure subjected to lateral loading. The gravity loads are applied and then lateral loading is applied first in X- direction starting at the end of the gravity push and next in y- direction again starting at the end of gravity push(1). The pushover analysis provides ample information on seismic demands imposed by the design ground motion on the structural system and its components. The objective of pushover analysis is to evaluate the expected performance of structural systems by estimating performance of a structural system by estimating its strength and deformation demands in design earthquakes by means of static inelastic analysis, and comparing these demands to available capacities at the performance levels of interest. The inelastic static pushover analysis can be viewed as a method for predicting seismic force and deformation demands, which accounts in an approximate manner for the redistribution of internal forces that no longer can be resisted within the elastic range of structural behavior (2).