Amlan Kumar Sengupta

The increased use of shear walls in buildings has necessitated the study for a better understanding of the modelling aspects of a wall and its behaviour under lateral loads. In a framed shear wall, the behaviour of the infill wall panels under lateral loads is governed by shear deformation and the frame-panel interaction. In the present study, a reinforced concrete low-rise multistoreyed building with a centrally located framed shear wall was investigated for two approaches of modelling the non-linear behaviour of the wall. In the first approach, the wall was modelled using multi-layered membrane elements (refined model). In the second approach, the wall was modelled using equivalent column elements (simplified model) with lumped plasticity at the ends. Pushover analysis and incremental dynamic analysis (IDA) were performed using these models. It was observed that the pushover curves and the IDA plots for both the models are reasonably close. From the pushover analyses, the prediction of lateral strength by the simplified model was slightly lower than the refined model due to the idealisation of the equivalent column elements. Nevertheless, the modelling of a framed shear wall using equivalent column elements is adequate in terms of quantifying the lateral stiffness, strength and overall behaviour of the structure under lateral loads, provided the hinge properties are defined properly.

The present paper provides methods for analyzing reinforced concrete column sections strengthened with concrete jacket. First, the prediction of the axial load versus moment interaction curve is presented based on a lamellar analysis and a simplified method of analysis. The predicted results are compared with experimental results of jacketed columns. Second, the prediction of the moment versus curvature behaviour of a retrofitted column section under an axial load, is presented based on both the methods of analysis. Finally, the lateral load versus displacement behaviour of a beam-column-joint sub-assemblage with retrofitted columns, is predicted using an incremental non-linear analysis. The predicted behaviours are compared with experimental results. It is concluded that the lamellar analysis provides good prediction of the strength, as well as the moment versus curvature behaviour of a retrofitted column section. The simplified analysis gives a conservative value of the strength. It cannot predict the ductility in the behaviour reasonably well. The incremental non-linear analysis provides substantial better prediction of the behaviour of a retrofitted sub-assemblage specimen, as compared to a conventional pushover analysis.

Shear walls in buildings are efficient under seismic load in terms of providing lateral strength and stiffness. A framed shear wall consisting of panels in a frame, can be constructed in a new building or in an existing building for seismic retrofitting. Their contribution needs to be verified by appropriate non-linear analysis. The present study investigated the different options of modelling a reinforced concrete framed shear wall in a pushover analysis of a regular low-rise building. Pushover analyses were carried out using two computational models. The refined model was developed using multi-layered membrane elements for the wall panels. A simplified model was proposed with equivalent column elements for the framed wall. The shear hinge properties for the equivalent column elements were developed using the softened truss model. The in-plane normal stresses generated in the panels of the refined model, due to the framepanel interaction, were considered in the analysis by the softened truss model. The pushover curve from the simplified model was close to that from the refined model. The simplified model was conservative in terms of predicting the lateral strength. However, the deformability was overestimated as the local stress concentrations at the corners of the panels were neglected. It was observed that a simplified model without considering the normal stresses in the generation of shear hinge properties for the equivalent column elements, provided reasonable results. Since, the later model was computationally less intensive, it is expected to be suitable for professional practice. © 2014 ACC Limited.