Influence of nonlinear modeling on capacity assessment of RC framed structures

Many existing buildings in the world present serious seismic deficiencies and need to be retrofitted. However, the basis for an effective seismic retrofit intervention is a reliable assessment of the structure. To this end, nowadays structural engineers can simulate the response of structures subjected to earthquake excitation by nonlinear numerical models. These models consider explicitly the mechanical nonlinearities of the structural members, identify the parts of the structure where yielding takes place, quantify the demand of plastic deformation and force. Furthermore, a number of models is available to carry out the nonlinear analysis of structures. All these models are able to provide a detailed representation of the seismic response of the structure. However, they are controlled by many parameters that need to be properly set to obtain an accurate prediction of the response. Based on the framework depicted above, the target of the Reinforced Concrete Work Package 2 of the ReLUIS 2018 project was to examine and compare different nonlinear modelling techniques used to evaluate the response of structures by pushover analysis. To this end, a case study building is analysed by the eight research units involved in the project by different nonlinear numerical models. The building presents very different lateral stiffness and strength in the longitudinal and transverse directions. Each numerical model is run two times including and not including the masonry infills. Furthermore, pushover analysis is run two times with forces in the longitudinal and transverse directions. Finally, the results are compared to illustrate advantages and limitations of each nonlinear modelling technique.