Non-linear Analysis and Design of Portal Frame under Lateral Loading

Abstract

Earthquake is an inevitable natural disaster. The structures built in India before 2001 were not ductile detailed. In a structure ductility is a very important parameter. Ductility is nothing but when a structure undergoes large inelastic deformation without significant loss of strength. So to evaluate the capacity of structures which are not ductile detailed, nonlinear analysis is helpful. A structure which is ductile detailed will give better performance than the one which is not ductile detailed. Ductility will increase the load carrying capacity of the structure also. In any Reinforced Concrete structure its joint plays a very important role. In modelling of the structure member nonlinearity, material nonlinearity is also very important. But recent studies shows that not only member nonlinearity, material nonlinearity but also joints non linearity plays a very important role. By incorporating the this into the structure it will give better and accurate results. For a structure not only using elastic capacity into consideration its nonlinear capacity should also be used. So to perform and show this, an experiment has been performed in which two portal frames one with configuration 1 having shear links at 50mm c/c at confined regions and at rest of the places it is 75mm c/c and the other with configuration 2 having shear links at 100mm c/c spacing throughout have been tested under lateral loading. All main reinforcement is of 8mm diameter. Use of Self Compacting Concrete has been done of M25 grade to avoid vibration of the concrete. Lateral displacements of both the columns and beam at various heights have been taken and graphs are plotted. In the second part of the work after experiment locations of the hinges have been found out and same has been given as an input in SAP2000 for doing Pushover Analysis. This analysis will give the actual strength of the structure and its displacement at highest load. Results obtained from the experiment and from Pushover Analysis shows similarity to some extent. The maximum displacement of the configuration 1 frame is 35.8mm and the results obtained from Analysis is 44.62mm. In configuration 2 frame the maximum displacement obtained from experiment is 35.28mm and that obtained from experiment is 34mm. Apart from that experiment shows that the load carrying capacity of configuration 1 frame is higher than configuration 2 frame but the displacement of configuration 2 frame is more than configuration 1 frame.