Experimental study on ductility emphasizing size effect for plain and Retrofitted Beam-Column joint under cyclic loading

Beam-column joint is one of the vital elements, whose behaviour during earthquake is very critical. The ability of a structural element to resist an earthquake depends to a large extent on its ductility. Available theories of material behaviour that predict size effect are receiving increasing attention in the technical literature nowadays. No study has been done till today covering the size effect aspect on ductility of plain and retrofitted beam-column joint under cyclic loading. Hence, in the present study, an experimental programme was undertaken by considering shear deficient beam-column joints. Two categories of specimens, viz. beam-column joint with beam weak in shear and beam-column joint with column weak in shear along with their corresponding retrofitted specimens were considered in the present study. Three geometrically similar specimens were considered as control specimens and three corresponding specimens were retrofitted by FRP (fibre reinforced polymer) under each category. Thus, total twelve specimens covering two different types and three different scales were tested under cyclic loading. The displacement amplitude in cyclic loading was chosen based on the prediction of numerical analysis carried out using ANSYS software. A constant axial load on the beam-column joint was maintained during testing. The recorded data were plotted to draw hysteretic response and calculation of ductility. Comparisons of results were made between control and retrofitted specimens in term ductility and conclusions were drawn regarding the benefit derived out of retrofitting. It was observed that the ductility increases as the specimen size decreases, i.e. follow principle of size effect.