Study on size effect of RC deficient beam-column joints with and without retrofitting under cyclic loading

Available theories of material behavior that predict size effect are receiving increasing attention in the technical literature nowadays. Beam-column joint is one of the vital elements, whosebehaviour during earthquake is very critical. No study has been done till today to establish the existence of size effect on beam-column joint. Hence, in the present study, an experimentalprogramme was undertaken by considering shear deficient beam-column joints. Three geometrically similar specimens were considered as control specimens and three corresponding specimens were retrofitted by FRP (fiber reinforced polymer). Cyclic loading with a constantaxial load on the beam-column joint was applied during testing. The recorded data were plotted to draw hysteretic response, envelope curve, energy dissipation etc. Comparisons of results were made between control and retrofitted specimens in term of all the above-mentionedproperties and conclusions were drawn regarding the benefit derived out of retrofitting. Further, the percentage gain in capacity due to retrofitting, energy dissipation etc were correlated with size of specimens. To compare the energy dissipation of specimens havingdifferent sizes, a new parameter, viz. energy dissipation per unit volume ( eN ) was introduced for the first time in the context of evaluation of size effect. eN was correlated with the size of the specimen at different drift angles. Stresses for all the specimens were calculated and bilogarithmic plots were drawn. It was observed that most of the properties follow principle of size effect. The most important finding is that- the bi-logarithmic plot of unit strength follows the established law proposed by Baz˘ant.

Keywords:

Beam-column joint , size effect , retrofitted , cyclic load , bi-logarithmic