EFFECT OF FRP WRAPPING ON STRENGTH AND DUCTILITY PARAMETER OF RC MEMBERS SUBJECTED TO AXIAL AND LATERAL LOADS

Abstract

Lessons learnt from past & most recent earthquakes, continuously call for the seismic strengthening of the structures. As a matter of fact, the number of lives & economic losses claimed by a disaster like earthquake isn’t due to the earthquake itself, it is primarily due to the collapse of civil engineering structures which are unable to withstand the ground motion induced due to earthquake. There is a famous quotation that “Earthquakes don’t kill people, buildings do”. This depicts the uttermost necessity to check for the seismic vulnerability of the structures & to make them able to withstand the earthquake forces that it may be subjected to throughout its remaining life or increased design period. In a country like us, where thick population can cause a magnified effect on the earthquake hazard, it is really of prime importance to strengthen the seismically vulnerable structures. Seismic retrofitting has been an interesting topic for researchers for quite some time. However, for our country hardly anything has been done in terms of code prescription or special design requirements for seismic load cases. An attempt has been made through this research procedure so as to represent seismic retrofitting technique a dearer one to the design offices and for practical implementation. In this study, an existing building which is primarily a Moment resisting frame of five storeys, has been analysed for gravity loading and seismic loading. The capacities of the existing and retrofitted buildings has been evaluated and compared through Non-linear static analysis of the frames. The local and global retrofitting techniques which has been used are FRP jacketing and installation of additional steel bracings in the building frame. The viability of the local retrofitting technique such as FRP jacketing of the columns and beams so as to boost the overall structural capacity of the structure has been investigated. The enhancement in the existing member capacities has been evaluated through their strength and ductility parameters, i.e., through axial load-moment interaction diagrams, Moment curvature diagrams and Moment-rotation diagrams. The global performance of the structure has been evaluated using the non-linear hinge parameters developed manually with the help of Microsoft Excel and feeding them into SAP2000. Also, the global performance of the structure after installation of additional steel bracings with and without FRP wrapping has been investigated through nonlinear static analysis of the retrofitted frames. The study shows that the enhancement in the global performance of the structure is insignificant when only columns are retrofitted with FRP strips, however, the ductility of the structure can be enhanced significantly when both the beams and columns are wrapped.