Study of SFRP and SFRG in Retrofitting of Columns

Abstract

Strengthening of RC structures using different retrofitting materials has a substantial growth in construction industry since last decade. Fiber reinforced polymer (FRP) composite materials have come to the forefront as promising materials and systems for structural retrofit. Today, mostly steel plates, carbon fiber reinforced polymers (CFRP) and glass fiber reinforced polymer (GFRP) are used as external reinforce- ment. Steel fiber reinforced polymer (SFRP) composite materials have recently been in- troduced as an alternative to glass and carbon fiber reinforced polymer (GFRP and CFRP) composite materials. There are many benefits to using SFRP over GFRP or CFRP. Significantly, the steel cords that make up SFRP have some inherent ductility. Also, when cementitious grout is used rather than epoxy as the bonding agent, the SFRG can exhibit excellent fire resistant properties. Similar SFRP/SFRG has advan- tage of being relatively lightweight in comparison to steel plates, making it relatively easy to install. The main objective of the present study is to evaluate axial load carrying capacity of SFRP/SFRG strengthened columns of M15 grade of concrete with and without rein- forcement.An experimental investigation carried out on P.C.C. and R.C.C. columns of square (200mm x 200mm) and circular (200mm dia) shaped having 1200mm length. Total 32 concrete column specimens were cast including 8 control specimens, 24 speci- mens were strengthened using SFRP/SFRG. A direct tension test and bond test were done for finding tensile strength and bond behavior of SSWM. Out of three sample of SSWM of different weight/sqm (GSM), wire dia and no of wires tested, best two SSWM material were used with two different bonding agent epoxy and polymer ce- ment grout. Based on results, it is observed that one layer of SFRP/SFRG increases compressive strength by 20-32% and two layers of SFRP/SFRG are further increase the strength by 65-89%. Wrapping effciency in circular column is better as compared to square column. The cost of SFRP/SFRG less than GFRP and CFRP, therefore it recommended to use SFRP and SFRG as a retrofitting material.