Repair of Fire Damaged Axially Loaded Short RC Columns Using GFRP Wrap

L.n.k Sai Madupu ,Khushi Ram

doi:10.13189/cea.2021.090632

Abstract

Fire damaged columns can be repaired with glass fibre reinforced polymer (GFRP) wrap to regain its full strength or even more. In the present work, short reinforced concrete (RC) rectangular columns which are exposed to elevated temperature at 4000℃ for 2 hours duration are repaired using GFRP wrap glued with epoxy resin. Strengthening of existing columns using GFRP wrap is a simple, easy and economical solution. GFRP wrap enhances the stiffness of the column in lateral direction, which improves the load carrying capacity of the column. The behaviour of GFRP wrapped column is different from the behaviour of column without GFRP wrap in response to the applied load. The behavior of GFRP strengthened column depends on various factors such as column cross sectional area aspect ratio, radius of rounded edges of the column, number of GFRP layers wrapped, width of GFRP strip, wrap pattern, epoxy properties etc. Various wrap patterns are tried to obtain effective one which greatly enhances the load taking capacity of short axially loaded columns. GFRP wrapping using strips showed good results than using continuous layer. The load carrying capacity of fire damaged GFRP repaired columns is increased by 42.3% compared with undamaged column without GFRP wrap and increased by 112.6% compared with fire damaged column without GFRP. Designer should fairly estimate the capacity of the strengthened column. Mathematical models are developed to predict the strength of repaired columns.

Highlights

The properties of concrete, reinforced steel and bond between them of an R.C. element subjected to elevated temperature are affected considerably
The minimum regain in capacity of fire damaged columns repaired with glass fibre reinforced polymer (GFRP) wrapping compared with corresponding fire damaged column without GFRP wrapping (TCC) is 1.145 (Table 2), i.e. the percentage increase in capacity is 14.5% which is observed in TFC column with aspect ratio 0.84
The minimum restoration in capacity of fire damaged columns repaired with GFRP wrapping is 0.737 times compared with corresponding undamaged column without GFRP wrapping (CC) which is observed in case of TFC column with aspect ratio 0.72 (Table 3)

Summary

Introduction

The properties of concrete, reinforced steel and bond between them of an R.C. element subjected to elevated temperature are affected considerably. An elaborated study with different cross section area aspect ratios of rectangular column, different widths of FRP strips and various stick patterns is needed. It is much complicated to develop a unified single expression to predict strength of GFRP repaired column considering all factors such as cross section aspect ratio, length of column, number of layers, width of strip, wrap pattern, corner radius etc. Each wrap pattern is considered separately and mathematical models are developed to predict the load carrying capacity of GFRP repaired columns having different aspect ratio (a/b) values. For each GFRP repair pattern, an equation is suggested to predict load carrying capacity (Ptr) of fire damaged GFRP repaired columns if the corresponding strength of fire damaged column with out GFRP wrapping (Pt) is known for different aspect ratios (a/b) between 0.5 and 1. The predicted load carrying capacities using the proposed expressions are matching well with the experimental results of the study

Materials

Experimental Procedure

Results and Discussion

Conclusions