REHABILITATION OF R.C. BEAMS FOR DYNAMIC LOAD

Abstract

The repair and strengtMiihg of existing distressed concrete structures is an acute problem faced by Civil Engineers. Concrete structures need repairing due to damages arising out of many reasons such as increased load, improper design, faulty construction etc. The problem of rehabilitation of concrete members subjected to dynamic loads is still more complicated. In this dissertation work, two types of R.C. beams have been tested under statically and dynamically applied loads, before and after rehabilitation. There are many different techniques of rehabilitation of distressed R.C. element/structures such as grouting with cement, epoxy grouting, guniting, stiching, ferrocement jacketing etc. The efficacy of these techniques under different situations and under static state of stresses, has been investigated by many investigators. However, there is very little information available regarding the relative performance of these techniques under dynamic loads. This study is an attempt in this direction. R.C. beams with two different steel been tested under static and dynamic loads. two point loading has been so kept that flexural failure in one type of beams and failure in the other type of beams. arrangements have The position of. it will induce a shear-flexural iv For the dynamic load tested the pulsating loads has been applied in the two ranges, from 25% to 50% of the ultimate static load in the first case and from 25% to 75% of the ultimate static load in the second case. The number of cycles required to cause failure in each case and the propagation of cracks up to failure have been determined. For better averaging two specimens for each case have been tested. In the second part of testing, the above distressed beams have been rehabilitated using the two tech-niques chosen for the study, namely the repairing by epoxy grouting and by ferrocement jacketing. These rehabilitated specimens have been tested exactly in the same manner as the corresponding original beams. Based upon the above test results, the efficacy of the two rapai.ring techniques chosen for the study has been investigated under static as well as dynamic loads. Under both static and dynamic loads, and for the two types of the beams A and B i.e. beams critical in shear and beams critical in flexural, rehabilitation by ferrocement jacketing gives increased strength and less deflections and crack widths as compared to the corresponding beams rehabilitated by epoxy grout. It is interesting to note that non of the cracks sealed by epoxy grouting had reopened, and the ultimate failure load for both the original and the beams repaired by epoxy grout is nearly the same.