Retrofitting of RC Beams Using Ultra High Performance Fiber Reinforced Concrete

Abstract

Reinforced concrete structural components are found to exhibit distress, even before their service period is over due to several causes. Such unserviceable structures require immediate attention, enquiry into the cause of distress and suitable remedial measures, so as to bring the structures back to their functional use again. This strengthening and enhancement of the performance of such deficient structural elements in a structure or a structure as a whole is referred to as retrofitting. The all important issue to be addressed in retrofitting is life safety .What can be done to prevent collapse of the structure and prevent injury or death to occupants? Some retrofit requirements may try to address only the issue of life safety, while acknowledging that some structural damage may occur. Structures that are deficient in shear can be strengthened or repaired by using various methods, e.g., external pre-stressing, shortcreting, polymer impregnation, steel plate bonding, fiber reinforced polymers (FRPs) and other cementitious materials including ultra high performance fiber reinforced concrete (UHPFRC). To overcome all the above problems faced in different retrofitting techniques, a new cementitious material with ultra high performance characteristics like very high compressive strength (above 110 MPa), high tensile strength due to addition of fibers, high flexural strength, very less permeable and high workability i.e. UHPFRC came into existance. UHPFRC with its remarkable characteristics as a repair material for concrete structures in harsh environmental conditions and high loads works excellent.

In the present thesis shear deficient RC beams initially stressed to a prefixed percentage i.e. 60% of the failure load are retrofitted using UHPFRC. Retrofitting is done using three different techniques i.e. Side face retrofitting, U-Type retrofitting and External 25 mm thick jacketing. From the study it is seen that the ultimate load carrying capacity of RC beams retrofitted with UHPFRC is significantly increased with Side face and U-type retrofitting. Moreover, this technique also increased the ductility and energy absorption of RC beams which resulted in the usefulness of UHPFRC as a retrofitted material. A comprehensive literature review is carried out for better understanding of UHPFRC as a retrofitting material compiled from many references representing research, development, and deployment efforts around the world, this thesis report provides a framework for gaining a deeper understanding of UHPFRC as a retrofitting material.