Evaluation of Ultimate Torque and Twist of Ferrocement Strengthened “U” Wrapped Beams: Different Approaches

Abstract

Man made havocs and natural calamities bring problems for all categories of structures and create a threat to human life. Havocs and natural calamities induce variable stresses which have necessitated constant attention, maintenance and upgradation of infrastructures. Strengthening of distressed structures is absolutely necessary when these structures are unable to resist the induced forces or incapable to meet the updated codal requirements. Concrete structures can be strengthened by retrofitting and “U” wrap is most suitable method of retrofitting for structures with extension of flanges. Retrofitting using FRP is costly and requires skilled workmanship for application. For developing countries ferrocement wrap is a better solution over FRP.The present research work focuses on quantification of torsional parameters like torque and twist at ultimate stage of a rectangular reinforced concrete (RC) beam with a ferrocement “U” wrap on three sides. Concrete strength and amount of longitudinal & transverse reinforcement are varied in this work. These factors can be determined by conducting experiments or developing models. These processes are tedious and prolonged. To make the prediction method simpler and quicker, techniques of soft computing is applied here. The two methods; MARS and WASPAS provide quick solutions to predict torsional strength and twist at ultimate stage of “U” wrapped beams closely to the experimental values. “U” wrapped beams are found with tremendous increase in torque and twist over their control specimens. A RC medium strength beam; over reinforced in both longitudinal and transverse direction is found to have 9.62 kNm ultimate torque while the same is found to be 12.91 kNm for high strength beam. Rotation capacity of ferrocement “U” wrap under reinforced beams exhibit maximum twist at ultimate torque than other categories of beams. Reinforcement in core concrete has more influence on torque and twist at ultimate stage than ferrocement reinforcement in outer wrap. MARS and WASPAS predicts torque and twist at ultimate with reasonable accuracy.KeywordsFerrocementU wrapUltimate torqueSoftened truss modelMARSWASPAS