Strengthening of reinforced concrete beams with insufficient lapped splice length of reinforcing bars

Abstract

The insufficient lapped splice length of reinforcing bars due to the design or construction errors reduces both the flexural strength and ductility of Reinforced Concrete (RC) beams. The defected RC beams need to be strengthened to allow structures to be ductile and robust in their design life. This paper reports experimental and numerical investigations into the flexural behavior of RC beams having insufficient lapped splice length of reinforcing bars strengthened by various techniques. Eleven RC beams have been tested to examine the effects of strengthening techniques and anchorage lengths of the strengthening materials on the performance of the beams. The test program and results are described on RC beam specimens strengthened by using the externally bonded stainless-steel (EBSS) sheets, the near surface mounted (NSM) steel bars, and the external prestressing system. Finite Element (FE) models are developed using ABAQUS to simulate the responses of strengthened RC beams in which the lapped splice length of reinforcement is inadequate. A parametric study is conducted using the validated FE models to examine the effects of the length of EBSS sheets and steel anchor bolts at the ends on structural behavior. An analytical model is proposed for calculating the ultimate capacity of beams strengthened by NSM technique. Experimental results reveal that the proposed strengthening methods can significantly improve both the cracking and ultimate loads of the defected beams. The application of the external prestressing method results in the largest increase in the cracking and ultimate loads of the defected beams calculated as 222 % and 213 %, respectively compared to the defected control beam. The ultimate load of the defected beam strengthened with EBSS sheet, NSM steel bars, and prestressing system with a length of 100D increases by 50 %, 109 %, and 182 %, respectively. It is shown that the developed FE models can accurately predict the behavior of strengthened beams having inadequate lapped splice length of reinforcing bars. The parametric study demonstrates that strengthening the entire clear span of the beam B-ESS-65D with EBSS sheet increases its ultimate load by 207 %. The failure mode of strengthened beams is ductile bending without debonding. The proposed analytical model is shown to yield accurate calculations of the ultimate loads of strengthened RC beams. • Tests of strengthened RC beams with insufficient lapped splice length of rebars are reported. • The beams were strengthened by stainless-steel sheets, steel bars, and external prestressing system. • FE models are developed to predict the behavior of strengthened RC beams with defects. • The strengthening methods significantly improve the performance of RC beams. • The FE models can capture well the performance of strengthened RC beams.