External strengthening of reinforced concrete beams with strand without stressing under flexural loading

Abstract

This research was purposed to study the composite behavior and the increased capacity of reinforced concrete beam strength under flexural loading caused by external strand strength without stressing. The specimen is divided into 2 types. Type-I specimen has (150 x 300 x 3200) mm dimension with center point loading, and distance of strand clamp as (Ubars) variable; whereas, the Type-II specimen has (200 x 300 x 3200) mm dimension with third point loading, and the number of strand as variable. The test is carried out by static-monotonic loading, and displacement control. Experimental test results shows that the addition of strand on the lower surface of the beam increase the beam’s load capacity. However, the use of U- bars affects the stability of the concrete. The tighter distance of the U-bars decrease the capacity of the strengthening occured. The increased load capacity of Type I specimens, S3-150, S5-150 and S9-150 are 33.2%, 17%, and 12.1% against control beam (BK-150), respectively. Whereas, the increased capacity of the type-II beam strength of test specimens B1-200 and B2-200 are 10% and 17% against control beam (BN-200), respectively. And the increase of initial stiffness of beam Type-I test specimen S3-150, S5-150, and S9-150 are 14%, 18% and 5% against control beam (BK-150), respectively. Meanwhile, the increase of initial stiffness of Type-II beam of test specimens B1-200 and B2-200 are 21% and 24% against control beam (BN-200), respectively. This study shows that concrete and strand bonding is not compatible. The concrete has been reaching the limit strain, as well as the steel reinforcement in the concrete has been in yielded; meanwhile, strand that has fy is much higher than fy of reinforced steel, is still in elastic condition.