Experimental and numerical study on flexural behaviors of damaged RC beams strengthened with UHPC layer using the bonding technology of post-installed reinforcing bar

Due to the outstanding mechanical and durability properties, Ultra-high performance concrete (UHPC) has been popularly used for strengthening of existing reinforced concrete (RC) beams. To improve the reliability of UHPC strengthening RC beams and enhance the effectiveness of its usage on site applications, bonding technology of post-installed reinforcing bar was proposed to connect the RC beams with UHPC layers. In this paper, a push-out test program was firstly carried out to study the shear properties of interface between UHPC and normal strength concrete (NSC) using the post-installed reinforcing bar connection technology, and to select suitable embedment length of the post-installed reinforcing bar in UHPC layer. Then, a bending test program consisted of three damaged RC beams strengthened with UHPC layers and one control RC beam was conducted to investigate the flexural behaviors of the damaged RC beams strengthened by UHPC layers using the bonding technology of post -installed reinforcing bar. Thereafter, three-dimensional FE models were developed to simulate the flexural performance of the strengthened RC beams, and the crucial parameters were investigated. The results of the present study revealed that the strengthening with reinforced UHPC layers could effectively improve the cracking and flexural performance of damaged RC beams. All the strengthened beams using the bonding technology of post-installed reinforcing bar failed in the typically flexural failure and no obvious interface cracks caused by the interface connection were observed throughout the bending test process.

Automated summary

The shear properties of the interface between UHPC and NSC using post-installed reinforcing bar connection technology were studied through a push-out test, and the suitable embedment length of the post-installed reinforcing bar in UHPC layer was determined. A bending test on damaged RC beams strengthened with UHPC layers using the bonding technology of post-installed reinforcing bar was conducted to investigate the flexural behaviors. Three-dimensional FE models were developed to simulate the strengthened RC beams and the crucial parameters were investigated. The results showed that the strengthened beams using the bonding technology of post-installed reinforcing bar effectively improved the cracking and flexural performance of damaged RC beams, without any interface cracks throughout the bending test process.