Experimental investigation of predamaged hollow core beams shear-strengthened with ESS-HCC

To solve the problem in which multiple diagonal cracks are present in the webs of hollow slab girders, a novel technique using early-strength self-compacting shrinkage-compensating high-performance cementitious composite (ESS-HCC) materials to enhance shear strength was developed by our research team. In previous investigations, scholars rarely considered the influence of the degree of predamage on a cracked hollow core beam (HCB) strengthened with ESS-HCC. Moreover, researchers have not accurately predicted the maximum diagonal crack widths in these shear-strengthened HCBs in past studies. Therefore, a series of HCB specimens were constructed and tested under concentrated loads in this paper. The key parameter investigated herein was the extent of predamage in the HCB specimen before strengthening. The experimental results indicated that ESS-HCC could completely restore the shear performance of the predamaged HCB specimens. Compared with that of the undamaged HCB specimen, the shear capacity of the predamaged HCB specimen increased by 29-50% after strengthening. However, the shear capacity of the predamaged HCB specimen strengthened with ESS-HCC was smaller than that of the undamaged specimen strengthened in the same manner. All the HCB specimens exhibited brittle shear failure, with shear cracks still propagating along the original cracks. Similarly, compared with that of the unstrengthened specimen, the diagonal crack width of the strengthened specimen decreased by 33-58%. To predict shear capacity, a modified model considering the predamage coefficient was proposed based on the JTG 3362-2018 standard. The theoretical results of the modified model were in good agreement with the experimental results. Finally, a simple model was devised to estimate the maximum diagonal crack width of the HCB specimen shear-strengthened with ESS-HCC, and the predicted results were reasonably accurate compared to the experimental data.