Shear behaviour and structural health monitoring performance of LWSCC beams strengthened with smart ULW-ECC-FRP mesh composite

Lightweight self-consolidating concrete (LWSCC) elements are prone to shear failure due to its intrinsic brittleness and weak shear transfer mechanism. Smart ultra-lightweight engineered cementitious composite (ULWECC) emerges as a suitable material for strengthening and self-sensing. In this paper, the shear behaviour and structural health monitoring (SHM) performance of reinforced LWSCC strengthened with the smart ULW-ECCFRP mesh composite were investigated. The results indicated that the shear strength and ductility of specimens only strengthened with ULW-ECC were maximally increased by 40.8 % and 26 %, respectively, because different configurations of ULW-ECC demonstrated varied shear transfer mechanisms and different material utilisation. Furthermore, ULW-ECC exhibited excellent SHM behaviour, which can discern the cracking stage and deformation through the variation of fractional change of impedance (FCI). Particularly, ULW-ECC in the compression zone displayed the best shear behaviour and remarkable self-sensing performance. The shear strength was also enhanced by FRP mesh, with the increase ranging from 23.6 % to 43.2 %, correlating with the tensile strength of FRP mesh. Glass FRP (GFRP) and basalt FRP (BFRP) had marginal effects on the crack pattern and SHM behaviour of strengthened specimens, and the latter showed better synergy with ULW-ECC. However, carbon FRP (CFRP) mesh adversely affected the failure mode and self-sensing behaviour of ULW-ECC, reducing the specimen ductility.