Strengthening Feasibility of Damaged Steel Plates Repaired by Self-Stressing SMA-CFRP Overlays

Abstract

In order to improve the strengthening efficiency of damaged steel plates, shape memory alloy (SMA) was introduced as a pre-stressing carrier into the strengthening scheme. As a novel strengthening method, firstly, the mechanical properties and thermodynamic properties of NiTiNb-SMA were tested to investigate related mechanical parameters and the heat recovery performance when applied to strengthening. A total of nine specimens were repaired by the stop-hole method, the carbon fiber reinforcement polymer (CFRP) pasting method and the NiTiNb-SMA–CFRP pasting reinforcement method. Subsequently, the stress characteristics in the direction of crack extension was explored through a comparative analysis of numerical and experimental results. Research results indicated that the stress–strain behaviors of NiTiNb-SMA material at room temperature and high temperature were quite different, but the elastic modulus and tensile strength were very close. At an activation temperature of 170°C, the recovery stress of NiTiNb-SMA with a heated length of 15 cm and a single-sided embedded length of 6 cm reached 293.7 MPa. The static repairing test showed that the load stress could be reduced effectively by pasting SMA-CFRP overlays. The proposed 3D FE repairing model appeared to be in reasonable agreement with test results. The findings of this work can lay the preliminary foundation for subsequent fatigue reinforcement tests.