Evaluation of shear characteristics of steel-asphalt interface under shear -resistant reinforcement constraint by oblique shear test method

Interlayer shear damage of steel bridge deck pavement (SBDP) represents a pivotal issue that hinders the durability of bridges. Shear reinforcement (SR) represents a novel form of interlayer reinforcing structure. The function of this reinforcement is to inhibit the longitudinal displacement of the pavement layer by welding the force with the bridge deck plate. This process significantly improves the performance of interlayer shear resistance. However, the underlying mechanisms of the macroscopic reinforcement effect, the restraining action mechanism and the damage mode remain to be elucidated, impeding the precise design in engineering applications. In this paper, the mechanical response of multi-parameter combination specimens is tested by an indoor inclined shear test system with temperature, shear angle and bar diameter as the key variables. The shear strength, displacement and stress-displacement curves under the SR constraint are obtained, which reveals the crack initiation, expansion path and distribution law. The interface shear strength envelope was constructed based on the Mohr-Coulomb strength theory, and the energy loss method was introduced to quantify the contribution of SR to the strength enhancement in order to elucidate the mechanism of its restraining effect. The findings indicate that ambient temperature exerts a substantial influence on the confinement effect. The enhancement effect of SR exhibits a marked increase with increasing temperature from -10°C to 60°C. On average, the shear strength of the reinforced specimen is augmented by 256% in comparison with that of the unreinforced specimen, while the increase at 60°C reaches 528%. The angle of shear has been demonstrated to influence the enhancement effect by altering the distribution of interlaminar stress. The concentration of interfacial shear stress is most evident when the temperature is increased from -10°C to 60°C, and it is more likely to induce bond damage inside the material. In the context of constant working conditions, an augmentation in bar diameter (6-10 mm) has been demonstrated to engender an enhancement in shear strength for both bare round and ribbed bar specimens. Specifically, it has been observed that when the diameter of the bar is increased by 55%, the strength of the two specimen types exhibits an average increase of 153% and 343%, respectively, when compared with that of unreinforced bar specimens. Moreover, the reinforcing effect of ribbed bar consistently surpasses that of bare round bar. The analysis of the contribution ratio of internal friction angle demonstrates that the contribution of reinforced specimens is significantly higher than that of unreinforced specimens, and increases exponentially with increasing temperature, with an increase of nearly 8 times at 60°C, which further confirms the confining effect of SR. The research results reveal the reinforcement mechanism of SR and provide theoretical support for the optimisation of the design and engineering application of SBDP interlayer reinforcement structures.