Direct shear behavior of segmented cast keyed-joint UHPC components: Effects of interface treatment method and shear plane height

Effectively transmitting shear stress through the weak shear wet-joint interfaces is crucial for ensuring the structural performance of segmented cast (SC) ultra-high-performance concrete (UHPC) components. This study aimed to explore the influences of interface treatment method, shear plane height, the ratio of the keyed-joint area to the total area of the shear plane, and keyed joint number on the direct shear performances of SC UHPC components. A total of 4 monolithic, 18 flat-wet-joint, and 13 keyed-wet-joint UHPC Z-shaped specimens were tested by direct shear loads . The findings revealed that the SC UHPC specimens , irrespective of the interface treatment, exhibited brittle failure characteristics, with cracking and failure occurring almost instantaneously. Notably, the prefabricated uneven plastic formwork method for roughening UHPC interfaces emerged as an effective and convenient technique for improving bonding strength in practical engineering applications . However, the average interface roughness should be no less than 3 mm. The non-uniform distribution and nonlinear changes of shear stress along the shear plane in UHPC structures led to a decrease in the ultimate shear strength of UHPC wet-joint specimens as the shear plane height increased. Besides, the shear resistance of UHPC specimens with keyed-wet-joints increased in correlation with the expansion of the keyed-joint area. The UHPC flat-wet-joint areas tended to crack before the keyed joint sections, and the relationship between the influence coefficient of asynchronous force and keyed-joint ratio was established. Finally, taking into account the adhesive strength of the wet-joint interface, the effect of shear plane height, and the asynchronous stress mechanism of various components at keyed-joint shear surfaces, a highly precise direct shear bearing capacity calculation method tailored for SC UHPC components with keyed joints was developed. • The direct shear capacity of segmented cast UHPC components varied with interface treatment method, shear plane height, keyed-joint ratio, and multiple keyed joints was experimentally investigated. • The non-uniform distribution and nonlinear changes of the shear stress along the shear plane in UHPC structures led to a decrease in the ultimate shear strength of UHPC wet-joint specimens as the shear plane height increased. • A highly precise direct shear bearing capacity calculation method tailored for segmented cast UHPC components with keyed joints was developed.