Yu Kun, Zhang Zhongya, Zou Yang, Jiang Jinlong, Zeng Xingqi, Tang Liang
State Key Laboratory of Mountain Bridge and Tunnel Engineering, School of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, China.
Department of Civil Engineering, School of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China.
Polymers (Basel). 2022 Mar 28;14(7):1364. doi: 10.3390/polym14071364.
Application of ultra-high-performance concrete (UHPC) in joints can improve the impact resistance, crack resistance, and durability of structures. In this paper, the direct shear performance of ultra-high-performance concrete (UHPC) adhesive joints was experimentally studied. Twenty-four direct shear loading tests of UHPC adhesive joints were carried out considering different interface types and constraint states. The failure modes and load-slip curves of different interfaces were studied. Results indicated that passive confinement could enhance the strength and ductility of the interface; the average ultimate bearing capacity of the smooth, rough, grooved, and keyway specimens with passive restraint were, respectively, increased by 11.92%, 8.91%, 11.93%, and 17.766% compared with the unrestrained ones. The passive constraint force changes with the loading and finally tends to be stable. The epoxy adhesive has high reliability as a coating for the UHPC interface. The adhesive layer is not cracked before the failure of the specimen, which is also different from the common failure mode of adhesive joints. Failure of all specimens occurred in the UHPC layer, and the convex part of the groove interface shows the UHPC matrix peeling failure; the keyway interface is the shear damage of the key-tooth root, and the rest of the keyway showed UHPC surface peeling failure. According to the failure mode, the shear capacity of UHPC keyway adhesive joints under passive restraint is mainly provided by the shear resistance of key teeth, the friction force of the joint surface, and the bonding force of the UHPC surface. The friction coefficient was determined based on the test results, and the high-precision fitting formula between the shear strength of the UHPC surface and the passive constraint force was established. According to the Mohr stress circle theory, the proposed formula for direct shear strength of UHPC bonded joints under passive constraint was established. The average ratio of the proposed UHPC adhesive joint calculation formula to the test results was 0.99, and the standard deviation was 0.027.
超高性能混凝土（UHPC）在节点中的应用可以提高结构的抗冲击性、抗裂性和耐久性。本文通过试验研究了超高性能混凝土（UHPC）粘结节点的直接剪切性能。考虑不同的界面类型和约束状态，进行了24个UHPC粘结节点的直接剪切加载试验。研究了不同界面的破坏模式和荷载-滑移曲线。结果表明，被动约束可以提高界面的强度和延性；与无约束试件相比，有被动约束的光滑、粗糙、开槽和键槽试件的平均极限承载力分别提高了11.92%、8.91%、11.93%和17.766%。被动约束力随加载而变化，最终趋于稳定。环氧胶粘剂作为UHPC界面涂层具有较高的可靠性。在试件破坏前，粘结层未开裂，这也与粘结节点的常见破坏模式不同。所有试件的破坏均发生在UHPC层，开槽界面的凸起部分表现为UHPC基体剥离破坏；键槽界面为键齿根部的剪切破坏，键槽其余部分表现为UHPC表面剥离破坏。根据破坏模式，被动约束下UHPC键槽粘结节点的抗剪承载力主要由键齿抗剪、节点表面摩擦力和UHPC表面粘结力提供。根据试验结果确定了摩擦系数，建立了UHPC表面抗剪强度与被动约束力之间的高精度拟合公式。根据莫尔应力圆理论，建立了被动约束下UHPC粘结节点直接抗剪强度的计算公式。所提出的UHPC粘结节点计算公式与试验结果的平均比值为0.99，标准差为0.027。
