When the structural capacity of precast concrete structures is to be determined, reliable and practical models for estimation of the ultimate load carrying capacity of the structural connections are essential. In this paper, rigid-plastic upper bound solutions for the load carrying capacity of keyed shear connections subjected to shear and normal forces are derived and compared to experimental results. The solutions are based on two idealized failure mechanisms involving complete key cut off and local key corner shearing, respectively. The solutions furnish a tool to design connections for the most ductile failure mode, which according to experimental observations is the one with local key corner shearing. Comparison with test results shows that satisfactory overall agreement is found, when appropriate material parameters are adopted. This includes an effectiveness factor, which in this study has been taken from previous studies of similar problems, and an internal angle of friction for mortar in the range of 30°–34°. The agreement is better for combinations of shear and compression, whereas the case of shear combined with large tension forces (i.e., half the yield capacity of the U-bars) is overestimated by the solutions. Based on the results, it can be recommended that the solutions may be applied in practice using the lower limit for the internal angle of friction, and provided that precaution are taken in cases where the connections are utilized to transfer tension.

中文翻译：

---

受法向力和剪切力作用的带环形 U 形杆的键控剪切连接第二部分——极限承载力的刚塑性建模

当要确定预制混凝土结构的结构能力时，用于估计结构连接的极限承载能力的可靠且实用的模型是必不可少的。在本文中，推导了承受剪切力和法向力的键控剪力连接的承载能力的刚塑性上限解，并与实验结果进行了比较。解决方案基于两种理想化的失效机制，分别涉及完全键切断和局部键角剪切。这些解决方案提供了一种工具，可以为最具延展性的破坏模式设计连接，根据实验观察，这种破坏模式是具有局部关键角剪切的模式。与测试结果的比较表明，当采用适当的材料参数时，发现了令人满意的总体一致性。这包括在本研究中从以前对类似问题的研究中提取的有效性因素，以及砂浆的内摩擦角在 30°–34° 范围内。该协议对于剪切和压缩的组合更好，而剪切与大拉力（即 U 形杆屈服能力的一半）结合的情况被解决方案高估了。根据结果​​，可以建议使用内摩擦角的下限在实践中应用这些解决方案，前提是在使用连接传递张力的情况下采取预防措施。该协议对于剪切和压缩的组合更好，而剪切与大拉力（即 U 形杆屈服能力的一半）结合的情况被解决方案高估了。根据结果​​，可以建议使用内摩擦角的下限在实践中应用这些解决方案，前提是在使用连接传递张力的情况下采取预防措施。该协议对于剪切和压缩的组合更好，而剪切与大拉力（即 U 形杆屈服能力的一半）结合的情况被解决方案高估了。根据结果​​，可以建议使用内摩擦角的下限在实践中应用这些解决方案，前提是在使用连接传递张力的情况下采取预防措施。