Shear connections in prefabricated concrete buildings are important for the structural performance in both the serviceability and the ultimate limit state. A normal force has a large impact on the shear strength and deformation capacity, however, no experimental record includes compression–shear and tension–shear interaction. This article presents an experimental investigation of keyed shear connections with looped U-bars subjected to combinations of shear and normal forces. The tests were performed in a custom-built double frame, where forces could be applied in two perpendicular directions, which was utilized to introduce normal and shear forces. The load combinations ranged from pure tension, over shear–tension and pure shear to shear–compression. The results include load–displacement relationships supplemented by digital image correlation (DIC) results to exemplify the experimental findings and underline the influence of a normal force on the behavior. It was found that a compressive normal force has a positive influence on the shear capacity in the entire displacement domain tested. A tensile normal force reduces not only the shear capacity but also the deformation capacity of the connection. The ultimate shear load was associated with failure in the joint mortar, which in all cases took place as a local key corner shearing. This article constitutes Part I of the investigation, while Part II introduces rigid-plastic modeling of the ultimate load carrying capacity.

中文翻译：

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带有受法向力和剪切力作用的环形 U 形杆的键控剪切连接第 I 部分：实验研究

预制混凝土建筑中的剪力连接对于适用性和极限状态下的结构性能都很重要。法向力对剪切强度和变形能力有很大影响，但是，没有实验记录包括压缩-剪切和拉伸-剪切相互作用。本文介绍了带有受剪切力和法向力组合作用的环形 U 形杆的键控剪切连接的实验研究。测试是在定制的双框架中进行的，其中可以在两个垂直方向上施加力，用于引入法向力和剪切力。载荷组合范围从纯拉力、过剪切-拉力和纯剪切到剪切-压缩。结果包括载荷-位移关系，并辅以数字图像相关 (DIC) 结果，以举例说明实验结果并强调法向力对行为的影响。发现压缩法向力对整个测试位移域中的抗剪承载力具有积极影响。拉法向力不仅会降低抗剪能力，还会降低连接的变形能力。极限剪切载荷与接缝砂浆的破坏有关，在所有情况下，它都是作为局部关键角剪切发生的。本文构成了调查的第一部分，而第二部分介绍了极限承载能力的刚塑性建模。发现压缩法向力对整个测试位移域中的抗剪承载力具有积极影响。拉法向力不仅会降低抗剪能力，还会降低连接的变形能力。极限剪切载荷与接缝砂浆的破坏有关，在所有情况下，它都是作为局部关键角剪切发生的。本文构成了调查的第一部分，而第二部分介绍了极限承载能力的刚塑性建模。发现压缩法向力对整个测试位移域中的抗剪承载力具有积极影响。拉法向力不仅会降低连接的抗剪能力，还会降低连接的变形能力。极限剪切载荷与接缝砂浆的破坏有关，在所有情况下，它都是作为局部关键角剪切发生的。本文构成了调查的第一部分，而第二部分介绍了极限承载能力的刚塑性建模。在所有情况下，这都是作为局部关键角剪切发生的。本文构成了调查的第一部分，而第二部分介绍了极限承载能力的刚塑性建模。在所有情况下，这都是作为局部关键角剪切发生的。本文构成了调查的第一部分，而第二部分介绍了极限承载能力的刚塑性建模。