Existing design guidelines for concrete hinges consider bending-induced tensile cracking, but the structural behavior is oversimplified to be time-independent. This is the motivation to study creep and bending-induced tensile cracking of initially monolithic concrete hinges systematically. Material tests on plain concrete specimens and structural tests on marginally reinforced concrete hinges are performed. The experiments characterize material and structural creep under centric compression as well as bending-induced tensile cracking and the interaction between creep and cracking of concrete hinges. As for the latter two aims, three nominally identical concrete hinges are subjected to short-term and to longer-term eccentric compression tests. Obtained material and structural creep functions referring to centric compression are found to be very similar. The structural creep activity under eccentric compression is significantly larger because of the interaction between creep and cracking, i.e. bending-induced cracks progressively open and propagate under sustained eccentric loading. As for concrete hinges in frame-like integral bridge construction, it is concluded (i) that realistic simulation of variable loads requires consideration of the here-studied time-dependent behavior and (ii) that permanent compressive normal forces shall be limited by 45% of the ultimate load carrying capacity, in order to avoid damage of concrete hinges under sustained loading.

中文翻译：

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混凝土铰链的蠕变和开裂：来自中心和偏心压缩实验的见解

现有的混凝土铰链设计指南考虑了弯曲引起的拉伸开裂，但结构行为被过度简化为与时间无关。这是系统地研究初始整体混凝土铰链的蠕变和弯曲引起的拉伸开裂的动机。对素混凝土试件进行材料试验，对边缘钢筋混凝土铰链进行结构试验。实验表征了中心压缩下的材料和结构徐变以及弯曲引起的拉伸开裂以及混凝土铰链徐变和开裂之间的相互作用。至于后两个目标，三个名义上相同的混凝土铰链接受短期和长期偏心压缩测试。发现获得的材料和结构蠕变函数与中心压缩非常相似。由于蠕变和开裂之间的相互作用，偏心压缩下的结构蠕变活动明显更大，即弯曲引起的裂纹在持续偏心载荷下逐渐张开和扩展。对于框架式整体桥梁结构中的混凝土铰链，得出的结论是 (i) 可变载荷的实际模拟需要考虑此处研究的时间相关行为，以及 (ii) 永久压缩法向力应限制为 45%的极限承载能力，以避免混凝土铰链在持续荷载作用下的损坏。由于蠕变和开裂之间的相互作用，偏心压缩下的结构蠕变活动明显更大，即弯曲引起的裂纹在持续偏心载荷下逐渐张开和扩展。对于框架式整体桥梁结构中的混凝土铰链，得出的结论是 (i) 可变载荷的实际模拟需要考虑此处研究的时间相关行为，以及 (ii) 永久压缩法向力应限制为 45%的极限承载能力，以避免混凝土铰链在持续荷载作用下的损坏。由于蠕变和开裂之间的相互作用，偏心压缩下的结构蠕变活动明显更大，即弯曲引起的裂纹在持续偏心载荷下逐渐张开和扩展。对于框架式整体桥梁结构中的混凝土铰链，得出的结论是 (i) 可变载荷的真实模拟需要考虑此处研究的时间相关行为，以及 (ii) 永久压缩法向力应限制为 45%的极限承载能力，以避免混凝土铰链在持续荷载作用下的损坏。