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High capacity saw tooth connections under cyclic loadsResearch of high-capacity saw-tooth-connections in cyclic loads for the transfer of extremely high and concentrated tangential forces between slender steel and concrete elements

循环载荷下的高容量锯齿连接研究循环载荷下的高容量锯齿连接，用于在细长钢和混凝土元件之间传递极高且集中的切向力

基本信息

批准号：
222695629
负责人：
Professor Dr.-Ing. Volker Schmid
金额：
--
依托单位：
Fachgebiet Entwerfen und Konstruieren - Verbundstrukturen
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/222695629?language=en
关键词：
capacity saw tooth connections under

项目摘要

In a current DFG research project the applicant of this research proposal demonstrated, that saw-tooth connections are exceptionally well suited to transfer very high and concentrated tangential forces from steel into concrete elements, for example in bridge structures. However, the analytical analyses and practical tests were only investigating static loads. In contrast, the most important applications of saw-tooth connections are in buildings and structures, which are predominantly exposed to dynamic loads. The goal of this research proposal is a first and fundamental investigation of saw tooth connections under cyclic loading. The theoretical pre-analysis, conducted so far, indicates, that saw tooth connections will show a very high load bearing capacity in cyclic loading. The main reasons are the large areas of concrete and steel, which are available for the bearing of the compressive forces. As a result, the stresses in the concrete and the steel are quite low and uniform, without high peaks of stresses. It is supposed, that the stresses in the steel are lower than its fatigue resistance. Until today there is no scientific research, theoretical or practical, available on this subject. The first preliminary tests of concrete prisms with inclined saw tooth connectors, were carried out by the applicant. They showed no reduction in the load capacity after 2 Mio load cycles, with a Pmax/Pu = 0,67 and a deltaP/Pu = 0,48. However, in reality and in contrast to the prism-tests, the load distribution along the saw tooth connector is not constant, but shows a peak of forces at the tip of the saw tooth connector. That is why the performance of saw-tooth connections in a more realistic component test cannot be predicted by today. In addition, the connections in the mid-span of continuous beams may be subjected to changing loading directions. The effect of changing loading directions will be examined, for the first time ever, in this research proposal. In the preliminary tests, small cracks parallel to the compression struts were observed in the concrete. In the case of changing loading directions, this would result in perpendicular cracks, with the compression struts crossing the cracks. It is absolutely not clear, how these cracks will influence the load bearing capacity of saw tooth connections under dynamic loads. For the first time, this effect will be investigated in the proposed research project. A continuous ultrasonic measurement will be used during the tests, to detect the areas of fractured concrete. The aim of this research project is the first fundamental research into the basic principles of the load bearing behavior of saw tooth connections under pulsating and alternating loads. Special emphasis is laid on the research into the effects of crossing cracks in the area of saw tooth connections.

在目前的DFG研究项目中，这项研究建议的申请人证明，锯齿形连接非常适合于将非常高和集中的切向力从钢转移到混凝土构件中，例如在桥梁结构中。然而，分析分析和实际试验只研究了静力荷载。相比之下，锯齿形连接最重要的应用是在建筑物和结构中，这些建筑物主要暴露在动态载荷下。本研究方案的目的是首次对循环载荷作用下锯齿连接进行基础性研究。到目前为止进行的理论预分析表明，锯齿连接在循环载荷下将显示出很高的承载能力。主要原因是混凝土和钢材面积较大，可用于承压。因此，混凝土和钢筋中的应力相当低和均匀，没有应力高峰值。据推测，钢中的应力低于其疲劳抗力。直到今天，还没有关于这一主题的科学研究，无论是理论上的还是实践上的。申请人进行了第一批带有倾斜锯齿连接件的混凝土棱镜的初步试验。在2个MIO负荷循环后，它们的负荷能力没有下降，Pmax/Pu=0.67，DeltaP/Pu=0.48。然而，在实际中，与棱镜试验相反，锯齿形连接件的载荷分布并不是恒定的，而是在锯齿形连接件的尖端出现一个力的峰值。这就是为什么锯齿形连接在更现实的部件测试中的性能到今天还无法预测的原因。此外，连续梁跨中节点可能会受到改变荷载方向的影响。在这项研究方案中，将首次研究改变加载方向的影响。在初步试验中，在混凝土中观察到平行于受压支柱的小裂缝。在改变加载方向的情况下，这将导致垂直裂缝，受压支柱穿过裂缝。目前尚不清楚，在动载荷作用下，这些裂纹会对锯齿连接的承载能力产生怎样的影响。这一影响将首次在拟议的研究项目中进行调查。在测试过程中，将使用连续的超声波测量，以检测混凝土断裂的区域。本研究项目的目的是首次对锯齿连接在脉动载荷和交变载荷作用下承载行为的基本原理进行基础性研究。重点研究了交叉裂纹对锯齿连接区域的影响。