In recent years, due to corrosion and the constant demand for increased traffic flow, it emerged that there is a need for an efficient system that can be used to repair and / or strengthen bridges and structures with steel–concrete composite section. There have been many strengthening techniques used to prevent such serious structural problems. One of these techniques, which has proven effective in repairing and strengthening structural members, is to use externally post-tensioned tendons. This study provides a recently completed experimental program on scaled bridge composite steel–concrete beams strengthened with external post-tensioning tendons to investigate the fundamental cyclic loading behavior. In addition to studying the effect of the strengthening system, there was another major factor under study which was the degree of shear connection. The study mainly relied on testing the beams under the influence of cyclic loads in addition to changing the degree of shear contact. Reducing the degree of shear connection simulates a form of composite action loss of composite beams due to cyclic loads. The study results provides modes of failure, characteristic points, load–deflection curves, slip between steel beam top flange and the concrete flange, the shear connector strains, and the concrete and steel beam bottom flanges strains. Based on the experimental results, adding external post-tensioning enhanced the overall performance of the composite beams under cyclic loading by significantly reducing strains of the shear studs, the concrete flange, and the steel I-beam at all loading stages. The strengthened specimens experienced an increase in the ultimate capacity and residual stiffness comparable to non-strengthened specimens, attributable to significant loss of composite action between concrete flange and steel beam through cyclic load test.

近年来，由于腐蚀和不断增加的交通流量的需求，出现了对一种有效的系统的需求，该系统可用于修复和/或加固具有钢混凝土组合截面的桥梁和结构。有许多用于防止这种严重结构问题的加固技术。这些技术中的一种已被证明有效地修复和加固结构构件，是使用外部后张预应力筋。这项研究提供了最近完成的试验计划，该试验程序是用外部后张预应力筋加固的比例尺桥梁组合钢-混凝土梁，以研究基本的循环荷载行为。除了研究加强系统的效果外，还有另一个主要因素正在研究中，即剪力连接的程度。该研究除了改变剪切接触的程度外，还主要依赖于在循环荷载作用下对梁进行测试。降低剪力连接的程度可模拟一种形式的复合梁由于周期性载荷而产生的复合作用损失。研究结果提供了破坏模式，特征点，载荷-挠度曲线，钢梁顶部法兰和混凝土法兰之间的滑动，剪切连接器应变以及混凝土和钢梁底部法兰的应变。根据实验结果，通过在所有载荷阶段显着减小剪力钉，混凝土法兰和工字钢的应变，在循环载荷下增加外部后张应力可以提高复合梁的整体性能。