Experimental Studies on Creep Behavior of Continuous Composite Girders using Precast Concrete Slab

在过去的30年里，关于预制混凝土板组合梁的研究已有大量的报道。自K. Sattler于1960年提出的，该研究已被许多参考文献所扩展，并由K. Roik通过高张力螺栓将预制混凝土板与钢梁组合在一起。此外，一些研究小组报告了在日本使用预制混凝土板的情况，并且这种类型的结构正在被普遍接受，特别是在西德国、瑞士、法国和美国。日本公路桥的大部分RC板仍然通过在现场浇筑混凝土来建造。然而，现浇混凝土板很难达到规定的质量要求，以减少人工和施工周期。此外，本发明还提供了一种方法，公路桥梁中钢筋混凝土板的损伤是一个严重的问题，如何快速修复和更换已损坏的钢筋混凝土板是一个重要的工程问题，本文对一种新型的预应力混凝土板组合钢梁的徐变性能进行了预测为研究预应力预制混凝土板（PPCS）法在不同工况下的徐变和松弛性能，采用PPCS法制作了连续组合梁模型，并进行了不同工况下的加载试验。将所得数据与基于组合梁粘弹性理论的分析结果进行了比较，并从不同角度讨论了它们的性质。此外，还讨论了利用混凝土等效杨氏模量比预测连续组合梁徐变应力的近似方法，并给出了算例，最后指出了今后有待解决的问题。

A great number of studies have been reported on the composite girders with precast concrete slabs in the last 3 decades. Since the pioneering work by K. Sattler in 1960, the study has been extended by many references and an innovative work by K. Roik composing precast concrete slab with steel girders through high tension bolts. Furthermore,the use of precast concrete slabs in Japan is reported by some of research groups and this type of construction is becoming universally accepted, particulary in West Germany, Switzerlan, France and U.S.A. Most of the RC slabs of Japanese highway bridges are still being built by pouring concrete at the sites. However, cast-in-place concrete slabs are quite difficult to meet the prescribed quality requirement, to cut down human labor and the construction period. In addition, damages of the RC slabs of highway bridges have been considered to be one of the most serious problems and the rapid repairing and replacement of the damaged slabs are among the most important engineering problems.Discussed in this study is the prediction of the creep behavior of a new type of steel girders composed with precast prestressed concrete slabs constructed with introduction of prestress force after the composition so referred to as the PPCS (Prestressed Precast Counste Slab) method.To investgate the creep and relaxation behavior of a continuous composite girder, model girders were built by the PPCS method and loaded under various conditions during past two years. Thus obtained data were compared with the analytical results based upon the visco-elastie theory of composite girders and their properties were discussed from various points of views. Moreover, and approximate method for predicting the creep stress of a continuous composite girder by using equivalent Young'smodulus ratio of the concrete is also discussed together with the numerical examples.Finally, it is directed that the remaining problems to be solved in the future.