Development of the most competitive performance-based limit state design method for composite girders

基于性能的极限状态设计方法（PB-LSD）已成为基础设施结构构件设计的国际标准。在Euro Code （EU）和AASHTO LRFD （USA）中，经过20年的积极活动，设计理念从许用应力设计（ASD）向PB-LSD的转变刚刚完成。在亚洲国家，预计未来的基础设施准备工作也有望成为有前途的市场，上述代码现在正变得流行。在日本，自闭症谱系障碍已经被使用了30多年。组合梁作为一种具有竞争力的结构构件，在设计中为了有效地利用其力学特性，引入LSD是不可避免的。从与EC （EU）和AASHTO LRFD（美国）竞争的角度来看，从ASD到LSD的转变必须立即完成。本研究在分析和试验研究的基础上，提出了组合梁极限挠曲、抗剪和相互作用强度的原始和竞争性计算公式，这是建立竞争性LSD的重要内容。在抗弯强度评价上，采用压实截面判定标准，给出了最经济的截面。在考虑混凝土破碎引起的塑性弯矩减小的延性条件下，给出了最优解。在对组合梁的抗剪、弯相互作用强度进行评估时，发现组合梁的相互作用效应可以忽略不计。如果钢梁（正在安装中），必须进行检查。同时，提出了原有的适用性极限状态检查规定。此外，还提出了双组合梁和复合混合梁的设计方法。

Performance-based Limit State Design Method (PB-LSD) for designing structural members for infrastructure is now global standard. In Euro Code (EU) and AASHTO LRFD (USA), after 20-year energetic activity, the shift of design concept from Allowable Stress Design (ASD) to PB-LSD has just finished. Among Asian countries, where future preparation of infrastructure is expected and also are expected to be promising market, the above codes are now becoming popular. In Japan, for more than 30 years, ASD has been used. On designing composite girders, which is competitive structural members, and has been employed worldwide, in order to effectively utilize its mechanical characteristics, introduction of LSD is inevitable. From a viewpoint of competing with EC (EU) and AASHTO LRFD (USA), a shift from ASD to LSD has to be done immediately. In this research, based on analytical and experimental studies, original and competitive formulae for evaluating ultimate flexure, shear and interactive strength for composite girders were proposed, which are the most important items on establishing competitive LSD. On evaluating flexural strength, the criterion for judging to be compact section gives the most economical section. Regarding ductility condition taking into account of the decrease of plastic moment due to concrete crushing, the most competitive solution was given. On evaluating flexure and shear interactive strength, it was found that the interaction effect can be neglected in case of composite girders. In case of steel girder (under erection), it has to be checked. Original provisions were also proposed on checking serviceability limit state. Furthermore, the design method for double-composite girders and composite hybrid girders was also proposed.