Behaviour of FRP-reinforced concrete beam-column joints

钢筋锈蚀导致混凝土结构尤其是在恶劣环境中建造的混凝土结构的维护和维修成本很高。最近的研究表明，单独的混凝土构件（梁，板，柱）与非腐蚀纤维增强聚合物（FRP）复合筋增强表现良好，在单调和循环荷载条件下。然而，对这些单独构件的连接（接头）进行了非常有限的工作，以形成框架结构。节点需要起到约束相邻柱和梁构件的作用，并在必要时发挥其全部非弹性承载力。由于FRP筋具有线性弹性行为直至失效，并且在弯曲或承受压缩应力时显示出降低的强度，因此当使用FRP筋时，特别是在地震荷载下，存在对这种接头的延性性能和完整性的关注。这项研究计划将集中在调查FRP钢筋混凝土梁柱节点的行为。研究计划包括实验室调查和分析建模。全尺寸FRP加固混凝土梁柱节点（内部和外部）将在实验室进行测试。试验参数将包括荷载类型（单调或循环）、节点核心的约束量（钢筋直径和FRP箍筋间距）、柱轴向荷载、混凝土强度、FRP主筋类型和比例以及钢筋详图。根据FRP与钢筋在力学性能和粘结特性上的本质差异，采用非线性有限元分析方法模拟节点板处复杂的应力和应变分布。该模型将被纳入计算机代码，该代码将根据实验结果进行校准。然后，计算机代码将用于进行参数研究，以调查预计会影响此类接头性能的各种因素。试验结果将被公式化为延性和整体梁柱节点的设计方程。这项研究导致新的结构具有更好的性能，更好的耐久性和更低的生命周期成本。

Corrosion of steel reinforcement has led to high maintenance and repair cost for concrete structures especially those built in harsh environments. Recent research indicated that the individual concrete members (beams, slabs, and columns) reinforced with the non-corrodible fibre reinforced polymer (FRP) composite bars behaved well under both monotonic and cyclic loading conditions. However, very limited work was conducted on the connections (joints) of these individual members to form a frame structure. Joints are required to function as restraint to adjoining column and beam members and develop their full inelastic capacity if necessary. Since FRP bars have a linear elastic behaviour till failure and show reduced strengths when bent or subjected to compressive stresses, there are concerns on the ductility performance and the integrity of such joints when FRP bars are use, especially under seismic loads. This research program will focus on investigating the behaviour of FRP-reinforced concrete beam-column joints. The research program consists of laboratory investigation and analytical modelling. Full-scale FRP-reinforced concrete beam-column joints (interior and exterior) will be tested in the laboratory. The test parameters will include the type of loading (monotonic or cyclic), the amount of confinement for the joint core (bar diameter and spacing of FRP stirrups), column axial load, concrete strength, FRP main reinforcement type and ratio, and detailing of reinforcement. Nonlinear finite element analysis will be used to model the complex distribution of stresses and strains at the joint panel in lights of the essential differences in mechanical properties and bond characteristics between FRP and steel bars. This model will be incorporated into a computer code, which will be calibrated against the experimental results. Then, the computer code will be used to perform parametric studies to investigate a wide range of factors that are expected to affect the behaviour of such joints. The test results will be formulated into design equations for ductile and integral beam-column joints. This research leads to new structures with improved performance, better durability and less life-cycle cost.