火灾后混凝土梁柱节点的锚钢加固机理研究

A majority portion of fire-damaged reinforced concrete (RC) frame structures can continue their service after proper rehabilitation. However, the enhancement of beams, floors and columns is the main concerning of most existing strengthening techniques, related studies on the beam-column joints, which are the most crucial parts of the frame structures under seismic loads, have yet been sufficient..Accordingly, based on the improvement and modification of the existing steel jacketing technique, this project will develop a strengthening method of bolting steel, which can suppress the adverse interfacial delamination and provide effective restraining and enhancement to the fire-damaged RC joints. Comprehensive experimental, numerical and theoretical studies will be conducted: The temperature-time based constitutive model of concrete after fire, and the tensile and shear capacity of anchor bolts post-installed in the fire-damaged concrete will be investigated firstly. The variation of the mechanical performance of the strengthened joints as the elevated temperature, the arrangement of steel angles and anchor bolts, along with the corresponding mechanisms, will be further studied. The overall strengthening effect to the fire-damaged frames beneficial from the combined retrofitting strategy, which includes the bolting steel of the beam-column joints, the bolted-side-plating of the main beams, and the post-compressed-plating of the columns, will also be investigated..In this project, the strengthening mechanism, the theoretical model, and the simplified formula of the bearing capacity will be developed for the fire-damaged RC joints strengthened by bolting steel. And a set of retrofitting strategy will be proposed for the fire-damaged RC frames as well. The outcomes of this project will provide theoretical base and technical supports for the strengthening design and construction of the fire-damaged RC frame structures.

火灾后大部分混凝土框架结构仅需适当修复即可继续使用，目前针对火灾后梁、板和柱的修复技术较多，然而对于地震作用下框架结构的核心部位——梁柱节点，其加固技术却亟待完善。.本项目拟对前期外包钢套法进行优化与改造，提出一种既可避免界面剥离、又可约束及增强节点核心区的锚钢加固法。并采用试验、模拟及理论分析相结合的方法，（1）以火灾后材料基于时-温耦合的残余力学性能、群锚连接受力性能为研究起点，（2）探究锚钢加固火灾后梁柱节点受力性能随温度场、角钢及锚栓布置等因素而改变的规律及其内在影响机制，（3）再进一步考察节点锚钢法与本项目组前期提出的梁侧锚钢法及柱侧预应力锚钢法相结合后，对火灾后混凝土框架结构的总体加固效果。.本项目拟揭示火灾后混凝土梁柱节点的锚钢加固机理，构建加固节点承载力计算理论模型和简化公式，并针对火灾后框架结构提出一整套加固技术，其成果可为该类结构的加固修复提供理论依据和关键技术支持。

受火后，混凝土结构、材料的力学性能都会出现下降，甚至出现破坏模式的转变，使结构无法满足当前抗震规范的要求。鉴于当前我国混凝土框架结构建筑的广泛存在、现阶段建筑火灾的频繁易发，以及国内外尚无针对火灾后混凝土梁柱（空间）节点较为完善成套的加固方法。本项目在课题组大量结构抗火、混凝土梁及节点加固研究的基础上，提出了一种新颖有效的高温（火灾）后钢筋混凝土梁柱节点抗震加固技术，即外加可更换式钢支撑体系加固法。.本项目以主要以高温（火灾）作用后的平面和空间梁柱节点作为研究对象，从试验、数值模拟和理论分析三个方面系统的考察了外加钢支撑体系对混凝土梁柱节点的抗震加固效果，研究因素主要包括是否受火、节点类型、钢支撑尺寸以及加固组合方式等。主要的研究内容和结论如下：.（1）试验共设计了15个钢筋混凝土框架梁柱节点，按是否受火和节点类型分别进行了以下3组试验进行研究，即外加钢支撑法加固高温（火灾）后混凝土梁柱平面、空间节点及常温下空间节点的抗震性能试验研究。.（２）利用ABAQUS和SAFIR有限元分析软件对外加钢支撑体系加固高温后混凝土梁柱节点进行了单调加载下的力学性能数值模拟。首先，选用合适的热工参数，建立了平面和空间节点的温度场模型，发现模拟值与试验值吻合度较高。其次，建立力学分析模型，详细介绍了建模要点，将温度场计算结果导入力学分析模型进行热-力耦合计算，得到各试件的梁端荷载位移曲线、损伤云图、应力应变云图等，并将节点承载力模拟值与试验值进行了对比，证明了模型的准确性。.（3）在试验和数值模拟的基础上进行了理论分析，探究了外加钢支撑体系加固高温（火灾）后受损混凝土梁柱节点的破坏机理，提出了相应的结构力学模型、承载力计算公式和简化设计方法，各试件承载力理论计算值与试验值基本吻合，验证了理论模型的准确性。