活性粉末混凝土梁柱节点抗震性能试验研究

Beam-column joints are very important element in the reinforced concrete frame structures, Beam-column joints which are hubs of forces the key component. The internal forces of beams and columns transfer through joints, so the safe and reliable of the joints' job is a premise to ensure the structure performs well in ductility, rigidity and energy dissipation. The seismic hazards show that the destructive of frame structures mostly concentrated in joints and near fields. It is very difficult to repair and consolidate. The seismic performance of Beam-column joints has drawn the most attention in civil engineering. Reactive powder concrete is a new kind of high-performance concrete, which has high strength, high durability and high toughness, especially for the main seismic components, such as beam-column joint, column and so on. the study on seismic performance of reinforced reactive powder concrete joints can provide the theoretical and experimental basis for application of reactive powder concrete in earthquake engineering.The seismic performance and failure mechanism will be studied by pseudo-static test for beam-column joint models. The factors affecting the seismic performance of joints will be analyzed; these factors include the longitudinal reinforcement ratio of beams and columns, the stirrup ratio of joint core, steel fiber content and axial compression ratio. According to the test results, the restoring force model and seismic design methods of RPC beam-column joints will be presented. The research can provide basis for seismic design of reinforced reactive powder concrete beam-column joint, which has important theoretical and practical value.

梁柱节点是钢筋混凝土框架的重要部位，是钢筋混凝土框架梁、柱的传力枢纽，是保证框架具有足够的延性、刚度及良好的耗能性的关键。震害表明，框架的破坏多集中于节点及其附近区域，且节点破坏后很难加固修复，节点的抗震问题倍受工程界关注。活性粉末混凝土（RPC）是一种新型建筑材料，具有超高强度、高耐久性和高韧性等特性，尤其适用于建筑结构中的梁柱节点、柱等主要抗震构件。活性粉末混凝土梁柱节点抗震性能（延性、滞回特性、破坏机理等）的研究，能为其在抗震工程中的应用奠定理论和试验基础。本项目拟对不同的梁配筋、柱配筋、节点核心区箍筋率、轴压比下活性粉末混凝土梁柱节点进行拟静力试验，研究其抗震性能和破坏机理，建立节点的恢复力模型，提出抗震设计方法，为其抗震设计提供理论依据，具有重要的理论和实际意义。

活性粉末混凝土（RPC）是一种具有超高强度、高耐久性、高体积稳定性的新型超高性能水泥基复合材料。RPC的采用能够大幅度提高钢筋混凝土结构的耐久性前提下，解决普通混凝土框架节点核心区箍筋配置过密的问题，提高框架节点抗震性能。.本项目通过试验研究了水泥强度等级、纤维掺量和养护方法等对RPC基本力学性能的影响，建立了RPC应力-应变关系方程。结果表明，高温蒸汽养护条件下，水泥强度的提高对RPC抗压强度的增长作用明显；钢纤维掺量在0.6%~2.0%范围内时，RPC的强度随钢纤维掺量增加而显著增大；当钢纤维掺量超过2.0%，抗压强度随钢纤维掺量增加增长变缓；高温养护条件有利于RPC的抗压强度的增强。为RPC的应用奠定了基础。.完成了12个RPC梁柱边节点和14个中节点试件的拟静力试验。研究了轴压比、核心区配箍率、贯通节点的梁内腰筋、柱内非角部钢筋等参数对RPC梁柱节点破坏机制、恢复力特性、承载力等性能的影响。结果表明，RPC梁柱节点的失效主要有3种类型：一是梁端弯曲破坏、二是核心区剪切破坏，三是梁端先形成不明显的塑性铰，反复荷载作用下节点剪切破坏。其中梁端弯曲破坏延性和耗能能力最好，核心区剪切破坏时的延性及耗能能力最差。采用高强钢筋可以提高节点的变形和耗能能力，减缓节点的刚度退化和承载力退化。在一定轴压比范围内，增加轴压比可以提高节点的刚度及受剪承载力。但会降低节点的延性、加速刚度退化。在节点核心区箍筋可以减缓节点核心区混凝土斜裂缝的开展，提高构件的承载力及耗能能力，延缓其强度及刚度退化。.通过理论分析和数据统计，建立了适用于RPC框架节点的三线型恢复力模型。提出了达到节点最大受剪承载力时节点箍筋应变沿截面高度的分布函数。考虑核心区RPC斜压杆作用、箍筋及腰筋的作用，建立了钢筋RPC梁柱节点受剪承载力、抗裂承载力计算公式，提出了节点核心区截面最大剪压比控制条件及核心区最小配箍控制条件。为RPC框架结构的抗震设计提供了依据。