新型配筋ECC-自预应力钢管混凝土组合柱及梁柱节点优化设计及抗震性能研究

Concrete filled steel tube structure is a kind of high performance composite structure with the advantages of light weight and high strength and high ductility，but as the outer layer the steel tube is prone to corrosion and its strength degrades quickly under high temperature, causing this kind of structure in short of good durability and fire resistance. In this study, a novel Reinforced ECC/Self-Prestressing Concrete Filled Steel Tube (R/ECC-SPCFST) composite structure is put forward for enhancing the safety, durability and fire resistance of the steel-concrete composite structure. For the R/ECC-SPCFST composite column, the outer ECC layer has super high ductility and crack control ability. High performance concrete with self-compacting and micro expansion properties is used as the core concrete for the concrete filled steel tube, which can produce pre-stressing in the steel tube caused by expansion of the core concrete and improve composition effect between steel tube and core concrete. Application of this kind of composite column can effectively improve the loading carrying capacity, durability and fire resistance of structures. Firstly, optimal mixture design will be conducted to establish high performance concrete and homemade PVA fiber based ECC materials with different strengths. Experimental studies will be conducted to obtain the mechanical properties and the stress-strain relationships in uniaxial tensile and compressive stress states. Then, the mechanical behaviors and failure mechanism of reinforced ECC columns, self-prestressing concrete filled steel tubes and R/ECC-SPCFST composite columns will be investigated. The stress-strain relationships of reinforced ECC and steel tube confined expansion concrete will be proposed by considering the effect of shrinkage and creep of the high performance concrete. The calculation model for predicting the load capacities of the composite column under centric or eccentric loading will be derived. Then, the seismic behaviors of R/ECC-SPCFST composite columns and the corresponding beam-column joint specimens will be studied through reversed cyclic loading tests, and the hysteretic models will be proposed. Finally, based on the elastoplastic mechanical analysis, a performance based method will be put forward for designing the R/ECC-SPCFST composite column and beam-column joints.

钢管混凝土组合结构强度高、自重轻、延性好，但外层钢管易锈蚀、高温性能差，使得其耐久性和抗火性能相对不足。据此，本项目提出一种新型配筋ECC-自预应力钢管混凝土组合结构，外层ECC具有超高的延性和良好的裂缝控制能力，内部钢管混凝土采用自密实微膨胀混凝土，通过混凝土微膨胀变形形成钢管约束混凝土预应力，增强了两者组合效应，大幅提升结构承载力、耐久性和抗火性能。首先，基于材料设计理论和方法，制备高性能混凝土和基于国产PVA纤维的ECC材料，得到其单轴拉压本构关系及力学性能参数；然后，研究配筋ECC柱、自预应力钢管混凝土柱和组合柱的受力破坏机理，建立箍筋约束ECC和考虑收缩徐变影响的自预应力钢管混凝土的本构关系，推导组合柱承载力计算模型；对组合柱及梁柱节点进行拟静力试验，研究其破坏机理并建立相应的恢复力模型。最后，进行弹塑性分析，建立基于性能的组合柱和梁柱节点的抗震设计方法，为工程应用提供理论依据。

钢管混凝土组合结构强度高、自重轻、延性好，但外层钢管易锈蚀、高温性能差，使得其耐久性和抗火性能相对不足。据此，本项目提出一种新型配筋ECC-自预应力钢管混凝土组合结构，外层采用具有超高的延性和裂缝控制能力的配筋ECC，内部钢管混凝土采用自密实微膨胀混凝土，大幅提升结构承载力、耐久性和抗火性能。.首先，基于国产PVA纤维和大掺量粉煤灰研制了低成本ECC，其拉伸延性和强度达到3%和6MPa，得到了其单轴拉压本构关系及性能参数；对自密实微膨胀混凝土配合比进行优化设计，建立了其随时间变化的自由变形计算模型，阐明了膨胀剂掺量及径厚比对自预应力钢管混凝土柱膨胀性能的影响规律；开展了自预应力钢管混凝土膨胀性能试验及轴心受压性能试验，得到了钢管混凝土环向应变随时间变化的规律，分析了不同参数对其轴压性能的影响。.然后，对钢筋增强ECC-钢管混凝土组合柱和钢管混凝土叠合柱进行轴压试验，分析了不同参数对组合柱轴压性能的影响；开展了钢筋增强ECC-钢管混凝土组合柱的偏压试验，建立组合柱的偏压承载力计算模型，并分析了不同参数对其偏压性能的影响；研究了钢筋增强ECC-钢管混凝土组合柱在低周反复荷载作用下的力学性能，澄清了箍筋间距、钢管直径及轴压比对组合柱抗震性能的影响，建立了组合柱的恢复力模型。接着，对ECC环梁节点进行了局部受压试验，在节点区用ECC可有效减小裂缝宽度，提高了环梁节点的承载力和延性；揭示了ECC环梁节点在局部受压下的受力机理，分析了不同参数对环梁节点受压性能的影响；基于拉杆拱模型建立了ECC环梁节点在局部受压下的承载力计算公式；澄清了RECC环梁节点在偏心荷载作用下传力机理，建立了RECC环梁节点的偏压承载力计算模型；对RECC环梁节点进行了低周反复试验，当破坏发生在梁端时，ECC试件的延性和耗能性能分别是混凝土试件的1.4倍和1.9倍；揭示了RECC环梁节点受剪破坏机理，基于软化拉压杆模型，建立了其抗剪承载力计算模型。.最后，基于试验结果、模拟分析和理论推导，对所提出的钢筋增强ECC-钢管混凝土组合柱构件及新型RECC环梁节点提出了相应的设计方法，为工程应用提供了理论依据。