钢管约束的钢管混凝土新型组合构件力学性能与设计

This application proposes an innovative steel-tube-confined concrete-filled steel tubes, which is composed of concrete-filled-steel-tube, outer steel tube and intermediate sandwich material. The outer steel tube and the intermediate sandwich material do not bear the loading directly, but provide high efficiency horizontal confinement to the concrete core passively. The confinement leads to better ductility and lesser brittle failure tendency. The proposed new members are of simple structures and clear load bearing mechanism. The new members can greatly upgrade the bearing capacities and ductility of traditional concrete filled steel tubes, improve the seismic behavior, fire and corrosion resistance. They can also eliminate fundamentally the potential gaps between steel tube and concrete. Comprehensive theoretical and experimental research will be carried out on steel-tube-confined concrete-filled-steel-tubes under static and hysteretic loadings. The key parameters include steel ratio, concrete strength, and compressive ratio and shear span ratio. The working mechanism among outer steel tube, inner steel tube and concrete will be scrutinized. Subsequently, regarding the proposed new members, proposition will be made on the calculation methods of bearing capacities, the design criteria and ductility for the new members under axial and eccentric compression. The proposition will also be made on the hysteretic models for the new members under axial and horizontal cyclic loading. In the end, suggestions will be provided for the static and aseismic design of the new steel-tube-confined concrete-filled-steel tubes.

本项目创新提出的钢管约束的钢管混凝土构件由钢管混凝土、外套钢管和夹层材料组成。外套钢管和夹层材料不直接承担外荷载，对核心混凝土提供高效侧向约束，能显著提高核心混凝土的变形能力，可避免核心混凝土的剪切脆性破坏。这种新型构件构造简单、受力明确，可明显提高传统钢管混凝土的承载力和延性，提升构件的抗震、耐火和耐腐蚀性能，可从根本上解决钢管与核心混凝土的脱开，便于构件在承载力不足和地震破损后的修复，具有优越的力学性能和构造优势。本项目将针对静力与低周往复荷载作用下钢管约束的钢管混凝土柱的性能进行系统深入的试验研究和理论分析，考虑含钢率、核心混凝土强度、轴压比和剪跨比等参数的影响，研究外套钢管、内层钢管与核心混凝土之间的相互作用机理，提出钢管约束的钢管混凝土柱的轴压及偏压承载力计算方法，提出构件承载力和延性的设计指标，建立往复荷载作用下构件的恢复力模型，给出钢管约束的钢管混凝土柱的静力与抗震设计建议。

钢管约束的钢管混凝土是在传统钢管混凝土外部套设外层钢管后，使用夹层材料填充两者间隙而形成的一种新型钢-混凝土组合柱。外层钢管不进入梁柱节点区域，基本不承担竖向荷载，可有效约束内部核心混凝土，提高构件承载力和变形性能。本项目首先对51个钢管约束的钢管混凝土短柱开展了轴压荷载作用下的试验研究，获得了构件的变形发展过程和破坏模式，分析了内层钢管和外层钢管应变和应力发展规律；进行了轴压有限元分析，明确了外层钢管、夹层材料、内层钢管和核心混凝土的相互作用，揭示了构件在轴压荷载作用下的工作机理；基于试验研究和有限元分析，提出了钢管约束的钢管混凝土短柱轴压承载力设计方法。其次，进行了14个钢管约束的钢管混凝土长柱偏压试验，对比了不同参数构件的试验现象和破坏模式；进行了长柱偏压有限元分析，揭示了钢管约束的钢管混凝土在偏压荷载作用下的工作机理。基于试验研究和有限元分析，提出了钢管约束的钢管混凝土压弯承载力设计方法。最后，开展了4个钢管约束的钢管混凝土柱试件在往复水平荷载作用下的滞回性能试验，观察并对比了各试件的破坏模态，分析了试件的滞回曲线、骨架曲线、刚度发展、强度退化规律和耗能能力；进行了相应的有限元分析，揭示了钢管约束的钢管混凝土柱滞回工作机理，得到了关键参数对其抗震性能的影响规律；基于试验和有限元分析，提出了钢管约束的钢管混凝土柱在往复水平荷载作用下的恢复力模型和抗震性能设计方法。研究成果将促进钢管约束的钢管混凝土柱在实际工程中的推广和应用。