强化型异形截面多腔钢管混凝土巨型分叉柱受力机理研究

Special-shaped concrete-filled steel tube tree megacolumns were adopted in the project of China Zun in Beijing. They consist of special-shaped multi-cell concrete-filled steel tube megacolumns with huge sections at the bottom, and tree megacolumns at the upper part connected by tree megajoints in the middle of the building. Model tests on the shaking table show that the section at the corner and the tree portion of megacolumns were damaged seriously under violent earthquakes. With regard to this, the tree megacolumn with strengthened section at corner and strengthened tree portions was proposed in this project. In order to investigate its stress mechanism, the compression and bending performance of special-shaped concrete-filled steel tube tree megacolumns with different construction details, the compression performance of typical tubes of megacolumns, as well as low cyclic loading tests of tree megacolumns will be conducted. The element constitutive relationship and the numerical analysis model will be established by considering the structure design of megacolumns in the project of China Zun, and combined with the common requirements of other similar projects. Based on combination of experimental study, theory analysis and numerical simulation, the load bearing capacity, stiffness, ductility and damage evolutionary process will be analyzed, and the stress mechanism will be revealed. The load bearing capacity model and resilience model of the strengthened tree megacolumns will be presented and the reasonable construction details will be provided so as to lay the foundation of theory and key techniques for structure design of strengthened special-shaped concrete-filled steel tube tree megacolumns.

北京“中国尊”大厦采用了异形截面多腔钢管混凝土巨型分叉柱，它由底部超大异形截面多腔钢管混凝土巨型柱、巨型分叉节点和上部巨型分叉柱构成。模型振动台试验表明，大震下巨型柱截面的角部和分叉部位损伤较严重，为此，本项目提出了角部和分叉部位强化型巨型分叉柱。为深化研究强化型异形截面多腔钢管混凝土巨型分叉柱的受力机理，将进行不同构造形式的异形截面多腔钢管混凝土巨型分叉柱的压弯性能、巨型柱典型腔体受压性能、巨型分叉柱低周反复荷载下抗震性能试验研究，结合“中国尊”大厦异形截面多腔钢管混凝土巨型分叉柱的工程设计，兼顾类似工程共性需求，建立单元本构关系和数值分析模型，采用试验研究、理论分析、数值模拟相结合的方法，分析其承载力、刚度、延性及损伤演化过程，揭示受力机理，建立强化型异形截面多腔钢管混凝土巨型分叉柱承载力计算模型和恢复力模型，提出合理构造措施，为强化型巨型分叉柱设计提供理论与关键技术支撑。

超高层建筑持续增多，建筑平面设计和立面设计的需求随之增加，异形截面多腔钢管混凝土巨型分叉柱，适应了超高层巨型框架结构的发展，满足了建筑平面设计与结构设计的需求，是一种受力性能良好的钢管混凝土柱。本项目首次提出了角部和分叉部位强化型巨型分叉柱，较系统进行了7个不同构造多腔钢管混凝土巨型分叉柱模型轴压、偏压性能试验研究，6个不同构造巨型分叉柱下部巨型柱模型轴压、偏压性能试验研究，6个不同构造多腔钢管混凝土巨型柱典型腔体模型轴压性能试验研究，13个不同构造多腔钢管混凝土巨型分叉柱模型低周反复荷载试验研究和10个不同构造巨型分叉柱下部巨型柱模型低周反复荷载试验研究。采用试验研究、数值模拟、设计研究相结合的方法，进行弹塑性有限元分析，阐明了损伤演化规律，揭示了体系延性屈服机制的实现条件，优化了构造和设计参数，提出了恢复力模型；提出了承载力模型和计算公式。研究表明：异形截面多腔钢管混凝土分叉柱的损伤破坏大多发生在截面突变的分叉界面处，主要破坏为焊缝边缘焊接热影响区的钢板撕裂；角部设置圆钢管加强试件滞回环饱满程度明显提高，屈服荷载和峰值荷载提升9.1%－13.1%；内置圆钢管能够有效的提高试件的偏压承载力，延性以及复位能力；设置竖向加劲肋，可明显提高试件刚度、承载力、延性和耗能；竖向肋板间焊接水平拉结筋后，在试件后期变形过程中可有效约束截面横向变形，提高受力性能；钢管内壁焊接栓钉可增强钢管与混凝土共同工作性能的作用，减缓峰值后的退化过程；钢管腔体内设置横隔板后，试件初始刚度有所增大，承载力提高19.1%、耗能能力提高12.9%；钢管腔体内增设钢筋骨架后，加载后期的受力性能更稳定，耗能能力提高20.0%；钢管壁厚应与混凝土强度合理匹配。本成果发展了异形截面多腔钢管混凝土巨型分叉柱设计理论与技术，针对北京“中国尊”大厦进行应用研究，为大型复杂超高层建筑抗震设计提供了高效的抗震措施和设计方法，具有重要的科学意义和工程价值。

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