新型钢-混凝土混合结构设计理论及地震破坏全过程试验研究

Novel steel-concrete mixed structure is a kind of muitl-lateral resistant mixed strucutre system,which is composed of buckling restrained brace, semi-rigid steel frame and concrete core tube. The yielding of many buckling constraints would dissipate lots of earthquake energy, which would protect the concrete tube and remarkedly improve the seismic behavior of the structure. Several stiffness-ratio parameters, which are used to reflect the relative strength among brace, frame and core tube in the elastic stage, should be put forward. Based on the mathematic and mechanic methods, at the condition of the whole elastic lateral stiffness keeping unchanged, the combination way of those stiffness-ratio parameters should be suggested as the peak of the elastic layers lateral displacement arrives its minimum. Using finite element method, at the condition of the whole elastic lateral stiffness keeping unchanged, the combination way of those stiffness-ratio parameters should be suggested as the peak of the elastic-plastic layers lateral displacement arrives its minimum and the failure mode meets the most optimal failure mode. According to the theoretic and FEM research results, a practical enquiry form of the most optimal stffness ratio parameter combination should be put forward for engineering design. The static reciprocating lateral loading tests should be conducted on three specimens of the novel steel-concrete mixed structures, and at the condition of the whole elastic lateral stiffness keeping unchanged, the relationship between the elastic and plastic peak of the layers lateral displacements, failure progress under the action of earthquake and the stffness ratio parameter combination way should be studied, and also the reliability of the design theory should be verified either.

新型钢-混凝土混合结构是由屈曲约束支撑、半刚性连接钢框架和混凝土核心筒组成的多重抗侧力混合结构体系。众多屈曲约束支撑率先屈服可耗散大量地震能量，对混凝土核心筒起到保护作用，显著提高结构的抗震性能。提出反映支撑、框架和核心筒在弹性阶段相对强弱程度的多个刚度比参数，利用数学及力学方法，研究在保持整体结构弹性侧移刚度不变的条件下，当弹性层间侧移峰值达到最小值时的刚度比参数组合。借助有限元程序，研究在保持整体结构弹性侧移刚度不变的条件下，当弹塑性层间侧移峰值达到最小值且破坏模式符合最优破坏模式时的刚度比参数组合。通过总结理论及有限元研究成果，提出工程设计中最优刚度比参数组合的实用查询表格。进行3个新型钢-混凝土混合结构试件的静力往复加载试验，研究在保持整体结构弹性侧移刚度不变的条件下，弹性及弹塑性层间侧移峰值、地震破坏全过程与刚度比参数组合的关系，并验证理论及有限元研究成果的可靠性。

为了改善钢框架-混凝土芯筒混合结构的抗震性能，提出了钢框架-屈曲约束支撑-混凝土芯筒多重混合结构形式。首先，建立了多重钢-混凝土混合结构的简化力学模型，根据弹性理论推导出在倒三角水平荷载、均布荷载和顶点集中荷载作用下侧移和内力简化算法。其次，提出了一种二阶段屈服防屈曲支撑，其屈服位移较小，可在主体结构破坏前率先屈服并耗散地震能量，保护主体结构，建立该新型支撑的力学模型，并推导了屈服承载力、屈服位移和轴向刚度计算公式，提出该支撑的各种破坏模式及设计流程。然后，为了研究芯筒支撑作用对屈曲模态和屈曲临界荷载的影响，建立了钢-混凝土混合结构体系简化力学模型，在大量有限元分析的基础上，研究了钢-混凝土混合结构体系中框架和支撑两部分之间的相对强弱关系对屈曲模态的影响，并将钢-混凝土混合结构体系划分为4种类型，归纳出可靠地的屈曲模态判断标准，并提出了各类屈曲模态对应的临界荷载简化计算公式。之后，根据竖向悬臂杆的边界条件、弯曲及剪切屈曲侧移曲线，选取了含有三角函数的表达式来近似表示竖向悬臂杆的弯曲分量和剪切分量，利用能量法推导了在轴向均布荷载作用下弯剪型悬臂杆的屈曲临界荷载简化计算公式。通过与有限元计算结果对比，验证了简化算法的可靠性。最后，对一个10层装配新型屈曲约束支撑钢-混凝土混合结构1/8缩尺模型振动台试验研究。研究了该结构体系的动力特性、破坏机理、裂缝出现情况、滞回性能、骨架曲线、弹性及弹塑性阶段的地震反应及抗震性能。分析发现：新型屈曲约束支撑屈服后仍具有稳定的轴向承载力和优越的耗能能力，分担了大量内力和地震能量，对剪力墙起到保护作用，改善了剪力墙的侧移分布特点和延性。