钢管桁架结构加强型K节点抗震破坏机理及设计对策

Unstiffened tubular joint is the key part of truss structure of steel tubular and the part which can dissipate the energy that produced by the infrequent earthquakes. Theoretical analysis and experimental study were conducted under low cycle load reversals to study the seismic behavior of unstiffened overlapped C-C and R-C reinforced K-joint of truss structure of steel tubular with the use of non-linear finite element analysis and full scale quasi-static tests and research status at home and abroad, different forms of reinforced K-joint seismic failure mechanism was explored. Mixed hardening constitutive model was established with the mixed hardening and the damage constitutive introduced to the three-dimensional large deformation finite element analysis under cyclic loading. The computer simulation of steel tubular connection joints hysteretic behavior to lay the foundation. To hysteretic characteristics of different type reinforced K-joints, the deformation capacity and energy dissipation capacity was quantitative evaluated, the reasonable value of the key parameters was acquired. Through the analysis of the testing data and finite element, restoring force model of reinforced K-joints was acquired, different type reinforced K-joints bearing capacity formula was raised, the practical design method for reinforced K-joints seismic was formed. Provide a theoretical basis and technical support for the design and construction of large-span steel truss structure.

节点是钢管桁架结构的关键部位也是地震作用耗散能量的部位。结合国内外研究现状，运用非线性有限元分析和钢模型足尺试验，对钢管桁架结构的主圆支圆（C-C）及主方支圆（R-C）K型搭接节点，在不同加强措施下的节点抗震性能进行了系统的理论分析及试验研究，以探究不同形式的加强型K节点的抗震破坏机理；将混合强化、损伤本构引入循环荷载三维大变形有限元分析中，构建混合强化本构模型，为管桁结构连接节点滞回性能的计算机模拟奠定基础；根据不同形式的加强型K节点的滞回特性，量化评价其变形能力和耗能能力，得到不同形式的加强型K节点关键参数的合理取值；通过试验及有限元分析得到加强型K节点的恢复力模型，提出不同形式加强型K节点的承载力计算公式，形成带有加强型K节点管桁结构的抗震实用设计方法，为大跨度钢管桁架结构的设计与施工提供理论依据和技术支撑。

节点是钢管结构的关键部位和罕遇地震下产生能量耗散的部位。直接焊接K型搭接节点是钢管结构的主要连接形式。这种直接焊接的管节点，其搭接处的内隐藏焊缝在实际工程中一般无法施焊。为提高施工效率，保证K型搭接节点搭接处的隐藏焊缝不焊接且承载力不至于大幅度降低，需要对该节点进行局部加强。该项目运用非线性有限元分析和钢模型足尺试验，对钢管桁架结构的主圆支圆（C-C）及主方支圆（R-C）K型搭接节点，在主管壁加垫板、主管内灌砼、主管内加套管夹层灌砼三种不同加强方式下的节点抗震性能进行了理论分析及试验研究，揭示了不同形式加强型K节点的抗震破坏机理，量化评价了其滞回耗能特征；通过管结构连接焊缝焊材标准件试验，建立了焊材损伤累积演化方程。基于Ramberg-Osgood模型，通过引入损伤变量，构建了考虑损伤累积影响的焊材损伤滞回模型；通过试验及有限元参数分析，得到了不同形式加强K节点的恢复力模型，提出各加强K节点关键参数的合理取值；将加强节点体系还原于桁架中，对Warren桁架在主管不同加强模式下的静力性能进行了研究，得到了其最优的加强模式。研究表明：对于焊接节点的母材与焊材，需要采用不同的本构模型，以满足连接节点的精确设计；主管壁加垫板的加强模式，垫板厚度的增加，延缓了主管的塑性变形，提高了节点承载力；主管灌砼的加强模式，在一定程度上降低了节点延性，但提高了节点承载力，延缓了节点刚度退化速度。主管中空夹层灌砼的加强模式，有效减缓了主管管壁的塑性屈曲破坏，提高了节点的承载力，使得支管先于主管破坏，是一种有效的加强方式。当主管内套管钢号低于主管钢号或主管空心率等于53%时，K节点耗能匹配最为合理；弦杆内填砼的加强桁架，是一种优越的加强方式。研究结果为直接焊接的钢管结构连接节点的精确设计及抗震性能分析提供了理论依据。