【作者】 于航；

【导师】 查晓雄；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2010， 博士

【摘要】 钢管混凝土结构作为一种组合结构形式,有着多种优良的力学特性和良好的抵抗极限荷载的能力。而钢管混凝土结构梁柱节点,对于此种结构在灾害荷载作用下的响应特点有着极为重要的影响。本文针对多种钢管混凝土柱-钢筋混凝土梁节点形式进行了研究,通过试验及有限元等方法对此类节点的抗震性能以及对结构的抗连续性倒塌性能的影响进行了分析。提出了结构连续性倒塌简化分析方法。主要研究内容如下:(1)分别对三种钢筋混凝土梁—钢管混凝土柱节点进行抗震性能试验。节点类型包括焊接节点、搭接节点以及新型钢筋套筒连接节点。通过试验获得了不同节点类型的荷载—位移滞回曲线。并通过试验对比了不同牛腿长度等因素对于节点抗震性能的影响。计算获得了节点的骨架曲线、延性系数、粘滞阻尼系数等参数。通过试验对比分析得出,焊接与钢筋套筒连接方式具有良好滞回性能以及耗能能力。搭接节点同样满足抗震延性要求,但由于试验开展初期裂纹较多,不适宜工程直接应用。同时,通过对试验过程及结果进行观察,分析得出新型钢筋套筒连接节点形式的破坏机理。说明牛腿在试验过程中,对于破坏形态的影响。(2)针对同一梁柱节点形式,分别进行了梁端与柱端低周往复加载试验,对比了两种试验方法获得的节点滞回性能以及不同加载方式所反应的受力特性的差别,分析说明了柱端加载方式更加吻合节点在地震过程中的受力特性,而梁端加载由于在加载过程中约束了沿梁方向的移动,使梁内部受到了拉力,钢筋与混凝土之间出现明显的滑移现象。建议在未来进行节点抗震性能试验研究时,采用柱端低周往复加载,以代替梁端加载的方式,从而获得更加真实的响应特点,以及为工程提供更可靠的参考依据,同时以利于不同节点的抗震性能对比。(3)通过有限元程序对钢管混凝土节点抗震试验进行了有限元模拟验证,结果吻合良好。并对新型钢筋套筒连接节点形式进行了一系列参数分析,分析了,梁、柱、牛腿以及环板等构件各主要的几何及材性影响因素。通过分析发现,柱截面的设计、牛腿上下翼缘厚度以及环板厚度等对节点滞回性能影响很小。而混凝土梁截面的设计抗弯强度对节点抗震性能影响较大。(4)提出了新型钢筋套筒连接节点的三段式骨架曲线模型。通过梁柱理论以及极限平衡等方法,给出了获得各阶段参数值的计算方法。并与有限元分析结果进行对比,验证该模型可以较好的描述节点的骨架曲线。(5)除了地震灾害对结构的危害较大,结构连续性倒塌近些年来也造成了较严重的结构破坏。本文通过对结构进行不同层级的简化分析,给出了简化的结构抗连续性倒塌性能的判定方法。并通过有限元分析进行了验证。此外,本文还对拟静力简化分析方法进行了验证与拓展,经验证适合于考虑楼板效应以及同时多个柱失效的结构连续倒塌工况。并依此提出了2D楼板效应放大系数。(6)采用以上所提出的方法,对采用新型钢筋套筒连接节点的钢管混凝土框架进行了拟静力分析,分析了不同影响因素对结构抗倒塌性能的影响。更多还原

【Abstract】 The concrete-filled-steel-tube (CFST) structure, which is a kind of composite structure, shows a variety of excellent mechanical properties and good resistance to extreme loading capacity. The CFST beam-to-column joint plays an important role when the structure subjected to extreme loading. In this paper, several kinds of reinforced concrete beam to CFST column joint has been investigated with both experimental and finite element methods, and the influences of these joints in seismic and structural progressive collapse has been analyzed. Moreover, the simplified progressive collapse analysis method is proposed.The main contents are as follows:(1) The seismic performance of three kinds of reinforced concrete beam to CFST column joints are studied with experimental methods. The joint types include welded joints, lap joints and new joint with reinforcement sleeve. The force-displacement hysteresis curves of these joints are obtained with experimental methods, and the influence of different bracket lengths are also studied as a parameter in the tests. The skeleton curves, ductility coefficient, viscos damping coefficient are obtained from the hysteresis curves. According to the test results, the welded joint and new joint with reinforcement sleeves show good performance in hysteretic loading and energy dissipation. However, the lap joints still meet the ductility requirement in seismic design, except for a great number of intial cracks in the beginning of the test, and it is not recommended for pratical use. Moreover, the failure mechanism of new joint with reinforced sleeves is discussed from the observation of the specimens during the tests, and the influence of steel bracket on the failure mode is also analyzed.(2) Cyclic loading on beam end and column top are carried on the same kind of joint. The hysteretic behavior obtained from the above two kinds of loading methods are compared and discussed. It is concluded that the loading on column top is more realistic than the other loading method, since the RC beam may subjected to tensile force when vertical load is applied on the beam end and the lateral displacement is restrained. The slippage of reinforcement is thus introduced obviously during the test. Accordingly, the experimental method with cyclic loading on column top is recommended in the future seismic experiments to replace the loading method with vertical loading on beam end. The previous loading method will provide more realistic joint response during earthquake, which will provide an important reference for practical design and for comparison.(3) Finite element analysis is carried on the specimens in the test, and the numerical results are in good agreement with the test results. A series of parametric analysis are conducted on the new joint with reinforcement sleeves, in which the beam, column, bracket and annular plate are investigated as geometry or material properties parameters. According to the FEA results, the design of column section, the thickness of steel bracket and the thickness of annular plate has little influence on the hysteretic behavior of the joints, while the design bending capacity of beam plays a more important role in seismic performance.(4) A three-stage skeleton curve model is proposed for the new joint with reinforcement sleeves. The calculation methods of the parameters in these stages are provided from the beam-column theory and limit equilibrium methods. FEA results are compared with the theoretical results, which show good agreement on the skeleton curves.(5) In addition to the great damage caused by the seismic hazard, the structural progressive collapse has also become a kind of severe structural damage reason in recent years. In this paper, several levels of simplified analysis methods are proposed for evaluating the potential of structural progressive collapse, and verified with finite element analysis method. Moreover, the simplified pseudo-static analysis method is also verified and developed in this paper, which is proven to be suitable for the situation with the membrane action of floor and the cases with several column deleted simultaneously. 2D floor membrane action amplification factor is thus proposed for the structures with floor.(6) The pseudo-static analysis method presented above are utilized to study the behavior of CFST structure with new reinforcement sleeve joint, and the influence of different factors on the potential of structural progressive collapse are analyzed based on the framework presented above.更多还原