【作者】 张连河；

【导师】 赖明； 李英民；

【作者基本信息】 重庆大学 ， 结构工程， 2009， 硕士

【摘要】 结构超强对结构在强烈地震中保持良好的性能具有重要的作用。在结构设计中,适当地考虑结构超强可以降低结构的设计地震作用,从而设计出更经济合理的结构。对于结构超强问题,国外研究开始较早,美国等国规范在确定设计地震作用时均考虑了超强系数;国内在此方面则起步较晚,研究成果较少,各自所得的结论也不尽统一,中国规范则未考虑结构超强的影响。基于上述现状,本文初步完成的工作如下:①严格按我国现行规范设计了10栋多高层钢筋混凝土框架结构,采用平面框架和三维框架模型进行静力弹塑性分析,求得各模型的超强系数,考察了按我国规范设计的钢筋混凝土框架结构潜在的超强能力;②分析了结构层数、抗震设防烈度、现浇楼板、填充墙、平面与三维框架分析方法等因素对超强系数的影响规律;③从构件超强角度阐述了应避免的超强因素,并基于梁弯曲超强对“强柱弱梁”的实现做了思考;还对由于楼板使梁弯曲超强可能引起结构破坏机制的变化做了初步分析;④为了对我国规范结构超强问题初步探讨,假定超强系数取为1.5,降低我国抗震规范所取的设计地震作用,设计了0.1g区、0.2g区的钢筋混凝土框架,进行静力弹塑性分析,考察其在中震、大震下的抗震性能。通过以上研究,得到的主要结论如下:①算例分析结果表明,严格按我国规范设计的钢筋混凝土框架结构的超强系数最小值可取为1.5;②各因素对超强系数的影响规律主要是:1)超强系数随着层数的增多逐渐减小;2)超强系数随着抗震设防烈度的增大逐渐减小;3)仅考虑楼板翼缘混凝土受压贡献,超强系数略有增大,考虑楼板及其配筋贡献,超强系数提高较大;4)填充墙均匀布置对超强系数提高显著;5)中间榀框架的超强系数大于边榀框架的超强系数;三维框架的超强系数介于中间榀与边榀之间;③基于梁弯曲超强对“强柱弱梁”的思考,提出了考虑梁的超强来实现结构“强柱弱梁”的设计思路;考虑现浇楼板参与工作后,按我国现行规范进行抗震设计,柱端可能较早进入塑性,结构可能出现柱铰机制。④算例分析结果初步表明:按中国现行规范的抗震措施考虑超强系数为1.5时,结构基本上仍可满足抗震规范要求。这一结论虽是基于算例得出的且有待更深入研究,但其反映出的问题值得规范今后修订时注意。更多还原

【Abstract】 Structure overstrength plays an important role in keeping satisfactory performance of structures during strong earthquake. Appropriately considering the overstrength of structre can be used to reduce the level of seismic in structural design, in order to design a more rational structure. Structure overstrength has been taken into consider in design codes of the United States, and other countries , however, domestic research startes late and few achievement is obtained. Overstrength effect is not embodied in domestic design codes.Based on the facts above, the main work finished preliminarily in this thesis is as follows:①Ten RC frame structures are designed strictly according to Chinese seismic code, and the two-dimensional frame and three-dimensional frame are analyzed to obtain the overstrength factors. Furthermore, structural overstrength capacity of reinforced concrete frames designed by domestic codes is studied.②contribution and discipline of influence factors are analyzed to make overstrength factors more reasonable.Influence factors considered in this article include number of stories, seismic fortification intensity, comparison of interior frames, exterior frames and three-dimensional frames, contribution of cast-in-place floors, infilled walls and so on. The infilled walls are divided into completely infilled walls and the cavity filled walls.③Not all the factors contribute to the overstrength, and this paper also analyzes factors with adverse effect, including the changes of collapse mechanism caused by beam bending overstrength, beam shear failure by beam bending overstrength, destruction of weak layer caused by participation of infilled walls, short column damage and so on. In addition, emphasis is put on the changes of collapse mechanism resulted from floor overstrength to beam.④In order to preliminary study to structure overstrength of chinese code. Overstrength factor is assumed as 1.5 and earthquake effect in domestic design code is reduced. RC frames are designed for 0.1g and 0.2g zones and static elasto-plastic analysis of those frams is finished. Aseismic performance in severe earthquake and moderate earthquake is researched.Through main work of the above, conclusions can be obtained as follows:①Based on an overall consideration of various factors, minimum value of overstrength factor is conservatively estimated as 1.5 for RC frame structures strictly designed by domestic codes.②The laws of the factors impacting on structural overstrength: 1) as the number of stories is increased, the overstrength factor is gradually decreased; 2) As the seismic fortification intensity is increased, the overstrength factor is gradually decreased; 3) If only considering compression of concrete flange of slabs, the overstrength factor increases slightly, when the roles of slab and its reinforcement are considered, the overstrength factor increases greatly; 4) The overstrength factor is significantly increased due to the infilled walls which are arranged uniformly, 5) The overstrength factor of interior frames is commonly greater than that of exterior frame. The overstrength factor of three-dimentional frames is commonly less than that of interior frame and close to that of exterior frame.③The unfavorable action of factors impacting on the structure overstrength: 1) the changes of collapse mechanism and shear failure caused by beam bending overstrength. Unreasonable and arbitrary actions to strengthen elements and improve reinforcement should be avoided in the design and construction; 2) considering participation of cast-in-place floor,“strong column weak beam" requirement may not be able to realized according to current approach in seismic design code. Column hinge mechanism may appear and specifications allowing to layout reinforcement which not exceeds the specified ratio in the certain scope outside the rib width (such as the United States code)are suggested; 3) The weak layer and short column damage may be caused by the stiffness effect and restraint effect of the infilled wall, and current codes are proposed to make clear the stiffness effect and restraint effect in certain circumstances so as to improve the design of structures with infilled walls.④Analysis results indicate that According to chinese current anti-seismic measures, when the overstrength factor is considered to be 1.5, the structure can basically meet requirements in the seismic code. This conclusion is obtained basing on numerical example, which needs to further study, but the problems reflected by the conclusion are worth to pay attention in the future amendment for codes.更多还原