地震次生火灾作用下震损混凝土构件承载力研究

发布时间：2018-03-18 02:23

本文选题：地震次生火灾　切入点：裂缝　出处：《西安建筑科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：我国是地震灾害频发的国家,地震引起的次生火灾造成的损失十分巨大,地震和火灾的耦合作用使得震损混凝土构件的高温性能变得复杂且难以预测。目前国内外关于构件和结构震后抗火的研究较少,因此,很有必要对震损混凝土构件的高温承载力进行深入研究,为震后结构的抗火性能提供坚实的理论依据。通过查阅现有混凝土构件和结构震害的资料,本文以裂缝和剥落作为混凝土构件主要的破坏形式,采用ABAQUS有限元软件,根据工程中构件的实际受火方式,以震损混凝土构件的裂缝深度和剥落宽度作为几何特征参数,建立地震次生火灾作用下震损混凝土构件的有限元计算模型,对其进行高温作用下的温度场分析,在此基础上,开展震损混凝土构件高温承载力的研究,并得到地震次生火灾作用下震损混凝土构件承载力折减系数的计算公式。通过有限元数值模拟分析得到以下主要结论:(1)裂缝对震损混凝土构件温度场分布的影响与裂缝处的受火情况有关,裂缝处的受火情况不同,裂缝震损混凝土构件的横截面温度场和轴向温度场的分布有很大区别。(2)剥落震损混凝土梁温度场的分布取决于剥落处和受火面的相对位置:梁底混凝土剥落时,梁底附近温度升高;梁顶混凝土剥落对温度场的分布没有影响。剥落震损混凝土柱温度场的分布受混凝土剥落的影响较大,相对剥落宽度越大,剥落处附近的温度场分布的凹凸变化越明显。(3)裂缝深度增加,裂缝震损混凝土梁抗弯承载力降低量增大,降低速率减小;裂缝震损混凝土柱抗压承载力降低量和降低速率均增加。裂缝处为绝热面时裂缝震损混凝土构件的承载力大于裂缝处为受火面时的震损混凝土构件承载力。(4)梁下端混凝土剥落的震损混凝土梁抗弯承载力的降低量和降低速率均大于梁上端混凝土剥落的震损混凝土梁。相对剥落宽度越大,剥落震损混凝土柱抗压承载力越低,不同位置的剥落震损震损柱承载力的降低量和降低速率的变化也不同。(5)同一时刻下,根据震损混凝土构件的高温承载力折减系数与震损尺寸的变化关系,得出震损混凝土构件的高温承载力退化与震损尺寸、受火时间三者之间的量化关系。
[Abstract]:China is a country with frequent earthquake disasters. The losses caused by secondary fires caused by earthquakes are enormous. The coupling effect of earthquake and fire makes the high temperature performance of seismic damaged concrete members more complicated and difficult to predict. At present, there are few researches on fire resistance of components and structures after earthquake, so, It is necessary to deeply study the high temperature bearing capacity of concrete members damaged by earthquake, so as to provide a solid theoretical basis for the fire resistance of post-earthquake structures. In this paper, cracks and spalling are taken as the main failure forms of concrete members, and ABAQUS finite element software is used. According to the actual fire mode of the members in engineering, the depth of cracks and the spalling width of damaged concrete members are taken as geometric characteristic parameters. The finite element model of seismic damage concrete members under the action of earthquake secondary fire is established, and the temperature field under the action of high temperature is analyzed. On this basis, the research on the high temperature bearing capacity of earthquake damaged concrete members is carried out. The formula for calculating the reduction coefficient of bearing capacity of seismic damaged concrete members under the action of earthquake secondary fire is obtained. Through the finite element numerical simulation, the following main conclusions are obtained: 1) the influence of cracks on temperature field distribution of seismic damaged concrete members. In relation to the fire at the crack, The fire at the crack is different, The distribution of temperature field in cross section and axial direction of crack damaged concrete members is different from that of axial temperature field.) the distribution of temperature field of spalling concrete beam depends on the relative position of spalling place and fire surface: when the beam bottom concrete is peeling off, The temperature near the bottom of the beam increases, and the spalling of concrete at the top of the beam has no effect on the distribution of the temperature field. The distribution of the temperature field of the spalling earthquake damage concrete column is greatly affected by the spalling of concrete, and the relative spalling width is larger. The more obvious the convexity change of the temperature field distribution near the spalling place is, the more the crack depth increases, the flexural bearing capacity of the crack damaged concrete beam increases and the reduction rate decreases. When the crack is on the adiabatic surface, the bearing capacity of the cracked concrete member is larger than that of the cracked concrete member under the beam. The reduction of flexural capacity and the reduction rate of seismic damage concrete beams with end concrete spalling are larger than those of upper end concrete spalling concrete beams. The relative spalling width is larger than that of upper end concrete spalling concrete beams. The lower the compressive capacity of spalling damaged concrete columns, the lower the bearing capacity of spalling damage columns at different locations and the different variation of the bearing capacity and the decreasing rate of the bearing capacity of the spalling damaged concrete columns at the same time. According to the relationship between the reduction coefficient of high temperature bearing capacity and the size of earthquake damage concrete members, the quantitative relationship between the degradation of high temperature bearing capacity of concrete members and the size of earthquake damage and the time of fire exposure is obtained.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU398.9;TU352

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