山地掉层RC框架结构强震破坏失效模式分析

发布时间：2018-08-28 06:15

【摘要】：按地貌类型划分我国有三分之一的国土属于山地,掉层框架结构是山地建筑中应用的最为广泛最具有代表性的建筑结构形式。掉层框架的不等高接地形式,决定了其受力性能与普通平地框架结构存在显著差异,目前国内外均无针对山地框架结构设计的成熟规范,山地框架结构的抗震性能研究显然已经滞后于实际工程的需要。尤其自汶川地震以来,诸多结构在强震下的破坏失效模式与结构设计时的预期有所较大的差别,同时由于大量频发地震带均属于山地地貌,有必要研究清楚山地掉层框架结构在强震下的破坏失效模式,同时因为结构多维理论研究进展缓慢及软件开发等历史原因,以往对于山地框架结构的地震响应分析长期以杆系简化模型为主,因此研究山地框架结构基于精细化实体模型的地震响应很有必要。首先以一个8度0.2g区的掉层框架结构作为研究对象,采用通用有限元分析软件ABAQUS,从结构混凝土塑性损伤系数、各个地震响应指标的时程曲线等方面,讨论与评价了基于精细化实体模型的空间掉层框架结构在强震下的破坏失效模式,并分析了有无楼板、楼板厚度、楼板梁端开缝形式等诸多因素对掉层框架结构的破坏失效模式的影响。进一步以另一个8度0.2g区的空间掉层框架结构作为研究对象,采用结构非线性分析与性能评估软件Perform-3D,从整体和局部两个层次上,讨论与评价了空间掉层框架结构在2组近断层地震动和2组远场地震动输入下的抗震性能,分析了在各条地震波作用下,改变掉层框架结构的柱截面尺寸、梁端配筋率、柱端配筋率、结构掉跨情形等因素对掉层框架结构的破坏失效模式的影响,并研究了近场脉冲对山地框架结构的影响。通过本文的研究,得到如下主要结论:(1)ABAQUS建立的精细化实体掉层框架模型在强震下显示出梁柱混合出铰的破坏失效模式,而SAP2000建立的杆系简化模型则显示为以梁铰为主的破坏失效模式,说明ABAQUS建立的精细化实体模型确实能够更加真实有效的反应出掉层框架结构在大震作用下的破坏失效模式;无楼板掉层框架结构中梁的破坏早于柱,且梁破坏更严重一些,偏向于“强柱弱梁”的失效模式,而有楼板的掉层框架结构,其破坏失效模式偏向于混合出铰模式;基于弹性楼板的假定下,ABAQUS计算结果不能真实反映结构在地震作用下的屈服顺序和塑性耗能分布,给出的结构地震失效描述没有弹塑性的科学合理;三种板厚变化(80mm-100mm-120mm)均为梁柱混合出铰模式,但板厚的增加更有利于延缓梁的破坏且加速加重柱的破坏;在掉层框架结构梁端现浇板设缝合适的时候,能够降低板对于梁抗弯承载能力的加强作用,结果表明柱子的损伤破坏情况得到了一定的延缓,有利于结构出现“强柱弱梁”的破坏失效模式。(2)梁端负筋的增多会导致柱子破坏的加速加剧,容易形成梁柱混合出铰的破坏失效模式;柱端配筋的增多能有效的强化柱子,使得结构更容易出现“强柱弱梁”破坏失效模式表明减小柱截面尺寸会严重不利于“强柱弱梁”,但过于加大柱截面尺寸也同样不利于柱的保护;从梁柱出铰的情况看来,减少掉跨数目,掉层框架结构柱端出铰率会增加,更容易出现梁柱混合出铰的破坏模式,适当增加掉跨数目,可以减少柱端出铰率,使结构更偏向于强柱弱梁的破坏模式。(3)含速度脉冲的近断层地震动的低频分量丰富,对中长周期(大于0.9s)结构产生更不利的影响;而远场地震动对短周期(小于0.9s)结构有较强的破坏作用。含速度脉冲的近断层地震动对掉层结构的地震反应(即结构的整体反应指标和局部反应指标)均有不同程度的放大作用。
[Abstract]:One third of China's land is in mountainous area according to geomorphological type, and the falling floor frame structure is the most widely used and representative building structure in mountainous area. Since the Wenchuan earthquake, the failure modes of many structures under strong earthquakes are quite different from the expectations of structural design. At the same time, because a large number of frequent earthquake zones belong to mountain landforms, the seismic performance of mountain frame structures has obviously lagged behind the actual needs of engineering. It is necessary to study the failure modes of frame structures in mountainous areas under strong earthquakes. Because of the slow progress of multi-dimensional theory research and the development of software, the simplified member model has long been the main seismic response analysis method for frame structures in mountainous areas. It is necessary to study the seismic response of a falling-floor frame structure in the area of 0.2g of 8 degrees. Using the general finite element analysis software ABAQUS, this paper discusses and evaluates the strength of the spatial falling-floor frame structure based on the refined solid model from the aspects of the plastic damage coefficient of the structure concrete and the time-history curves of each seismic response index. The failure modes of frame structures with or without floor slabs, floor thickness, and the cracks at the end of floor beams are analyzed. The nonlinear analysis and performance evaluation software Perform-3D is used to analyze the failure modes of frame structures with or without floor slabs. On the whole and local levels, the aseismic performance of spatial frame structures with floor dropping is discussed and evaluated under two groups of near-fault ground motions and two groups of far-field ground motions. The factors such as changing the column section size, beam-end reinforcement ratio, Column-end reinforcement ratio and structure span dropping are analyzed under the action of each seismic wave. The main conclusions are as follows: (1) The refined entity falling story frame model established by ABAQUS shows the failure mode of beam-column mixed with hinges under strong earthquakes, while the simplified model established by SAP2000 shows the failure mode of beam-column mixed with hinges. For the failure mode of beam hinge, it shows that the refined entity model established by ABAQUS can reflect the failure mode of the frame structure more truly and effectively under the action of large earthquakes; the failure of the beam in the frame structure without floor falling is earlier than that of the column, and the failure of the beam is more serious, and it tends to the failure of the "strong column and weak beam". Based on the assumption of elastic floor, the results of ABAQUS can not truly reflect the yield order and plastic energy dissipation distribution of the structure under earthquake, and the seismic failure description of the structure is not reasonable and scientific. Both of them are beam-column mixed hinge mode, but the increase of plate thickness is more conducive to delaying the damage of beam and accelerating the damage of column; when the cast-in-place slab at the beam end of the frame structure is sutured properly, the strengthening effect of slab on the bending capacity of beam can be reduced, and the results show that the damage and failure of column is certain. (2) the increase of the negative reinforcement at the end of the beam will accelerate the failure of the column, which is easy to form the failure mode of beam-column mixed hinge; the increase of the reinforcement at the end of the column can effectively strengthen the column, making the structure easier to appear the failure mode of "strong column and weak beam". Reducing the section size of columns is not conducive to "strong columns and weak beams", but increasing the section size of columns is also not conducive to the protection of columns. (3) The low-frequency component of near-fault ground motions with velocity pulses is abundant, which has a more adverse effect on Medium-long Period structures (greater than 0.9s); and the far-field ground motions have a stronger destructive effect on short-period structures (less than 0.9s). The seismic response of story structures (i.e. the overall response index and the local response index) can be amplified to varying degrees.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU375.4

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