超长地下室设计中的关键技术问题的应用研究
发布时间：2018-08-20 18:14
【摘要】：随着国民经济的迅速发展,城市建设规模的日益扩展,土地供应量日趋紧张,致使地下车库建设与日俱增。地下车库设计的现状是:车库单体面积日益增大,尤其是车库长度不断扩大,地下室的平面尺寸越来越大,有些甚至达到或超过200～300米,设计超长车库时势必会面临很多难题。目前,结构师设计大型车库时主要考虑的是正常使用工况,对施工工况缺少关注。设计人员常认为顶板上有覆土,季节温差很小,如已按规范要求设置温度后浇带则无需计算温度应力。但实际情况是,施工方常将地下室顶板作为施工场地,或认为设计设置后浇带已经考虑了温度应力,即使在温度后浇带封闭之后也未及时覆土,而导致地下室顶板、外墙大面积开裂,甚者,突遇强降雨,导致地下室局部抗浮破坏。故设计文件应对施工覆土的时间以及施工期间地下水位控制提出明确要求,以使现场情况与设计成果相符。虽然平板式筏板基础在纯地下室工程中的应用已经很广泛,但是,在工程设计中存在着柱墩尺寸偏大,筏板厚度偏厚,选取的基床系数与地基条件、筏板的实际受力情况不相符,特别是柱墩的配筋偏大等设计不合理、不经济的现象。基于以上情况本文通过计算实例,对影响平板式筏板基础内力的主要因素进行了详细的分析,以找出其中的变化规律。本文主要针对四个关键技术问题进行阐述:包括(1)大型地下室顶板的温度应力及裂缝分布;(2)地下室外墙的温度应力及裂缝分布;(3)纯地下室筏板基础的优化设计;(4)地下室未覆土前,按空腹桁架模型及整体有限元分析地下室的局部抗浮问题。取得的主要成果如下:1.讨论了超长混凝土结构间接作用的构成及相应的计算方法,对混凝土结构的间接作用和荷载作用进行了比较。在超长混凝土结构工程设计中,将混凝土收缩等效为温差,考虑徐变作用为结构弹性解乘以近似0.3的折减系数,是一种实用有效的方法。2.超长混凝土结构间接作用下的内力分析需要考虑混凝土开裂后的影响,讨论了超长混凝土结构在间接作用下的内力分析方法,并对南通某安置房住宅项目的地下室顶板、外墙在间接作用下的内力进行了分析。超长地下室顶板周边有地下室外墙约束的部位,楼板的面外刚度对温度应力的影响不容忽视,需考虑降温和升温两种工况,并对楼板分别采用考虑及不考虑面外刚度两种假定进行分析。3.设计超长混凝土结构时,不仅要考虑使用工况下的荷载,还应适当考虑在施工工况下可能出现的不利情况,如:因未及时覆土而引起的较大温度应力,甚至地下室抗浮事故。边跨梁端的抗弯配筋和边跨柱顶的抗弯、抗剪配筋一般由施工工况控制,设计时需对相关部位进行加强。4.采用有限元软件进行分析,以确定不同参数(基床系数、柱墩厚度、筏板厚度、柱墩平面尺寸等)对纯地下室筏板基础受力性能的影响。在满足抗渗、抗浮要求的前提下,合理地选取底板的厚度,并优化底板配筋以减少底板裂缝。5.计算地下室局部抗浮时,整体分析比等代框架简化计算内力有着明显的优势,整体分析结果与实测值吻合得较好;而在等代框架计算过程中,荷载传递和结构刚度经常要采用简化措施,难以考虑垂直方向框架的刚度贡献,并且,取一榀框架计算时,其计算跨度也需要通过取平均值简化,分析结果的误差较大。6.因局部抗浮破坏的柱的裂缝特征和破坏形态与在足够大水平荷载作用下,多层框架结构中框架梁产生的裂缝特征和破坏形态十分相似,其原因:如果把地下车库底板、顶板看成"框架柱",把地下车库柱看成"框架梁",因"框架柱"截面和刚度较大,"框架梁"截面和刚度较弱,在"水平荷载"作用下,必然"框架梁"即实际地下车库柱首先开裂,而且在足够大"水平荷载作用"下,其破坏较严重。
[Abstract]:With the rapid development of the national economy and the expansion of the scale of urban construction, the supply of land is becoming increasingly tense, resulting in the construction of underground garage increasing day by day. At present, the main consideration of structural engineers in designing large-scale garages is the normal working conditions, and the lack of attention to the construction conditions. In other words, the construction side often takes the basement roof as the construction site, or considers that the temperature stress has been taken into account in the design and setting of the post-pouring zone, even after the closure of the post-pouring zone, the soil is not covered in time, which leads to the basement roof, external wall cracking in a large area, or even sudden heavy rainfall, leading to the local anti-floating damage of the basement. The time of overlying soil and the control of groundwater level during construction are clearly required in order to make the field situation coincide with the design results. Although flat raft foundation has been widely used in pure basement engineering, there are some problems in engineering design, such as large pier size, thick raft thickness, selected foundation coefficient and foundation conditions. The actual force of raft is not consistent, especially the unreasonable and uneconomical design of column pier. Based on the above situation, this paper analyzes the main factors affecting the internal force of raft foundation in detail by calculating examples, and finds out the changing rules of the raft foundation. This paper expounds the following aspects: (1) temperature stress and crack distribution of the roof of large basement; (2) temperature stress and crack distribution of basement exterior wall; (3) optimization design of pure basement raft foundation; (4) local anti-floating problem of basement is analyzed by hollow truss model and integral finite element method before the basement is covered with soil. The composition of indirect action of super-long concrete structure and the corresponding calculation method are discussed. The indirect action and load action of concrete structure are compared. In the design of super-long concrete structure, the shrinkage of concrete is equivalent to the temperature difference, and the elastic solution of structure is taken into account the creep action and multiplied by the reduction coefficient of approximate 0.3. 2. The internal force analysis of super-long concrete structure under indirect action needs to consider the effect of concrete cracking. The internal force analysis method of super-long concrete structure under indirect action is discussed, and the internal force of basement roof and external wall under indirect action is analyzed. The influence of out-of-plane stiffness on temperature stress should not be neglected because there are basement outer wall restraints around the slab. The two assumptions of cooling and heating should be taken into account, and the two assumptions of out-of-plane stiffness should be considered respectively. 3. When designing super-long concrete structures, not only the load under service conditions should be considered, but also appropriate. When considering the disadvantage that may occur under the construction conditions, such as: large temperature stress caused by not covering the soil in time, even the basement anti-floating accident. In order to determine the influence of different parameters (bed coefficient, pier thickness, raft thickness, pier plane size, etc.) on the mechanical properties of pure basement raft foundation, the thickness of the bottom plate is reasonably selected and the reinforcement of the bottom plate is optimized to reduce the cracks in the floor. 5. Compared with the equivalent frame, the simplified calculation of internal forces has obvious advantages, and the overall analysis results are in good agreement with the measured values; while in the process of equivalent frame calculation, load transfer and structural stiffness often adopt simplified measures, it is difficult to consider the stiffness contribution of vertical frame, and the calculation span of one frame also needs to pass. 6. The crack characteristics and failure modes of columns with local anti-floating failure are very similar to those of frame beams in multi-storey frame structures under sufficiently large horizontal loads. The reason is that if the floor and roof of underground garage are regarded as "frame columns", the underground garage is regarded as "frame columns". Columns are considered as "frame beams". Because the section and stiffness of "frame columns" are larger, the section and stiffness of "frame beams" are weaker. Under the action of "horizontal load", the "frame beams" are bound to crack first in the actual underground garage columns, and the failure is more serious under the action of "horizontal load".
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU926
本文编号：2194556
[Abstract]:With the rapid development of the national economy and the expansion of the scale of urban construction, the supply of land is becoming increasingly tense, resulting in the construction of underground garage increasing day by day. At present, the main consideration of structural engineers in designing large-scale garages is the normal working conditions, and the lack of attention to the construction conditions. In other words, the construction side often takes the basement roof as the construction site, or considers that the temperature stress has been taken into account in the design and setting of the post-pouring zone, even after the closure of the post-pouring zone, the soil is not covered in time, which leads to the basement roof, external wall cracking in a large area, or even sudden heavy rainfall, leading to the local anti-floating damage of the basement. The time of overlying soil and the control of groundwater level during construction are clearly required in order to make the field situation coincide with the design results. Although flat raft foundation has been widely used in pure basement engineering, there are some problems in engineering design, such as large pier size, thick raft thickness, selected foundation coefficient and foundation conditions. The actual force of raft is not consistent, especially the unreasonable and uneconomical design of column pier. Based on the above situation, this paper analyzes the main factors affecting the internal force of raft foundation in detail by calculating examples, and finds out the changing rules of the raft foundation. This paper expounds the following aspects: (1) temperature stress and crack distribution of the roof of large basement; (2) temperature stress and crack distribution of basement exterior wall; (3) optimization design of pure basement raft foundation; (4) local anti-floating problem of basement is analyzed by hollow truss model and integral finite element method before the basement is covered with soil. The composition of indirect action of super-long concrete structure and the corresponding calculation method are discussed. The indirect action and load action of concrete structure are compared. In the design of super-long concrete structure, the shrinkage of concrete is equivalent to the temperature difference, and the elastic solution of structure is taken into account the creep action and multiplied by the reduction coefficient of approximate 0.3. 2. The internal force analysis of super-long concrete structure under indirect action needs to consider the effect of concrete cracking. The internal force analysis method of super-long concrete structure under indirect action is discussed, and the internal force of basement roof and external wall under indirect action is analyzed. The influence of out-of-plane stiffness on temperature stress should not be neglected because there are basement outer wall restraints around the slab. The two assumptions of cooling and heating should be taken into account, and the two assumptions of out-of-plane stiffness should be considered respectively. 3. When designing super-long concrete structures, not only the load under service conditions should be considered, but also appropriate. When considering the disadvantage that may occur under the construction conditions, such as: large temperature stress caused by not covering the soil in time, even the basement anti-floating accident. In order to determine the influence of different parameters (bed coefficient, pier thickness, raft thickness, pier plane size, etc.) on the mechanical properties of pure basement raft foundation, the thickness of the bottom plate is reasonably selected and the reinforcement of the bottom plate is optimized to reduce the cracks in the floor. 5. Compared with the equivalent frame, the simplified calculation of internal forces has obvious advantages, and the overall analysis results are in good agreement with the measured values; while in the process of equivalent frame calculation, load transfer and structural stiffness often adopt simplified measures, it is difficult to consider the stiffness contribution of vertical frame, and the calculation span of one frame also needs to pass. 6. The crack characteristics and failure modes of columns with local anti-floating failure are very similar to those of frame beams in multi-storey frame structures under sufficiently large horizontal loads. The reason is that if the floor and roof of underground garage are regarded as "frame columns", the underground garage is regarded as "frame columns". Columns are considered as "frame beams". Because the section and stiffness of "frame columns" are larger, the section and stiffness of "frame beams" are weaker. Under the action of "horizontal load", the "frame beams" are bound to crack first in the actual underground garage columns, and the failure is more serious under the action of "horizontal load".
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU926
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