温度和收缩裂缝控制措施在超长混凝土框架结构中的应用

发布时间：2018-08-15 16:44

【摘要】：随着大型商业综合体、航站楼等超长混凝土结构在我国大量兴建，连续不设缝结构的工程应用日渐增多。在混凝土收缩及温度作用下，超长混凝土框架结构的梁板中因受到约束而产生较大的拉应力，造成结构的开裂。因此，超长混凝土框架结构必须通过有效的设计和合理的施工对裂缝进行控制。本文运用SAP2000有限元软件，首先对300米~500米超长混凝土框架结构的温度收缩效应进行了系列模拟分析，总结了其内力及应力分布规律。然后，分析了补偿收缩混凝土、预应力技术、后浇带布置以及其它施工构造等裂缝控制措施。①在补偿收缩混凝土方面：分析膨胀混凝土的补偿收缩效果，并总结了其在超长混凝土结构中的应用原则；②在预应力技术方面：总结了预应力技术在超长结构中的设计原则，分析了次轴力对预应力效应的影响，提出了次轴力系数在框架结构中的取值范围；③在后浇带布置方面：通过结合预应力筋张拉对后浇带提出了新的划分方案，并运用算例分析，评价了后浇带布置的新方案；④在其它施工构造措施方面：结合算例，分析了结构端部若干排设定向滑动支座方案的有效性。最后，提出了500米内超长混凝土框架结构的设计方案及设计步骤，并通过具体结构算例对所提出的设计方案进行了验证。依据以上计算及分析内容得到结论如下： ①在均匀降温作用下，框架结构随其纵向长度的增长，温度内力的分布规律是一致的，其具体分布规律如下：由端部到中部节点变形、梁柱截面的峰值内力及应力逐渐减小，梁板中的平均内力及应力逐渐增大；框架柱的最大拉应力出现在边柱底端截面，框架梁的最大拉应力出现在边梁靠近边柱的端截面，楼板的最大拉应力出现在结构对称轴处截面。在多层框架结构中，各层温度作用的分布规律与单层的相似；随着楼层的增加，温度收缩效应迅速衰减，，只在底部两层较为显著，以至于其余楼层可以忽略不计。 ②对预应力的配筋设计除考虑预应力损失外，还应计及次轴力的不利影响。通过结合后浇带的划分方案张拉预应力筋可以部分的提高预压力效应，减弱结构中的次轴力。由此得到考虑了预应力筋张拉的后浇带设置原则为：后浇带所划分的预应力筋张拉单元的跨数宜少；后浇带浇筑完成后，预应力筋张拉单元的跨数应少（建议不超过两跨），且在结构中部应布置跨数少的预应力筋张拉单元。 ③结构端部若干排设定向滑动支座可以有效减弱超长混凝土框架结构的温度收缩作用。在结构端部的减弱作用最显著，越向结构中部减弱作用逐渐下降。 ④对于500以内的超长混凝土结构，按照本文提出的裂缝控制设计方法，采用高性能补偿收缩混凝土、结合预应力筋张拉的后浇带合理布置方案以及在结构端部设定向滑动支座等措施，可以满足我国现行规范对裂缝控制的要求。
[Abstract]:With the large-scale commercial complex and the large-scale construction of super-long concrete structures such as terminal buildings in China, the application of continuous jointless structures is increasing day by day. The structure must be controlled by effective design and reasonable construction.
In this paper, the temperature shrinkage effect of 300-500 m super-long concrete frame structure is simulated and analyzed by using SAP2000 finite element software, and the internal stress and stress distribution are summarized.
Then, the crack control measures such as shrinkage compensating concrete, prestressing technology, post-pouring zone layout and other construction structures are analyzed. The design principle of force technology in super-long structure is analyzed, the influence of secondary axial force on prestressing effect is analyzed, and the value range of secondary axial force coefficient in frame structure is proposed. 3. In the layout of post-pouring belt, a new division scheme of post-pouring belt is proposed by combining the tension of prestressing tendon, and the layout of post-pouring belt is evaluated by an example analysis. In other construction measures, the effectiveness of several rows of sliding bearings at the end of the structure is analyzed by an example.
Finally, the design scheme and design steps of the super-long concrete frame structure within 500 meters are proposed, and the proposed design scheme is verified by a concrete structural example.
Based on the above calculation and analysis, the conclusions are as follows:
(1) Under the uniform cooling effect, the temperature internal force distribution law of the frame structure is consistent with the increase of its longitudinal length. The concrete distribution law is as follows: from the end to the middle node deformation, the peak internal force and stress of the beam-column section gradually reduce, the average internal force and stress in the beam-slab gradually increase; the maximum tensile stress of the Frame-Column appears. In the bottom section of the side column, the maximum tensile stress of the frame beam appears at the end section near the side column, and the maximum tensile stress of the floor appears at the symmetrical axial section. It is so obvious that the remaining floors can be neglected.
In addition to prestressing loss, the negative influence of secondary axial force should be taken into account in the design of prestressing reinforcement. The prestressing effect can be partially increased and the secondary axial force can be weakened by tensioning the prestressing reinforcement in combination with the dividing scheme of post-cast strips. The span of the prestressed tendon tension element should be less than two spans, and the span of the prestressed tendon tension element should be less than two spans, and the prestressed tendon tension element with fewer spans should be arranged in the middle of the structure.
(3) Several rows of sliding bearings at the end of the structure can effectively reduce the temperature shrinkage of the super-long concrete frame structure.
(4) For the super-long concrete structure within 500 years, according to the crack control design method proposed in this paper, adopting high performance shrinkage compensating concrete, combining with the reasonable layout of post-cast-in-place belt stretched by prestressed tendons and setting sliding bearings at the end of the structure, can meet the requirements of the current code for crack control in China.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU375.4

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