典型超高层混凝土框架—核心筒结构的抗火性能研究

发布时间：2018-06-04 06:34

本文选题：超高层混凝土结构 + 数值模拟　；参考：《清华大学》2015年硕士论文

【摘要】：近年来高层建筑发展迅速,研究其防灾减灾问题具有重要的科学意义和工程价值。火灾是超高层结构安全的主要威胁之一,本文以钢筋混凝土(RC)框架-核心筒结构作为主要研究对象,研究了其整体结构层次的抗火问题以及极端火灾下结构的抗倒塌性能,并基于本文提出的分析方法,对实际工程结构进行了抗火分析,为今后超高层建筑的抗火设计提供参考。本文的主要工作如下:1、提出并介绍了可以用于超高层整体结构抗火分析的方法和流程,并对使用的数值模型进行了验证和讨论。2、分析了材料热应变对火灾下RC梁、柱构件力学性能的影响。通过分析发现热应变对三面受火RC梁构件的影响最小,对三面受火RC柱和四面受火RC柱的影响都比较大。混凝土的热徐变对各种构件变形的影响都较小,简化计算时可以将其忽略。除钢筋的热膨胀应变外,梁构件的其他热应变在简化计算时可以忽略。3、分析了典型的超高层混凝土框架-核心筒结构在常规火灾作用下的整体结构抗火性能。分析结果表明在常规的火场条件下,超高层混凝土结构自身具有良好的抗火性能,可满足承载力的要求。然而对于楼板构件和结构的上部构件,受火后会发生较大的变形而影响火灾后的正常使用,建议采取额外的防火保护措施。4、分析了典型的超高层混凝土框架-核心筒结构在超常规火灾作用下的整体抗倒塌性能。在极端火灾作用下,结构处于火灾区域中的框架结构会发生连续倒塌,但是由于整体结构冗余度较大能够有效发挥替代传力路径的作用,使得其他部位不会继续发生连续倒塌。超高层框架-核心筒结构中框架部分的倒塌是由于楼盖系统热膨胀产生外推力而引发与其相连的外围柱的受弯破坏而引起的。5、分析了实际工程的整体结构抗火性能。通过分析可知在受火过程中巨型构件截面内部的大部分区域没有显著的温度上升,因而具有良好的抗火性能;同时由于其抗侧刚度较大,所以巨型构件不会因为周围楼板系统的热膨胀而发生受弯破坏。次框架以及楼板等结构的次要构件需要进行相应的防火保护,否则在火灾下将因为发生较大变形而失效。
[Abstract]:With the rapid development of high-rise buildings in recent years, it is of great scientific significance and engineering value to study the problem of disaster prevention and mitigation. Fire is one of the main threats to the safety of super high-rise structures. In this paper, the fire resistance of the whole structure and the collapse resistance of the structures under extreme fire are studied with the reinforced concrete frame and core tube structure as the main research object. Based on the analysis method proposed in this paper, the fire resistance analysis of practical engineering structures is carried out, which provides a reference for the fire resistant design of super high-rise buildings in the future. The main work of this paper is as follows: 1. The method and flow chart of fire resistance analysis of super high-rise whole structure are proposed and introduced. The numerical model used in this paper is verified and discussed, and the effect of material thermal strain on RC beam under fire is analyzed. Effects of mechanical properties of column members. It is found that the thermal strain has the least influence on the RC beams with fire on three sides, but it has a great effect on the RC columns with fire on the three sides and the RC columns on the four sides. The thermal creep of concrete has little effect on the deformation of various members, which can be ignored in simplified calculation. In addition to the thermal expansion strain of steel bar, the thermal strain of beam members can be neglected in simplified calculation. The fire resistance of typical super-tall concrete frame-core tube structure under conventional fire is analyzed. The results show that the super-tall concrete structure has good fire resistance and can meet the requirements of bearing capacity under conventional fire conditions. However, for the upper members of floor members and structures, large deformation will occur after fire, which will affect the normal use after fire. It is suggested that additional fire protection measures should be taken to analyze the overall collapse resistance of typical super-tall concrete frame-core tube structures under the action of supernormal fire. Under the action of extreme fire, the frame structure in the fire area will collapse continuously, but because the redundancy of the whole structure can play an effective role in replacing the load transfer path, other parts will not continue to collapse. The collapse of the frame part in the super-high-rise frame-core tube structure is caused by the bending failure of the surrounding columns connected with the outer thrust caused by the thermal expansion of the floor system. The fire resistance performance of the whole structure of the actual engineering is analyzed. Through the analysis, it can be seen that there is no significant temperature rise in most areas of the cross-section of the giant members during the fire, so it has good fire resistance, and because of its large lateral stiffness, So giant members will not be subjected to bending damage due to the thermal expansion of the surrounding floor system. The secondary components of the secondary frame and floor need to be protected against fire, otherwise they will fail because of the large deformation in the fire.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU973.17;TU973.34

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