预应力混凝土连续刚构桥合拢问题的相关研究
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摘要
连续刚构桥设计水平和施工技术在我国发展迅速,很多大跨刚构桥不断涌现,展示出我国桥梁建设的地位。近年来各学者对于连续刚构桥开裂、下挠研究较多,也提出了较多的实用改善方法；混凝土收缩徐变一直是困扰连续刚构桥的问题,其对连续刚构桥成桥后期主墩受力很不利,容易导致主墩产生严重的偏心受力,该论文主要对这一问题的改善方法做了相关分析；同时对于合拢段施工时的临时锁定措施、不同合拢方案也做了相应的探讨。
连续刚构桥成桥后,由于混凝土的收缩徐变影响,跨中会出现下挠、主墩会出现较严重的偏心受力；主墩偏心受力严重时,其局部会出现拉应力,拉应力的存在会影响结构后期运营安全。为改善墩截面在成桥后期的偏心受力,可通过顶推施工改善。该论文通过查阅资料以及自己掌握的相关知识,探讨了连续刚构桥主墩抗推刚度的计算方法,并推导出计算顶推力的解析式。其解析式计算的顶推力值与有限元方法计算出的顶推力值比较接近,在运用该方法计算顶推力时,可以乘以1.2的系数。同时,通过分析发现,顶推力的取值不宜太大,其取值以改善后期收缩徐变效应影响值的70%即可。
连续刚构桥合拢段混凝土质量对全桥作用比较关键,通过对很多已建的桥梁观测发现,连续刚构桥合拢段常会发生底板开裂,而且严重的还出现了底板混凝土崩裂的情况。这不仅与设计有关,也与施工时的施工工艺有很大联系。该论文通过分析发现,合拢段施工时,环境温差对合拢段混凝土影响较大,而采用劲性骨架、临时束临时锁定合拢段可以有效改善温差效应的影响,临时束可以只张拉顶底板最短的预应力束,其张拉吨位取值可考虑为设计张拉值的35%。
该论文对不同合拢方案分析发现,不同合拢方案对桥梁线形影响大于对结构内力的影响；而且对称合拢较非对称合拢对成桥更有利。
The techniques of designing and constructing continuous rigid frame bridge developed rapidly. As many large span rigid frame bridge emerge, all these facts show that our status of bridge construction in China. Recent years, many investigations about cracking down deflection of continuous rigid frame bridge have been done by scholars who also made lots of practical improvement. Bad stress state after the bridge is completed and Serious Eccentric in Main Pier can be caused by Shrinkage and creep as a problem of continuous rigid frame bridge. In this article mainly analysis about the above problems has been done by the author.
Due to the shrinkage of concrete creep effect, deflection in the mid-span and eccentric in the pier will seriously appear after the bridge construction; serious eccentric in the pier will lead local tensile stress, and the tensile stress could lead to the safety problem during the operation. In order to improve the eccentric after the construction, pushing construction should be used. The calculation method of main pier anti-push rigidity of continuous rigid frame bridge and deduced the analytical formula of jacking force are in detail analyzed by the author in this paper. The analytical formula of jacking force is close to the result that is analyzed by finite element method, we can use this method after the result multiplied by the coefficient1.2. At the same time, through the analysis other conclusion can be found that the value of the jacking force should not be too large, and its value to improve70%of the value of the post-shrinkage and creep effects can be.
Close concrete quality of continuous rigid frame bridge play a critical role of full-bridge, according to many bridges that have been built, crack usually appears in the bottom slab of closure segment, sometimes concrete crack also can appear in the bottom slab. It related to not only design but also construction technology in the construction process. According to the analysis, environmental temperature has a great affect in the close concrete during the closure segment construction, and the usage of rigid support and temporary prestressed reinforced could improve the affect effectively. The shortest temporary prestressed reinforced in the bottom slab can be only tensioned, and its tension tonnage values can be considered for the design of tension value of35%.
In this paper, the bridge linear effect of the program on the bridge is greater than the impact of structural forces and symmetric closed is more favorable than asymmetric close to the bridge, which can be found in the different program of close analysis.
连续刚构桥成桥后,由于混凝土的收缩徐变影响,跨中会出现下挠、主墩会出现较严重的偏心受力；主墩偏心受力严重时,其局部会出现拉应力,拉应力的存在会影响结构后期运营安全。为改善墩截面在成桥后期的偏心受力,可通过顶推施工改善。该论文通过查阅资料以及自己掌握的相关知识,探讨了连续刚构桥主墩抗推刚度的计算方法,并推导出计算顶推力的解析式。其解析式计算的顶推力值与有限元方法计算出的顶推力值比较接近,在运用该方法计算顶推力时,可以乘以1.2的系数。同时,通过分析发现,顶推力的取值不宜太大,其取值以改善后期收缩徐变效应影响值的70%即可。
连续刚构桥合拢段混凝土质量对全桥作用比较关键,通过对很多已建的桥梁观测发现,连续刚构桥合拢段常会发生底板开裂,而且严重的还出现了底板混凝土崩裂的情况。这不仅与设计有关,也与施工时的施工工艺有很大联系。该论文通过分析发现,合拢段施工时,环境温差对合拢段混凝土影响较大,而采用劲性骨架、临时束临时锁定合拢段可以有效改善温差效应的影响,临时束可以只张拉顶底板最短的预应力束,其张拉吨位取值可考虑为设计张拉值的35%。
该论文对不同合拢方案分析发现,不同合拢方案对桥梁线形影响大于对结构内力的影响；而且对称合拢较非对称合拢对成桥更有利。
The techniques of designing and constructing continuous rigid frame bridge developed rapidly. As many large span rigid frame bridge emerge, all these facts show that our status of bridge construction in China. Recent years, many investigations about cracking down deflection of continuous rigid frame bridge have been done by scholars who also made lots of practical improvement. Bad stress state after the bridge is completed and Serious Eccentric in Main Pier can be caused by Shrinkage and creep as a problem of continuous rigid frame bridge. In this article mainly analysis about the above problems has been done by the author.
Due to the shrinkage of concrete creep effect, deflection in the mid-span and eccentric in the pier will seriously appear after the bridge construction; serious eccentric in the pier will lead local tensile stress, and the tensile stress could lead to the safety problem during the operation. In order to improve the eccentric after the construction, pushing construction should be used. The calculation method of main pier anti-push rigidity of continuous rigid frame bridge and deduced the analytical formula of jacking force are in detail analyzed by the author in this paper. The analytical formula of jacking force is close to the result that is analyzed by finite element method, we can use this method after the result multiplied by the coefficient1.2. At the same time, through the analysis other conclusion can be found that the value of the jacking force should not be too large, and its value to improve70%of the value of the post-shrinkage and creep effects can be.
Close concrete quality of continuous rigid frame bridge play a critical role of full-bridge, according to many bridges that have been built, crack usually appears in the bottom slab of closure segment, sometimes concrete crack also can appear in the bottom slab. It related to not only design but also construction technology in the construction process. According to the analysis, environmental temperature has a great affect in the close concrete during the closure segment construction, and the usage of rigid support and temporary prestressed reinforced could improve the affect effectively. The shortest temporary prestressed reinforced in the bottom slab can be only tensioned, and its tension tonnage values can be considered for the design of tension value of35%.
In this paper, the bridge linear effect of the program on the bridge is greater than the impact of structural forces and symmetric closed is more favorable than asymmetric close to the bridge, which can be found in the different program of close analysis.
引文
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