【作者】 徐杰；

【导师】 万水；

【作者基本信息】 东南大学 ， 桥梁与隧道工程， 2019， 硕士

【摘要】 钢桁腹-混凝土组合梁桥是一种将传统混凝土腹板替换为钢桁腹杆,在构造上由混凝土顶底板、钢桁腹杆、体内外预应力钢筋构成并共同工作的组合结构体系。移动车辆经过桥梁会引起桥梁的振动,桥梁设计中通常用动力冲击系数IM来表征移动车辆对桥梁的动力冲击作用,冲击系数的合理取值关系着桥梁设计的安全性。本文以钢桁腹-混凝土简支组合梁桥为研究对象,对其动力特性及移动车辆荷载作用下的车桥耦合振动响应进行了分析,为了解该新型组合结构的动力性能提供理论基础。主要研究工作和成果包括:(1)利用换算薄壁箱梁法,按照剪切刚度一致原则将钢桁腹杆等效为平钢腹板,并结合Hamilton原理推导了考虑桥梁剪切变形与箱梁截面剪滞效应的钢桁腹-混凝土简支组合梁桥的弯曲振动频率理论公式。(2)分析了跨高比、悬翼比、宽高比、腹杆截面形式与尺寸对钢桁腹-混凝土组合梁桥弯曲振动基频理论公式精度的影响,结果表明:悬翼比、宽高比、腹杆截面形式与尺寸对理论公式精度的影响较小,三者变化时,理论公式的精度均较高;跨高比对弯曲振动基频理论公式精度的影响较大,随着跨高比的减小,理论公式精度变差,当跨高比l/h取在8~25之间时,理论值与有限元值最大偏差在10%以内,满足工程应用的精度要求。(3)基于ANSYS平台,编制车桥耦合振动响应分析程序,并通过两个算例的验证,说明本文所采用的数值分析方法具有较高精度。(4)以一座38.4m的单箱单室钢桁腹-混凝土简支箱梁桥为例,研究了车辆加载模式、速度以及桥面不平度对该类型桥梁典型位置处动力响应的影响规律,结果表明:双车道同向并行、双车道对向行驶及单车道偏心加载下,钢桁腹-混凝土简支组合梁车桥耦合振动响应均围绕静载作用下的响应曲线上下波动;随着路面状况的恶化,振动响应的波动幅度越来越大。(5)变化结构参数,在更广泛的范围内讨论了钢桁腹-混凝土简支组合梁桥动力冲击系数计算值与规范规定值之间的差异,分析我国现行规范关于这类新型桥梁冲击系数计算公式的准确性与适用性,结果表明:随着路面状况的恶化,钢桁腹-混凝土简支组合梁桥动力冲击系数计算值急剧增大;速度对钢桁腹-混凝土简支组合梁桥各响应类型冲击系数的影响非常复杂,未发现明显规律;单车道偏心行驶时,下桥端腹杆轴力冲击系数远大于上桥端腹杆轴力冲击系数,设计与计算时应予以关注;响应类型对钢桁腹-混凝土简支组合梁冲击系数取值的影响较大,相同条件下IM最大值易出现在下桥端腹杆轴力或跨中截面扭转角上,工程计算时,为偏于安全,可优先计算下桥端腹杆轴力IM值和跨中截面扭转角IM值。更多还原

【Abstract】 The prestressed concrete composite girder bridge with steel truss webs is a combined structural system which replaces the traditional concrete web with the steel truss web,and is composed of concrete top and bottom slabs,steel truss webs,and internal and external prestressed steel bars.Moving vehicles passing through the bridge will cause vibration of the bridge.In the bridge design,the dynamic impact coefficient IM is usually used to characterize the dynamic impact of the moving vehicle on the bridge.The reasonable value of the impact coefficient is related to the safety of the bridge design.In this paper,the prestressed concrete composite girder bridge with steel truss webs is taken as the research object,and its dynamic characteristics and the vehicle-bridge coupled vibration response under the load of moving vehicles will be analyzed,which will provide a theoretical basis for understanding the dynamic performance of the new composite structure.Details of this study are summarized as follows:(1)By using the thin-walled box girder method,the steel truss web is equivalent to the flat steel web according to the principle of uniform shear stiffness.Combined with the Hamilton principle,the theoretical formula of bending vibration frequency of the composite girder bridge with steel truss webs is derived,considering the shear deformation of bridges and the shear lag effect of box girder sections.(2)The effects of span-height ratio,overhang ratio,width-height ratio,web profile and size on the accuracy of the theoretical formula of bending vibration frequency of the composite girder bridge with steel truss webs are analyzed.The results indicate that the overhang ratio,width-high ratio,and web profile and size have little effect on the accuracy of the theoretical formula.When these three parameters change,the accuracy of the theoretical formula is very high.The span-height ratio has a large effect on the accuracy of the theoretical formula.As the span-height ratio is reduced,the accuracy of the theoretical formula becomes worse.When the span-height ratio l/h is conventionally taken from 8 to 25,the maximum deviation between the theoretical value and the finite element value is within 10%,which satisfies the accuracy requirements of engineering applications.(3)The computation program for analyzing vehicle-bridge coupled vibration is compiled based ANSYS.Through the verification of two examples,the numerical analysis method used in this paper is basically feasible and has high precision.(4)Taking a single cell box girder with the span of 38.4 m as an example,the influence of vehicle loading mode,speed and pavement roughness on the dynamic response at typical positions of this type of bridge is studied.The results indicate that under the two-lane parallel loading,two-lane counter loading and single-lane eccentric loading,the coupled vibration responses of the composite girder bridge with steel truss webs are all around the fluctuation of the response curve under static load.With the deterioration of pavement condition,the fluctuation range of vibration response becomes larger and larger.(5)The structural parameters are changed,and the difference between the calculated value of the dynamic impact coefficient of the composite girder bridge with steel truss webs and the value determined by the General Code for Design of Highway Bridges and Culverts(JTG D60-2015)is discussed in a wider range,Analyzing the accuracy and applicability of the calculation formula of the impact coefficient in the current code for such new bridges.The results indicate that with the deterioration of road surface conditions,the calculated value of the dynamic impact coefficient of the composite girder bridge with steel truss webs increases sharply.The effect of speed on the impact coefficient of each response type of the composite girder bridge with steel truss webs is very complicated,and no obvious law is found.In the single-lane eccentric loading mode,the axial force impact coefficient of the lower side is much larger than that of the upper side.The design and calculation should be paid attention to.The response type has a great influence on the value of the impact coefficient of the composite girder bridge with steel truss webs.Under the same conditions,the IM maximum value is easy to appear on the axial force of the lower side or the torsion angle of mid-span.In order to be safe in engineering calculation,the IM value of the axial force of the lower side and the torsion angle of mid-span can be calculated first.更多还原