空间预应力束作用下箱梁横向应力分析
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摘要
预应力混凝土箱梁桥广泛应用于高速铁路和城市轨道交通领域。随着技术的发展,箱形截面的结构形式逐渐向宽翼缘薄腹板发展,预应力束布置为空间曲线。部分箱梁在施工建设中或运营阶段都发生了明显的开裂情况。空间预应力束对箱梁的应力状态有重要影响。
本文选取客运专线标准预应力混凝土简支箱梁为研究对象,进行预应力作用下箱梁应变测试,建立包含空间预应力束箱梁三维有限元模型。研究了预应力混凝土简支箱梁的空间应力分布和受力特征。根据梁体预应力筋的张拉顺序和张拉控制力的大小,计算预初张拉阶段和终张拉阶段的箱梁受力性能,探讨其空间应力状态。对比分析有限元计算值与测试值之间的差异,计算了包含空间力筋影响的箱梁顶板和底板的裂缝宽度。论文主要研究结论如下：
1.终张拉完成以后,各截面底板的横向应力值较大,在2MPa左右。虽然还没有超过混凝土的拉应力限值,但是在自重、二期恒载和活荷载的共同作用下,截面极有可能开裂,产生纵向裂缝；
2.有限元分析的计算结果与试验测试数据较为吻合,为箱梁的横向配筋提供了可靠的数据支持,可以根据有限元分析的计算结果,采取合理的措施,有效地控制纵向裂缝的宽度；
3.通过分析空间预应力作用之下的横向应力分布情况,发现顶板和腹板交界处、顶板中心线处以及底板和腹板交界处、底板中心线处均存在较大的拉应力,在设计中应当针对截而形式和荷载工况的不同来确定横向预应力钢筋的数量及布置形式；
4.采用平面框架分析法分析了不同荷载作用下的顶板横向应力分布,提出顶板的控制工况,对于自重+预应力+二期恒载+特种活载的形式,由单线偏载来控制顶板的横向配筋。
Prestressed concrete box girder bridges are widely applied to the high-speed rail network and urban railway transport. With the development of construction technology, the box girder has developed to widened-flange and thinned-web gradually, and contains with spatial curved prestressing tendons. Part of the bridges crack obviously during construction or operation stage. Spatial curved prestressing tendons have crucial influence on the stress state of the box girder.
Simply supported prestressed concrete box girder in Passenger Dedicated Line is research object of this thesis. Based on strain monitoring test, spatial model with curved prestressing tendons is created by ANSYS program to study the spatial stress distribution and mechanics characteristics of the bridge. According to the tensioning order and the initial stresses of tendons, transverse stress transformation characteristics of the box girder in the initial tensioning stages and final tensioning stages are studied. Through calculation and analysis to several sections in the initial and final tensioning stages, the spatial stress state of the box girder and the transverse stress distribution characteristics of the upper and bottom slabs are discussed. The width of crack of upper slab with spatial curved prestressing tendons are compared between experimental results and calculated value by ANSYS, main research conclusions of the thesis are drawn and listed as follows:
1. After the final tensioning stages, transverse stress of bottom slab reaches to a relatively large value of 2MPa, though this value is smaller than tensile stress limits of concrete, longitudinal cracks are likely to generate under synergetic effects of various loads such as dead load, secondary dead load and live load.
2. As theoretically calculated values are agreeable to experimental results, reliable data support are provided to the transverse rebar design of the box girder, the width of longitudinal cracks can be controlled effectively.
3. Through analysis of the transverse stress distribution under spatial prestressing effect, significant tension stress is found in border between upper and flange slab, center line of the roof and border between bottom and flange slab, therefore the number and arrangement of the transverse prestressing tendons should be determined by section patterns and loads distribution in design.
4. Through analysis of transverse stress distribution of upper slab under different load combination by the plane frame analysis method, the controlled situation of the upper slab was obtained. With the combinated effect of the "dead load" + "prestressing force" + "secondary dead load" + "special live load", the transverse rebar is controlled by single side load.
Keywords:Spatial prestress; Boxgirder; Transverse stress; Passenger Dedicated Line; Experiment; Finite element model.
本文选取客运专线标准预应力混凝土简支箱梁为研究对象,进行预应力作用下箱梁应变测试,建立包含空间预应力束箱梁三维有限元模型。研究了预应力混凝土简支箱梁的空间应力分布和受力特征。根据梁体预应力筋的张拉顺序和张拉控制力的大小,计算预初张拉阶段和终张拉阶段的箱梁受力性能,探讨其空间应力状态。对比分析有限元计算值与测试值之间的差异,计算了包含空间力筋影响的箱梁顶板和底板的裂缝宽度。论文主要研究结论如下：
1.终张拉完成以后,各截面底板的横向应力值较大,在2MPa左右。虽然还没有超过混凝土的拉应力限值,但是在自重、二期恒载和活荷载的共同作用下,截面极有可能开裂,产生纵向裂缝；
2.有限元分析的计算结果与试验测试数据较为吻合,为箱梁的横向配筋提供了可靠的数据支持,可以根据有限元分析的计算结果,采取合理的措施,有效地控制纵向裂缝的宽度；
3.通过分析空间预应力作用之下的横向应力分布情况,发现顶板和腹板交界处、顶板中心线处以及底板和腹板交界处、底板中心线处均存在较大的拉应力,在设计中应当针对截而形式和荷载工况的不同来确定横向预应力钢筋的数量及布置形式；
4.采用平面框架分析法分析了不同荷载作用下的顶板横向应力分布,提出顶板的控制工况,对于自重+预应力+二期恒载+特种活载的形式,由单线偏载来控制顶板的横向配筋。
Prestressed concrete box girder bridges are widely applied to the high-speed rail network and urban railway transport. With the development of construction technology, the box girder has developed to widened-flange and thinned-web gradually, and contains with spatial curved prestressing tendons. Part of the bridges crack obviously during construction or operation stage. Spatial curved prestressing tendons have crucial influence on the stress state of the box girder.
Simply supported prestressed concrete box girder in Passenger Dedicated Line is research object of this thesis. Based on strain monitoring test, spatial model with curved prestressing tendons is created by ANSYS program to study the spatial stress distribution and mechanics characteristics of the bridge. According to the tensioning order and the initial stresses of tendons, transverse stress transformation characteristics of the box girder in the initial tensioning stages and final tensioning stages are studied. Through calculation and analysis to several sections in the initial and final tensioning stages, the spatial stress state of the box girder and the transverse stress distribution characteristics of the upper and bottom slabs are discussed. The width of crack of upper slab with spatial curved prestressing tendons are compared between experimental results and calculated value by ANSYS, main research conclusions of the thesis are drawn and listed as follows:
1. After the final tensioning stages, transverse stress of bottom slab reaches to a relatively large value of 2MPa, though this value is smaller than tensile stress limits of concrete, longitudinal cracks are likely to generate under synergetic effects of various loads such as dead load, secondary dead load and live load.
2. As theoretically calculated values are agreeable to experimental results, reliable data support are provided to the transverse rebar design of the box girder, the width of longitudinal cracks can be controlled effectively.
3. Through analysis of the transverse stress distribution under spatial prestressing effect, significant tension stress is found in border between upper and flange slab, center line of the roof and border between bottom and flange slab, therefore the number and arrangement of the transverse prestressing tendons should be determined by section patterns and loads distribution in design.
4. Through analysis of transverse stress distribution of upper slab under different load combination by the plane frame analysis method, the controlled situation of the upper slab was obtained. With the combinated effect of the "dead load" + "prestressing force" + "secondary dead load" + "special live load", the transverse rebar is controlled by single side load.
Keywords:Spatial prestress; Boxgirder; Transverse stress; Passenger Dedicated Line; Experiment; Finite element model.
引文
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[29]过镇海.钢筋混凝土原理[M].清华大学出版社,1999.
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[3]吴新强.连续梁桥预应力设计研究[D].合肥工业大学,2007.57-58.
[4]孙远.铁路箱梁空间力学特性分析[D].中南大学,2007.7-8.
[5]马海英.预应力混凝土斜拉桥主梁横向应力分布研究[D].同济大学,2007.17-18.
[6]谭竣.预应力混凝土连续箱梁桥的顶板力学性能研究[J].中外公路,2009.29(5)：131-134.
[7]高猛.分段施工预应力混凝十箱梁横向受力行为研究[D].西南交通大学,2009.9-13.
[8]冯建明.大跨径预应力连续刚构桥施工监控混凝土应力测试研究[D].重庆交通大学,2007.
[9]苏杭.预应力混凝十箱梁桥腹板受力分析及预应力损失研究[D].武汉理工大学,2007.
[10]付永强,张小水,胡成.预应力混凝十结构施加预应力的Ansys模拟[J].工程与建设,2008,22(6).
[11]铁路桥涵钢筋混凝土和预应力混凝土结构设计规范(TB10002.3—2005)[S].中华人民共和国交通部.2005.
[12]项海帆.高等桥梁结构理论[M].北京：人民交通出版社,2001.
[13]邵容光,夏淦.混凝土弯梁桥[M].北京：人民交通出版社,1996.
[14]郭金琼.箱形梁设计理论[M].北京：人民交通出版社,2007.
[15]郭金琼等.箱形梁的剪力滞效应[J].土木工程学报,1983.
[16]范立础.桥梁工程(上)[M].北京：人民交通出版社,2002.
[17]吴海林,季文玉,许克宾.秦沈客运专线箱梁空间应力分析[J].北方交通大学学报,2001,25(1)：39-42.
[18]徐艳秋,许克宾.薄壁弯梁桥空间有限元分析[J].土木工程学报,2003,6(2)：58-62.
[19]张启亮.混凝土箱梁顶板横向预应力框架效应分析[J].石家庄铁道学院学报.2007,20(2)：49-51.
[20]陈培奇,李忠献.箱梁横向内力的有限条法[J].天津城市建设学院学报,2009,9(3)；168-172.
[21]程翔云.梁桥理论与计算[M].北京：人民交通出版社,1990.
[22]程翔云.双室箱梁顶板的横向计算研究[J].中国公路学报,1996,9(4).
[23]Zihai Shi, Masaaki Nakano. Three-dimansional finite element analysis on crack behaviors of RC cantilever decks [J]. Construction and Building Materials,1999, Vol.13:33-47.
[24]张永厚.箱形混凝土梁荷载横向分布影响及剪力滞效应的试验研究[J].铁道建筑,2001.
[25]杨培捷.方志和.对几种箱梁横向内力计算方法的评估[J].北京市政设计院.
[26]梁春华.箱梁横向预应力的计算[J].交通部公路规划设计院.
[27]Dritsos SE.Distortion of Concrete Box Beam due to Eccentric Transverse Loads [J].J Struct Engng ASCE,1991,113(1):113-117.
[28]AASHTO.AASHTO LRFD Bridge design specifications SI units first edition[S].The American Association of State Highway and Transportation Officials, Washington, D.C., 2004.
[29]过镇海.钢筋混凝土原理[M].清华大学出版社,1999.
[30]李国平.预应力混凝土结构设计原理[M].北京：人民交通出版社,2000.
[31]张士铎.邓小华.王文州.箱形薄壁梁剪力滞效应[M].人民交通出版社,1998.
[32]王新敏.ANSYS工程结构数值分析[M].北京：人民交通出版社,2007.
[33]卢树圣.现代预应力混凝土理论与应用[M].北京：中国铁道出版社,2000：134-147.
[34]吴先树.大跨径预应力混凝土箱梁受力裂缝分析[D].江苏：东南大学,2000.
[35]彭卫.张新军.朱汉华.箱形梁桥的空间有限元分析[J].工程设计CAD与智能建筑,2002(6)：46-49.
[36]徐庆华.黎平原.预应力箱梁施工裂缝的成因与防治.建筑技术开发[J],2004.31(7)：84-103.
[37]刘明辉.预应力混凝土卜箱梁桥的空间非线性分析研究[D].长沙理工大学,2004.
[38]张十铎.箱形薄壁梁剪力滞效应[M].北京：人民交通出版社,1998.
[39]M.Ala Saadeghvaziri,M.ASCE and Rambod Hadidi,S.M.ASCE.Transverse Cracking of Concrete Bridge Decks:Effects of Design Factors. JOURNALL OF BRIDGE ENGINEERING@ASCE,SEPTEMBER/OCTOBER.2005:511-519.
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