双柱花瓶墩预应力盖梁计算分析.pdf

为尽可能减少对桥梁下部道路通行的影响和满足城市景观的需求，双柱花瓶墩预应力盖梁常作为城市高架桥的优选方案。传统的杆系结构受力分析无法准确模拟墩顶处预应力盖梁的受力特征，以某城市高架桥项目为依托，采用通用有限元软件针对墩柱及盖梁进行实体单元建模，应力和抗裂性等指标的验算结果均验证了设计方案的合理可靠。关键词：城市高架桥；双柱花瓶墩；预应力盖梁；受力分析中图分类号：U443.2文献标志码：B文章编号：10 0 9-7 7 16(2 0 2 3)0 6-0 10 3-0 320000引言32.5H1为解决城区新建道路占地受限的问题，城市快ostoot速路或城郊高速通常采用高架桥形式 1-2 ,随着周边环境、下部交通要求和城市景观需求等因素，对桥梁下部结构形式提出了更高的要求。目前，双柱花瓶墩预应力盖梁 3结合预制小箱梁的结构形式不仅造型简洁美观，同时有效减少桥墩横向尺寸，节省桥下空间，满足交叉口的视距和通透性的要求,因此在市区高架桥的建设中得到广泛地应用。盖梁作为桥梁结构中承上启下的重要构件，其受力较为复杂，使用阶段承受的荷载较为复杂，对盖梁的应力影响较大 4。本文以某城市高架桥项目为例，通过对双柱花瓶墩大悬臂预应力盖梁的建模分析，来验证预应力盖梁的构造设计和钢束布置的合理性。1设计概况1.1依托工程介绍城市高架桥项目在城区近郊采用双柱花瓶墩预应力盖梁的结构形式，上部梁体以30 m小箱梁为主。桥墩盖梁结构尺寸为：全宽为2 0 m，悬臂4.5m，盖梁为等高盖梁，高度为2.5m，桥墩顺桥向断面宽度为2.4m，具体构造如图1所示。1.2主要设计指标（1)设计安全等级：一级；收稿日期：2 0 2 2-0 6-2 1作者简介：张安宇（19 8 9 一），男，硕士，工程师，从事高速公路技术管理工作。1905%H330450275200150 2007255500550十图1桥墩构造图（单位：cm）(2)设计环境类别：I类；（3）桥面宽度：0.6 m（防撞护栏）+19.4m（桥面净宽）+0.6 m（防撞护栏）;（4)桥梁荷载等级：公路-I级；（5)设计基本地震加速度：0.10 g；(6)设计特征周期:0.45s。1.3盖梁施工情况按A类预应力混凝土构件进行盖梁设计，混凝土材料等级为C45,预应力钢束采用d=15.2mm低松弛钢绞线,fpk=1860MPa,波纹管均采用塑料波纹管，且要求采用真空灌浆技术，钢束规格均为15.2-13，盖梁内共布置13根预应力钢束，盖梁预应力钢束布置情况如图2、图3所示。预应力盖梁在施工过程中,其截面上下缘应力应满足公路钢筋混凝土及预应力混凝土桥涵设计规范（JTG3362一2 0 18)7.2.8 条对短暂状况应力状态的相关要求，在盖梁混凝土达到设计强度的9 0%且1031%H42757252地面线100450-7路计线城市道桥与防洪张安宇，等：双柱花瓶墩预应力盖梁计算分析2023年第6 期达到7 天龄期后进行盖梁预应力张拉，预应力张拉完成后并在孔道压浆后拆除盖梁支架。其中钢束分批张拉步骤为：（1)依次张拉N1、N3、N2,应两边对称均匀张拉；（2)施工桥面铺装及附属设施等二期恒载。图5悬臂根部弯矩/剪力不利活载布置图（单位：kN）广A张拉端N1N2N3LAL-B图2 盖梁钢束立面布置图240240-4013030L402X50回回4060回 回331304010044039(a)A-A剖面图3盖梁钢束横断面布置图（单位：cm）2建模分析2.1有限元模型建立采用通用有限元软件对双柱花瓶墩及盖梁进行建模，混凝土盖梁及墩柱均采用实体单元模拟。承托处采用四面体二次单元C3D10，其余采用六面体线性单元C3D8，钢绞线采用桁架单元模拟，单元类型为T3D2，忽略钢绞线体积的影响，将钢绞线嵌入到梁体中进行节点耦合，墩柱高度取10 m，如图4所示。FB回8回回3口锚固端30/3X20/2X30/3X2030日。28691330:40100(b)B-B剖面F4=204.77kN,F5=-9.48 kN,F6=-16.56 kN,受压为负值，受拉为正值，频遇组合和准永久组合均不考虑冲击系数，组合系数分别为0.7 和0.4。2.3验算指标9091根据公路钢筋混凝土及预应力混凝土桥涵设40730计规范（JTG3362一2 0 18），A类预应力混凝土构件g99的指标验算有如下要求。(1)应力验算标准组合下，正截面最大压应力：0 0.5fek=14.8MPa,最大主压应力:0.6fek=17.8MPa。(2)抗裂性验算频遇组合下，正截面最大拉应力0.7 fi=1.757MPa,最大主拉应力0.5fik=1.255MPa。准永久组合下，正截面最大拉应力：0。2.4预应力荷载模拟计算钢绞线预应力损失后，有效预应力Npe=1648kN即单根钢绞线pe=16481000/4000=1177MPa。采用降温法模拟预应力荷载，每根钢绞线需降温：T=0 pS.S11e.1.2 10-x1.95 10=503(平均:7 5%)117728图4有限元实体模型图6 钢束有效预应力（单位：MPa）2.2计算荷载采用降温法模拟有效预应力为117 6 MPa，相对恒载包括预制小箱梁自重，二期恒载等，通过支误差（117 7-1158)/1158=1.6%。说明预应力模拟满座传递至盖梁。汽车荷载考虑车道的最不利布置，按足实际要求，预应力桁架单元与混凝土实体单元耦横向加载进行计算，相应的汽车荷载通过支座传递合较好，模型可靠，可用于结构验算。至盖梁。其中悬臂根部弯矩/剪力影响线及其车辆最不利布置如图5所示。通过建模计算得到支座反力从左侧到右侧分别为 F1=-336.15 kN,F2=-1 150.75kN,F3=-342.83kN,3计算分析结果3.1应力验算结果标准组合下，盖梁最大压应力和最大主压应力均位1042023年第6 期张安宇，等：双柱花瓶墩预应力盖梁计算分析城市道桥与防洪于悬臂根部梁底位置，正截面最大压应力为10.0 MPa0.5fak=14.8MPa,最大主压应力为17.0 MPa0.6fek=17.8MPa,均满足规范要求。如图7 和图8 所示。S,S11(平均：7 5%)+4.423e-01-4.214e-01-1.285e+00-2.149e+00-3.013e+00-3.876c+004.740e+00-5.604e+00-6.467e+00-7.331e+00-8.195e+00-9.059e+00-9.922e+00S,S11(平均：7 5%)+3.775e-01-4.049e-01-1.187e+00-1.970e+00-2.752e+003.535e+00-4.317e+00-5.099e+00-5.882e+00-7.447e+00-6.664e+00-8:229c+00-9.012e+00Min:775图9频遇组合下正应力分布（单位：MPa）S,Max,Principal(平均：7 5%)+7.885e-01图7标准组合下正应力分布（单位：MPa）S,Min.Principal(平均：7 5%)-5.417e-01-1.914e+00-3.287e+00-4.659e+00-6.032e+00-7.404e+00-8.777e+00-1.015e+01-1.152e+01-1.289e+01-1.427e+01-1.564e+01-1.701e+01+6.485e-01+3:686e-01+5.086e-01+2.286e-01+8.867c-0229e-312e-913e15le-011eMin:-8.911e-01图10频遇组合下主拉应力分布（单位：MPa）S,S11(平均:7 5%)2.993e+003894e+003.444e+00-4.344e+004.5.2795e+00图8 标准组合下主压应力分布（单位：MPa）245e+00-5.696c+006146eH-7.047e+00596e+003.2抗裂性验算结果频遇组合下，正截面最大拉应力=0.38MPa0.7fik=1.757MPa,最大主拉应力=0.79MPa0.5fi=1.255MPa，满足规范要求。准永久组合下,正截面最大拉应力：=-3.0MPa0,满足规范要求。如图9 至图11所示。4结语本文结合某城市高架桥项目，通过对双柱花瓶墩大悬臂预应力盖梁的建模分析，验证了盖梁的构造设计和钢束的布置的合理性，计算分析结果表明预应力盖梁的应力和抗裂性均满足规范要求，可为同类型盖梁设计提供借鉴和参考。-7.497e+00-8.398e+00.948e+00图11准永久组合下，正应力分布（单位：MPa）参考文献：1荣向波，李学有.大悬臂预应力混凝土盖梁计算分析 .交通科技，2016(3):14-17.2李华.城市高架桥宽幅预应力盖梁优化设计分析 J.上海公路，2 0 2 1(1):41-46,119.3肖溢华.城市高架桥双柱花瓶墩设计及计算案例分析 J.安徽建筑，2021,28(5):158,167.4李锦,刘刚,刘宇.大悬臂预应力混凝土盖梁配束研究及空间力学分析 J.城市道桥与防洪，2 0 18(12)：7 6-7 9,8 4.5JTG33622018,公路钢筋混凝土及预应力混凝土桥涵设计规范 S城市道桥与防洪杂志是您合作的伙伴，为您提供平台，携手共同发展！欢迎新老读者订阅期刊欢迎新老客户刊登广告投稿网站:http:/电话：[phone]联系邮箱： ZHANG Anyu,ZHOU Yuli,GUO Yawen（1 0 3 )to reach the purpose of seismic mitigation and absorption.This will result in a change in restraint system.This problem is particularly prominent in the single-pylon asymmetric self-anchored suspension bridge.Based on the four-span single-pylon asymmetric self-anchored suspension bridge across Fenhe River inTongda Street of Taiyuan City,a finite element model of the whole bridge is established to analyze theinfluence of the different restraint systems on the stress of the whole bridge under the static and dynamicconditions,which provides the basis for the design of the similar structures in the future.Keywords:self-anchored suspension bridge;single-pylon asymmetric;restraint system;finite elementmethod;statically indeterminateCalculation and Analysis on Prestressed Bent Cap of Double-column Vase-shaped PierAbstract:In order to reduce the influence on the road traffic under bridge possibly and meet the demand ofurban landscape,the prestressed bent cap of double-column vase-shaped pier is frequently use as apreferred scheme of urban viaduct.The conventional force analysis of skeletal structures cannot accuratelysimulate the stress characteristics of prestressed bent cap at the pier top.Based on an urban viaduct project,the universal finite element software is used to carry out the solid element modeling for the pier column andbent cap.The calculated results of the stress,crack resistance and other indexes all verify that the designscheme is rational and reliable.Keywords:urban viaduct;double-column vase-shaped pier;prestressed bent cap;stress analysisHorizontal Static Load Test and Numerical Simulation Analysis of Large-diameter Single Pile under GeologicalConditions of Beaded Karst Cave in Sandy Gravel StrataWU Ziru(106)Abstract:At present,the research on the horizontal bearing capacity and deformation mechanism of bridgepile foundation under the geological conditions of sandy gravel and beaded karst cave is not sufficient.Inorder to reasonably determine the horizontal bearing capacity of pile foundation of unhinged arch bridgeunder this geological condition,the on-site horizontal static load test is carried out,and the reasonable valueof horizontal bearing capacity of pile foundation under this kind of geological condition is analyzed in order toprovide the reference for similar projects.And the GTS finite element software is used to carry out thenumerical simulation.The Mohr Coulomb model is modified through the modeling to simulate the sandygravel strata.The Goodman contact element is set up between the pile and the soil,and the pile tip element isset up at the pile tip.At the same time,it is assumed that the beaded karst cave is distributed in ellipsoidalstate.In order to prevent the calculation from the non-convergent situation,the interior of the cavity isspecially treated.The unified theory is used to simulate the steel casing and the concrete in it On this basis,the H-Y curve and H-YO /H c u r v e o f t h e p i l e t o p u n d e r l o a d i n g a r e a n a l y z e d,a n d t h e n u me r i c a l r e s u l t sare compared with the measured results.The results show that the results of finite element numericalsimulation are in good agreement with the field test results under the rational use of constitutive model andgeotechnical parameters.The finite element software can be used as a powerful technical means to determinethe horizontal bearing capacity of pile foundation under this special geological condition,which provides anew idea for determining the horizontal bearing capacity of a single pile.Keywords:constitutive model;Goodman contact element;pile tip element;horizontal static load test ofpile foundation;load-displacement curveDesign of PLC Pile Cofferdam in Deep Water FoundationCHAI Shizong,LAN Haitao(110)