【作者】 张鑫；

【导师】 秦煜； 王威娜；

【作者基本信息】 重庆交通大学 ， 土木工程（专业学位）， 2024， 硕士

【摘要】 高速铁路采用单箱单室混合梁具有节省造价、方便施工和后期养护等优点。但是,高速铁路单箱单室混合梁斜拉桥工程实践尚少,其主梁的力学状态、收缩徐变的影响机理和最优化的成桥状态尚未明确。因此,有必要研究高速铁路单箱单室混合梁斜拉桥的最优化成桥状态、主梁的力学状态和收缩徐变的影响机理。本文围绕某高速铁路单箱单室混合梁斜拉桥,采用理论分析、数值模拟、最优化算法等研究方法,开展了其最优化成桥状态、主梁的力学状态和收缩徐变影响机理的研究。本文主要研究内容及结论如下:(1)阐明了施工阶段单箱单室混合梁和斜拉索的力学状态。首先,研究了施工全过程的主梁应力状态。其次,分析了典型施工工况下主梁和斜拉索的力学状态。最后,研究了单箱单室钢-混结合梁的受力分布和传力路径。研究结果表明:箱梁、桥面板、钢梁的应力分别在辅助墩、桥塔、1/4中跨处最大;结合梁的位移改变较大,斜拉索索力均匀;单箱单室钢-混结合梁符合平截面假定且剪力滞效应较弱,钢梁和桥面板的传力基本相同,钢梁中,底板及U肋为主要传力构件。(2)揭示了混凝土收缩徐变对跨中主梁位移的影响机理,提出了调控措施。首先,研究了各混凝土构件收缩徐变对主梁位移的影响占比。其次,分析了桥塔和桥面板收缩徐变对主梁位移的影响机理。最后,提出了消除该不利影响的调控措施。研究结果表明:桥塔、桥面板、箱梁影响占比在施工阶段分别为58%,32%和10%,在运营阶段分别为48%,38%和14%;位移的主因是收缩和徐变状态下的桥塔竖向缩小与桥面板纵桥向缩小;预抬高桥塔锚点位置、桥面板预制存放6个月、延迟90天铺轨等措施,可减小跨中主梁向下位移3%～38%。(3)提出了高速铁路混合梁斜拉桥的合理成桥状态,建立了索力优化数学模型。首先,建立合理成桥状态优化的最优化数学模型并使用MATLAB工具箱求解。其次,分析了施工过程中影响斜拉桥成桥状态的因素。最后,提出了面向合理成桥状态的施工索力优化方法。研究结果表明:以主梁弯曲能量最小为目标,主梁和桥塔位移、斜拉索索力及均匀性为约束,可获得较好的成桥状态;合龙段的强制合龙、钢-混结合梁的分阶段施工等会影响最终的成桥状态,其本质是无应力状态的不同;无应力状态法结合最小二乘法可使最终实际成桥接近合理成桥状态。更多还原

【Abstract】 The use of single-box single-chamber hybrid girder in high-speed railway has the advantages of saving cost,convenient construction and later maintenance.However,the engineering practice of single-box single-chamber hybrid girder cable-stayed bridge for high-speed railway is still few,and the mechanical state of the main girder,the influence mechanism of shrinkage and creep and the optimal completed state of the bridge are not yet clear.Therefore,it is necessary to study the optimal bridge state,the mechanical state of the main girder and the influence mechanism of shrinkage and creep of the single-box single-chamber hybrid girder cable-stayed bridge of high-speed railway.This paper focuses on a single-box single-chamber hybrid girder cable-stayed bridge of a high-speed railway.The research methods such as numerical simulation and optimization algorithm establishment are used to carry out the research on the optimal completed state,the mechanical state of the main girder and the influence mechanism of shrinkage and creep.The main research contents and conclusions of this paper are as follows:(1)The mechanical state of single-box single-chamber hybrid beam and stay cable in construction stage is clarified.Firstly,the stress state of the main beam in the whole construction process is studied.Secondly,the mechanical state of main girder and stay cable under typical construction conditions is analyzed.Finally,the stress distribution and force transmission path of single-box single-chamber steel-concrete composite beams are studied.The results show that the stress of box girder,bridge deck and steel beam is the largest at the auxiliary pier,bridge tower and 1/4 middle span respectively.The displacement of the combined beam section changes greatly,and the cable force is uniform.The steel-concrete composite beam with single box and single chamber conforms to the plane section assumption and the shear lag effect is weak.The force transmission of steel beam and bridge deck is basically the same,and the bottom plate and U rib of steel beam are the main force transmission members.(2)The influence mechanism of concrete shrinkage and creep on the displacement of mid-span girder is revealed,and the control measures are put forward.Firstly,the proportion of the influence of shrinkage and creep of each concrete member on the displacement of the main beam is studied.Secondly,the influence mechanism of shrinkage and creep of bridge tower and bridge deck on the displacement of main girder is analyzed.Finally,the control measures to eliminate the adverse effects are put forward.The results show that the influence proportion of bridge tower,bridge deck and box girder is 58%,32% and 10% respectively in the construction stage,and 48%,38% and 14% respectively in the operation stage.The main cause of the displacement is the vertical reduction of the bridge tower and the longitudinal reduction of the bridge deck in the state of shrinkage and creep.Measures such as pre-raising the anchor point position of the bridge tower,pre-fabricating and storing the bridge deck for 6 months,and delaying the track laying for 90 days can reduce the downward displacement of the main girder in the mid-span by3%～38%.(3)The reasonable completed state of the hybrid girder cable-stayed bridge for highspeed railway is proposed,and the mathematical model of cable force optimization is established.Firstly,the optimal mathematical model of reasonable bridge state optimization is established and solved by MATLAB toolbox.Secondly,the factors affecting the bridge state of the cable-stayed bridge during the construction process are analyzed.Finally,a construction cable force optimization method for reasonable bridge state is proposed.The results show that with the minimum bending energy of the main beam as the goal,the displacement of the main beam and the bridge tower,the cable force and the uniformity as the constraints,a better bridge state can be obtained.The forced closure of the closure section and the phased construction of the steel-concrete composite beam will affect the final bridge state,which is essentially the difference of the stress-free state;the stress-free state method combined with the least squares can make the final bridge state close to the reasonable bridge state.更多还原