超大跨径UHPC连续梁桥优化设计研究

发布时间：2018-10-19 07:19

【摘要】：将超高性能混凝土（Ultra-high Performance Concrete，UHPC）运用于梁桥，充分利用其超高的材料强度、优良的耐久性及超低的收缩徐变性能，设计新型的桥梁结构形式，从而实现结构轻型化，解决常规混凝土梁桥自重过大、跨中长期下挠发展、箱梁易开裂、跨径难以突破300m的难题。该新型结构突出特点是箱梁全面的薄壁化，同时提出密集横隔板的设计思想，解决由薄壁化引起的畸变和剪力滞效应过大问题，还能改善箱梁横向受力，变三向预应力为单向预应力，方便施工。拟定主跨400m的连续梁桥为工程背景，通过优化设计，研究该桥边跨比、梁高、板厚及密集横隔板等各参数的合理取值。本文开展的主要研究及其结论如下：（1）利用MIDAS软件建立主跨400m连续薄壁箱梁桥空间梁单元模型，对箱梁桥的整体参数（边跨比、梁高、板件厚度、预应力筋）进行优化。根据各参数对桥梁整体性能影响的大小顺序以及各参数自身的特点选择合适的目标函数和约束条件分别进行优化分析，后者的优化分析以前面的分析结果为基础。经一系列优化分析可得：①最优边跨—主跨跨径比为0.6，合理的取值范围为0.55~0.65；②最优中支点梁高与主跨跨径比1/22.2，合理的取值范围为1/20~1/25；③最优跨中梁高与支点梁高比为1/1.8077，合理的取值范围为1/1.8~1/2.3；④最优中支点底板厚度与主跨跨径比1/500，合理的取值范围为1/300~1/500；⑤合理的顶板、跨中底板厚度和跨中腹板厚度取其构造最小厚度20cm，合理支点腹板厚度可取35cm。（2）通过对新型箱梁桥的初步徐变分析，建议在设计时UHPC梁桥的长期挠度增长系数取1.3，同时研究表明支点底板厚度对徐变下挠有较大影响，建议在确定其厚度时考虑徐变下挠的因素，，不宜取得过小。（3）利用有限元分析软件ANSYS建立半桥实体模型，分两步对密集横隔板进行优化：密集横隔板间距和横隔板上、下弦板高度和侧板宽度。全面分析横隔板间距对箱梁畸变、剪力滞和桥面板局部受力方面的影响以得到较优的间距范围。横隔板上、下弦板高度和侧板宽度优化则从合理的尺寸分布对减小桥梁局部受力的贡献分析。经优化分析得到较优的横隔板间距范围为3~5m；分配密集横隔板尺寸时宜适当增加密集横隔板上弦板高度和横隔板厚度，以改善箱梁桥的局部受力状态。
[Abstract]:The ultra-high performance concrete (Ultra-high Performance Concrete,UHPC) is applied to the beam bridge to make full use of its super high material strength, excellent durability and ultra low shrinkage and creep property, and design a new type of bridge structure form, thus realizing the light weight of the structure. To solve the problem that the weight of conventional concrete beam bridge is too large, the span is long term deflection development, the box girder is easy to crack and the span is difficult to break through 300m. The outstanding feature of the new structure is the overall thin-wall of the box girder. At the same time, the design idea of the dense transverse diaphragm is put forward to solve the problem of excessive distortion and shear lag caused by the thin-walled structure, and the transverse force of the box girder can also be improved. Changing three-way prestress to one-way prestressing is convenient for construction. The continuous beam bridge with 400m main span is selected as the engineering background. Through the optimization design, the reasonable selection of the bridge side span ratio, beam height, plate thickness and dense transverse partition are studied. The main research and conclusions in this paper are as follows: (1) the spatial beam element model of 400m continuous thin-walled box girder bridge with main span is established by using MIDAS software. The integral parameters of box girder bridge (side span ratio, beam height, plate thickness) are analyzed. Prestressing tendons) are optimized. According to the order of the influence of each parameter on the overall performance of the bridge and the characteristics of each parameter, the appropriate objective function and constraint conditions are selected for optimization analysis respectively. The optimization analysis of the latter is based on the results of the previous analysis. Through a series of optimization analysis, the following conclusions can be obtained: (1) the optimum ratio of side span to main span is 0.6, the reasonable value range is 0.55 ~ 0.65 ~ 2, the optimum ratio of height to span of middle fulcrum beam is 1 / 22. 2, and the reasonable value range is 1 / 20 / 1 / 25; (3) the optimum ratio of midspan height to fulcrum beam height is 1 / 1.8077, and the reasonable value range is 1 / 1. 8 / 1 / 2. 3 / 3. 4 the optimal ratio of bottom thickness to main span is 1 / 500, and the reasonable value range is 1 / 300 / 1 / 5005. The thickness of the bottom plate of span and the thickness of web plate of span center are taken as the minimum thickness of the structure 20 cm, and the thickness of the web plate of the reasonable fulcrum can be 35 cm. (2) the preliminary creep analysis of the new type box girder bridge is carried out. It is suggested that the long-term deflection growth coefficient of UHPC girder bridge should be 1.3.The study shows that the thickness of fulcrum bottom plate has great influence on creep deflection, and it is suggested that the factors of creep deflection should be taken into account when determining the thickness of UHPC girder bridge. (3) using the finite element analysis software ANSYS to establish the solid model of half-bridge, and optimize the dense transverse diaphragm in two steps: the spacing of the dense transverse diaphragm, the height of the lower chord plate and the width of the lateral plate. The influence of the distance between the transverse partitions on the box girder distortion, shear lag and local force on the bridge deck is analyzed in order to obtain a better range of spacing. The optimization of the height of the lower chord plate and the width of the lateral plate on the transverse diaphragm is analyzed from the contribution of the reasonable size distribution to the reduction of the local force of the bridge. Through the optimization analysis, the optimum spacing range of the transverse diaphragm is 3 ~ 5 m, and the appropriate increase of the height and thickness of the upper chord plate and the thickness of the transverse partition plate should be appropriately increased to improve the local stress state of the box girder bridge.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U448.215

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