设计总说明：本次毕业设计题目为南沟二桥桥设计，该毕设要求我们设计一座桥长200m，双向四车道，时速可达100km/h的一级公路桥梁。设计结果必须满足国家现行设计规范要求，首先根据任务书，了解该地地形气候等自然条件，拟定了简支梁桥，斜拉桥，连续梁3种方案进行比选,综合考量施工方面、工程造价、环保和美观性等多方面因素后，最后决定采用55m+90m+55m分离式变截面连续梁。其中箱梁截面为单箱单室变截面，其中跨中处梁高2.5m，支点梁高5m。梁体采用C50混凝土，预应力钢筋采取使用自锚式拉丝锚固体系，用1X7-15.2-1860预应力钢绞线。主梁采用悬臂浇筑施工，先浇筑墩顶0#块，并张拉预应力束，然后在0#号两端依次对称浇筑1#号、2#号、3#号、至11#号块，直到形成最大双悬臂状态。利用midas建立模型，对其进行运营和施工阶段的内力计算，在依据内力组合布置钢筋后，对进行最终的强度、刚度验算。

关键词： 公路桥梁；预应力；连续梁

Design of the second of Nangou Brige

Design of general description: this graduation project topic is the design of the second bridge of nangou bridge, which requires us to design a first-class highway bridge with a length of 200m, two-way four lanes and a speed requires 100km/h. Design results must meet the current national design specification requirements, first of all, according to the specification, know where the natural conditions such as topography and climate, and formulate the simply supported girder bridge, cable-stayed bridge, continuous beam three schemes comparison, comprehensive consideration construction, engineering cost, environmental protection and beautiful sex factors, finally decided to adopt 55 m + 90 m + 55 m separate variable cross-section continuous beam. Among them, the box girder section is the single box single chamber variable section. As the web is close to the fulcrum gradually increased from 2.5m to 5m, The beam body is made of C50 concrete, and the prestressed reinforcement is made of self-anchored wire-drawing anchoring system, with 1x7-15.2-1860 prestressed steel strand. Cantilever is used for the main girder construction, the first casting pillar top 0 # block, and tensioned prestressed beam, and then on both ends of 0 # , in turn, symmetrical casting  1 #, 2 #, 3 #......11 # block, until the maximum double cantilever state formation. Midas was used to build the model to calculate the internal force during operation and construction, and the final strength  and rigidity  were checked after the reinforcement was arranged according to the internal force combination.

Key words: Highway bridge; Prestressed; Continuous beam

目录

1设计资料 1

1.1 桥梁位置及地质情况 1

1.2 主要技术标准 1

1.3设计规范 1

1.4 主要工具 2

2 方案比选 2

2.1 构思宗旨 2

2.2 设计原则 2

2.3 设计方案 3

2.4 方案比选 6

3选定方案尺寸拟定 9

3.1 截面尺寸 9

3.2 桥面布置 10

4内力计算 11

4.1模型简介 11

4.2内力计算结果 12

5预应力钢筋面积的估算与钢束布置 15

5.1 估计方法和原则 15

5.2 计算表格 15

5.3 刚束布置 16

6强度验算 19

6.1持久状况承载能力极限状态验算 19

6.2 持久状况正常使用极限状态验算 22

6.3持久状况构件应力验算 24

6.4 短暂状况构件应力验算 27

7刚度验算及预拱度设置 29

7.1刚度验算 29

7.2预拱度设置 29

8结论 30

致谢 31

参考文献 32

1设计资料

1.1 桥梁位置及地质情况

该桥位规划起于K24+300m，止于K24+500m，全长200米，地面标高最大为712.38m，最小为681.86m,设计标高为705.88m。地层分为强风化层、中风化层和弱风化层，桥桩需要延伸至中风化层。