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【设计总说明】预应力混凝土连续梁桥以结构受力性能好、变形小、伸缩缝少、行车平顺舒适、造型简洁美观、养护工程量小、抗震能力强等而成为最富有竞争力的主要桥型之一。由于悬臂施工方法的应用，连续梁在预应力混凝土结构中有了飞速的发展。目前，无论是城市桥梁、高架道路、山谷高架栈桥，还是跨河大桥，预应力混凝土连续梁都发挥了其独特的优势，成为优胜方案。
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本次毕业设计采用箱形截面，箱形截面是一种闭口薄壁截面，其抗扭刚度大，并具有较T型截面高的截面效率指标，同时它的顶板和底板面积均比较大，能有效地承担正负弯矩，并满足配筋的需要。此外，当桥梁承受偏心荷载时，箱形截面梁抗扭刚度大，内力分布比较均匀；在桥梁处于悬臂状态时，具有良好的静力和动力稳定性，对悬臂施工的大跨度梁桥尤为有利。随着交通量的快速增长，车速提高，人们出行希望有快速、舒适的交通条件，预应力混凝土连续箱梁桥能适应这一需要。连续梁桥是工程上广泛使用的一种桥型,它不但具有可靠的强度,刚度及抗裂性,而且具有行车舒适平稳,养护工作量小,设计及施工经验成熟的特点。预应力结构通过高强度钢筋对混凝土预压，不仅充分发挥了高强度材料的性能，而且提高了混凝土的抗裂性，促使结构轻型化，因而预应力混凝土结构具有比钢筋混凝土结构大得多的跨越能力，其适用跨径在60~150m。21609
随着悬臂浇注施工和悬臂拼装施工法的不断改进、完善和推广应用，在跨度为40——200米范围内的桥梁中，连续梁桥逐步占据了主要地位。本次毕业设计当中，主桥上跨规划Ⅲ航运河道，河道规划宽度160m，特别适合此方法成桥。
本设计的主要内容是苏州市吴中区新家桥设计，设计方案分别为简支梁桥、T形钢构和预应力混凝土连续梁桥，推荐方案为预应力混凝土连续梁桥。
本次设计为(50+75+50)m预应力砼连续梁，桥宽为37m，分为两幅，设计时只考虑单幅的设计。梁体采用单箱双室箱型截面，全梁共分178个单元一般单元长度分为1m（特殊除外）。顶板、底板、腹板厚度均不变。由于多跨连续梁桥的受力特点，靠近中间支点附近承受较大的负弯矩，而跨中则承受正弯矩，则梁高采用变高度梁，按二次抛物线变化。这样不仅使梁体自重得以减轻，还增加了桥梁的美观效果。
全桥被对称的划分为 178 个单元，利用电算程序计算恒活载以及各施工阶段内力。然后对内力进行组合，计算后对全桥进行预应力束的配置，经验算可以满足规范要求。由于预应力混凝土连续梁桥为超静定结构，手算工作量比较大，且准确性难以保证，所以采用有限元分析软件—MIDAS进行，这样不仅提高了效率，而且准确度也得以提高。
【毕业论文关键词】 箱型截面；悬臂法施工；预应力
The bridge design of Su Zhou Xinjiaqiao project
（Continues Bridge）
【Abstract of the project】Prestressed concrete continuous beam bridge to the most competitive bridge structure by good mechanical properties, deformation, less joints, smooth driving comfort, style simple and beautiful, small conservation engineering, seismic capability, etc. Due to the application of the continuous beam cantilever construction method,the prestressed concrete structure has developed rapidly.Currently, both the city bridges, viaducts, elevated trestle valley or river-crossing bridge, prestressed concrete continuous beam has played its unique advantages, has became the winning solution.
The graduation design uses the box-section,Box section is a closed thin-walled section, the torsional stiffness, and has higher efficiency than the T index section,While its roof and floor area are relatively large, they can effectively undertake positive and negative moments, and meet the needs reinforcement.In addition, when the bridge under eccentric load, the box girder torsional stiffness, internal forces more evenly distributed;When the bridge in the state of the cantilever, with good static and dynamic stability,cantilever construction of large-span bridges are particularly advantageous.With the rapid growth of traffic and the speed increased, people want to have fast and comfortable transport conditions, prestressed concrete continuous box girder bridge can accommodate this need.Continuous girder bridge is a bridge-type widely used in engineering,It not only has a reliable strength, stiffness and crack resistance, but also has a smooth ride comfort, a small conservation work, design and construction experience mature characteristics.Prestressed concrete structures are preload by high-strength reinforced ,not only full play to the performance of high-strength materials, and improve the crack resistance of concrete, prompting the structure lighter,and prestressed concrete structures is much bigger than the reinforced concrete structure of spanning capacity, its applicable span in 60 ~ 150 m.