【作者】 薛兴伟；

【导师】 袁鸿；

【作者基本信息】 暨南大学 ， 工程力学， 2013， 博士

【摘要】 由于各种原因，大量大跨预应力混凝土（Prestressed Concrete）梁桥都出现了许多不同性质的挠度过大和梁体裂缝问题，而且随着桥梁跨度的增大，挠度过大和裂缝问题呈现出更为严重的现象。过大的跨中下挠和裂缝的发展影响着大跨PC梁桥的耐久性和安全性，研究桥梁跨中下挠和裂缝控制方法具有重要的工程价值和社会意义。本文结合数值模拟、试验分析和工程案例，对大跨PC梁桥挠度和裂缝控制进行了深入系统的研究，主要工作包括：1、系统研究了通过钢束配置控制跨中下挠的方法。恒载零弯矩法是一种大跨PC梁桥挠度控制的方法，通过对其弯矩叠加过程发现恒载零法弯矩一般都因为最后节段配置较少的钢束而引起结构较大的挠度，因此提出“大悬臂配大束、小悬臂配小束”钢束配置改进方法，解决了恒载零弯矩法的这一缺点。基于挠度控制原则，利用ANSYS的Apdl程序语言软件编写了悬臂施工阶段预应力钢束配置的优化设计程序，通过在专业软件读取的基本数据输入后计算可得到结果。通过程序优化设计，可以得到一定材料数量下钢束的最优配置和最小挠度。2、研究了通过跨中顶推、边跨压重等施工控制力控制跨中下挠的方法。中跨合拢前在跨中顶推可有效降低大跨刚构桥主墩的永存弯矩，有利于主墩的耐久性和安全性，可把跨中顶推作抵消大跨刚构桥主墩永存弯矩的基本方法。通过边跨压重的施工控制力可平衡双肢薄壁墩刚构桥主墩两支墩轴力、减小跨中挠度；边跨压重的施工控制力可改善主墩的跨中挠度。边跨压重的施工控制力均会加大双肢、单肢薄壁墩刚构桥主墩弯矩，可在利用边跨压重减小跨中挠度的同时，结合跨中顶推工况减小主墩弯矩，使得主墩处于良好的受力状况。同时提出了各种桥型顶推、边跨压重等施工控制力的施加原则。3、提出并研究将边支座主动沉降法应用于大跨PC梁桥的挠度控制。研究表明边支座主动沉降法对刚构桥、连续梁桥等大跨PC梁式桥都可以有效减少跨中挠度，如某200m跨刚构桥，边支座下沉200mm，跨中挠度可减小40.3%。4、对箱梁腹板、梁高对结构受力和挠度影响进行深入研究并明确了刚度指标。腹板厚度的增加对结构抗剪、主拉应力都有着很大改善效果，在设计中应适当加大腹板厚度。增大箱梁跨中梁高、根部梁高对提高梁体刚度、减小跨中挠度、改善结构受力都有着极大的帮助。对桥梁刚度指标进行了深入的分析和探讨并确定了桥梁刚度检验指标。5、为提高混凝土结构的抗裂性能，对钢纤维混凝土进行了试验研究和分析。通过试验得到了钢纤维混凝土的基本特性，针对现行主要抗剪公式存在纵向受拉钢筋抗剪贡献、钢纤维体积含量使用范围、钢纤维抗剪贡献参数选取等问题，利用ANSYS优化设计功能拟合试验数据，得到了钢纤维混凝土梁的极限抗剪公式。更多还原

【Abstract】 Due to various reasons, a lot of big span prestressed concrete bridges appeare problems:different nature large mid-span deflection and too much cracks. With the increase of bridge span,cracks and excessive deflection problem appear more serious phenomenon. Large mid-spandeflection and too much cracks development affect the durability and safety of long-span PCbeam bridges. Study the large deflection of the bridge middle and the crack control method hasimportant engineering value and social significance. Based on the numerical simulation,experimental analysis and the engineering case, the thorough system research of the deflectionand crack control of the long-span PC beam bridge is carried on, and main work is shown asfollow.1. To study the steel beam configuration method, it can well control the deflection. Thepresented dead load zero moment method is a method to control the deflection, through the zerobending moment method of superposition process found that the presented moment is generallythe last segment configuration with less steel cable. It often causes large deflection of structure,and then put forward the improvement of the "big cantilever with large steel cable and smallcantilever beam with small" of the dead load zero moment method. Based on the deflectioncontrol principle, the optimization design procedures of the cantilever construction stage ofprestressed steel beam configuration are written using the APDL program language of ANSYSsoftware. Through the professional software read, the basic calculation results can be obtainedafter data input. Through optimization design program, the optimal configuration of steel beamand the minimum deflection can be obtained under a certain number of materials.2. The construction control of middle span pusher and side span heavy is studied. Before themiddle span folded, the pusher can effectively reduce the perpetuation bending moment of mainpier of long-span rigid frame bridge, and it is advantage to the durability and safety of the mainpiers, so the pusher can be as the basic method that put to offset bending moment of main piersof large-span rigid-frame. The construction control of side span weight can balance two piersaxial force and reduce the mid-span deflection of the main pier of the double limb thin-walledpier rigid frame bridge. The construction control of side span pressure heavy can improve themid-span deflection of main piers. The construction control of side span pressure weight increase bending moment of both limbs and single limb thin-walled pier bridge main pier, at the sametime in the side span pressure weight reducing the deflection, combined with middle span pushercase to reduce bending moment of the main piers, and the stress of the pier is in good condition.3. The edge support active settlement method is put forward and studied. The research showsthat the method can effectively reduce the mid-span deflection of PC beam bridges, such as rigidframe bridge and continuous girder bridge. For example, a rigid frame bridge with200m span,edge support sinks200mm, and mid-span deflection can be reduced40.3%.4. The box girder web plate and the influence of the beam high to structure stress anddeflection are thorough studied, and clear the stiffness index. The increase of web thickness has abig improvement to structural shear strength and the main tensile stress, so in the design it shouldbe appropriate increase the web thickness. The increase of the mid-span and root height of boxgirder is of great help to minimize mid-span deflection. The bridge stiffness index is carried outin-depth analysis and discussion, and the bridge rigidity test indexes are determined.5. The test of steel fiber reinforced concrete beams is carried out, the basic features of the steelfiber reinforced concrete beams is obtained by experiment. Aiming at the problem existing in themain shear formula, such as the contribution of longitudinal tensile reinforcement to the shear,the using range of steel fiber volume content and the parameter selection of shear contribution ofsteel fiber, ANSYS optimization design function is used fitting the experimental data, and theultimate shearing resistance formula of steel fiber reinforced concrete beam is obtained.更多还原