桥梁设计存在的主要问题(中英文翻译)

道路桥梁与渡河工程专业英语Road Bridge and River-Crossing EngineeringSpecialized English学 院：土木工程班 级：道桥09-01班姓 名：*学 号：090580136日 期：2011-11-4THE MAIN PROBLEMS OFDOMESTIC BRIDGE DESIGNINGNow, the countrys structural design process, such tendencies: more intensity considered in the design and durability consider less attention intensity limit to the use of state without limit state, and throughout the life cycle of the most important when it is precisely the use of performance; attention to the construction of the structure without attention to the maintenance of the structure. In fact, the current design of the bridge for more durability is a concern, as a concept, did not explicitly put forward the request of the use of life, nor the durability of specialized design. These tendencies to a certain extent, led to the current project accidents, the use of poor performance, the short life of the adverse consequences of structural engineering with the increasing emphasis on international durability, safety, contrary to the trend of applicability; does not conform to the structure dynamic and comprehensive economy requirements.Bridge safety, durability, the main reason for poor 1) Construction and management of low level More bridges at home and abroad destruction and the sudden collapse of the bridge has been engineering more concerned about security issues. The general view is that the current project is barbaric incident management and construction caused by corruption. For the short term, such as the destruction and collapse of a sudden, mostly because of construction quality did not meet specifications and design requirements, typical problems include inadequate and construction materials intensity of failure; also exist, such as individual bridge jerry serious management issues, but also on bridge safety of the fatal damage.And a large number of bridges in the far did not achieve the expected life time, there has been affecting the normal use of disease and deterioration, especially in a number of bridges in use only a few years, or even just completed soon on the serious problem of insufficient durability, which and the low quality of construction is an important relationship, the typical problems of inadequate protection of reinforced and the current widespread in the construction site of the serious problem of cracking component. These construction, although short-term deficiencies of the bridge will not be the normal use of a clear impact, but the long-term durability of the structure will have a very negative hazards.2) Design theory and structure of the system is not perfect enoughWhile acknowledging the existence of the problem, but it also, it is undeniable that bridge design fields, in particular on the bridge construction and use of the issue of safety there is still much improvement. Structural design first and foremost task is the choice of reasonable economic programmer, followed by the structural analysis and design of components and connections, and access to regulate the safety factor specified or reliability of indicators to ensure the safety of the structure.Many designers often complacent with norms on the structural strength of the safety of the need, and ignore the structural system, structure, structure, structure of materials, structure maintenance, as well as from the structural durability of the design and construction process to make use of that often appear in the man-made wrong areas to strengthen and guarantee the safety of the structure. Some structural integrity and ductility inadequate redundancy small, but some of Schema and the uncertainty of the line, causing partial excessive force; some concrete strength grade too low to protect slice through small diameter steel micromanage , a thin cross-section components of these structures have weakened the durability, it would seriously affect the safety of the structure. Many bridges, although the design specifications meet the requirements of the strength of only 5 to 10 years because of the durability of the problems affecting structural safety. Structural Durability shortage has become one of the most realistic security issues, from design to construction and materials, such as angle of measures to strengthen the durability of the structure.Of the environment and the use of different conditions, different design of the structural system will target different aspects of the layout and structure requirements. Norms can not cover in detail the design staff should solve the various problems in the updated norms faster can also adapt to new understanding, new technologies, new materials, rapid development of the structure of the new requirements. Therefore, reasonable and reliable addition to the structures is designed to meet the requirements of norms, and to design a structure to the correct understanding of nature, rich experience and accurate judgments.And the need to improve efforts in the direction 1) Should pay more attention to the durability of structural problemsBridge in the construction and use of the process, will be subject to environmental, and the erosion of harmful chemical substances, and to bear vehicles, wind, earthquake, fatigue, overloading, human factors, such as external role, and bridge materials used by the self-degradation of performance will continue , resulting in the structure of the different degrees of damage and deterioration. In the field of long-span bridges, and from the country since the 1980s, the construction of a large number of cable-stayed bridge, although so far there collapse or serious damage to the few examples, but has more bridges because of the durability of cable to the problem advance for cable, and this not only affects the use of increased economic losses.Needs to be pointed out is that many of these problems and did not conduct a reasonable durability of the design, which has also prompted renewed awareness of durability of the bridge. Diseases are a lot of examples of that, in addition to construction materials and the reasons for a decisive impact on the durability of the structure from the structural factors (is design) flaws. From the country in the 1990s started to attach importance to the durability of the structure of the study, has also made quite a few successes. Most of these studies and statistics from the analysis of the material point of view, on how to structure and design from the perspective of how and the design and construction staff to be readily accepted and operation of the bridge approach to improving the durability has been little research. Moreover, for a long time, people have always been emphasis on the methods of calculation on the structure; it ignores the details of the overall structure and processing concern. Design and durability of the structure of the structural design of a conventional nature of the difference between the current efforts will be needed on the durability of the qualitative analysis to the quantitative analysis of development.2) Emphasis on the study of fatigue damageBridge structure to withstand the vehicle load and wind load are dynamic load will be in a cycle of change within the structure of the stress, not only will cause the vibration of the structure, but also from the structure of the accumulated fatigue damage. The bridge is not used by the material is uniform and continuous, in fact there are many tiny flaws in the role of cyclic loading, these deficiencies will be progressive development of micro, a merger of injury, and gradually formed in the material macro cracks. If the crack is not effective macro-control, is very likely to cause material, the structure of brittle fracture. Early fatigue damage is not always easy to be detected, but the consequences are often disastrous.Fatigue damage has been considered in the design of steel bridge is the core issue of fatigue caused by the steel structure of steel crack more cases, many caused by fatigue fracture bridge collapse example. Over the past 20 years, fatigue injury research has entered the concrete structure, but by the use of corrosion of reinforced concrete structures dynamic performance and fatigue properties of need to be strengthened. On the fatigue damage of not only refers to the entire structure, the bridge structure often as a matter of fact some of the key parts of local fatigue failure of the entire structure and lead to failure, such as the cable-stayed bridge cables anchoring end of the fatigue damage.3) Pay full attention to the problem of overloading the bridgeThere are three main vehicle overloading: One is the early construction of the old bridge overage load carriers and the other is the passage of vehicular traffic bridge over the original design; the other is illegal overloading of vehicles. The first two are the main reasons for the changes in the design load and the increase in the volume of traffic; users of the latter are illegal overloading of vehicles operating, the latter two phenomena of overloading in road transport in China is more common.On the one hand, overloading the bridge may trigger fatigue. Overloading bridge would increase the rate of fatigue stress injury aggravated, or even some structural damage caused by overloading accidents. On the other hand, due to overloading of the bridge caused internal damage can not be restored, the bridge will be made of the work under normal load conditions change, which could endanger the safety of bridges and durability. For example, the concrete bridge has always been regarded as an adequate durability, but the overloading of the vehicle, cracking may occur; cracks even in the load will be able to divest closed, but the internal structure of concrete has been damage, cracking component from the lower bend, Stiffness decline was in the normal use of load, should not have been cracking or structural cracks have become smaller cracks in excess of the norms to allow a larger cracks or deformation. These will be used for structural performance and long-term durability has a negative impact, in addition to the Traffic Control departments should strengthen management, but also the need for overloading the consequences of research, analysis.4) Actively learn from foreign experience and results Domestic bridge design the main problems is the use of the normal structure of poor performance (referring compared with the design expectations can be attributed to poor performance of the application, including the bridge too much vibration, linear irregularity, joints, diarrhea, excessive structural cracking and deformation, etc.), durability and safety of the poor (including short life span, high maintenance costs, and more frequent accidents, etc.). While these issues have with the current domestic construction quality and management level lower, but to be fair, since this situation can not be resolved in the short term, then as engineers we should address this issue in the premise, are fully taken into account stage of construction and management and materials technology, the use of appropriate security, the appropriate way to ensure that the design of a bridge to the use of the performance, this is a more proactive and effective means. Especially the durability of the bridge and safety of many problems with the structure or the use of material selection are unreasonable and improper handling of the structural details.In European countries (such as Germany, Denmark, etc.), attached great importance to the structure of a performance-based design (PBD, Performance Based Design), which includes structural deformation, cracks, vibration, strong, handsome, durability, fatigue and so on. PBD study is to enable operators in the structure of the process, in addition to the guaranteed minimum security requirements; the idea of the use of performance should be good (including life and durability, corrosion resistance, fatigue resistance, aesthetics, etc.). By their very nature, the European countries PBD theory, research in the use of structure in the course of performance out of service, the performance by the weakening of the reasons for its occurrence and the mechanism of the law, to seek a new structural design concepts and methods.From the point of view of Europeans, PBD seems to be to the durability of the structure at the core of the comprehensive use of performance indicators to consider. This is the domestic engineering should be based on the Enlightenment. At present the domestic design can be seen as static design, built only at the design definition of a structures ability and performance, and during the performance of operating time and the actual deterioration of the performance of the lack of sufficient awareness and consideration; In other words, the economic point of view is to consider only the construction cost, the expense of operating and maintenance costs and service life should be the relative cost-effectiveness.Bridge safety and durability shortage has become an urgent need to address the problem, we should actively learn from successful foreign experiences and practices, in addition to strengthening the construction quality management, bridge design concepts and from the structure and tectonic perspective to the design of durability. At the same time need to study fatigue and overloading the durability of the bridge structure effects.国内桥梁设计存在的主要问题现在，国内的结构设计过程中，有这样的倾向：设计中考虑强度多而考虑耐久性少；重视强度极限状态而不重视使用极限状态，而结构在整个生命周期中最重要的却恰恰是使用时的性能表现；重视结构的建造而不重视结构的维护。实际上，目前的桥梁设计中，对于耐久性更多的只是作为一种概念受到关注，既没有明确提出使用年限的要求，也没有进行专门的耐久性设计。这些倾向在一定程度上导致了当前工程事故频发、结构使用性能差、使用寿命短的不良后果；也与国际结构工程界日益重视耐久性、安全性、适用性的趋势相违背；也不符合结构动态和综合经济性的要求。 桥梁安全性、耐久性差的主要原因 1）施工和管理水平低 国内外多座桥梁的突然破坏与倒塌，已使工程界对桥梁安全性问题倍加关注。一般的看法认为当前的工程事故主要是野蛮施工和管理腐败所导致。对于短期内发生的诸如突然破坏与倒塌，多是由于施工质量没有达到规范和设计要求，典型的问题包括材料强度不足和施工工艺不合格等；也有个别桥梁存在诸如偷工减料、以次充好等严重的管理问题，更是对桥梁安全造成致命的损害。 而大量的桥梁在远没有达到预期使用寿命时，出现了影响正常使用的病害与劣化；特别是一些桥梁在只使用了几年、甚至刚建成不久就出现严重的耐久性不足的问题，这也与施工质量低下有重要关系，典型的问题有钢筋保护层不足及目前广泛存在于施工现场的严重的构件开裂问题。这些施工上的缺陷虽然短期不会对桥梁的正常使用产生明显的影响，但却会对结构的长期耐久性产生非常不利的危害。 2）设计理论和结构构造体系不够完善 在承认施工存在问题的同时，也不可否认，在桥梁设计领域，特别是关于桥梁施工和使用期安全性的问题还有许多可以改进的地方。结构设计的首要任务是选择经济合理的结构方案，其次是结构分析与构件和连接的设计，并取用规范规定的安全系数或可靠性指标以保证结构的安全性。 许多设计人员往往只满足于规范对结构强度计算上的安全度需要，而忽视从结构体系、结构构造、结构材料、结构维护、结构耐久性以及从设计、施工到使用全过程中经常出现的人为错误等方面去加强和保证结构的安全性。有的结构整体性和延性不足，冗余性小；有的计算图式和受力路线不明确，造成局部受力过大；有的混凝土强度等级过低、保护层厚度过小、钢筋直径过细、构件截面过薄；这些都削弱了结构耐久性，会严重影响结构的安全性。不少桥梁、虽然满足了设计规范的强度要求，仅用了510年就因为耐久性出了问题影响结构安全。结构耐久性不足已成为最现实的一个安全问题，设计时要从构造、材料等角度采取措施加强结构耐久性。 不同的环境和使用条件、不同的设计对象都会对结构体系提出不同的布局和构造等方面的要求。规范再详细也不能包罗本应由设计人员解决的各种问题、规范更新得再快也适应不了新认识、新技术、新材料快速发展对结构提出的各种新的要求。因此，合理可靠的结构设计除了满足规范的要求外，还要求设计人员具有对结构本性的正确认识、丰富的经验和准确的判断。 需要改进和努力的方向 1）应该更加重视结构的耐久性问题 桥梁在建造和使用过程中，一定会受到环境、有害化学物质的侵蚀，并要承受车辆、风、地震、疲劳、超载、人为因素等外来作用，同时桥梁所采用材料的自身性能也会不断退化，从而导致结构各部分不同程度的损伤和劣化。在大跨桥梁领域，国内从上世纪80年代以来，修建了大量的斜拉桥；虽然迄今为止出现倒塌或严重损害的例子很少，但已经有多座桥梁因为拉索的耐久性问题而不得不提前换索，既影响了使用又增大了经济损失。 需要指出的是，很多这类问题与没有进行合理的耐久性设计有关，这也促使人们重新认识桥梁的耐久性问题。大量的病害实例也证明，除了施工和材料方面的原因，影响结构耐久性的决定性因素是来自构造上（也即设计上）的缺陷。 国内从上世纪90年代开始重视了对结构耐久性的研究，也取得了不少成果。这些研究大多是从材料和统计分析的角度进行的，对如何从结构和设计的角度及如何以设计和施工人员易于接受和操作的方式来改善桥梁耐久性却很少有人研究。而且，长期以来，人们一直偏重于结构计算方法的研究，却忽视了对总体构造和细节处理方面的关注。结构的耐久性设计与常规的结构设计有着本质的区别，目前需要努力将耐久性的研究从定性分析向定量分析发展。 2）重视对疲劳损伤的研究 桥梁结构所承受的车辆荷载和风荷载都是动荷载，会在结构内产生循环变化的应力，不但会引起结构的振动，还会引起结构的累积疲劳损伤。 由于桥梁所采用的材料并非是均匀和连续的，实际上存在许多微小的缺陷，在循环荷载作用下，这些微缺陷会逐渐发展、合并形成损伤，并逐步在材料中形成宏观裂纹。如果宏观裂纹不得到有效控制，极有可能会引起材料、结构的脆性断裂。早期疲劳损伤往往不易被检测到，但其带来的后果往往是灾难性的。 疲劳损伤过去一直被认为是钢桥设计中的核心问题，由钢结构疲劳引起的钢材开裂案例较多，亦有不少因疲劳断裂引起桥梁垮塌的例子。近20年来，疲劳损伤的研究已进入混凝土结构，但对于使用期受腐蚀的钢筋混凝土构件的动态性能和疲劳性能的研究还需加强。 对疲劳损伤的研究不仅仅指对整个结构而言，事实上桥梁结构常常由于某些关键部位的局部疲劳失效而导致整个结构的失效，例如斜拉桥拉索锚固端的疲劳损害。 3）充分重视桥梁的超载问题 汽车超载主要有三种情况：其一是早期修建的老桥超龄负载运营；其二是桥梁通行的车流量超过原设计；另一种是车辆违规超载。前两种产生的原因主要是设计荷载的变化和交通量的增加；后者是车辆使用者违法超载营运，后两种超载现象在我国公路运输中较为普遍。桥梁的超载一方面可能引发疲劳问题。超载会使桥梁疲劳应力幅度加大、损伤加剧，甚至会出现一些超载引发的结构破坏事故。另一方面，由于超载造成的桥梁内部损伤不能恢复，将使得桥梁在正常荷载下的工作状态发生变化，从而可能危害桥梁的安全性和耐久性。例如，混凝土桥梁一直被认为具有足够的耐久性，但在汽车超载作用下，可能发生开裂；裂缝即使在荷载卸除后能够闭合，但由于混凝土结构内部已经受到损伤，构件的开裂弯矩降低、刚度下降；于是在正常使用荷载作用下，本来不该开裂的结构产生裂缝或本来较小的裂缝成为超出规范允许的裂缝或产生较大的变形。这些都会对结构长期的使用性能和耐久性产生不利的影响，因此除了交管部门要加强管理外，也需要对超载带来的后果进行研究、分析。 4）积极借鉴国外的经验和成果 国内桥梁设计存在的主要问题是结构正常使用性能差（指与设计期望相比，可归结为适用性能差，包括桥梁的过大振动、线形不平顺、接头跳车、结构开裂和过大的变形等）、耐久性和安全性差（包括使用寿命短、维护费用高、安全事故较频繁等）。这些问题的产生固然与目前国内施工质量和管理水平较低有关，但平心而论，既然这种现状不能在短期内得到解决，那么作为工程设计人员就应该在正视这一问题的前提，充分考虑到现阶段的施工和管理水平和材料工艺水平，采用适当的安全度、适当的设计方法来保证桥梁使用性能的达到，这才是更为主动和有效的方法。特别是桥梁存在的耐久性和安全性问题很多与结构体系或使用材料选择不合理及结构细节处理不当有关。 在欧洲国家（如德国、丹麦等），非常重视对结构物进行性能设计（即PBD， Performance Based Design），内容包括结构的变形、裂缝、振动、强健性、美观、耐久性能、疲劳性等。PBD研究主要是为了使结构在运营过程中除了保证最低的安全性要求外，尚应有良好的使用性能（包括寿命和耐久性、抗腐蚀、耐疲劳性、美观等）。就其本质而言，欧洲国家的PBD理论，主要研究结构在使用过程中表现出来的服务性能，分析使性能受到弱化的原因和其发生的机理、规律，寻求新的结构设计理念和方法。 从欧洲人的观点来看，PBD似乎是对以耐久性为核心的结构使用性能指标的综合考虑。这一点对国内工程界应该是有启示的。目前国内的设计可视为静态的设计，它只定义了设计建成时刻结构具有的工作能力和性能，而对营运期间性能随时间的劣化及其实际的性能表现缺乏足够的认识和考虑；换言之，从经济性的角度讲是只考虑了建造成本，而忽视了营运期的维护成本和与使用寿命相对应的成本效益。 桥梁安全性和耐久性不足已成为迫切需要解决的问题，要积极借鉴国外成功的经验和做法，除了加强施工质量管理外，要从桥梁设计理念和结构体系和构造的角度做好耐久性的设计。同时需要研究疲劳和超载对于桥梁结构耐久性的影响。