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 Engineering

Specialized English

学 院：土木工程 班 级：道桥09-01班 姓 名：**

学 号：090580136 日 期：2011-11-4

THE MAIN PROBLEMS OF DOMESTIC BRIDGE DESIGNING

Now, the country's 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 enough

While 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 problems

Bridge 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 damage

Bridge 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 bridge

There 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