橋梁設計存在的主要問題(中英文翻譯)(共7頁)

1、THE MAIN PROBLEMS OF DOMESTIC BRIDGE DESIGNINGNow, 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

2、 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,

3、 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 t

4、rend 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 engineeri

5、ng 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 de

6、sign 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

7、, 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 proble

8、ms 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 w

9、ill 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 im

10、provement. 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.Ma

11、ny 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 o

12、ften 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 s

13、lice 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 becaus

14、e 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 d

15、ifferent 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, n

16、ew 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

17、 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,

18、 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 larg

19、e 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 thes

20、e 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

21、 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

22、 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

23、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

24、.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.

25、 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-

26、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

27、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.

28、 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 attenti

29、on 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 ar

30、e 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 fa

31、tigue. 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

32、 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 structur

33、e 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 perf

34、ormance 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

35、 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.), dur

36、ability 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 a

37、s 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

38、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

39、 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; th

40、e 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 w

41、eakening 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 th

42、e 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 structure's ability and performance, and during the performance of operating time and the actual deterioration of the performance of

43、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 urge

44、nt 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 s

45、tudy fatigue and overloading the durability of the bridge structure effects.國內(nèi)橋梁設計存在的主要問題現(xiàn)在，國內(nèi)的結構設計過程中，有這樣的傾向：設計中考慮強度多而考慮耐久性少；重視強度極限狀態(tài)而不重視使用極限狀態(tài)，而結構在整個生命周期中最重要的卻恰恰是使用時的性能表現(xiàn)；重視結構的建造而不重視結構的維護。實際上，目前的橋梁設計中，對于耐久性更多的只是作為一種概念受到關注，既沒有明確提出使用年限的要求，也沒有進行專門的耐久性設計。這些傾向在一定程度上導致了當前工程事故頻發(fā)、結構使用性能差、使用壽命短的不良后果；也與國際結構

46、工程界日益重視耐久性、安全性、適用性的趨勢相違背；也不符合結構動態(tài)和綜合經(jīng)濟性的要求。 橋梁安全性、耐久性差的主要原因 1）施工和管理水平低 國內(nèi)外多座橋梁的突然破壞與倒塌，已使工程界對橋梁安全性問題倍加關注。一般的看法認為當前的工程事故主要是野蠻施工和管理腐敗所導致。對于短期內(nèi)發(fā)生的諸如突然破壞與倒塌，多是由于施工質量沒有達到規(guī)范和設計要求，典型的問題包括材料強度不足和施工工藝不合格等；也有個別橋梁存在諸如偷工減料、以次充好等嚴重的管理問題，更是對橋梁安全造成致命的損害。 而大量的橋梁在遠沒有達到預期使用壽命時，出現(xiàn)了影響正常使用的病害與劣化；特別是一些橋梁在只使用了幾年、甚至剛建成不久就出

47、現(xiàn)嚴重的耐久性不足的問題，這也與施工質量低下有重要關系，典型的問題有鋼筋保護層不足及目前廣泛存在于施工現(xiàn)場的嚴重的構件開裂問題。這些施工上的缺陷雖然短期不會對橋梁的正常使用產(chǎn)生明顯的影響，但卻會對結構的長期耐久性產(chǎn)生非常不利的危害。 2）設計理論和結構構造體系不夠完善 在承認施工存在問題的同時，也不可否認，在橋梁設計領域，特別是關于橋梁施工和使用期安全性的問題還有許多可以改進的地方。結構設計的首要任務是選擇經(jīng)濟合理的結構方案，其次是結構分析與構件和連接的設計，并取用規(guī)范規(guī)定的安全系數(shù)或可靠性指標以保證結構的安全性。 許多設計人員往往只滿足于規(guī)范對結構強度計算上的安全度需要，而忽視從結構體系、結

48、構構造、結構材料、結構維護、結構耐久性以及從設計、施工到使用全過程中經(jīng)常出現(xiàn)的人為錯誤等方面去加強和保證結構的安全性。有的結構整體性和延性不足，冗余性??；有的計算圖式和受力路線不明確，造成局部受力過大；有的混凝土強度等級過低、保護層厚度過小、鋼筋直徑過細、構件截面過??；這些都削弱了結構耐久性，會嚴重影響結構的安全性。不少橋梁、雖然滿足了設計規(guī)范的強度要求，僅用了510年就因為耐久性出了問題影響結構安全。結構耐久性不足已成為最現(xiàn)實的一個安全問題，設計時要從構造、材料等角度采取措施加強結構耐久性。 不同的環(huán)境和使用條件、不同的設計對象都會對結構體系提出不同的布局和構造等方面的要求。規(guī)范再詳細也不能

49、包羅本應由設計人員解決的各種問題、規(guī)范更新得再快也適應不了新認識、新技術、新材料快速發(fā)展對結構提出的各種新的要求。因此，合理可靠的結構設計除了滿足規(guī)范的要求外，還要求設計人員具有對結構本性的正確認識、豐富的經(jīng)驗和準確的判斷。 需要改進和努力的方向 1）應該更加重視結構的耐久性問題 橋梁在建造和使用過程中，一定會受到環(huán)境、有害化學物質的侵蝕，并要承受車輛、風、地震、疲勞、超載、人為因素等外來作用，同時橋梁所采用材料的自身性能也會不斷退化，從而導致結構各部分不同程度的損傷和劣化。在大跨橋梁領域，國內(nèi)從上世紀80年代以來，修建了大量的斜拉橋；雖然迄今為止出現(xiàn)倒塌或嚴重損害的例子很少，但已經(jīng)有多座橋梁

50、因為拉索的耐久性問題而不得不提前換索，既影響了使用又增大了經(jīng)濟損失。 需要指出的是，很多這類問題與沒有進行合理的耐久性設計有關，這也促使人們重新認識橋梁的耐久性問題。大量的病害實例也證明，除了施工和材料方面的原因，影響結構耐久性的決定性因素是來自構造上（也即設計上）的缺陷。 國內(nèi)從上世紀90年代開始重視了對結構耐久性的研究，也取得了不少成果。這些研究大多是從材料和統(tǒng)計分析的角度進行的，對如何從結構和設計的角度及如何以設計和施工人員易于接受和操作的方式來改善橋梁耐久性卻很少有人研究。而且，長期以來，人們一直偏重于結構計算方法的研究，卻忽視了對總體構造和細節(jié)處理方面的關注。結構的耐久性設計與常規(guī)的結構設計有著本質的區(qū)別，目前需要努力將耐久性的研究從定性分析向定量分析發(fā)展。 2）重視對疲勞損傷的研究 橋梁結構所