1、*学 院 毕 业 设 计文献翻译院 （ 系 ） 名 称 建 筑 工 程 学 院专 业 名 称 土 木 工 程学 号 000学 生 姓 名 000指 导 教 师 000 2012 年 5 月 20 日土建结构工程的安全性与耐久性 一土建结构工程的安全性 结构安全性是结构防止破坏倒塌的能力，是结构工程最重要的质量指标。结构工程的安全性主要决定于结构的设计与施工水准，也与结构的正确使用（维护检测）有关，而这些又与土建工程法规和技术标准（规范规程条例等）的合理设置及运用相关联。 1我国结构设计规范的安全设置水准 对结构工程的设计来说，结构的安全性主要体现在结构构件承载能力的安全性结构的整体牢固性与结构
2、的耐久性等几个方面。我国建筑物和桥梁等土建结构的设计规范在这些方面的安全设置水准，总体上要比国外同类规范低得多。 1.1 构件承载能力的安全设置水准 与结构构件安全水准关系最大的二个因素是：1）规范规定结构需要承受多大的荷载（荷载标准值），比如同样是办公楼，我国规范自 1959 年以来均规定楼板承受的活荷载是每平方米 150 公斤(现已确定在新的规范里将改回到 200公斤)，而美英则为 240 和 250 公斤；2) 规范规定的荷载分项系数与材料强度分项系数的大小，前者是计算确定荷载对结构构件的作用时，将荷载标准值加以放大的一个系数，后者是计算确定结构构件固有的承载能力时，将构件材料的强度标准
3、值加以缩小的一个系数。这些用量值表示的系数体现了结构构件在给定标准荷载作用下的安全度，在安全系数设计方法(如我国的公路桥涵结构设计规范)中称为安全系数，体现了安全储备的需要；而在可靠度设计方法(如我国的建筑结构设计规范)中称为分项系数，体现了一定的名义失效概率或可靠指标。安全系数或分项系数越大，表明安全度越高。我国建筑结构设计规范规定活荷载与恒载（如结构自重）的分项系数分别为 1.4 和 1.2，而美国则分别为 1.7和 1.4，英国 1.6 和 1.4 ；这样根据我国规范设计办公楼时，所依据的楼层设计荷载（荷载标准值与荷载分项系数的乘积）值大约只有英美的 52%（考虑人员和设施等活载）和 8
4、5%（对结构自重等恒载。一些发展中国家的结构设计多根据发达国家的规范，就如我国解放前和建国初期的结构设计方法参照美国规范一样。至于中国的香港和台湾，至今仍分别以英国和参考美国规范为依据。这里需要说明的是，在其他建筑物的活荷载标准值上，与国外的差别并没有象办公楼公寓宿舍中这样大。不同材料不同类型的结构在安全设置水准上与国际间的差距并不相同，比如钢结构的差距可能相对小些。1.2 结构的整体牢固性 除了结构构件要有足够承载能力外，结构物还要有整体牢固性。结构的整体牢固性是结构出现某处的局部破坏不至于导致大范围连续破坏倒塌的能力，或者说是结构不应出现与其原因不相称的破坏后果。结构的整体牢固性主要依靠结
5、构能有良好的延性和必要的冗余度，用来对付地震爆炸等灾害荷载或因人为差错导致的灾难后果，可以减轻灾害损失。唐山地震造成的巨大伤亡与当地房屋结构缺乏整体牢固性有很大关系。2001 年石家庄发生故意破坏的恶性爆炸事件，一栋住宅楼因土炸药爆炸造成的墙体局部破坏，竟导致整栋楼的连续倒塌，也是房屋设计牢固性不足的表现。 1.3 结构的耐久安全性 我国土建结构的设计与施工规范，重点放在各种荷载作用下的结构强度要求，而对环境因素作用（如干湿冻融等大气侵蚀以及工程周围水土中有害化学介质侵蚀）下的耐久性要求则相对考虑较少。混凝土结构因钢筋锈蚀或混凝土腐蚀导致的结构安全事故，其严重程度已远过于因结构构件承载力安全水
6、准设置偏低所带来的危害，所以这个问题必须引起格外重视。我国规范规定的与耐久性有关的一些要求，如保护钢筋免遭锈蚀的混凝土保护层最小厚度和混凝土的最低强度等级，都显著低于国外规范。损害结构承载力的安全性只是耐久性不足的后果之一；提高结构构件承载能力的安全设置水准，在一些情况下也有利于结构的耐久性与结构使用寿命。 二土建结构工程的耐久性 土建结构工程的耐久性与工程的使用寿命相联系，是使用期内结构保持正常功能的能力，这一正常功能包括结构的安全性和结构的适用性，而且更多地体现在适用性上。 1 土建结构工程的耐久性现状 大多数土建结构由混凝土建造。混凝土结构的耐久性是当前困扰土建基础设施工程的世界性问题，
7、并非我国所特有，但是至今尚未引起我国政府主管部门和广大设计与施工部门的足够重视。耐久性问题的严重性和迫切性在于我们许多正在建设的工程仍未吸取国际和国内的大量惨痛教训，还沿着老路重蹈覆辙。一些北方城市新建成的立交桥和高速公路桥，仍没有在材料性能和结构构造等方面采取必要的防治冻融和盐害的综合措施。甚至大型工程如 2000 年投入运行的珠海莲花跨海大桥，其主体结构在浪溅区仍采用不耐海水干湿交替侵蚀的 C30 混凝土与 34cm 厚的保护层厚度。 2土建结构工程使用阶段的正常检测与维护 结构耐久性和使用寿命的概念，与使用阶段的检测维护和修理不能分割，对处于露天和恶劣环境下的基础设施工程来说尤其如此。为
8、了保证结构安全性和耐久性，一些工程在建成后的使用过程中，应该进行定期检测和维护。我国有结构工程的设计规范与施工规范，但没有如何使用的规范。有些工程倒塌事故，例如最近四川宜宾的南门大桥发生桥面坍落事故，就是因为桥面结构与主拱之间的吊杆在连接处发生锈蚀，如果有定期的检测要求，这样的事故很有可能避免。 三技术规范的作用与管理 长期以来，受计划经济体制的影响，我们往往视技术规范为法，将规范的具体规定和要求等同于法律条文来对待。技术规范或规程，与各种技术条例技术要求工法指南等技术文件一样都是技术标准，本身不具有法律作用，只当工程各方（业主设计施工企业）认同作为设计与施工的依据并在契约的基础上，才能作为法
9、律仲裁的依据。将技术问题法制化并强制执行，不利于技术进步和创造性的发挥，反而容易成为推卸责任的借口。当然，政府部门从国家和公众的整体利益出发，需要在安全环保等重大原则上对土建工程的设计施工提出必须满足的最低要求并制定相应的法规，但法规一般并不需要提供如何达到这些要求的具体技术途径和方法，后者是技术标准的任务。政府也可以原则认可或批准某些重要的技术规范或其中某些内容使用。 我国幅员广阔，各地经济发展很不平衡，技术力量悬殊，环境条件各异，客观上要求规范能给设计人员更多灵活性，少一些强制性，这样才能更好地在规范的指导下，根据工程的特点和具体条件去解决问题。总之，在规范标准上，要摆脱计划经济年代遗留下
10、来的过分强求统一较少考虑个性和缺乏实事求是灵活性的倾向。要提倡和鼓励各省市编制地方性规范，在工程的安全性和耐久性标准上，可有不同的设置水准。比如上海北京广州这些大城市应该高些，在抗震防灾要求上，更应区别对待。 全国性的规范订得愈详细，其适用性可能变得愈差，造成的混乱也可能愈多；特别象岩土工程那样的规范更是如此。Civil engineering structure security and the durabilityOne, the civil engineering structure safetyStructure safety is to prevent the destruction
11、 of the collapsed structure, structure of the project is the most important quality index. Structural engineering safety depends mainly on the structural design and construction standards, and structure of the correct use of ( maintenance, testing ), and these with civil engineering regulations and
12、technical standards ( standards, rules, regulations and so on ) the rational setting and the associated.1 Chinas structural design specifications of standard security settingsIn the structure design of the project, the safety of the structure are mainly embodied in the carrying capacity of structura
13、l elements in the security, the overall structure of the firmness and durability etc Chinese buildings and bridges and other civil engineering structural design specifications in these aspects of security level, on the whole than the similar foreign standards much lower.1.1 bearing capacity standard
14、 security settingsWith the structure safety level between two of the biggest factors are: 1) the specification structure needs to bear big load ( load standard value), such as office buildings, our standard since 1959are provided with floor bearing live load is150 kilograms per square meter ( now id
15、entified in the new standard will be back to200 kg ), and the United States, Britain was 240and 250 kg;2) the standard load factor and material strength subentry coefficient, the former is calculated to determine the load on the structure of the role, will load standard value of the amplification of
16、 a coefficient, which is calculated to determine the structure inherent in the load carrying ability, the component material strength standard values can be reduced by a factor. These quantities expressed by the coefficient reflects the structural member in a given standard load margin of safety, th
17、e safety coefficient design method ( such as our country highway bridge and culvert structure design code ) is called the safety coefficient, reflect the safety need; and in the method of reliability design ( such as the code for design of building structure ) is called the subentry coefficient, ref
18、lecting certain nominal failure probability and reliability index. The safety factor or subentry coefficient is bigger, show higher degree of safety. China architecture design specifications of live load and dead load ( such as the weight of the structure ) the subentry coefficient were 1.4 and1.2,
19、and the United States were 1.7and 1.4,1.6and 1.4; then according to our country codes for design of office buildings, the floor design load ( standard load value and the load factor product ) value only about52% ( and consider personnel and facilities such as living Load ) and 85% ( on the structure
20、 weight load. 1.2 structural integrityThe addition of structural members have enough bearing capacity, structure and integrity. Structural integrity rely mainly on the structure has good ductility and necessary redundancy, used to deal with the earthquake disaster, explosion load or due to human err
21、or leads to catastrophic consequence, can reduce disaster losses. Tangshan earthquake caused huge casualties and the local housing structure lack of integrity has the very big relations. In 2001, Shijiazhuang vandalism exploded, a residential building for soil explosive walls from the local damage,
22、have led to the whole building progressive collapse, but also lack of housing design firm performance. These quantities expressed by the coefficient reflects the structural member in a given standard load margin of safety, the safety coefficient design method ( such as our country highway bridge and
23、 culvert structure design code ) is called the safety coefficient, reflect the safety need; and in the method of reliability design ( such as the code for design of building structure ) is called the subentry coefficient, reflecting certain nominal failure probability and reliability index.1.3 struc
24、ture durability safetyCivil engineering structural design and construction standards, focusing on various loads of structural strength requirements, and the role of environmental factors ( such as dry and wet, freezing air erosion and Engineering around the water, soil erosion of harmful chemical me
25、diators ) the durability requirements are relatively less attention. Concrete structure due to reinforcement corrosion or concrete corrosion caused by the structural safety accident, its severity have been far too because of structure bearing capacity safety level low the harm, so this problem must
26、be paid great attention to. Chinas regulations and durability in relation to the number of requirements, such as protection against corrosion of reinforced concrete protective layer minimum thickness and concrete strength grade were significantly lower than the lowest, foreign standard. Two durabili
27、ty of Civil Structural EngineeringDurability of civil structural engineering and the service life of the project phase, is the period of use of structure to maintain normal functional capacity, this normal function including the structure safety and the applicability of the structure, and reflect mo
28、re applicability.1.1 durability of civil structural engineering statusThe majority of civil structure from concrete construction. The durability of concrete structures is currently troubled by civil infrastructure engineering problem all over the world, is not unique to China, but has not caused by
29、Chinas government departments and the general design and construction branch is enough take seriously. Durability of the seriousness of the problem and pressing sex that many of us are building the project has yet to learn the international and domestic large number of painful lessons, also along th
30、e old road recommit the same error. Some of the northern city of new built bridge and highway bridge, still not in material properties and structure and so on to take necessary prevention freeze-thaw and salt comprehensive measures. Even large projects such as the2000 and put into operation the Zhuh
31、ai Lotus Bridge, its main structure in splash zone still use seawater alternate erosion C30concrete with 3 4cm thickness of protective layer thickness.1.2 civil engineering structures using the phase of the normal detection and maintenanceThe structure durability and life concept, and use of phase d
32、etection, maintenance and repair cannot be divided, in the open air and under the harsh environment of the infrastructure project especially. In order to ensure the structural safety and durability, some projects in the completion of the use of the process, should conduct regular inspection and main
33、tenance. These quantities expressed by the coefficient reflects the structural member in a given standard load margin of safety, the safety coefficient design method ( such as our country highway bridge and culvert structure design code ) is called the safety coefficient, reflect the safety need; an
34、d in the method of reliability design ( such as the code for design of building structure ) is called the subentry coefficient, reflecting certain nominal failure probability and reliability index. The structural engineering design specifications and construction standards, but not how to use the co
35、de. Some engineering collapse accident, such as the recent Sichuan Yibin South Gate Bridge Deck slump accidents occur, because the bridge structure and the main arch between the boom in connection with rust, if have regular testing requirements, such accidents are likely to avoid.1.3 technical speci
36、fication and the role of managementThe long-term since, suffer the effect of planned economy system, we tend to see technical specification method, which will regulate the specific provisions and requirements is equivalent to the legal framework to treat. Technical specifications, and various techni
37、cal regulations, technical requirement, construction method, guide and other technical documents are the same as the technical standards, itself does not have legal effect, but the parties to the project (owner, design, construction enterprises) identity as design and construction of the basis and o
38、n the basis of contract, as a legal basis to arbitration. The technical problem of legality and enforcement, is not conducive to technical progress and creativity of the play, but easy to be shirk responsibility excuse. Our country has a vast territory, regional economic development is not balanced,
39、 technology gap, environmental conditions are different, the objective requirements of specification can give designers more flexibility, less mandatory, so as to better in the normative guidance, based on the engineering characteristics and specific conditions to solve problems. In short, the stand
40、ard, in order to get rid of the planned economy era legacy too uniform, less consider the personality and lack of flexibility tendency to seek truth from facts. Such as Shanghai, Beijing, Guangzhou, the city should be higher, in earthquake disaster prevention requirements, more should be distinguished treat. National standard for more detail, its applicability is likely to become worse, causing the disorder may also be more; especially as geotechnical engineering such specification is even more so.
