代写范文

留学资讯

写作技巧

论文代写专题

服务承诺

资金托管
原创保证
实力保障
24小时客服
使命必达

51Due提供Essay,Paper,Report,Assignment等学科作业的代写与辅导,同时涵盖Personal Statement,转学申请等留学文书代写。

51Due将让你达成学业目标
51Due将让你达成学业目标
51Due将让你达成学业目标
51Due将让你达成学业目标

私人订制你的未来职场 世界名企,高端行业岗位等 在新的起点上实现更高水平的发展

积累工作经验
多元化文化交流
专业实操技能
建立人际资源圈

Assignment代写:The effect of temperature on cracks

2018-05-07 来源: 51due教员组 类别: 更多范文

下面为大家整理一篇优秀的assignment代写范文- The effect of temperature on cracks,供大家参考学习,这篇论文讨论了温度对裂缝的影响。混凝土在现代工程建设中占有重要地位,而绝大多数混凝土建筑中都有裂缝,裂缝不仅影响美观,让使用的人没有安全感,而且当裂缝达到一定的宽度,建筑物就有很大的安全隐患。在大体积混凝土中,温度应力及温度控制对于混凝土的开裂具有重要意义。这主要是由于两方面的原因。一是在施工中混凝土常常出现温度裂缝,影响到结构的安全性和耐久性。二是在使用过程中,温度变化对结构的应力状态具有显著的不容忽视的影响。

crack,裂缝,assignment代写,美国作业代写,作业代写

Concrete occupies an important position in modern engineering construction, and the vast majority have cracks in concrete structures, the cracks do not affect beautiful, make use of insecurity, and when the crack reaches a certain width, the building has a great potential safety hazard. In mass concrete, temperature stress and temperature control are important for cracking of concrete. This is mainly due to two reasons. Firstly, temperature cracks often appear in concrete during construction, which affect the safety and durability of the structure. Secondly, in the process of use, the temperature change has significant influence on the stress state of the structure. The main problems we encountered are temperature cracks and shrinkage cracks in construction, so this paper only discusses the causes and treatment measures of concrete cracks in construction.

The trend of temperature crack is usually not regular, and large area structure crack is often crisscroped. The structure with large length and size of girder slab is parallel to short side. Deep and penetrating temperature fractures are generally parallel or parallel to the short side, and the cracks appear along the long side sections, which are dense in the middle. The width of the crack is different, the temperature change is more obvious, the winter is wider, the summer is narrower. The crack of concrete temperature caused by high temperature expansion is usually thin at both ends, and the thickness of the shrinkage crack is not obvious. The appearance of such cracks will cause corrosion of steel reinforcement, carbonization of concrete, and reduce the anti-freeze, fatigue and anti-seepage ability of concrete.

Cracks in concrete has a variety of reasons, mainly is the change of temperature and humidity, the brittleness of concrete and the non-uniformity, and the structure is unreasonable, the unqualified raw materials, the deformation of the template, foundation uneven settlement, etc. During the hardening of concrete, the cement releases a lot of hydration heat, and the internal temperature rises constantly, causing tensile stress on the surface. Later in the cooling process, due to the constraints of the foundation or existing coagulation, the tensile stress will appear in the concrete. The decrease of temperature also causes a great tensile stress on the concrete surface. Cracks occur when these tensile stresses exceed the crack resistance of concrete. Many of the concrete's internal moisture changes are small or slow, but the surface humidity may vary greatly or dramatically. If the maintenance is not week, dry time wet, the surface dry shrinkage deformation is restrained by the internal concrete, also often leads to the cracking. Concrete is a brittle material, because of the uneven raw materials, water cement ratio is not stable, and segregation phenomenon in the process of transporting and pouring, in the same piece of concrete in its tensile strength is uneven, there is a lot of tensile capacity low, easy to crack the weak positions. In reinforced concrete, the tensile stress is mainly borne by the steel bar, and the concrete is only subjected to compressive stress. The tensile stress in plain concrete must be borne by the concrete itself. In general design, there is no tensile stress or only small tensile stress. However, during the construction, the concrete is cooled to the stable temperature during the operation period, and often causes considerable tensile stress inside the concrete. Sometimes the temperature stress can exceed the stress caused by other external loads. Therefore, it is very important to understand the changing law of temperature stress for the reasonable structure design and construction.

There are no constraints or completely static structures on the boundary, and if the internal temperature is nonlinear, the temperature stress occurs due to the constraints of the structure itself. For example, the bridge pier, the structure size is relatively large, the surface temperature is low when the concrete is cooled, the internal temperature is high, the tensile stress appears on the surface, and the compressive stress occurs in the middle.

The whole or part of the structure of the structure is bound by the outside world and cannot be freely deformed. Such as box girder roof concrete and guardrail concrete. These two temperature stresses are often combined with the stress caused by dry shrinkage of concrete.

It is a complicated task to accurately analyze the distribution and size of temperature stress according to the known temperature. In most cases, model tests or numerical calculations are required. The creep of concrete makes the temperature stress quite loose, and the influence of creep must be considered when calculating the temperature stress.

Construction personnel did not according to the characteristics of commercial concrete, cooperate with the second vibration and many times the surface, let plastic settlement crack and dry shrinkage crack in time to be healed. Because of the use of mixing truck to transport the concrete, the concrete slump is larger and the coagulation time is longer. The concrete initial setting time is more than 10 hours, or even longer. Even in the hot summer, after the concrete mixed with high efficient retarding water reducing agent, the surface is the sun exposure, moisture evaporates quickly, the surface layer of a few millimeters thick "quilt", it looked as though concrete has condensation, in fact it was still far from reaching a internal initial setting, can even flow. If such concrete does not perform a secondary vibration and multiple surfaces, the concrete surface will inevitably crack. The crack is superficial and narrow. If it is not dealt with in time, the crack will expand. Due to stress concentration, the final crack is likely to be penetrating. The secondary vibration can eliminate the inner layer caused by the plastic settlement, block the coherent channel left by the bleeding, improve the structure of the aggregate interface, and improve the strength of concrete and the resistance to infiltration. When two or more times a plaster, had better use hand pressure machine, can effectively improve due to bleeding and weaken the concrete surface strength, eliminate the phenomenon of "quilt", make the concrete plastic cracking caused by moisture evaporation and get the heal in time. Some people are afraid that the second vibration will affect the concrete strength. In fact, the second vibration of concrete before the initial coagulation will not reduce the strength, but will increase the strength.

Concrete cracks are unavoidable in architecture, but it is a phenomenon that can never be ignored. It is closely related to the life of a building and the life and property of people. So you have to understand it, control it! More than just some long see views on crack, it is not enough, will be necessary to a more profound understanding, found that more can improve the technology and materials, so as to be foolproof.

51due留学教育原创版权郑重声明:原创assignment代写范文源自编辑创作,未经官方许可,网站谢绝转载。对于侵权行为,未经同意的情况下,51Due有权追究法律责任。主要业务有assignment代写、essay代写、paper代写、美国作业代写服务。

51due为留学生提供最好的assignment代写服务,亲们可以进入主页了解和获取更多assignment代写范文 提供作业代写服务,详情可以咨询我们的客服QQ:800020041。

上一篇:Assignment代写:Cezanne 下一篇:Assignment代写:Journalist interv