The ties for the anchored bulkhead shown in Figure 9-16 are located four feet from the top of the sheetpiling and are spaced at fifteen feet centers. The end of the tie is secured to two anchor piles raked as indicated. The active earth pressure may be assumed equivalent to a fluid pressure of 30 pounds per square foot per foot and passive pressure may be assumed equivalent to a fluid pressure of 400 pounds per square foot per the depth of penetration indicated, calculate the value of the total active pressure on the back of the wall, the value of the total passive pressure on the front of the wall, and the moment of all forces about the tie point. Determine the forces in the tie, the maximum shear and the maximum moment in the wall, and the forces in the compression and tension anchor piles. The fill behind the retaining wall in Figure 9-17 has a unit weight of 110 pounds per cubic foot with an equivalent fluid pressure of 30 pounds per square foot per foot. Passive earth pressure may be assumed equivalent to a fluid pressure of 300 pounds per square foot per foot and the coefficient of friction at the underside of the base is . All concrete has a compressive strength of 3000 pounds per square inch and reinforcement consists of Grade 60 deformed bars. Neglecting the effects of the shear key, determine the factor of safety against overturning and the bearing pressure distribution under the base. Using factored loading, determine the reinforcement, calculate the minimum depth of the shear key to provide a factor of friction against mass concrete gravity dam shown in Figure 9-18 is 20 feet high. Determine the minimum base width if no tensile stresses are allowed in the concrete and the water level is at the top of the dam wall. Details of a counterfort retaining wall are shown in Figure 9-19. The fill behind the wall has an equivalent fluid pressure of 40 pounds per square inch and reinforcement consists of Grade 60 determined bars. Determine the horizontal reinforcement required at the base of the stem in the front and earth faces, the reinforcement required at the base of the the required penetration of the sheetpile retaining wall shown in Figure 9-20 if active earth pressure may be assumed equivalent to a fluid pressure of 35 pounds per square foot per foot and passive pressure may be assumed equivalent to a fluid pressure of 450 pounds per square foot per foot. Calculate the force in the tie and the location and magnitude of the maximum shear and the maximum moment in the shestpiling. 翻译:由于对土木工程方面没有研究,所以很多专业术语是靠GOOLE差找和个人猜测,可能会不尽准确,甚至有所错误,但是本着学习的态度,我还是很认真地翻译了。我猜测,这可能是某本英文版建筑教材后面的习题吧?所以我用了习题的语气做的翻译。望对你有所帮助。图9-16所示的防水隔层定点的联结点位于板桩顶部4英尺处,且以15英尺为间隔居中隔开。联结点的末端被两个锚杆斜拉以保证安全。设松软土层的主动压力等同于30磅每平方英尺每英尺的液压,被动压力等同于400磅每平方英尺每英尺的液压。在必要灌注深度的条件下,求墙体背面主动压力总值,墙体正面被动压力总值,以及所有连接点的扭矩力。测定联结处所受的力,墙体的最大抗减承载力,最大瞬间扭矩力,和锚杆的压拉力。图9-17所示的挡土墙后填充物单位重量为110磅每立方英尺,具有约等于30磅每平方英尺每英尺的液压的压力。设被动土压约等于300磅每平方英尺每英尺的液压以及底部摩擦系数为;所有混凝土抗压强度为3000磅每立方英寸并且由级别60的不规则钢筋加固;忽略剪切键。求底部填充物的抗破坏及承压安全系数。 用你所计算的系数,求加固强度,计算在抗滑动摩擦系数为情况下,剪切键的最小深度。图9-18所示的的混凝土浇筑拱坝的高为20英尺。假设混凝土中不允许出现拉力、且水位高度刚好在大坝顶部,求其底宽的最小值。图9-19中给出了拱柱型挡土墙的具体数值,墙后填充物具有约等于40磅每平方英尺每英尺的液压的压力,且由级别60的不规则钢筋加固。求正面茎干底部以和地面水平加固要求、以及拱柱底部加固要求。求图9-20所示的板桩挡土墙的必要灌注深度。假设其中:主动土压约等于35磅每平方英尺每英尺的液压、被动压力约等于450磅每平方英尺每英尺的液压。计算板桩最大剪切和最小剪切情况下,接点处受的力,以及接点位置和数量
Traditional Construction ProceduresAs mentioned before, construction under the traditional construction procedure is performed by contractors. While they would like to satisfy the owner and the building designers, contractors have the main objective of making a profit. Hence, their initial task is to prepare a bid price based on an accurate estimate of construction costs. This requires development of a concept for performance of the work and a construction time schedule. After a contract has been awarded, contractors must furnish and pay for all materials, equipment, power, labor, and supervision required for construction. The owner compensates the contractors for construction costs and general contractor assumes overall responsibility for construction of a building. The contractor engages subcontractors who take responsibility for the work of the various trades required for construction. For example, a plumbing contractor installs the plumbing, an electrical contractor installs the electrical system, and an elevator contractor installs elevators. Their contracts are with the general contractor, and they are paid by the general , in addition to a general contractor, the owner contracts separately with specialty contractors, such as electrical and mechanical contractors, who perform a substantial amount of the work require for a building. Such contractors are called prime contractors. Their work is scheduled and coordinated by the general contractor, but they are paid directly by the also, the owner may use the design-build method and award a contract to an organization for both the design and construction of a building. Such organizations are called design-build contractors. One variation of this type of contract is employed by developers of groups of one-family homes or low-rise apartment buildings. The homebuilder designs and constructs the dwellings, but the design is substantially completed before owners purchase the of the construction procedure often is difficult. Consequently, some owners seek assistance from an expert, called a professional construction manager, with extensive construction experience, who receives a fee. The construction manager negotiates with general contractors and helps select one to construct the building. Managers usually also supervise selection of subcontractors. During construction, they help control costs, expedite equipment and material deliveries, and keep the work on schedule. In some cases, instead, the owner may prefer o engage a construction program manager, to assist in administrating both design and contractors employ labor that may or may not be unionized. Unionized craftspeople are members of unions that are organized by construction trades, such as carpenter, plumber, and electrician unions, Union members will perform only the work assigned to their construction, all work should be inspected. For this purpose, the owner, often through the architect and consultants, engages inspectors. The field inspectors may be placed under the control of an owner’s representative, who may be titled clerk of the works, architect’s superintendent, engineer’s superintendent, or resident engineer. The inspectors have the responsibility of ensuring that construction meets the requirements of the contract documents and is performed under safe conditions. Such inspections may be made at frequent addition, inspections also are made by representatives of one or more governmental agencies. They have the responsibility of ensuring that construction meets legal requirements and have little or no concern with detailed conformance with the contract documents. Such legal inspections are made periodically or at the end of certain stages of construction. One agency that will make frequent inspections is the local or state building department, whichever has jurisdiction. The purpose of these inspections is to ensure conformance with the local or state building is a description of the basic traditional construction procedure for a multistory the award of a construction contract to a general contractor, the owner may ask the contractor to start a portion of the work before signing of the contract by giving the contractor a letter of intent or after signing of the contract by issuing a written notice to proceed. The contractor then obtains construction permits, as required, form governmental agencies, such as the local building, water, sewer, and highway general contractor plans and schedules construction operations in detail and mobilizes equipment and personnel for the project. Subcontractors are notified of the contract award and issued letters of intent or awarded subcontracts, then are given, at appropriate times, notices to construction starts, the general contractor orders a survey to be made of adjacent structures and terrain, both for the record and to become knowledgeable of local conditions. A survey is then made to lay out offices for the contractor are erected on or near the site. If desirable for safety reasons to protect passersby, the required to be removed from the site are demolished and the debris is carted , the site is prepared to receive the building. This work may involve grading the top surface to bring it to the proper elevations, excavating to required depths for basement and foundations, and shifting of utility piping. For deep excavations, earth sides are braced and the bottom is construction starts with the placement of foundations, on which the building rests. This is followed by the erection of load-bearing walls and structural framing. Depending on the height of the building, ladders, stairs, or elevators may be installed to enable construction personnel to travel from floor to floor eventually to the roof. Also, hoists may be installed to lift materials to upper levels. If needed, temporary flooring may be placed for use of the building rises, pipes, ducts, and electric conduit and wiring are installed. Then, permanent floors, exterior walls, and windows are constructed. At the appropriate time, permanent elevators are installed. If required, fireproofing is placed for steel framing. Next, fixed partitions are built and the roof and its covering are put is place,Finishing operations follow. There include installation of the following: ceilings; tile; wallboard; wall paneling; plumbing fixtures; heating furnaces; air-conditioning equipment; heating and cooling devices for rooms; escalators; floor coverings; window glass; movable partitions; doors; finishing hardware; electrical equipment and apparatus, including lighting fixtures, switches, transformers, and controls; and other items called for in the drawings and specifications. Field offices, fences, bridges, and other temporary construction must be removed from the site. Utilities, such as gas, electricity, and water, are hooked up to the building. The sit is landscaped and paved. Finally, the building interior is painted and owner’s representatives then give the building a final inspection. If they find that the structure conforms with the contract documents, the owner accepts the project and gives the general contractor final payment on issuance by the building department of a certificate of occupancy, which indicates that the completed building meets building-code requirements.传统的施工程序众所周知,在传统的施工程序中进行施工的承包商。尽管他们想满足业主和建筑设计师的要求,但是最终还是以赚取利润为主要目标的。因此,他们最初的任务是对编写投标价格的建筑成本进行准确的估计。这就需要进行前期调查的工作并且做出施工时间表。等合约批出后,施工方必须提供所有材料并支付其费用,设备,电力,劳动力。业主此时需要进行必要的监督。一个总承包商承担一个建筑整体的责任。从事分包的承建商则需承担建造工程所需的各个工作。例如,管道承包商安装水管,电业承办商安装电气系统,电梯则由电梯承包商安装。他们与总承包商签订合同,费用由总承包商支付。有时候,除了一个总承包商,还有各种专业承包商,如电气和机械承包商,执行工作时需要与业主签订合同。这种承包商被称为间接承包商。他们的工作,由总承包商协调,但它们都是由业主直接联系。还有些时候,业主可以使用设计建造方法同时兼有设计和建筑施工单位的职能。这些单位被称为设计建造承包商。这方面的一个类型的合同聘用的变化是由一户住宅或低层住宅建筑群的开发。在房屋建筑设计和建造的住房,但设计之前需要由购买房屋的业主完成。施工过程管理往往是困难的。因此,一些业主会去寻求专家的协助,这些专家被称为专业施工经理,他们具有丰富的施工经验。施工经理与总承包商进行谈判,并选择其中一个项目。施工经理通常还监督分包商。在施工期间,它们有助于控制成本,加快运送设备和材料,并保持工作的进度。在依法行政,协助设计和建设的情况下,业主可以选择从事建筑项目经理。建筑承包商雇用的劳动力,一般有大工和小工。大工再建筑工程中从事技术活,如木工,管道工,工会成员和电工工会,小工则执行了分配给他们的工作。在施工期间,一切工作都要验收。因此,业主通过建筑师和监理经常进行督查。可能是名为工程员,建筑师或驻地工程师。作为业主的代表实地视察。核查人员必须确保工程符合合同文件的要求,并在安全的条件下进行的责任。这种检查可作出重复。此外,验收还是需要一个或多个政府机构的代表。他们必须确保工程符合法律要求,并负责检查与合同文件是否一致。这种视察一般定期或在某些阶段施工结束以后进行。地方或国家建设部门具有管辖权。这些检查的目的是确保符合当地或国家的建筑规范。以下是传统多层建筑施工的基本程序。建造开始后合同授予开发商,业主可要求开发商开始施工之前签约给或之后签约发出书面通知的同时另一部分工作继续进行。紧接着施工方根据需要获取建筑许可证,例如当地的建设,供水,污水处理,政府机构和公路部门。总承包商的计划和进度详细施工作业以及动员项目设备和人员。分包商得到通知后,做出签订合同的意向或授予分包合同书,然后给出在适当的时候进行通知。在施工前启动,总承包商要进行的一项调查就是邻近结构和地形,这些都要记录在案,并要熟悉当地情况。这项调查结束以后,随即进行布局建设。承建商的现场办事处都建在施工现场或附近。为了安全起见,必须从脚手架上移除的东西,产生的碎片都要运走。下一步,该网架是为建设工程准备的。这项工作为地下室开挖和基础开挖的深度,以及公用事业管道转移找到正确的标高。深挖掘,土方支撑,底部排出。建筑开始于基础上,然后是承重墙和结构框架的施工。梯子,楼梯,或电梯的安装,可让施工人员往返于各个楼层。此外,可安装卷扬机来运送材料。由于建筑高度的上升,管道,电力管道和线路安装以及永久地板,外墙,窗户和构造的影响。在适当的时候,永久的电梯安装。再需要的情况下可以安装防火卷帘。其次,屋顶等地方也需要安装。精加工工序安装有包括以下内容:天花板,瓷砖,墙板,墙壁镶板,水管装置,加热炉,空气调节设备,加热和冷却室装置;自动扶梯;地板,窗户玻璃;活动板,门;电气设备和仪器,包括照明灯具,开关,变压器,控制器,遵照项目的图纸和规格。外地办事处,围栏,桥梁和其他临时建筑,公共设备,如天然气,电力管道,水管,都连接到建筑上。最后,是建筑物内部的打扫和清洗。业主的代表,会给建设工程作最后检查。如果他们满意并认为符合合同文件,那么业主接受该项目,并交给总承包商的一个占用证书,这表明,总承包商已完成建设,建设部门再根据建筑规范的要求发放最后付款。
The principle of the analysis of concrete structures, the implementation of the correct application of the project, and grasp of the Xu-shaped concrete shrinkage and creep of the process, control of harmful cracks in concrete to enhance the structural safety and durability.
Abstract: In the modern construction of concrete plays an important role, but the concrete cracks are more common. This article analyzes the causes of concrete cracks is proposed measures to control and prevent the cracks, and curing of the concrete problems early. Key words: concrete crack; cracks; Cracks; conservation First, micro-cracks in concrete Cracks in reinforced concrete structures is to work with. Rather, the hardening process of concrete in the condensation, there exist micro-cracks, because the concrete in the cement and aggregate changes in temperature and humidity conditions to produce the volume of non-uniform deformation, and they bonded together and can not free-form deformation, so the formation of mutual restraint stress; Once the cement and aggregate constraint between the stress is greater than the bond strength and tensile strength of cement itself, will produce micro-cracks. Second, the causes of concrete cracks Concrete cracks are the result of the development of micro-cracks. Concrete cracks for many reasons, for its part, considered to be bound by the deformation of concrete due to tensile stress than the material's sake. 1. Optional inappropriate material defects and the formation of cracks. Expired cement, aggregate excess mud, with active SiO 2 , high alkali cement, limestone aggregate, cement hydration heat and so on. 2. Construction of mishandling the formation of defects and cracks. Plastic concrete sink, was the top bar of the resistance, the formation of cracks along the reinforcement; concrete vibration is not dense, there cellular, easy to form the starting point for a variety of stress fractures; concrete mixer, transit time is too long, so that water evaporation, causing low slump concrete pouring, making the concrete volume in the mesh irregular cracks; rapid drying of concrete made when the initial curing of concrete contact with the atmosphere in the irregular mesh surface cracks; early form removal, concrete not yet established sufficient strength to impose its own components in the actual gravity load, prone to all kinds of stress cracks. 3. Because of the force components, deformation and crack formation of defects. Center tension; center compression; bending; shear; by punching; beam concrete shrinkage and temperature deformation; plate of concrete shrinkage and temperature deformation; in reinforced concrete, the tensile stress is mainly borne by the reinforced concrete is exposed stress. In plain concrete or reinforced concrete on the edges if the tensile stress within the structure there shall be to rely on concrete to bear. General design requirements in both the tensile stress does not appear or appear only very small tensile stress. However, the maximum temperature of concrete in construction to the operation of the cooling period of steady temperature, often caused by a large concrete internal tensile stress. 4. Because of environmental factors affect the formation of defects and cracks. Mainly temperature and humidity changes, the brittleness of concrete and uneven, as well as unreasonable structure, failure of raw materials (such as alkali-aggregate reaction), template deformation, differential settlement of foundation. Concrete dissolution cycles many times by the freeze, the stress generated in the concrete, and promote the development of existing cracks, loose structure, surface cracks, surface spalling or overall collapse. Third, measures to control and prevent the cracks 1. Of cement, water, aggregate, admixtures, reinforcement materials, the improper selection of the formation of cracks on the entry of raw materials must be in accordance with national standards for strict inspection and acceptance of the approach to prevention, where the unqualified use of defective materials shall be , or reduce the level of test use; of these have occurred due to improper selection of materials defects or cracks in concrete produced must be observed in detail for the long term (due to some problems take a while to find), carefully identify its causes and Quality of the problem, study and formulate their treatment and reinforcement. This is because once occurred due to improper material selection, quality problems, often with the universal reason. 2. As long transport time of concrete mixing, pouring too fast, the vibration is not real, it is improper construction joint, move the template the formation of cracks and other reasons can follow the "concrete order" strict implementation of concrete mixing, transport, pouring, vibration pound set and the old concrete construction joint connection. Templates, and form removal, and conservation requirements to prevent, the occurrence of such cracks in the component have been, but also distinguish the type of component, component of the force characteristics of the site where the cracks and the extent of serious cracks were commonly used in concrete cracks reinforcement measures or by filling concrete, steel anchor reinforcement, and even stick steel reinforcement, prestressed reinforcement remedial measures. 3. Due to dry weather, the initial maintenance is not good, the early cold concrete and large changes in temperature and humidity of the cracks were used to enhance the natural hardening process of concrete Results conservation, conservation of heat storage, the use of air-entraining agent to uniform distribution of air bubbles inside the concrete, measures such as temperature expansion joint repair reserved. Severe cold components, some should be removed, some should be reinforced before being used. 4. Because the components have to withstand loads too wide cracks, reasonably designed to prevent the emergence of these cracks; cracks have been too broad component appears to be reinforced by strengthening measures. 5. The foundation of unequal settlement of large cracks too broad and reasonably in the design of the building when checking in the use phase of the settlement to prevent the emergence of these cracks, these cracks have occurred on the structure, to use ground-based control measures proper handling of the foundation, then building the structure reinforcement measures adopted to solve. 6. On the environmental conditions and changes in the use of the crack occurred, according to different properties to different control measures, such as: (1) the use of temperature and humidity changes during the formation of cracks, usually difficult to eradicate, to adopt the protection of reinforced concrete measures to reduce atmospheric humidity changes of the component is appropriate; (2) The cracks resulting from repeated freezing and thawing, in addition to defects and damage has been formed in part to be reinforced or reinforced, but should add insulation on the cold concrete measures; (3) The corrosive medium in the resulting defects and damage a large area, in addition to corrosion and damage should be removed by the site to be reinforced or reinforced, shall use the acid water glass slag cement concrete or concrete overlay to protect; (4) damage due to earthquake seismic structural measures should be adopted to prevent; have been generated by the earthquake damage is not severe earthquake damaged buildings may refer to repair and reinforcement of the solution to the problem. In addition, temperature control and improved from the constraints of the two aspects. Used to improve the aggregate gradation, with a dry hard concrete, mixed with mixture, add air-entraining agent or a plasticizing agent measures to reduce the amount of cement in concrete; water when mixing concrete or gravel with water cooling to reduce the concrete pouring temperature; hot days when the pouring of concrete pouring to reduce the thickness of heat by pouring level; in the concrete laying pipes, pass into the cold water temperature; set reasonable removal time, the surface heat when temperatures plunged to avoid dramatic concrete surface temperature gradient ; Construction of Concrete Blocks and long-term exposure to surface or thin-walled structure, insulation measures taken in the cold season. Measures to improve the constraints are: a reasonable parting block; to avoid excessive fluctuations basis; reasonable arrangements for the construction process, to avoid the excessive height and long-term exposure to the side. In addition, to improve the performance of concrete and improve the crack resistance, enhance conservation, to prevent surface shrinkage, in particular, to ensure the quality of concrete is very important to prevent fractures, special attention should be avoided through the cracks, appears to restore its structural integrity is difficulties, so the construction should be to prevent the occurrence of cracks in the main cross-cutting. Fourth, early curing of concrete Practice shows that cracks in concrete common, most of the surface cracks of different depth, mainly because of the temperature gradient caused by the sudden drop in temperature in cold areas are also easy to form cracks. Therefore, the concrete surface of the insulation to prevent early cracking is particularly important. From the viewpoint of thermal stress, thermal insulation should meet the following requirements: (1) prevent the concrete and the concrete surface temperature difference between inside and outside the gradient, to prevent surface cracks; (2) to prevent the concrete super cool, should try to try to make concrete the construction period of not less than the minimum temperature on the stability of the temperature of concrete used; (3) to prevent cold and old concrete to reduce the constraints between the new and old concrete. Early curing of concrete, the main purpose is to maintain proper temperature and humidity conditions in order to achieve the effect of two aspects, one of the concrete from adverse temperature and humidity deformation of the invasion, to prevent the harmful shrinkage and shrinkage. On the one hand to smooth the cement hydration in order to meet the design strength and crack resistance. V. Conclusion Cracks in concrete above the relationship between the various effects of the theory and practice discussed, although the academic cracks in the concrete and calculation methods are different theories, but for specific advice for prevention and improvement measures more unified, but in practice of effects are good, concrete construction depends on our seeing much comparison, more analysis after problems, and more sum up, with a variety of preventive treatment measures, concrete cracks are completely avoidable.
Based on the analysis of the concrete structure in the correct application of project implementation, and grasp the shrinkage of concrete creep form of creep of concrete crack control process, the structure, the promotion harmful safety and durability.
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