1、 Construction Engineering Construction engineering is a specialized branch of civil engineering concerned with the planning, execution, and control of construction operations for such projects as highways, buildings, dams, airports, and utility lines. Planning consists of scheduling the work to be d
2、one and selecting the most suitable construction methods and equipment for the project. Execution requires the timely mobilization of all drawings, layouts, and materials on the job to prevent delays to the work. Control consists of analyzing progress and cost to ensure that the project will be done
3、 on schedule and within the estimated cost. Planning. The planning phase starts with a detailed study of construction plans and specifications. From this study a list of all items of work is prepared, and related items are then grouped together for listing on a master schedule. A sequence of constru
4、ction and the time to be allotted for each item is then indicated. The method of operation and the equipment to be used for the individual work items are selected to satisfy the schedule and the character of the project at the lowest possible cost. The amount of time allotted for a certain operation
5、 and the selection of methods of operation and equipment that is readily available to the contractor. After the master or general construction schedule has been drawn up, subsidiary detailed schedules or forecasts are prepared from the master schedule. These include individual schedules for procurem
6、ent of material, equipment, and labor, as well as forecasts of cost and income. Execution. The speedy execution of the project requires the ready supply of all materials, equipment, and labor when needed. The construction engineer is generally responsible for initiating the purchase of most construc
7、tion materials and expediting their delivery to the project. Some materials, such as structural steel and mechanical equipment, require partial or complete fabrication by a supplier. For these fabricated materials the engineer must prepare or check all fabrication drawings for accuracy and case of a
8、ssembly and often inspect the suppliers fabrication. Other construction engineering duties are the layout of the work by surveying methods, the preparation of detail drawings to clarify the design engineers drawings for the construction crews, and the inspection of the work to ensure that it complie
9、s with plans and specifications. On most large projects it is necessary to design and prepare construction drawings for temporary construction facilities, such as drainage structures, access roads, office and storage buildings, formwork, and cofferdams. Other problems are the selection of electrical
10、 and mechanical equipment and the design of structural features for concrete material processing and mixing plants and for compressed air, water, and electrical distribution systems. Control. Progress control is obtained by comparing actual performance on the work against the desired performance set
11、 up on the master or detailed schedules. Since delay on one feature of the project could easily affect the entire job, it is often necessary to add equipment or crews to speed up the work. Cost control is obtained by comparing actual unit costs for individual work items against estimated or budgeted
12、 unit costs, which are set up at the beginning of the work. A unit cost is obtained by dividing the total cost of an operation by the number of units in that operation. Typical units are cubic yards for excavation or concrete work and tons for structural steel. The actual unit cost for any item at a
13、ny time is obtained by dividing the accumulated costs charged to that item by the accumulated units of work performed Individual work item costs are obtained by periodically distributing job costs, such as payroll and invoices to the various work item accounts. Payroll and equipment rental charges a
14、re distributed with the aid of time cards prepared by crew foremen. The cards indicate the time spent by the job crews and equipment on the different elements of the work. The allocation of material costs is based on the quantity of each type of material used for each specific item. When the compari
15、son of actual and estimated unit costs indicates an overrun; an analysis is made to pinpoint the cause. If the overrun is in equipment costs, it may be that the equipment has insufficient capacity or that it is not working properly. If the overrun is in labor costs, it may be that the crews have too
16、 many men, lack of proper supervision, or are being delayed for lack of materials or layout. In such cases time studies are invaluable in analyzing productivity. Construction operations are generally classified according to specialized fields. These include preparation of the project site, earthmovi
17、ng, foundation treatment, steel erection, concrete placement, asphalt paving, and electrical and mechanical installations. Procedures for each of these fields are generally the same, even when applied to different projects, such as buildings, dams, or airports. However, the relative importance of ea
18、ch field is not the same in all cases. Preparation of site. This consists of the removal and clearing of all surface structures and growth from the site of the proposed structure. A bulldozer is used for small structures and trees. Larger structures must be dismantled. Earthmoving. This includes exc
19、avation and the placement of earth fill. Excavation follows preparation of the site, and is performed when the existing grade must be brought down to a new elevation. Excavation generally starts with the separate stripping of the organic topsoil, which is later reused for landscaping around the new
20、structure. This also prevents contamination of the nonorganic material which is below the topsoil and which may be required for fill. Excavation may be done by any of several excavators, such as shovels, draglines, clamshells, cranes, and scrapers. Efficient excavation on land requires a dry excavat
21、ion area, because many soils are unstable when wet and cannot support excavating and hauling equipment. Dewatering becomes a major operation when the excavation lies below the natural water table and intercepts the groundwater flow. When this occurs, dewatering and stabilizing of the soil may be acc
22、omplished by trenches, which conduct seepage to a sump from which the water is pumped out. Dewatering and stabilizing of the soil may in other cases be accomplished by wellpoints and electroosmosis. Some materials, such as rock, cemented gravels, and hard clays, require blasting to loosen or fragmen
23、t the material. Blast holes are drilled in the material; explosives are then placed in the blast holes and detonated. The quantity of explosives and the blast-hole spacing are dependent upon the type and structure of the rock and the diameter and depth of the blast holes. After placement .of the ear
24、th fill, it is almost always compacted to prevent subsequent settlement. Compaction is generally done with sheeps-foot, grid, pneumatic-tired, and vibratory-type rollers, which are towed by tractors over the fillas it is being placed. Hand-held, gasoline-driven rammers are used for compaction close
25、to structures where there is no room for rollers to operate. Foundation treatment. When subsurface investigation reveals structural defects in the foundation area to be used for a structure; the foundation must be strengthened. Water passages cavities fissures, faults, and other defects are filled a
26、nd strengthened by grouting. Grouting consists of injection of fluid mixtures under pressure. The fluids subsequently solidify in the voids of the strata. Most grouting is done with cement and water mixtures, but other mixture ingredients are asphalt, cement and clay, and precipitating chemicals. St
27、eel erection. The construction of a steel structure consists of the assembly at the site of mill-rolled or shop-fabricated steel sections. The steel sections may consist of beams, columns, or small trusses which are joined together by riveting, bolting, or welding. It is more economical to assemble
28、sections of the structure at a fabricating shop rather than in the field, but the size of preassembled units is limited by the capacity of transportation and erection equipment. The crane is the most common type of erection equipment, but when a structure is too high or extensive in area to be erect
29、ed by a crane, it is necessary to place one or more derricks on the structure to handle the steel. In high structures the derrick must be constantly dismantled and reerected to successively higher levels to raise the structure. For river bridges the steel may be handled by cranes on barges, or, if t
30、he bridge is too high, by traveling derricks which ride on the bridge being erected. Cables for long suspension bridges are assembled in place by special equipment that pulls the wire from a reel, set up at one anchorage, across to the opposite anchorage, repeating the operation until the bundle of
31、wires is of the required size. Concrete construction. Concrete construction consists of several operations: forming, concrete production, placement, and curing. Forming is required to contain and support the fluid concrete within its desired final outline until it solidifies and can support itself.
32、The form is made of timber or steel sections or a combination of both and is held together during the concrete placing by external bracing or internal ties. The forms and ties are designed to withstand the temporary fluid pressure of the concrete. The usual practice for vertical walls is to leave th
33、e forms in position for at least a day after the concrete is placed. They are removed when the concrete has solidified or set. Slip-forming is a method where the form is constantly in motion, just ahead of the level of fresh concrete. The form is lifted upward by means of jacks which are mounted on
34、vertical rods embedded in the concrete and are spaced along the perimeter of the structure. Slip forms are used for high structures such as silos, tanks, or chimneys. Concrete may be obtained from commercial batch plants which deliver it in mix trucks if the job is close to such a plant, or it may b
35、e produced at the job site. Concrete production at the job site requires the erection of a mixing plant, and of cement and aggregate receiving and handling plants. Aggregates are sometimes produced at or near the job site. This requires opening a quarry and erecting processing equipment such as crus
36、hers and screens. Concrete is placed by chuting directly from the mix truck, where possible, or from buckets handled by means of cranes or cableways, or it can be pumped into place by special concrete pumps. Curing of exposed surfaces is required to prevent evaporation of mix water orto replace mois
37、ture that does evaporate. The proper balance of water and cement is required to develop full design strength. Concrete paving for airports and highways is a fully mechanized operation. Batches of concrete are placed between the road forms from a mix truck or a movable paver, which is a combination m
38、ixer and placer. A series of specialized pieces of equipment, which ride on the forms, follow to spread and vibrate the concrete, smooth its surface, cut contraction joints, and apply a curing compound. Asphalt paving. This is an amalgam of crushed aggregate and a bituminous binder. It may be placed
39、 on the roadbed in separate operations or mixed in a mix plant and spread at one time on the roadbed. Then the pavement is compacted by rollers. Taken from Wikipedia 建筑工程建筑工程是土木工程的一个专业分支，它涉及道路、建筑物、大坝、机场和公用事业管线等项目的规划、实施及建设过程的管理控制。建设规划包括安排工程项目的施工内容以及选择最为合适的施工方法和施工设备。项目的实施要求及时调动所有的设计图纸、施工平面布局图以及施工中的建筑材
40、料以防治工作的延误。管理控制涉及施工进展及工程造价的分析，以确保工程项目准时完工以及工程造价控制在预估造价范围内。规划：项目规划阶段开始于施工计划和设计说明书的详细研究。从研究中，可以获得包含所有工作项目的列表，然后相关项目组合在一起列成总安排表。每个工作项目的施工内容以及所需时间都可以从总安排表中体现出来。单个工程项目的施工方法以及施工设备都应认真选择，从而以最低可能的造价来满足施工安排以及项目的特征。分配给一定项目的施工时间及其改项目的施工方法和设备的选择对承包商来说应该是完全可以得到的。总体建设安排制定后，详尽辅助的安排就可以根据总体安排来制定。详尽建设安排包括：材料、设备、劳务获取的安
41、排以及工程成本和收入的预估。项目的实施：项目的快速实施需要所有材料、设备、劳务随时完备供应。建筑工程师通常负责绝大多数建筑材料的购买以及催促这些材料尽快运送到项目中。如结构钢和机械设备类的材料需要供应商对这些材料做部分或全部的加工制作。对于加工制作的材料，工程师还必须准备正确的加工制作图纸或者检查所有加工图纸的正确性以及配件装配情况，而且还要经常检查供应商的加工制作情况。其他得建设工程任务包含有:审定施工方法后布置工作内容、为施工队准备施工详图、检查工作情况以确保其符合计划和设计说明书。在大多数大型工程项目中，有必要为临时建设工程设计和准备施工图纸，比如说排水结构、便道、储存室、模板以及围堰。
42、其他的问题是选择电气与机械设备，设计混凝土原料加工与搅拌厂的结构以及设计压缩空气分配系统、配水配电系统。管理控制：进度控制是通过比较实际工作中的进度与总安排或详尽安排中的预期进度来实行的。由于一个项目的延误很容易影响整个工作的进行，所以经常有必要增加设备和人员来加速工作的进行。成本控制是通过比较单个工作项目的实际单位成本与预估或预算单位成本来进行的，而预算单位成本则是在工作开始时就做好的。项目单位是用施工总成本除以施工项目的单位数量得到的。挖方工程或混凝土工程的典型单位是立方米，而结构钢的典型单位是吨。任何工作单元在任何时候的单位实际造价可以用已支付的累计费用除以施工完成的累计工作单元得到。单
43、独工作项目的成本可以通过定期分配工作成本（如工资单和发票）到各种工作项目帐户里获取。工资和设备租赁费是根据施工队工头所准备的出勤时间记录卡来分配，出勤时间记录卡可以显示项目各工序上劳工和设备所花费的时间。材料成本的分配则根据花费在每个明确项目上每类材料的数量。当实际单位成本与预估单位成本比较后显示出超支时，则要分析并查明原因。如果是设备成本超支，则可能是设备没有充足的容量或者设备没有正确的操作运行；假如是劳务成本超支，则可能是工程队有太多的劳动力而又缺乏恰当的监管，或者是由于材料缺乏或布局不合理而引起的延误。在这些情况下，分析施工生产中进行工期研究是十分有价值的。施工操作通常是根据专业领域来分
44、类的，这些包括：项目现场的准备、土方运输、基础处理、钢筋装配、混凝土浇筑、沥青摊铺以及电气和机械设备的安装。甚至当这些施工操作运用于不同的工程项目上时，每种专业领域的操作程序通常时相同的，比如房屋建筑、大坝或飞机场等工程领域。然而在所有情况下，每个专业领域的相对重要性却并不相同。施工现场的准备：包括移除并清理表面结构物及种植物。推土机经常用于小型结构物和树木的清除，大型结构物则需要拆除。土方运输：包括填土的挖掘和放置。当现有的坡度必须挖到一个新的高度时，挖土则要按照现场准备来实施。挖土通常开始要挖除表层有机土壤带，然后将其用于布置心建筑物的周围，这样也会防止有机土层下非有机材料的污损。土方挖掘
45、可以用任意几种挖掘机，比如挖铲、索斗铲、抓斗、起重机、铲运机。在地上进行有效挖掘要求一个干燥的挖掘区域，因为土壤处于潮湿情况下是不稳固的，也不能支撑挖掘及托运设备。当在自然地下水位以下进行挖掘时，且又可能阻挡地下水流时，排水就成为了主要的工作；这种情况发生时，排水并稳定土的工作则可以通过设置沟渠来完成，沟渠引导水流渗流到排水坑中并被抽出。在其他情形下，排水并稳定土的工作也可以通过井点和电渗方法来完成。对于一些像岩石、水泥固结砂砾和硬土等材料，需要用炸药炸开以疏松或破碎这些材料。爆炸孔钻进材料中，然后将炸药放置其中并引爆。炸药量以及炸药孔间隔取决于岩石类型和结构以及炸药孔深度和直径。填土摊铺后，
46、通常要进行碾压以防止后续的沉降。碾压通常可以采用羊角碾、方格压印滚筒、轮胎碾、振动碾。这些碾压机是通过置于 上的拖拉机来牵引的。碾压机不能操作的紧挨结构物的空间可以采用手握式撞锤以及气动锤来进行压实。基础处理：当地质调查显示结构物的基础区域有结构缺陷时，则必须加强基础。渗水、洞穴、裂缝、断层以及其他缺陷则可以通过涂水泥砂浆来填充及加强。用水泥砂浆填充就是在压力下注射流体混合物，然后流体混合物则会在土层空隙里固结。绝大多数的水泥砂浆是用水泥和水混合制成的，但其他混合物成分还包含沥青、水泥和粘土、凝结化学物。钢筋装配:钢筋结构的施工包括工厂预制钢筋或卷钢厂钢筋的现场装配。钢材可能有钢梁、钢柱或通过
47、铆钉、螺钉或者焊接连接而成的小型构件。较为经济的结构钢筋装配是在预制工厂而不是在现场；但预制装配构件的尺寸由于运输设备容量或装配设备受限时则应在现场装配。起重机时最普通的装配设备，但当结构太高或面积太大时，有必要在结构上放置多个起重机来处理钢筋。在高层结构物上，起重机必须经常拆卸并且重新被架设在更高的位置以便举起结构钢筋。对于河流上的桥梁，钢筋可以通过驳船上的起重机来处理，或者如果桥梁太高，则可以通过临时桥上的移动起重机来处理。长大悬索桥的悬索可以用特殊设备在现场装配，这种特殊设备先拉直卷轴上的钢丝，并在一个锚固架立固定，而后再横跨过另一个锚固点，重复这种操作，直到钢丝到达要求的尺寸。混凝土施
48、工：混凝土施工包含一下几个操作，模板制作，混凝土生产、浇注及养护。模板要求包围并支撑住液体混凝土以保持混凝土理想的最终轮廓，直到混凝土固结并达到足够强度时，模板才能被拆除。模板可以用木材、钢材或两者组合而制成。混凝土浇注期间要用外部支撑或内部系杆将模板固定在一起，模板以及系杆支撑可以抵挡混凝土的临时液体压力。常用的直立墙是为了在混凝土浇筑后至少一天以上移除现场模板。当混凝土固结或硬化时模板则被移除。模板需不断移动的地方，即在新浇混凝土位置前面，设置滑动模板则是一种有用的方法。模板可以通过千斤顶得到举高，而千斤顶架立于插入混凝土中的立柱上，且沿着结构的周围分隔布置。滑动模板可以用在像竖井、蓄水池、烟囱等高结构物中。如果施工场地紧挨着商业混凝土制作工厂，混凝土可以从这种工厂获取，这种工厂会将混凝土通过搅拌大卡车运送到施工现场，也可以在施工现场进行生产。施工现场混凝土的生产需要架立混凝土搅拌工厂、水泥和骨料接收及处理工厂。骨料有时候可以在施工现场及附近制作，这就要求开放一个采石场以及架立像粉碎机和筛子之类的生产处理设备。可能情况下，混凝土可以通过斜槽直接从搅拌车滑下进行浇筑，或者可以从起重机或架空索道控制的铲斗里倒下浇筑，还可以通过特殊混凝土泵浇筑于现场。暴露于外的表面混凝土养护则是防止混合水的蒸发或替代
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