1、Text1 Costs Associated with Constructed Facilities The costs of a constructed facility to the owner include both the initial capital cost and the subsequent operation and maintenance costs.Each of these major cost categories consists of a number of cost components.The capital cost for a construction
2、 project includes the expenses related to the initial establishment of the facility:Land acquisition,including holding and improvement Planning and feasibility studiesArchitectural and engineering design Construction,including materials,equipment and labor Field supervision of constructionConstructi
3、on financingInsurance and taxes during constructionOwners general office overheadEquipment and furnishings not included in construction Text Inspection and testingThe operation and maintenance cost in subsequent years over the project life cycle includes the following expenses:Land rent,if applicabl
4、e.Operating staff.Labor and material for maintenance and repairs.Periodic renovations.Insurance and taxes.Financing costs.Utilities.Owners other expenses.The magnitude of each of these cost components depends on the nature,size and location of the project as well as the management organization,among
5、 many considerations.The owner is interested in achieving the lowest possible overall project cost that is consistent with its investment objectives.TextIt is important for design professionals and construction managers to realize that while the construction cost may be the single largest component
6、of the capital cost,other cost components are not insignificant.For example,land acquisition costs are a major expenditure for building construction in high-density urban areas,and construction financing costs can reach the same order of magnitude as the construction cost in large projects such as t
7、he construction of nuclear power plants.From the owners perspective,it is equally important to estimate the corresponding operation and maintenance cost of each alternative for a proposed facility in order to analyze the life cycle costs.The large expenditures needed for facility maintenance,especia
8、lly for publicly owned infrastructure,are reminders of the neglect in the past to consider fully the implications of operation and maintenance cost in the design stage1.In most construction budgets,there is an allowance for contingencies or unexpected costs occurring during construction.This conting
9、ency amount may be included within each cost item or be included in a single category of construction contingency.The amount of contingency is based on historical experience and the expected difficulty of a particular construction project.TextFor example,one construction firm makes estimates of the
10、expected cost in five different areas:Design development changes.Schedule adjustments.General administration changes(such as wage rates).Differing site conditions for those expected.Third party requirements imposed during construction,such as new permits.Contingent amounts not spent for construction
11、 can be released near the end of construction to the owner or to add additional project elements.2 Approaches to Cost EstimationCost estimating is one of the most important steps in project management.A cost estimate establishes the base line of the project cost at different stages of development of
12、 the project.A cost estimate at a given stage of project development represents a prediction provided by the cost engineer or estimator on the basis of available data.TextAccording to the American Association of Cost Engineers,cost engineering is defined as that area of engineering practice where en
13、gineering judgment and experience are utilized in the application of scientific principles and techniques to the problem of cost estimation,cost control and profitability.Virtually all cost estimation is performed according to one or some combination of the following basic approaches.(1)Production f
14、unction.In microeconomics,the relationship between the output of a process and the necessary resources is referred to as the production function.In construction,the production function may be expressed by the relationship between the volume of construction and a factor of production such as labor or
15、 capital.A production function relates the amount or volume of output to the various inputs of labor,material and equipment.For example,the amount of output Q may be derived as a function of various input factors x1,x2,xn by means of mathematical and/or statistical methods.Thus,for a specified level
16、 of output,we may attempt to find a set of values for the input factors so as to minimize the production cost.The relationship between the sizes of a building project(expressed in square feet)to the input labor(expressed in labor hours per square foot)is an example of a production function for const
17、ruction.Text(2)Empirical cost inference.Empirical estimation of cost functions requires statistical techniques which relate the cost of constructing or operating a facility to a few important characteristics or attributes of the system2.The role of statistical inference is to estimate the best param
18、eter values or constants in an assumed cost function.Usually,this is accomplished by means of regression analysis techniques.(3)Unit costs for bill of quantities.A unit cost is assigned to each of the facility components or tasks as represented by the bill of quantities3.The total cost is the summat
19、ion of the products of the quantities multiplied by the corresponding unit costs.The unit cost method is straightforward in principle but quite laborious in application.The initial step is to break down or disaggregate a process into a number of tasks.Collectively,these tasks must be completed for t
20、he construction of a facility.Once these tasks are defined and quantities representing these tasks are assessed,a unit cost is assigned to each and then the total cost is determined by summing the costs incurred in each task.The level of detail in decomposing into tasks will vary considerably from o
21、ne estimate to another.Text(4)Allocation of joint costs.Allocations of cost from existing accounts may be used to develop a cost function of an operation.The basic idea in this method is that each expenditure item can be assigned to particular characteristics of the operation.Ideally,the allocation
22、of joint costs should be causally related to the category of basic costs in an allocation process.In many instances,however,a causal relationship between the allocation factor and the cost item cannot be identified or may not exist.For example,in construction projects,the accounts for basic costs ma
23、y be classified according to:labor.material.construction equipment.construction supervision.general office overhead.These basic costs may then be allocated proportionally to various tasks which are subdivisions of a project.Text3 Types of Construction Cost Estimates Construction cost constitutes onl
24、y a fraction,though a substantial fraction,of the total project cost.However,it is the part of the cost under the control of the construction project manager.The required levels of accuracy of construction cost estimates vary at different stages of project development,ranging from ball park figures
25、in the early stage to fairly reliable figures for budget control prior to construction.Since design decisions made at the beginning stage of a project life cycle are more tentative than those made at a later stage,the cost estimates made at the earlier stage are expected to be less accurate.Generall
26、y,the accuracy of a cost estimate will reflect the information available at the time of estimation.Construction cost estimates may be viewed from different perspectives because of different institutional requirements.In spite of the many types of cost estimates used at different stages of a project,
27、cost estimates can best be classified into three major categories according to their functions.A construction cost estimate serves one of the three basic functions:design,bid and control.For establishing the financing of a project,either a design estimate or a bid estimate is used.TextDesign Estimat
28、es For the owner or its designated design professionals,the types of cost estimates encountered run parallel with the planning and design as follows:(1)Screening estimates(or order of magnitude estimates).(2)Preliminary estimates(or conceptual estimates).(3)Detailed estimates(or definitive estimates
29、).(4)Engineers estimates based on plans and specifications.For each of these different estimates,the amount of design information available typically increases.In the planning and design stages of a project,various design estimates reflect the progress of the design.At the very early stage,the scree
30、ning estimate or order of magnitude estimate is usually made before the facility is designed,and must therefore rely on the cost data of similar facilities built in the past.A preliminary estimate or conceptual estimate is based on the conceptual design of the facility at the state when the basic te
31、chnologies for the design are known.TextThe detailed estimate or definitive estimate is made when the scope of work is clearly defined and the detailed design is in progress so that the essential features of the facility are identifiable.The engineers estimate is based on the completed plans and spe
32、cifications when they are ready for the owner to solicit bids from construction contractors.In preparing these estimates,the design professional will include expected amounts for contractors overhead and profits.The costs associated with a facility may be decomposed into a hierarchy of levels that a
33、re appropriate for the purpose of cost estimation4.The level of detail in decomposing the facility into tasks depends on the type of cost estimate to be prepared.For conceptual estimates,for example,the level of detail in defining tasks is quite coarse;for detailed estimates,the level of detail can
34、be quite fine.As an example,consider the cost estimates for a proposed bridge across a river.A screening estimate is made for each of the potential alternatives,such as a tied arch bridge or a cantilever truss bridge.As the bridge type is selected,e.g.the technology is chosen to be a tied arch bridg
35、e instead of some new bridge form;a preliminary estimate is made on the basis of the layout of the selected bridge form on the basis of the preliminary or conceptual design.TextWhen the detailed design has progressed to a point when the essential details are known,a detailed estimate is made on the
36、basis of the well defined scope of the project.When the detailed plans and specifications are completed,an engineers estimate can be made on the basis of items and quantities of work.Bid Estimates For the contractor,a bid estimate submitted to the owner either for competitive bidding or negotiation
37、consists of direct construction cost including field supervision,plus a markup to cover general overhead and profits.The direct cost of construction for bid estimates is usually derived from a combination of the following approaches.(1)Subcontractor quotations.(2)Quantity takeoffs.(3)Construction pr
38、ocedures.The contractors bid estimates often reflect the desire of the contractor to secure the job as well as the estimating tools at its disposal.TextSome contractors have well established cost estimating procedures while others do not.Since only the lowest bidder will be the winner of the contrac
39、t in most bidding contests,any effort devoted to cost estimating is a loss to the contractor who is not a successful bidder5.Consequently,the contractor may put in the least amount of possible effort for making a cost estimate if it believes that its chance of success is not high.If a general contra
40、ctor intends to use subcontractors in the construction of a facility,it may solicit price quotations for various tasks to be subcontracted to specialty subcontractors.Thus,the general subcontractor will shift the burden of cost estimating to subcontractors.If all or part of the construction is to be
41、 undertaken by the general contractor,a bid estimate may be prepared on the basis of the quantity takeoffs from the plans provided by the owner or on the basis of the construction procedures devised by the contractor for implementing the project.For example,the cost of a footing of a certain type an
42、d size may be found in commercial publications on cost data which can be used to facilitate cost estimates from quantity takeoffs.However,the contractor may want to assess the actual cost of construction by considering the actual construction procedures to be used and the associated costs if the pro
43、ject is deemed to be different from typical designs.Hence,items such as labor,material and equipment needed to perform various tasks may be used as parameters for the cost estimates.Text Control Estimates For monitoring the project during construction,a control estimate is derived from available inf
44、ormation to establish:(1)Budget estimate for financing.(2)Budgeted cost after contracting but prior to construction.(3)Estimated cost to completion during the progress of construction.Both the owner and the contractor must adopt some base line for cost control during the construction.For the owner,a
45、 budget estimate must be adopted early enough for planning long term financing of the facility.Consequently,the detailed estimate is often used as the budget estimate since it is sufficient definitive to reflect the project scope and is available long before the engineers estimate.As the work progre
46、sses,the budgeted cost must be revised periodically to reflect the estimated cost to completion.A revised estimated cost is necessary either because of change orders initiated by the owner or due to unexpected cost overruns or savings.TextFor the contractor,the bid estimate is usually regarded as th
47、e budget estimate,which will be used for control purposes as well as for planning construction financing.The budgeted cost should also be updated periodically to reflect the estimated cost to completion as well as to insure adequate cash flows for the completion of the project.New Words and PhrasesP
48、rofits,n.利润overhead,n.企业一般管理费用control estimate,.控制估价budget estimate,.财务预算cost estimation,.成本估算 land acquisition,土地获得 project life cycle,项目生命周期 land rent,.土地租金 periodic renovations,.周期性更新 financial costs,.财务成本 construction cost,.施工建设费unexpected costs,.不可预见费用 cost engineers,造价工程师 cost engineering,工程估价
49、cost control,成本控制production function,产出函数 bid estimate,投标估价 the amount or volume of output,产出总量 production cost,生产成本 empirical cost inference,经验成本推论 bill of quantities,工程量清单 unit cost,单位成本 New Words and Phrasesjoint costs,联合成本 accuracy of cost estimates,估价精度 design estimate,设计估价 direct construction
50、cost,直接施工成本 initial capital,创办成本；初始投资 field supervision of construction,现场施工监督 operation and maintenance costs,运行与养护费用 detailed estimates(or definitive estimates),详细估计(或确定估计)preliminary estimates(or conceptual estimates),初步估算(或概念性估算)screening estimates(or order of magnitude estimates),筛选估计；匡算Notes（1
