1、Unit11Construction PlanningText1 Basic Concept in the Development of Construction PlansConstruction planning is a fundamental and challenging activity in the management and execution of construction projects.It involves the choice of technology,the definition of work tasks,the estimation of the requ
2、ired resources and durations for individual tasks,and the identification of any interactions among the different work tasks1.A good construction plan is the basis for developing the budget and the schedule for work.Developing the construction plan is a critical task in the management of construction
3、,even if the plan is not written or otherwise formally recorded.In addition to these technical aspects of construction planning,it may also be necessary to make organizational decisions about the relationships between project participants and even which organizations to include in a project.For exam
4、ple,the extent to which sub-contractors will be used on a project is often determined during construction planning.In developing a construction plan,it is common to adopt a primary emphasis on either cost control or on schedule control.Some projects are primarily divided into expense categories with
5、 associated costs.TextIn these cases,construction planning is cost or expense oriented.Within the categories of expenditure,a distinction is made between costs incurred directly in the performance of an activity and indirectly for the accomplishment of the project.For example,borrowing expenses for
6、project financing and overhead items are commonly treated as indirect costs.For other projects,scheduling of work activities over time is critical and is emphasized in the planning process.In this case,the planner insures that the proper precedence among activities is maintained and that efficient s
7、cheduling of the available resources prevails.Traditional scheduling procedures emphasize the maintenance of task precedence(resulting in critical path scheduling procedures)or efficient use of resources over time(resulting in job shop scheduling procedures).Finally,most complex projects require con
8、sideration of both cost and scheduling over time,so that planning,monitoring and record keeping must consider both dimensions.In these cases,the integration of schedule and budget information is a major concern.Text2 Choices of Technology and Construction MethodAs in the development of appropriate a
9、lternatives for facility design,choices of appropriate technology and methods for construction are often ill-structured yet critical ingredients in the success of the project2.For example,a decision whether to pump or to transport concrete in buckets will directly affect the cost and duration of tas
10、ks involved in building construction.A decision between these two alternatives should consider the relative costs,reliabilities,and availability of equipment for the two transport methods.Unfortunately,the exact implications of different methods depend upon numerous considerations for which informat
11、ion may be sketchy during the planning phase,such as the experience and expertise of workers or the particular underground condition at a site3.In selecting among alternative methods and technologies,it may be necessary to formulate a number of construction plans based on alternative methods or assu
12、mptions.Once the full plan is available,then the cost,time and reliability impacts of the alternative approaches can be reviewed.This examination of several alternatives is often made explicit in bidding competitions in which several alternative designs may be proposed or value engineering for alter
13、native construction methods may be permitted.TextIn this case,potential constructors may wish to prepare plans for each alternative design using the suggested construction method as well as to prepare plans for alternative construction methods which would be proposed as part of the value engineering
14、 process.In forming a construction plan,a useful approach is to simulate the construction process either in the imagination of the planner or with a formal computer based simulation technique.By observing the result,comparisons among different plans or problems with the existing plan can be identifi
15、ed.For example,a decision to use a particular piece of equipment for an operation immediately leads to the question of whether or not there is sufficient access space for the equipment.Three dimensional geometric models in a computer aided design(CAD)system may be helpful in simulating space require
16、ments for operations and for identifying any interference.Text3 Defining Work Tasks At the same time that the choice of technology and general method are considered,a parallel step in the planning process is to define the various work tasks that must be accomplished.These work tasks represent the ne
17、cessary framework to permit scheduling of construction activities,along with estimating the resources required by the individual work tasks,and any necessary precedence or required sequence among the tasks.The scheduling problem is to determine an appropriate set of activity start time,resource allo
18、cations and completion times that will result in completion of the project in a timely and efficient fashion.Construction planning is the necessary fore-runner to scheduling.In this planning,defining work tasks,technology and construction method is typically done either simultaneously or in a series
19、 of iterations.More formally,an activity is any subdivision of project tasks.The set of activities defined for a project should be comprehensive or completely exhaustive so that all necessary work tasks are included in one or more activities.Typically,each design element in the planned facility will
20、 have one or more associated project activities.Execution of an activity requires time and resources,including manpower and equipment.The time required to perform an activity is called the duration of the activity.The beginning and the end of activities are signposts or milestones,indicating the pro
21、gress of the project.TextIt is generally advantageous to introduce an explicit hierarchy of work activities for the purpose of simplifying the presentation and development of a schedule.For example,the initial plan might define a single activity associated with site clearance.Later,this single activ
22、ity might be sub-divided into re-locating utilities,removing vegetation,grading,etc.However,these activities could continue to be identified as sub-activities under the general activity of site clearance.This hierarchical structure also facilitates the preparation of summary charts and reports in wh
23、ich detailed operations are combined into aggregate or super-activities.In practice,the proper level of detail will depend upon the size,importance and difficulty of the project as well as the specific scheduling and accounting procedures which are adopted4.However,it is generally the case that most
24、 schedules are prepared with too little detail than too much.It is important to keep in mind that task definition will serve as the basis for scheduling,for communicating the construction plan and for construction monitoring.Completion of tasks will also often serve as a basis for progress payments
25、from the owner.Thus,more detailed task definitions can be quite useful.But more detailed task breakdowns are only valuable to the extent that the resources required,durations and activity relationships are realistically estimated for each activity.Providing detailed work task breakdowns is not helpf
26、ul without a commensurate effort to provide realistic resource requirement estimates.As more powerful,computer-based scheduling and monitoring procedures are introduced,the ease of defining and manipulating tasks will increase,and the number of work tasks can reasonably be expected to expand.Text4 D
27、efining Precedence Relationships among ActivitiesOnce work activities have been defined,the relationships among the activities can be specified.Precedence relations between activities signify that the activities must take place in a particular sequence.Numerous natural sequences exist for constructi
28、on activities due to requirements for structural integrity,regulations,and other technical requirements.Some activities have a necessary technical or physical relationship that cannot be superseded.For example,concrete pours cannot proceed before formwork and reinforcement are in place.Some activiti
29、es have a necessary precedence relationship over a continuous space rather than as discrete work task relationships.Some precedence relationships are not technically necessary but are imposed due to implicit decisions within the construction plan.5 Estimating Activity DurationsIn most scheduling pro
30、cedures,each work activity has associated time duration.These durations are used extensively in preparing a schedule.All formal scheduling procedures rely upon estimates of the durations of the various project activities as well as the definitions of the predecessor relationships among tasks.A strai
31、ghtforward approach to the estimation of activity durations is to keep historical records of particular activities and rely on the average durations from this experience in making new duration estimates.Text6 Estimating Resource Requirements for Work ActivitiesIn addition to precedence relationships
32、 and time durations,resource requirements are usually estimated for each activity.Since the work activities defined for a project are comprehensive,the total resources required for the project are the sum of the resources required for the various activities.By making resource requirement estimates f
33、or each activity,the requirements for particular resources during the course of the project can be identified.Potential bottlenecks can thus be identified,and schedule,resource allocation or technology changes made to avoid problems.Many formal scheduling procedures can incorporate constraints impos
34、ed by the availability of particular resources.Another type of resource is space.The initial problem in estimating resource requirements is to decide the extent and number of resources that might be defined.At a very aggregate level,resources categories might be limited to the amount of labor(measur
35、ed in man-hours or in dollars),the amount of materials required for an activity,and the total cost of the activity.At this aggregate level,the resource estimates may be useful for purposes of project monitoring and cash flow planning.However,this aggregate definition of resource use would not reveal
36、 bottlenecks associated with particular types of equipment or workers.TextMore detailed definitions of required resources would include the number and type of both workers and equipment required by an activity as well as the amount and types of materials5.Standard resource requirements for particula
37、r activities can be recorded and adjusted for the special conditions of particular projects.As a result,the resources types required for particular activities may already be defined.Reliance on historical or standard activity definitions of this type requires a standard coding system for activities.
38、From the planning perspective,the important decisions in estimating resource requirements are to determine the type of technology and equipment to employ and the number of crews to allocate to each task.Clearly,assigning additional crews might result in faster completion of a particular activity.How
39、ever,additional crews might result in congestion and coordination problems,so that work productivity might decline.Further,completing a particular activity earlier might not result in earlier completion of the entire project.New Words and PhrasesDuration，n.持续时间，期间 interaction，n.交互，相互作用 schedule，n.进度
40、，日程安排 orient，v.以为中心，面向 incur，v.招致,发生 prevail，v.优先 dimension，n.维度 appropriate，adj.合适的，适合的，适宜的，适当的 simulate，v.模拟，仿真 geometric，adj.几何(学)的 interference，n.干涉，干扰parallel，adj.平行的 precedence，n.紧前工作iteration，n.迭代，重复 exhaustive，adj.全面的,详尽的 hierarchy，n.层级 presentation，n.表达vegetation，n.植被 grading，n.坡度aggregate，
41、n.总体commensurate，adj(在时间和空间上)相等的 integrity，n.完整New Words and Phrasesreinforcement，n.钢筋bottleneck，n.瓶颈crew，n.班组allocate，vi.分配,分派congestion，n.拥挤 in the management of，prep.-在-的管理be the basis for，prep.-依据是-even if，adv.即使In addition to，prep.-除了-be necessary to，adj.-是必要的-include in，vi.包括be used on，vi.被用于d
42、ivided into，vi.分为 in the performance of，prep.-在-的性能is critical in，adj 至关重要的over time，prep.随着时间的result in，v.导致in a series，n.一系列the sum of，adj.-的总和-the amount of，n.-的数量-for purposes of，prep.-为了-Notes（1）It involves the choice of technology,the definition of work tasks,the estimation of the required res
43、ources and durations for individual tasks,and the identification of any interactions among the different work tasks.它涉及技术的选择,工作任务的定义,所需资源的估计和个人任务的持续时间,以及不同工作任务之间相互作用的识别鉴定。（2）As in the development of appropriate alternatives for facility design,choices of appropriate technology and methods for constr
44、uction are often ill-structured yet critical ingredients in the success of the project.在开发适当的替代品设施设计过程中,选择合适的施工技术和方法通常是不良的结构，然而在项目的成功中起到关键作用。（3）Unfortunately,the exact implications of different methods depend upon numerous considerations for which information may be sketchy during the planning phase
45、,such as the experience and expertise of workers or the particular underground condition at a site.不幸的是，不同方法的确切含义取决于众多因素，在计划阶段中信息可能是粗略的，例如有经验和专业知识的工人或者在一个站点特定的地下条件。Notes（4）In practice,the proper level of detail will depend upon the size,importance and difficulty of the project as well as the specifi
46、c scheduling and accounting procedures which are adopted.在实践中,细节的适当水平取决于大小,重要性和项目的困难程度以及所采用的具体的调度和会计程序。（5）More detailed definitions of required resources would include the number and type of both workers and equipment required by an activity as well as the amount and types of materials.所需资源更多的详细定义包括
47、工人和设备的数量和类型两个方面，需要通过一个活动以及材料的数量和类型。Exercise（Translate the following Chinese into English,or English into Chinese）（1）At a very aggregate level,resources categories might be limited to the amount of labor(measured in man-hours or in dollars),the amount of materials required for an activity,and the tot
48、al cost of the activity.（2）Within the categories of expenditure,a distinction is made between costs incurred directly in the performance of an activity and indirectly for the accomplishment of the project.（3）In selecting among alternative methods and technologies,it may be necessary to formulate a n
49、umber of construction plans based on alternative methods or assumptions.（4）In forming a construction plan,a useful approach is to simulate the construction process either in the imagination of the planner or with a formal computer based simulation technique.（5）At the same time that the choice of tec
50、hnology and general method are considered,a parallel step in the planning process is to define the various work tasks that must be accomplished.Exercise（Translate the following Chinese into English,or English into Chinese）（6）工程质量的优劣直接关系到工程的适用性，不仅与企业本身的经济效益有关，而且与社会的经济效益、生态效益密切相关，影响着众多企业的发展。（7）随着工程量的加
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