《专业英语》课件Unit_11.pptx
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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
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