By Prof Syed Sabihuddin Head Department of Civil Engineering PRMCEAM,Badnera 1

 Planning can be defined as drawing up a method or scheme of acting, doing, proceeding, making, etc developed in advance.  In construction of large projects different agencies are involved like client/owner, designer, consultants and contractors. They carry out their own working plans, it is important to have proper coordination between these agencies to serve a common goal.  Plans are drawn up at each of the stage or phase of project, though different terminologies are used at times like feasibility plan, preliminary plan and construction plan etc.  Some of the activities involved in construction planning are as,  Defining the scope of work: since all activities involve different resources up to certain extents hence important to define scope of work completely. Any addition, deletion or modification can affect time of completion and cost.  Identifying activities involved: depending upon scope of work identifying activities involved in a particular job. 2

 Establishing project duration: It can be done only with clear knowledge of required resources, productivity and interrelationships. This information is used to prepare network and other schedules.  Defining procedures for controlling and assigning resources: Defining procedure to be followed for procurement and control of resources for different activities, such as manpower, machines, material and money.  Developing appropriate interfaces: Planner needs to plan an appropriate management information system. Tools such as computers and formats for reporting are widely used. Several software are also readily available.  Updating and revising plans: Construction plan needs to be continuously updated and revised during monitoring and executing various construction activities, looking to input, process involved, time and productivity aspect. 3

 Schedule, cost, quality and safety can be identified as specific items on which the success of any project is evaluated. Although there is a complex interrelationship between these, hence consider them separately as time plan, cost plan, quality plan and safety plan. Sometimes one may also need to deal with plant & equipment plan, maintenance plan and staff deployment plan. It should be emphasized that all the independent plans must be in line with the master plan.  1)Time plan: Time is important factor in all construction project, may award bonus for completion of work ahead or may cause penalties for late completion of work. Some of the common reasons for delay could be sluggish approach in planning, delay in award of contract, changes during execution, delay in payments, slow decision-making, delay in supply of drawings and materials and the labor problems. Several well-established techniques are available and commonly used for time planning activities such as CPM, PERT, LOB etc. 4

 2)Manpower plan: This plan focuses on estimating the size of workforce, division in functional teams and scheduling the deployment of manpower. Also involving labor productivity standards, providing suitable environment and financial incentives etc.  3)Material plan: This involve identification of required materials, estimation of required quantities, defining specification and forecasting material requirement.  4)Construction equipment plan: Modern construction is highly mechanized and role of heavy equipment is very important for timely completion of project. Use of equipment also improve productivity and quality. For preparing plans of equipment one should have knowledge of equipments.  5)Financial plan: For large construction project huge investment is required for long time at different time interval. Hence careful planning is required for funds and finance. 5

 Work-breakdown structure is a technique in which the project is broken down into manageable chunks.  WBS represents a task oriented family tree of activities, and organizes, defines and graphically displays the total work to be accomplished in order to achieve the final objectives of the project.  This provides a central organizing concept for the project and serves as a common framework for the other exercises such as planning, scheduling, cost estimating, budgeting, monitoring, reporting, directing and controlling the entire project.  As the project grows in complexity and number of activities get involved and their interrelationship becomes simply too complex to handle using conventional methods, in such cases utility of this method can be clearly demonstrated.  A project is split into different levels from top to bottom. Consider an example, which shows whole to part relation between the project, sub- project, work packages, tasks and activities. 6

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 Event: Event is a point in time when certain conditions have been fulfilled, such as the start or completion of one or more activities. Neither it consumes time nor any other resource.  Activity: Activities take place between events. It is an item of work consume various resources and produce quantitative results.  Dummy activity: This activity does not consume any resource, and therefore dose not need any time to be completed. It is used to define interdependence between activities and included in network for logical reason. Figure represent the dependence of activity D on activities A and C. 8

 Network: Network consisting of nodes and arrows are the graphical representation of activities, showing logical dependence between them.  While drawing network certain rules are followed for numbering the events or nodes. 1)Same node number can not be used twice in the network. 2)Tail node number must be smaller than head node. 3)Numbering starts from left hand top and ends in right hand bottom.  For construction planning two kinds of network can be used, activity on arrow (AOA) and activity on node (AON).  In AOA, the activities are shown as arrows leading from one node to another node, and nodes can be looked as either the starting or end point of an activity.  In AON, the activities are denoted by nodes and the immediate predecessor relationship between two activities is shown by an arrow connecting two nodes.  It can be noted that before an activity begins, all activities preceding it must be completed, and that an arrow implies only a logical precedence. 9

 Consider a simple project (construction of wall), can be broken down in to activities such as earthwork, brickwork, and plastering in fig 6.4. Each activity is defined in terms of two nodes (i, j) such that i and j represent start and end of the activity. For fig 6.4 activities represented as (10,20) (20,30) and (30,40). 10

 In this type of network, the activities are denoted by circles or boxes called nodes, and the immediate predecessor relationship between the two activities is shown by an arrow connecting the two nodes.  Network shown in fig 6.9 presents activity on node network for AOA example shown in fig 6.8. it can be noticed that for same number of activities and similar relationship AON has not used a single dummy activity while AOA has used two dummy activities. AOA is convenient for simple network while AON is convenient for large and complex network. 11

 Precedence: this is a logical relationship implying that an activity needs one or more activities to be completed before start of this activity. For example, in order to start with plastering work, the brickwork needs to have been completed.  Network logic: Some of the common logical ways useful in preparing a network are shown below.  Fig 6.10 shows an example of burst situation, wherein two activities are starting. Fig 6.11 shows an example of merge situation, wherein two activities getting completed. Fig 6.12 shows incorrect way of showing three parallel activities and corrected in fig

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 Duration of an activity: Duration of an activity(i,j) is denoted by D(i,j). This is the length of time required to carry out an activity(i,j) from the beginning to its end. Duration may be expressed in days, weeks or months.  Earliest start time of an activity: This is the earliest, that an activity(i,j) can be started. Denoted by EST(i,j).  Earliest finish time of an activity: This is the earliest, that an activity (i,j) can be completed. Denoted by EFT(i,j).  Latest finish time of an activity: This is the latest, that an activity needs to be completed in order that there is no delay in the project completion. Denoted by LFT(i,j).  Latest start time of an activity: This is the latest, that an activity must be started in order that there is no delay in the project completion. Denoted by LST(i,j). 14

 Forward pass moves from the start node towards the finish node, and basically calculates the earliest occurrence times of all events. Earliest occurrence time for any node can be estimated from the maximum time taken to reach that node from the different incoming arrows.  Consider the network given in fig 6.22 defining the relationship between activities.  Earliest occurrence times for various nodes can be found out by Ej=Ei + D(i,j) and only for node 5 (two incoming arrows from node 3 and 4) found out by Ej=Maxi(Ei + D(i,j))  Backward pass is made in a similar manner to that of the forward pass, except that the process is carried out in reverse through the nodes, starting from the end node and finishing at the start node.  Late occurrence time for various nodes can be calculated by Li=Lj - D(i,j) and only for node 2 (when two outgoing arrows) found out by Li=Mini(Lj - D(i,j))  It can be seen that for some events (nodes), the two values (E & L) are same, then these events constitute the critical events, and the continuous path through them gives the critical path. 15

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 Total float: It is the amount of time by which the start of the activity may be delayed without causing a delay in the completion of project. Calculated as TF(i,j)=LST(i,j)-EST(i,j) & TF(i,j)=LFT(i,j)-EFT(i,j)  Free float: Free float is the amount of time by which the start of an activity may be delayed without delaying the start of a following activity. Calculated as FF(i,j)=Ej-Ei-D(i,j)  Independent float: It is the amount of time by which the start of an activity may be delayed without affecting the preceding or the following activity. Denoted by IF(i,j) and calculated by IF(i,j)=Ej-Li-D(i,j)  Interference float: Defined as the difference in total float and free floa. Interference float=TF(i,j)-FF(i,j)  Fig pg

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 Any series of activities connecting the starting node to the finishing node can be said as a path, in a project several activities and several such path can be identified. Among these paths, the critical path is defined as one that gives the longest time of completion of project, which also defines the shortest possible project completion time. Critical path does not contain any float. Fig 6.22 shows critical path marked with bold line. 19

 CPM is a method or technique used for planning and managing all kind of construction activities. It is a representation of project plan by a network that shows the sequence and inter-relationship of various construction activities of a project.  CPM identify the tasks that are on the critical path and any delay in completion of those tasks can lengthen overall project duration.  CPM takes in to account uncertainty or variations involved in a job at the planning stage itself.  In CPM the workflow can be shown schematically by means of arrows, where the logical relationship between the various activities can be seen clearly.  In CPM also, similar process of forward and backward paths calculations to find start and finish time, floats, critical activities and length of critical path are adopted. 20

 Advantages of CPM  1)Entire project can viewed as single unit. 2)Project duration can be found out. 3)Interdependence of various activities known. 4)Critical activities can be found out. 5)Gives detail about optimum use of resources. 6)Helps in cost controlling. 7)Progress can be assessed at any stage.  Sequence of project management using CPM  1)Planning of task or activity. 2)Forming network. 3)Allocation of time to different activities. 4)Deciding the critical path. 5)Review of network. 6)Controlling operations. 7)Cost programming.  21

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 Bar chart is a graphical representation of a project.  Bar charts are easy to understand and useful in reviewing construction progress.  It is one of the oldest methods and an effective technique for overall project planning.  This method also referred as Gantt charts.  In a bar chart, activities are shown as horizontal bars on horizontal time scale.  Logical interdependency can not be found out.  Critical activities can not be assessed easily. 23

 Creating a network diagram involves preparing a work- breakdown structure for the project, determining the interdependency among the activities, estimating the duration for each activity and finally drawing the network.  Once an initial draft of the network is prepared, the analysis is carried out using a forward and backward pass to determine critical path in the project and the activities lying on it. 24

 PERT is more commonly used in manufacturing industry, especially in research and development type of programmes. It is assumed that activities and their interdependence are well defined, though it recognizes uncertainty in the time estimate of an activity. PERT incorporates uncertainties in activity durations in its analysis, requiring three durations for each activity, which are the most probable (t m ), the optimistic (t o ) (shortest) and the pessimistic (t p ) (longest) duration.  For example, let an activity ‘design foundation’, the optimistic, most likely and pessimistic time estimate for completing this activity be 14 days, 18 days and 28 days respectively. PERT technique assumes that the three time estimates of an activity are random variables, and the frequency distribution of duration of an activity takes the shapes of beta distribution shown in fig.  The average or expected time ‘t e ’ is calculated by t e =(t o +4 t m + t p )/6 25

 In order to measure the uncertainty associated with the estimate of duration of an activity, the standard deviation (S t ) and the variance (V t ) are determined, by S t =(t p -t o )/6 and V t =(S t ) 2.  26

 For example consider, two sets of estimates provided by different estimator for ‘design foundation’ activity. In order of (t o, t m, t p ), let the sets of estimate are (14,18,28) and (17,18,25).  The expected or average activity duration comes out to be t e =19 in both the cases. Accordingly the standard deviation (S t ) and the variance (V t ) would be 2.33 days and 5.44 for first set and 1.33 days and 1.77 for second set respectively.  The expected length or duration of project T e is calculated by summing up the expected duration t e of activities on the critical path. The critical path is determined following the forward pass and backward pass. The variance associated with the critical path is the sum of variances associated with the activities on the critical path. T e =∑t e, V T =∑ V t, S T =√V T, V T and S T represent variability in the expected project duration.  Let us suppose that it is required to compute the probability of completing the project within a target duration of TD days. Ratio called standardized deviation or normal deviate Z is derived as Z=(TD- T e )/ S T 27

 Consider an example to illustrate the application of PERT to small project. 28

 After determining critical path, calculate the expected duration of project T e =∑t e = t e (10,20)+ t e (20,40)+ t e (40,50)+ t e (50,60)= =36 days. The variance, V T =∑V t = V t (10,20)+ V t (20,40)+ V t (40,50)+ V t (50,60)= =30, and thus S T =√V T = √30=5.48 days. 29