AR 523A: PROJECT MANAGEMENTFinals Handouts 1. Procurement Processes In project construction, the importance of the procurement liability for getting the right materials delivered from the suppliers to the site on time cannot be taken for granted. A minor item or low value material not available when needed can stop the construction activities, put people out of work and delay of completion. For instance, in the absence of a common wire nails carpentry work activities could be paralyzed. In general, the purchasing agent is made responsible for maintaining the following major procurement factors: 1. Quality of the materials 2. Quantity of the materials 3. Time of delivery 4. Price of the materials The procurement department and his agent are expected to: 1. Know and maintain records showing the materials and their possible substitute, sources of-supply, prices and quantities available. 2. Review specifications for possible simplifications and standardization of materials as for unreasonable requirements. 3. Negotiate with suppliers for possible extension of credit. 4. Gather and analyze price quotations and fluctuations' 5. Place orders with suppliers 6. Follow up purchase orders for delivery as specified 7. Audit invoices to check compliance with agreed terms and conditions 8. Maintain records of all purchases 9. Coordinate with other departments on all matters pertaining to Procurement. The prerequisite of any purchasing contract is meeting of the minds "at to the exact nature of the materials required and to be furnished. Material standard which define; the major requirements such as; size, color, forms, composition, performance of the materials and also the state acceptance terms' and shipping conditions requires purchase specifications. These are materials which are purchased by catalogue number, description or by its name. This practice is practically simple but because of specifications of banded catalogue items are often subject to change. Purchase order usually starts from a Purchase requisition. It specifies the kind, quantity and when is to be delivered. Purchase requisitions are serially numbered as an in filing and follow up. For items ordered regularly, a travelling requisition is used. This is a card carrying the usual information on the purchase requisition but with space for the word “repeat order”. This is used over and over again without the retrying data. This procedure, eliminate clerical works and the need for a separate purchase history record. Materials bought under continuing contract or those purchased repeatedly do not require quotations from the supplier since all the necessary information is already available to both parties. In case of repeat order, the purchase order form might include the phrase "as previously furnished on our PO No. __. The unit price and discount expected will likewise be shown as with the purchase order number and that of the original requisition. a. Inventory Control Effective inventory control is aimed at providing an adequate but not excessive supply of materials at hand at all times to meet operating requirements. However, for most companies, inventories perform two functions: 1. They act as safety stock of materials or in effect, short term insurance against fluctuations in supply. 2. Inventories permit a company to operate with disconnected processes in the construction and disbursement cycle. 2. Site Management of the Work Safety in the project construction must be given primary considered from the mechanical side to the legal angles of workmen's compensation or even as a matter of training and motivation toward safe work practices for workers. The immediate supervisor's responsibility is to see to it that the working place is properly arranged and maintained wherein the equipment, scaffoldings and the like are all in safe operating conditions. He should strictly see to it, that all workers do follow the safe working habits. Regardless of the exact percentage relationship, influencing human motivation to work safely is an important responsibility of the foreman and supervisors. Safety must begin from the drawing board. In the original design of the layout of work place or tools, accident hazards may be built in or eliminated. A safety minded project engineer will make adequate provisions for safety measures to: tip\ 523A\ lesson\ prelims.doc\ 11/2/2014\ 9:51:40 PM Page 1 of 16 Will insulate all live wires and screen high pressure areas. When failure does occur. that many break downs occur suddenly and without warning. The question is: does an ounce of prevention really affect a pound of cure. 2. 3. and statistical records are kept to indicate whether or not the preventive maintenance program is effective and working. Records should be maintained and analysis made of repetitive failure. Maintenance for the machine and equipment is very costly. Knowing the probability of breakdowns and their associated costs. Minimize manual handling hazards of materials. a complete safety program has to do with promotion of workers health. Equipment Rental The trend in construction business is to have equipment rented. investigation is made to know the cause. General inspection of machinery can be scheduled at intervals of perhaps 3 to 4 months depending upon the volume of service or operations. Important items of equipment that requires regular cleaning and maintenance or liable to sudden failure should be ready at hand for substitution at any time of failure or signs bf approaching failure. Planned maintenance is an organized attempt to prevent sudden breakdown in equipment and periodic shut down for repairs. Dirt gradually finds its way into many types of equipment. failure is prohibitive from the standpoint both of property damage and of employee safety. is highly important for some of the materials being used might be flammable. Planned Maintenance Effective maintenance of the plant and construction equipment is a prerequisite to efficient operation and uninterrupted construction activities. which revealed the interval between overhauls that minimizes maintenance costs. The frequency of inspections will depend upon the name of. a limit switch that suddenly fails to operate a transformer that blows up? These are only few of equipment breakdown head ache which are difficult if not impossible to cure by the inspection medicine. are subject to wear and tear from use. vibration. 2. or does a pound of prevention result in only an ounce of cure? Where machine and equipment have been in operation for a considerable period of time. with prevention of such occupational diseases and fire prevention. On some items of equipment. Regular and prescribed inspections should be made for signs of impending failure. the expected expenses of different maintenance policies are calculated. Machine and equipment likewise. It is accomplished under the program of preventive maintenance. Down time of each equipment for servicing is planned in advance. A number of engineers feel that in the long run. Preventive maintenance has long been an economic necessity for construction equipment which must operate on a continuous process. 1. a sticky hydraulic valve. Moisture seeps into electrical windings and breaks down insulation. Will locate control and fuse panels where they can be reached safely. Machine tend to got out of adjustment not only as the result of use. Continuity of operations demand that the following general procedures should be carried but: 1. a. the facility or item being checked" its importance to the continuity of operations or to the safety at the plant and workers and the time interval from the first indication of trouble to the actual failure. They pointed out. but also because of temperature changes. a definite program of periodic cleaning. the cost of regular inspections of equipment exceeds the cost of failures that are hereby prevented. To counteract the effect of all these inherent diseases in equipment. Fire protection as safety function. 'While deterioration of building cannot be stopped. Will install strong and rigid forms and scaffoldings 4. 5.doc\ 11/2/2014\ 9:51:40 PM Page 2 of 16 . Preventive maintenance program is indicative of the value of calculation. records of the timing and extent of failures are available. In very recent years there has been a significant swing toward the rental of equipment as opposed to outright purchase. inspection and replacement of worn parts. How does one foresee a fractured drive shaft. predicting the approach of such failures is statistical improbable. the only wonder drug that could be prescribed is proper periodic maintenance. it can be retarded by maintenance. Will adequately guard belting and line shafting even if it is normally accessible. tip\ 523A\ lesson\ prelims. 3. This trend has found particular favor in rental plans for construction equipment delivery trucks. Economic reasoning frequently must bow to other considerations. seasoning of machine parts and a host of other causes. Time is likewise a factor as corrosion forms in-bodies and on various vital parts of the machine. Thus. 4. The safety minded engineer is one representative of management whose interest is primarily on safety. servicing. every case of preventive maintenance inspection must be weighed on the balance scale of cost. In addition to accident prevention. Hence. materials handling trucks and office equipment. which is simply called PERT. The use of PERT began in 1958 through the joint efforts of the Lockheed Aircraft. estimates of the work items. scheduling. evaluation. a person in charge of each work and the project manager know what is supposed to happen and when it is supposed to happen.doc\ 11/2/2014\ 9:51:40 PM Page 3 of 16 . the government shall make an estimate of the actual number of working days required to complete the project through PERT/CPM analysis of the project activities and corrected for holidays and weekends. CPM in application was demonstrated in a real success. PERT and CPM were developed independently in the later part of 1950's.S. The U. the concept was formulated by the research team and is then called Program Evaluation and Review Technique.S. Kelly of the Remington Rand Corp. It serves as an aid to the construction manager but it does not make decision for him nor does it guarantee good management.000 sub-contractors with several thousands of work activities. among others things.R. no maintenance or servicing worries for the user. The Polaris Missile project is a large one involving over 3. used for planning and coordinating large scale projects. yet. early completion of the project was given top priority. 1968. PERT was developed as a result of looking for an improved method of planning and evaluating progress of a large scale research and development program. These two are networks. CPM originally made no provisions for variable time estimates.S. PERT/CPM is a control tool for defining the parts of construction job and then putting them together in a network form. Navy Special Project Office and the consulting firm of Booz. By April 1958. Whether the long range cost of such rental’s compared with ownership is lower is a debatable point which each company must decide on the merits of its own case. from a conceptual analysis. CPM was designed as a tool for planning. government to speed up the Polaris Missile project. For instance. and control of construction work. Under Presidential Decree (PD) 1594. For practical purposes. A Special operations research team was directed to formulate a new approach considering that the management concepts and methods at that time were not adequate. However. the U. Users adopted certain features from one technique for use with the other. and M. they have a great deal in common. In 1956. the Critical Path Method which is simply called CPM was developed by J. ether of the two techniques can be used with deterministic or probabilities of time. It answers the questions such as: "Is this a feasible schedule? And what are the probabilities of making it? Although PERT and CPM were developed independently. In contrast. The network diagram defined and focused attention on the job to be accomplished. prior to the development of PERT. The schedule derives the earliest and the latest times for their start and finish. Guidelines." On January 27. It encourages periodic re-evaluation and providing an accurate measure of progress. Marcos issued Memorandum Circular No. might gained nuclear superiority over the U. most of these differences were relatively minor. CPM is the Critical Path Method. PERT/CPM Project Requirements Today.000 contractors and 11. the two techniques are the same. Allen & Hamilton in the efforts of the U. and rental cost fully deductible on income tax classified as current business expense.E. Program Evaluation and Review (PERT) and Critical Path Method (CPM) Introduction What is PERT and what is CPM? PERT is a Program Evaluation and Review Technique. The use of PERT in this large scale project was proven successful in shortening the length of the project completion time. President Ferdinand E. In all major projects of the government. in the preparation of the bidding documents. government's apprehension that the Soviet Union.. 153 which provides that: "In order that the performance discipline on the field could be controlled and easy reporting system could be made to facilitate the monitoring. 3. It was designed to provide the management a periodic reporting of current status and an outlook for the future on meeting approved plans and schedules. quantities. PERT originally stressed probabilistic activity time estimate because the field in which it was developed was typified by high uncertainty.S. Thus. comments and procedures described will apply to both PERT and CPM project analysis. Walker of Du Pont in an effort by commercial industry to make an advanced scheduling and cost control methods. Renting equipment offers the advantages of no capital outlay. inspection completion of infrastructure projects. The remarkable historical record of PERT and CPM on large scale projects accomplishment has gained worldwide acceptance. Its emphasis was on the work or activities to be managed. Rules and Regulations for government infrastructure contracts provides that: "The program of work shall include. PERT and CPM network is a mandatory requirements. PERT/ CPM only serves the project manager to see the whole picture of the entire job. Prescribing Policies. all heads of departments and chief of bureaus and offices concerned are hereby required to tip\ 523A\ lesson\ prelims. costs and a PERT/CPM network of the project activities. Thus. A Technique. any claim if any. 5979 requires the application of PERT/ CPM technique to all projects with an estimated cost of P100. PEM/CPM offers a means of re- scheduling the operations but still to be completed at the least increase in cost. the project manager can easily obtain the following information: 1. 8. shortening all operations at the same time may only increase project cost more than what is necessary to obtain the desired decrease of construction time. However. there is a danger that shortening a single operation may only increase project cost but may not shortened construction time considering that other operations have not been shortened.000 or more. PERT/CPM now has become an integral part as requirement of project construction management. When the contract time is less. Consequently. shift of work. 4. to speed up construction work requires higher direct cost because of overtime. 5. 2. Control-Monitor PLANNING is defined as determining the relationship between the work operation and the sequence in which they are to be performed. 1968. With the critical path schedule as revised to reflect the change order. 4. With the use of PERT/CPM. and work hours. This gives planning information as to time and cost in choosing methods." On June 19. Most construction projects have specified time of staff and time of completion. equipment. additional manpower and equipment and various expensive methods which are not done on normal construction operations with sufficient time duration. 10." Section 6 of R. the Executive Committee for Infrastructure Program implemented the Presidential Order in a letter to all implementing agencies to wit: "Your attention is invited to a Presidential Order requiring the preparation of a PERT/CPM diagram for every major project prior to their actual construction. 7. The graphical display of project activities 2.doc\ 11/2/2014\ 9:51:40 PM Page 4 of 16 . in order to catch-up with the allotted time. 9. The information on float time will give the project manager that opportunity to maneuver in their planning and control of the operations. Planning 2. late material or equipment delivery the network can be revised at that stage and new computation is made to determine the new critical operation if any and revised float times determined for the non-critical operations. Each work operation can be performed in different ways at different costs and in different time duration. 3. Scheduling or sequence involves distribution of work time to each work operation and determining when to start and when to finish. Scheduling 3. The Critical Path Method (CPM) offers the solution through systematic approach. It shows the most advantageous scheduling for all operations. It offers a means of assessing the effect on the overall project variations in one operation such as change orders. On the other hand. crew. for additional payment will be understood both by the owner and the contractor. An estimate of how long will the project last 3. tip\ 523A\ lesson\ prelims. PERT/CPM pinpoints the particular work operations whose completion times are responsible for controlling the completion date. PERT/CPM indicates the earliest starting date for each work operations and sub-contracts for supply and delivery of materials. Thus. 4. Determine which activities are the most critical to timely project completion. Determine how long any activity can be delayed without lengthening the project. It gives a time leeway or float available for each of the non-critical work operation. 6. It provides a means of speeding up a project without excessive costs for overtime. Strict compliance herewith is enjoined. In case of serious delay due to weather. Phases of PERT/CPM The three phases of PERT/CPM are: 1. It establishes time boundaries for operations with possibilities of shifting resources' equipment and manpower to meet time requirements. In case of change order where the owner would not want to extend the contract time. in effect it requires higher indirect costs. Without the use of PERT/CPM when speeding up the project overtime expenditures may be in total waste.A. The specific information provided by the CPM are enumerated as follows: 1. some of the operations must be speeded-up. Thus. change the old system of preparing the work programs of said projects from the Gantt Chart (Bar Type) to the PERT/CPM network. The contractor is supplied with cost status reports showing how much money is being disbursed for what type of expenses. By performing the work personally. The Earliest Finish date for each activity d. Trade indicators (responsibility) for activity grouping. From the Schedule Phase. there are four outputs that can be obtained: 1. 2. The duration of activities 3. If the contractor wants an effective approach and use of the construction management. 1. 5. The Earliest Start date for each activity c. The schedule of activities in the network showing the following: a. experiences. The contractor should be supplied with those reports as frequently as desired or required to maintain control over the project. resources. 2. This is done by the day date table converting working days into calendar days which permits the inclusion of weekends. All crew and management restraints along the critical path should be verified and the restraints should be adjusted to give satisfactory project completion. Cost estimates of the activities for monitoring cost. The diagram must show the status of the project at any time and indicate which activiti6s can be started and to pinpoint the cause of the delay. To keep the schedule more up to date and meaningful. The Latest Start date for each activity e. The Latest Finish date for each activity tip\ 523A\ lesson\ prelims. Gathering of all the necessary input data to make the PERT/CPM works. Time discrepancies 2. All activities should be checked with the day to day table. 3. In the Planning Phase. The contractor can seek assistance for the accomplishment of his work particularly the gathering of data. Progress along the arrow diagram should be up dated for immediate references. weather and other time lost. CONTROLLING and MONITORING Flexibility and updated re-computations brought about by changing conditions is the key to a successful network programming. The PERT/CPM schedule shows the relationships between the operations and the leeway limitations. The contractor has the complete perception. SCHEDULING is defined as the process of translating the arrow diagram into time table of calendar days. The contractor is supplied with time status reports showing the overall status of the project in general and in particular. The PERT/CPM diagram should be updated periodically to account for: 1. A network diagram defining the activities in the project. he must do it himself. 7. days the project is out of schedule. and interest in getting the project done in the best possible time and cost. The planning stages give the contractor a "Dry Run" on the construction of the project 6. The Critical Activities b.doc\ 11/2/2014\ 9:51:40 PM Page 5 of 16 . Job control through the use of PERT/CPM give the management a reliable system identifying job problems within days instead of months. one obtains intimate firsthand knowledge of the job and gain insight and details of anticipated problems. Deliveries 3. Non critical activities can be scheduled to more efficiently utilize manpower and available resources. Planning phase is the main work of the contractor for being familiar and knowledgeable of his costing methods of doing business. Resource Estimates 5. Updating of the diagram is based on the number of. holidays. Unexpected events or conditions. 4. there are five inputs that can be obtained: 1. cash flow requirements 4. planning is the most important consideration which includes: 1. The contractor is provided with revised schedules which reflect the actual work conditions and the project status. it can be done by hand but is more easier and less in cost if it is done with the assistance of computer to have the following output. Weather 4. but his basic responsibility on this matter cannot be delegated to any outsider group. 2. 3. 4. In any project construction undertaking s. Change orders 5. f.This refers to the new activities 2. Lack of financial planning 3. The network describes sequential relationships among different activities of the project. description. Unlike activities. Poor cost control 5. Deletion from the project 3. Revised resource analysis 5. Actual starting dates 5. manpower. For instance. The Control Monitor Phase uses actual data which includes: 1. equipment and others that are required for each day of the project. cost estimates or resource estimates. Activities can be referred to in two ways. The Output Phase consists of the following: 1. Changes as to duration. The precedence diagram. A Bar Chart or a Time Scaled Network (arrow diagram network for the project). Revised cash flow predictions 6.doc\ 11/2/2014\ 9:51:40 PM Page 6 of 16 . etc. Additions to the project . One of the main features of PERT and CPM is their use of a network or precedence diagram which is the key in solving typical problems. 4. Time status report 2. clearly indicate which of the activities must be performed in the sequence and which can be performed independently with each other. A Cash Requirement prediction indicating how much cash to be disbursed for the job and the amount of money that will be collected as a result of work accomplishment. activity 2-3 cannot be started according to the network until activity 1-2 has been completed tip\ 523A\ lesson\ prelims. One is by their end points such as activity 1-2 and the other is by a letter assigned to an arrow such as activity a. The network diagram is composed of a number of Arrows and Nodes. Cost status reports There are three major reasons for construction failure: 1. THE NETWORK FUNDAMENTALS Network Conventions The making and reading of a network diagram requires some familiarity of the network conventions. A Resource Analysis showing the number and kind of resources. Revised Bar Charts/ Arrow Diagram or Network 4. 4. they do not consume either resources or time. 3. which are called event. 2. There are two slightly different conventions for making a network diagram" They are: The Nodes in the AOA approach represents the beginning and the end of activities. trade indicators. Unbalanced organization due to lack of planning and scheduling. Revised schedules 3. Actual finishing dates. Events are point in time. 2.b. The Float which refers to the amount of extra time available for an activity.c. What activities must be completed before this one can start? 2. In this figure. 2 That an activity has a single definite starting point and a single definite ending point. An arrow in the network must satisfy two basic questions: 1. the three activities of staking. batter boards and digging which start from event 5 must wait until all activities entering event 5 have been entirely completed.doc\ 11/2/2014\ 9:51:40 PM Page 7 of 16 . Hence. In this diagram (Figure 5-6). Principle No. 1 That everything in the network or arrow diagram must have a meaning. Thus. What activities cannot be started if this one is not completed? tip\ 523A\ lesson\ prelims. pouring of footing slab and pedestal depends upon completion of the two activities that enter into their common starting point 3. it is impossible to pour concrete on footing slab or pedestal until after making both forms and delivery of cement have been completed. The Elements of Networking Diagramming Principles in Networking or Arrow Diagram Principle No. The accomplishment of the schedule made in the network diagram is influenced by several number of people who have something to do with the project and should be consulted when making the network. 3 The network (arrow diagram) does not describe time relationships but rather dependency relationships. the sub-contractors and suppliers should be asked to review the network to be sure that the activities affecting their participation are accurately and realistically described.cedes forms assembling and forms assembling precede digging. 4 That the network (arrow diagram) is hardly ever done by a single person. The arrows should always point to the right. Events . Event and Time Activity .doc\ 11/2/2014\ 9:51:40 PM Page 8 of 16 . ellipse or any form of geometrical symbols with a number written therein for identification. pouring of footing pre. They might but probably will not. 2. Principle No.Is the work operations required to complete a task or in some cases. one or more dummy activities may be used in a network. The event is indicated on the network as a circle. 1. Similarly.Is a point in time signifying the beginning or end of one or more activities. Numbering the events follows the construction of the network. No two events shall have the same identification number in the network. 3. block laying precedes pouring of footing. What is important to note here is that these two activities are independent. It denotes the completion of all preceding or predecessor activities and the beginning of one or more succeeding activities. The description of the activity is written along the arrow. block laying cannot be started until after the pouring of concrete footing is finished. From the figure 5-7. excavation. Likewise. a segment of that task. square. pouring of footing cannot be done unless the forms and digging have been completed. foundation and concreting works are indicated by an arrow on the project network. tip\ 523A\ lesson\ prelims. Figure 5-8: The arrow diagram defines the activity dependency situations that exist. In short. And arrow which represents activity is identified by a numbered circle at its tail and another number circle at its point. the inter- relationships of the activities were. Fundamental Elements of PERT/CPM Networking The fundamental elements of PERT/CPM networking activities are: Activity. Activities B and C does not mean that both activities must be conducted at the same time. In short. For example: each particular work such as clearing. The length and direction of an activity arrow has no relationship with the amount of time required to accomplish the work presented by it. For this reason. it is the actual work between events. Similarly. Principle No. two activities starting with the same event do not necessarily occur at the same time. doc\ 11/2/2014\ 9:51:40 PM Page 9 of 16 . The network diagram indicates sequence of relationships among major activities on a project. Path l-3-5-6 Comment: 1. The path with the longest time catches management interest because it governs the project completion time. Therefore. 2.Is the time it takes an activity to be finished. Paths that are shorter than the critical path may experience some delay but may not affect the overall project completion time as long as the ultimate path time does not exceed the length of the critical path. Every project is composed of works. there are certain basic characteristics. 8. 6. manpower. They are: a. But generally. To complete the project with a minimum capital investment without causing undue delay. administrative or construction have their own unique characteristics. For instance. The longest path is the critical path and. dummy activity does not represent actual work efforts. which are common to any project. Duration activity is the span of time from the Early Start to its Early Finish or from its Late Start to its Late Finish. 3. For management to function effectively. The critical path then has a zero slack or float. etc. In short. 5.Is an arrow on a network showing the dependent relationship between two activities. activity 2-4 cannot be started according to the network until after activity 1-2 is completed. they must all be completed because the main goal is to finish the project under the following objectives. In short. activities. this is the normal time duration of a task. 4. Dummy Activity . tasks or functions that are related to one or the other in some manner. 2. etc. However. and do not consume time. any attempt to shorten the project completion time must concentrate on the longest sequence of activities because of its relation to the completion time. Duration of an Activity . 7. To use any available manpower. facilities and equipment. 9. its activities are called the critical activities. To complete the project at the earliest minimum time. The length or time of any path can be determined by adding the expected time of the activities along that path. Activities can either be: 1. 1. tip\ 523A\ lesson\ prelims. naturally there is also a corresponding delay in project completion time. By letter assigned to an arrow such as. However. c. If there are delays along the longest path. the expected duration of a project is equal to the expected time of the longest path. Dummy activity may be used in the network to distinguish between two or more parallel activities. b. equipment and other resources 3. 2. the sequence I-2-4-6 in the network of Figure 5-9 is a path. By their end points such as l-2. Introduction All kinds of project be it engineering. The options could be a possibility of utilizing its full resources such as money. The allowable slippage for any path is called the path slack or floats time. the project planning system used must consider all available alternatives.A Path is a sequence of activities that leads from the starting node to the finishing node. Thus. 2-4. The Network Diagram a. Path . There are two paths from the starting node to the finishing node. Path l-2-4-6 b. Only when management knows and learn how to use these options can it discharge its responsibilities. a. It indicates the difference between the length of a given path and the length of the critical path. Definition of Terms In developing a Network Diagram. Resources can be time. To have available sequential arrangement of the jobs.is only secondary to planning. we will be lost in the process of network diagramming. It is numerically equal to the length of the critical path minus the longest path from the project and event to the event in question. A further review should be entertained to ascertain that all phases of works should appear. 2. the logical sequence of the job to be performed must be formalized under the following considerations: 1. Construction management basically considers Time as the controlling factor of all available resources from money. The answer is PERT/CPM. Activities along the critical path are called Critical Activities of the project and any delay in their completion may result in the delay of the entire project. Management must review the plans and the resource requirements and then select a project plan that offers the best for the project. It is the process of allocating calendar dates to jobs based on the approved plan. facilities and money. The point of an arrow is called j-node. 3. As the controlling factor: Time versus number of manpower Time versus number of equipment Time versus Peso b. i. To establish a medium for estimating the time. Earliest Event . That the scope of work is correctly interpreted. manpower or other resources necessary for each job. Planning Objectives The project manager's objective in planning could be summarized as follows: 1. To represent graphically the specific job and the proper sequence of the job. the time required to complete a project is numerically equal to the length of the route which is called critical path. General time boundaries are determined for each job during the process of planning. manpower.node Early Start is not necessarily the point in time that the activity will be over. Critical Path . an accurate estimate of resources and the alternative plans based on the scope of work. which will utilize all resources effectively as possible.is the latest time the event may occur without delaying project completion. Unless these terms are known. manpower. A basic tool that will tell the management how to build a project on a pre-determined activities and number of days at a projected cost. The logic of its sequence must be reviewed for correctness. tip\ 523A\ lesson\ prelims. Planning and Scheduling In Planning. The sum of the activities duration along this route is the duration of the project. The Earliest Start of an activity cannot be earlier than the earliest event time of the event. the Earliest Event Time of the starting event is assumed to be zero. Therefore: ES = ES + Duration or EF = Early Event + Duration The Latest Event time . equipment. but it is the earliest time that it can occur. c. There may be more than one critical path in a network and the critical path may shift as the project moves toward the completion. Scheduling . there are important terms that we must be familiar with because of their importance and functions in the network. 3. The Earliest Finish of an activity is equal to its Earliest Start plus its duration or time.This is a management problem of how to select the plan. It is the earliest time an event can happen without delaying the Earliest Start of any activity. In other words. In other words.doc\ 11/2/2014\ 9:51:40 PM Page 10 of 16 . Resources which are required in performing each job must be in place and available when needed. the Earliest Start of any activity is always equal to the Earliest Event at the beginning of an arrow which is sometimes called i-node.Is the earliest time occurrence of an event sometimes called Earliest Event Time or Early Event Time. It is the first day after the physical assumption of the activity. 2.node j. Unless specified. facilities and equipment.Is the longest route in the network of activities representing a project. The Earliest Event time is numerically equal to the longest path of activities in series from the project start to the finish. Is the span of time an activity can be delayed after its earliest start time without delaying the project completion.ES = Total Float The activity Free Float . It is numerically equal to the ES of the succeeding real activities minus the LF of the preceding activities minus the duration of activity in question. In short. FF = ES .(ES+D) or LS . An algorithm is used to develop four types of information’s about the network activities. After determining the value of each activity. all activities with the same J-node have the same late finish which is the same as the latest event time at their common node. The slack time 3. for nodes with multiple entering arrows. EF = ES + t Rule No. It is numerically equal to the ES of any of its succeeding rear activities minus the Earliest Finish (EF) of an activity in question. 1 The Earliest Finish @F) for any activity is equal to its earliest starting time plus its expected duration time t. d.doc\ 11/2/2014\ 9:51:40 PM Page 11 of 16 . The Latest Finish of an activity cannot be later than the latest event time of its j-node.is the span of time an activity can be delayed after its Early start without delaying the Earliest start of any succeeding actual activity that may be availed of and still allow its succeeding real activities to begin at their Earliest Start time.D Activity Total Float or Activity Total Slack . 1.(LF-D) When the result of applying this formula is negative. The independent float is equal to zero. IF = ES . LS + D = LF or LS = LF . it means that there is no independent float. LS Latest time the activity can Start and not delay the project LF Latest time the activity can Finish and not delay the project. Determine which activity falls under the critical path. they are: ES The Early Start of time activity. It is numerically equal to the total time for the activity minus the activity duration. 2 For nodes with one entering arrow' ES for activities at such node is equal to EF of the entering arrow. LF .EF = Total Float or LS + D . we can proceed to find the following. Rules in computing the ES and the EF Rule No. EF Early Finish of time activity.Is that portion of the activities Free Float that would remain if all its preceding activities used up all their float. This is assuming that all preceding activities start at the earliest time. Expected duration of the project 2.(ES+D) Independent Float . Computing the Early Start and the Early Finish For large project networks which contain hundreds or even thousands of activities. the ES for activities leaving such node is equals the largest EF of the entering arrow. Activity Free Float is equals the Early Event time at the i-node of the next succeeding real activity minus the EF of the activity. The Latest Start plus Duration is equals the Latest Finish. computers are used to analyze the programs considering that the computation is exceedingly complex and time consuming which could not be done manually. tip\ 523A\ lesson\ prelims. the EF of activity 1-3 becomes the ES for activity 3-5. Similarly. The corresponding time for these activities are: EF 2-4 = 10 + 8 = 18 EF 2-5 = 10 + 13 = 23 EF 3-5 = 6 + 12 = 18 5. Summary of the above computations: Activity Duration Early Start ES Early Finish EF 1-2 10 0 10 1–3 6 0 6 2–4 8 10 18 2–5 13 10 23 3–5 12 6 18 4–5 4 18 22 5-6 2 23 25 Note: The Latest Finish is the duration of the project. 22. The EF time for these activities are: 1. ILLUSTRATION 1 Using the following network diagram. and 23. Therefore: ES 2-4 = 10 ES 2-5 = 10 ES 3-5 = 6 4. compute for the value of ES and EF times.Duration ILLUSTRATION 2 Determine the Latest Starting time (LS) and the Late Finish (LF) for each activity of the following network. Hence. the early finish EF. Activity 5-6 with three predecessors has an early starting time ES equal to 18. The activity 4-5 has an early starting time ES equal to EF2-4 = 18 and an early finish time of 18 + 4 = 22.doc\ 11/2/2014\ 9:51:40 PM Page 12 of 16 . tip\ 523A\ lesson\ prelims. e. activities l-2 and 1-3 as starting activities are assigned to 0. 3. Select the largest number which is 23 plus duration 2 = 25. Computing the Last Start and the Last Finish The Latest Start (LS) of an activity plus the duration is equal the Latest Finish (LF) LF = LS + Duration or LS = LF . 6. the expected length of the project is 25 weeks. The Early Finish (EF) of activity 1-2 becomes the ES for the two activities 2-4 and2-5 that follows it. SOLUTION: Assume an Early Start (ES = 0) for activities-without predecessors or we start from 0. Therefore. The EF 1-2 = 0 + 10 = 10 and EF 1-3 = 0 + 6 = 6 2. Take note that in node (2) we use the smallest value of 10 not 11 weeks in solving backward for LS/LF. the activity's Early Finish (EF) is equal to the Early Start (ES) of any of its successors. LS 1 – 3. Solve for the values of LS going Backward from node (6) starting from 25 weeks. 3.2 subtract. For activity 4-5.12 = 11 7. LS 1 – 2.12 = 10 For activity 2 . = 19 – 8 = 11 For activity 1 . that is activity 2-4 with LS = 11 and activity 2-5 with LS = 10 the Latest Finish (LF) for activity 1-2 which is 10 will be used being the smallest LS for a leaving arrow. For activity 3 . LS 5 . When an activity is the only predecessor of one or more successors.doc\ 11/2/2014\ 9:51:40 PM Page 13 of 16 .4 subtract. Since there are two arrows leaving Node 2. SOLUTION: 1. subtract . subtract .4 subtract.4 = 19 6. = 10 – 10 = 0 8. EF= LF = 25 weeks 2. For activity 5-6 to start not later than week 23 all immediate predecessors must be finished not later than that time. = 23 . = 23 . LS 2 – 4. LS 4 – 5. In the same manner: For activity 2 . = 23 . The value of LF and LS found will be tabulated as follows: Activity Duration Late Finish LF Late Start LS 5–6 2 25 23 4–5 4 25 19 3–5 12 23 11 2–5 13 23 10 2–4 8 19 11 1–3 6 11 5 1-2 10 10 0 The activity oriented CPM network diagram is made under the following Rules: 1.5. Thus.2 (time) = 23 4. tip\ 523A\ lesson\ prelims. = 11 – 6 = 5 For activity 1 . 5.5 subtract . Unlike that in illustration 6-1 we use the largest value of ES as we go forward for the next value of EF.6 = 25 . This is true because a successor activity cannot start until its predecessor activity has not been completed. LS 4 – 5. 9. LS 2 – 5. It was found in illustration 1 that EF 5-6 = 25 and this EF is automatically becomes the LF. At this point. The Early Start (ES) . activity 4-5 has an ES of 8 and an EF of 8 + 3 = 11 days. Thus.in days d. 2. B. The Latest Start (LS) . This is so because a Successor activity cannot start until its predecessor activity has been finished. its Early Start @S) is equal to the Latest Early Finish of its predecessors. 'When an activity has only one Successor Activity. In this case we will adopt 8 days being larger than 6. the Latest Start (LS) of the successor activity is equal to the Latest Finish (LF) of any of its predecessor activities. ILLUSTRATION 3 From the following network diagram. when an activity has more than one predecessor. its Latest Finish (LF) is equal to the Latest Start (LS) of the Successor. Thus. This is so because the Latest Finish (LF) of an activity cannot be later than the Latest Start (LS) of any of its successor activities. Solve for the Early Start (ES) and the Early Finish (EF) 1. 5. and provided that their LF do not exceed the LS of their predecessor. This value 5 days being the EF of activity 1-2 is at the same time the ES for the activity 2-5 and 2-4. 3. Hence. Note that. 4. The largest value which is 11 is the expected project duration. Take note again that the EF's of the activities entering the final Node (5) has 9 and 11 days.doc\ 11/2/2014\ 9:51:40 PM Page 14 of 16 . the Latest Finish (LF) of the activity is equal to the Earliest of the Latest Start of its successor activities.in days c. both activities must be finished by that time. The Latest Finish (LF) . When an activity has two or more successors. 3. 5. if two or more activities are entering the node the Earliest Start ES is the Largest value of EF. the question is: What will be the Earliest Start for activity 4-5? Will it be after activity 3-4 which is 4 + 2 = 6 or after activity 2-4 which is 5+3 = 8? 4. Solve for the Late Start (LS) and Late Finish (LF) 1.in days SOLUTION: A. Determine the value of LS and LF by working back starting from Node (5) using EF = 11 tip\ 523A\ lesson\ prelims. activity 2-4 and activity 2-5 cannot start earlier than 5 days. project completion will not be delayed. the latter's Early Start (ES) is equal to the Latest Early Finish of its predecessors. This is true because a successor activity can only start after all its predecessor activities have been completed. Activity l-2can start at ES = 0 with a time of 5 days it can finish at EF + 5 = 5 days 2. In short. determine the following: a. When two or more activities have only one successor activity. This is true because an activity cannot start until all of its predecessor activities have been completed. When two or more activities have a common successor. The Early Finish (EF) .in days b. Since activity 1-2 precede both of these activities. The Slack or Float Time is computed by using either of the following equations: Float = LS . Slack or Float is the word used for those activities which do not fall on the critical path.LF Activity LS ES Slacks or LF EF Slacks 1–2 0 0 0 5 5 0 1–3 2 0 2 4 2 2 2–4 5 5 0 8 8 0 2–5 5 5 0 9 9 0 3–4 4 2 2 8 6 2 4–5 8 8 0 11 11 0 The activities with Zero Slack Time indicate the critical path. Activity 2-5 has an LF of 9 days minus 4 days = 5 days. the Latest Start of activity 2-5 is 5 days and the latest activity 2-4 can start is 8 .3 equals 4 and its LS is equal to 4-2 = 2 days. Solving the Float or Slack Time The term Slack is used by PERT which is equivalent to Float of CPM network system. Therefore. Meaning. Activity 3-4 now has an LS time of 8 .doc\ 11/2/2014\ 9:51:40 PM Page 15 of 16 .3 = 8.4 = 4 making the LF of activity l . 3.3 = 5 days.the Early Start (ES) time for leaving activities of that Node is the Largest EF of the entering activities. 2. 5. activity 1-2 has LF of 5 and an LS of 5-5 = 0 7. Activity 2-4 with LF time of 8 days has an LS of 8 .ES or Float = LF . 4. f. the LS will be 11 .EF tip\ 523A\ lesson\ prelims. their LF times are 8 days. This means that activity 2-4 and 3-5 must have been both finished not later than 8 days. that these activities have scheduling Time Leeway that can be used without adverse effect on the project time completion.3 = 5 days 6. Therefore.EF. Compute the Slack Time using the equation LS . In the case of Activity 4-5. Therefore. the critical paths are activities I-2-4-5 having 11 days duration. In this particular problem.ES or LF . it can finish not later than the Smallest Value of LS at Node (2) which is 5. FIGURE 6-5 SHOWING ES – EF AND LS . For Nodes with several entering activities. solve for the value of Float or Slack. b. Jr. The length of each path. de Villa February 2012 tip\ 523A\ lesson\ prelims. the manager has a wider detail for planning the allocation of limited resources and for directing control towards those activities that are susceptible to delaying the project. 2-5. If two activities are both on the same path like activities 1-3 and 3-5 with a . Figure 6-6. The activity float time are based on the 4ssumption that all of the activities on the same path should be started as early as possible and never to exceed their expected time. activities L-2. Source: Project Construction Management Max B. Thus. Referring to the previous tabulation of activities in Illustration l and 2 we can tabulate the result of LS and ES to find the value of Float as follows: Activity LS ES Float ( LS – ES ) 1–2 ( 10 – 10 ) = 0 At (1) = 0 0 1–3 ( 11 – 6 ) = 5 (6–6) = 0 5 2–4 ( 19 – 8 ) = 11 ( 0 + 10 ) = 10 1 2–5 ( 23 – 13 ) = 10 ( 0 + 10 ) = 10 0 3–5 ( 23 – 12 ) = 11 (0+6) = 6 5 4–5 ( 23 – 4 ) = 19 ( 10 + 8 ) = 18 1 5-6 ( 25 – 2 ) = 23 ( 10 + 13 ) = 23 2 The Critical Path using the above tabulation is indicated by activities with Zero Float Time. said activities have a Shared Slack or Shared Float.doc\ 11/2/2014\ 9:51:40 PM Page 16 of 16 . if one of the activity consume all this float time. Fajardo. those number of weeks will be the total float available for both activities. Thus. the other activities will have a zero float for all the following activities on that same direction. The critical path and c. In other words.Length in Weeks = Float or Slack LLUSTRATION 5 From Illustration 6-4. ILLUSTRATION 4 From the following diagram determine each of the following: a. SOLUTION: We have two options to use in solving the value of Float. By the use of formula ( LS -ES ) or ( LF -EF ). Path Length in Weeks Float / Slack 1–2–4–5–6 10 + 8 + 4 + 2 = 24 25 – 24 = 1 1–2–5–6 10 + 13 + 2 = 25* 25 – 25 = 0 1–3–5–6 6 + 12 + 2 = 20 25 – 20 = 5 * Critical Path . Dennis C.float of 5 and activities 2-4 and 4-S with float of one week respectively. The amount of float time for each path. Knowing the float time. and 5-6 are all critical activities.