======================================================================= Practical Network Planning Precedence Diagramming is a powerful modelling technique for the analysis and control of project schedules. Implemented with the flexibility and sophistication of a computer program like PROPLAN, it equips the Project Manager with a practical tool that is useable in day-to-day job management. Its power can be enhanced to the extent that the user is aware of some of the practicalities of Project Scheduling. While not an essential part of a software user's manual it may be of advantage to list some of these techniques that can improve the effectiveness of the whole scheduling process. Task Numbering The six character alphanumeric code that identifies an activity is normally used in a systematic way to facilitate the addition of new activities, identify the type and location of the work, etc., and provide a simple way of selecting and sorting tasks. For instance, it is common to have:- * the first character identify the project stage or area, * the second character identify the trade, subcontractor or type of work, and * the next two or more characters used to ensure uniqueness, or further divide the first two categories. Hammock coding should follow the same pattern. Task Descriptions Task descriptions should be systematic - "inventory" style if possible - and should conclude with some right-justified quantity information which will be of assistance when durations are revised in the light of actual production rates. For example:- AREA 4A-ASPHALT PAVING (1789t) PIER 5-PILE DRIVING (23No) PIER 5-FORM AND POUR FTG (98m3) CASTING SHED-ELEC ROUGHIN (140MH) 8TH FL-STRUCT STEEL ERECTION (62T) JOB176-DAY ST-COUNCIL APPROVAL LOT 6 DRAINAGE-DRAWING APPROVALS FRAME 8-SUB-ASSY 1214A-TESTING A/R REPORT MODULE-CODING (190MH) A/R REPORT MODULE-BETA TEST Selectcodes Selectcodes can be used as a basis for both selecting tasks to be included in reports and sorting the report. If the task codes have been assigned as suggested above, the selectcodes will often reflect the same breakdown. Hence the first two selectcodes may be the same as the first two characters of the task code. Where more involved report manipulation is necessary selectcodes may be used to signify:- * the individual or department responsible for the task; * whether the task has major lead time procurement needs; * if prior approval by a particular authority is required. Durations Durations are often dependent upon the allocation of resources to the task. Durations should be first estimated on the basis of the most economic and practical way of completing that activity alone. When the network has been processed and project duration and resource loadings assessed, some activities may warrant a second look with a view to accelerating the schedule. Durations should be all inclusive and realistic and must include the lead in and tapering off times that characterise much construction and development work. Lags should recognise this all inclusive type of duration. PROPLAN shows remaining duration for incomplete activities and calculates an "actual" duration for completed activities from the given start and finish dates. It assumes that the activity progressed continuously and in accordance with its assigned calendar. Actual dates are accepted as factual - even if they fall on a day that has been defined as a holiday in the activity calendar. The "actual" durations calculated and shown on Bar Charts may not be correct as work will often take place on defined holidays and not always proceed without interruptions (which are usually not retroactively recorded in work calendars.) Relationships Many schedulers overuse "normal" relationships - particularly if they have been "brought up" on arrow diagramming techniques which typically only allow this type of link. The real world is not that simple and the "normal" Finish to Start link is often, in fact, a Start to Start link, a Finish to Finish link - or both. A network that overuses Normal links will show many out of sequence effects in updating and actual dates that refute the reality of the link. While PROPLAN handles minor logic conflicts in a forgiving way, you can still improve the reality of your network by carefully examining Normal links to see if they should really be another type. Normal links are NOT - in fact - normal! Specified Dates If the project has a contractual or "target" completion date, you may use this date as the project Specified end date. If the calculated finish date is earlier than this, the network will have positive float and no true critical path. To ensure that the most critical activities are still easily seen, you may wish to "flag" the finish activities with Critical flags. This will ensure that criticality is always shown and negative float still appears if - and when - the specified date is not going to be met. Standardised Calendars PROPLAN allows you to define and use up to sixteen user defined calendars in each job. Most projects will use no more than five or six of these so you can set aside several of these numbers for standard calendars to be used throughout the organisation. The Calendar menu, Copy Holidays option, provides a fast way of "building" calendars. First define the calendar having the least number of holidays then add these to other calendar numbers. Alternatively, define an unused calendar as a seven day work week, add all standard Public Holidays, etc., to this calendar, and use it as a template to add this pattern automatically to several other calendars after their basic work day pattern has been specified. If most of your work is subject to some form of periodic approval - e.g., local council authorisation, monthly design coordination meetings, etc., - you should set aside one calendar to cover this process (even if it only has one "work day" each month) and use it consistently throughout your networks. Standard calendars should be placed in a calendar library file so they can be easily copied into new networks. If the same library file is being used in setting up the calendars for each new job it can be transferred into the system directory so the process is automated. (See Part C - Page C-2) Hammocks Hammocks are a summary pseudo "activity" representing a group of related activities that collectively cover some portion of a project. In the early stages of the development of a complex network, you can use a long duration activity where a hammock - and its set of activities will later reside. As time permits, and your understanding of the project increases, a hammock can be entered and the original activity "exploded" into a mini-network covering the work in full detail. This technique of "progressive detailing" of a large complex network is particularly effective on "fast-track", design and construct, or research and development projects, where it is often impractical to prepare detailed logic diagrams for the execution of work that has yet to be fully specified and designed. Control Activities Many projects - particularly "linear" construction like highway, railway or pipeline work - consist of several loosely related mini-projects that could proceed in parallel if unlimited resources were available, (e.g. earthworks between mass haul points of balance.) Much of the constraint in the schedule is, in reality, the economic one of providing reasonable levels of equipment, labour or supervision, at any one time. This problem can be addressed with the techniques of resource constrained scheduling or resource levelling. However, there are serious practical difficulties in implementing either of these approaches and computer models will always produce results which are sub-optimal and do not reflect the complexities of real projects. A more realistic analysis is often possible if "control" activities are used. A "control" activity is defined covering the total amount of each work type (e.g. asphalt paving) embodied in the separate activities from the "mini-projects". The duration of the control activity is the total duration for that type of work given reasonable and "economic" resource levels. The individual activities are linked to the control with Finish links of zero lag. The effect within the network is to make the control activity critical while the individual activities "float" within the span of the control. (It may not be important to be paving in any one area of the job, as long as paving is underway at maximum output in some location.) A sequence of control activities can themselves be linked with appropriate logical links and lags. This produces a much more realistic network model that recognises the multiple resource constraints without suppressing the inherent real flexibility that exists in the way individual activities and areas of the project can be worked. The Project Manager is able to exercise his judgment in assigning priorities within this overall framework. That judgment will reflect his explicit - or intuitive - assessment of complex issues such as resource substitution, the "costs" of idle or poorly utilised resources, uncertainty in duration and productivity estimates, the relative importance of certain tasks, as well as the risk associated with delaying those tasks in a way that still defies computer modelling. Scheduling Small Projects PROPLAN has the flexibility to handle the concurrent scheduling of a number of small projects. One network can include numerous small jobs which have little or no logical interdependence. Resource plots can be used to examine total resource demands - or demand coming from a particular project - and the hammocking facility provides summarising capabilities at job level as well as across work categories. The Utility menu allows cloning and deletion of whole projects within one network so the creation and maintenance of the network is very easy. Network Libraries Planning is sometimes repetitive. If similar work is required in different locations on a single job, sets of activities should be cloned. (See Cloning on page D-2.) If complete networks are often similar, you should use the PROPLAN library facility to establish "standard" libraries of activities, hammocks and resources. These can be copied when a new network is prepared. (See page D-2.) The library can even be used to import selective data directly from another network. If you often copy the same set of library records into new networks, you can automate this process with library "batch" files. (See Auto Library Batchfiles, page C-2.) Estimating and Scheduling If you are using PROBID - PROCON's Estimating & Tendering System - to produce your project estimates and tenders, you can export activities, operations, resources, sets and costs directly from the estimate to create a basic network plan. PROPLAN can then refine this network and produce Bar Charts, Resource Loading histograms, Cash Flow histograms, etc., that support the tender submission and help in the estimate analysis of resource requirements and overheads. General project information like the job name, password, department, job number, start date, duration and finish date is copied from the estimate to create an equivalent PROPLAN network. The project start and finish dates become the network data date and specified end dates respectively. Some of the PROBID items, operations, resources, sets and costs are also copied to the network. The data files are saved in the directory \PROPLAN\DATA - if it exists - otherwise they are placed in the PROBID system directory. A PROPLAN activity is created for each operation assigned an Activity Code. The activity description, calendar, duration, start and finish date, costcode, measure unit and budget quantity are taken directly from the PROBID operation. PROPLAN treats Start dates as "PUSH" (Earliest Start) dates, and Finish dates are "PLUG" (Latest Finish) dates. Any difference between the dates and the duration is float. Any PROBID resource or set, used by an activity, is copied into the PROPLAN network as a resource. (Sets are treated as if they were a resource.) Allocations of defined resources and sets are treated as assignments of consumable PROPLAN resources. These allocations are treated as fixed amounts equal to the calculated element quantity. Any other operation costs (i.e., from subcontractors or undefined resources or sets), are assigned to the activity's direct budgeted fixed cost or budgeted unit cost - as appropriate. PROPLAN can then be used immediately to produce a simple Barchart or Resource Loading histogram or the network can be further developed by defining specific work calendars, logic links, milestone dates and hammocks. PROBID also exports all estimate cost and revenue data in a form designed to assist the estimator in producing a quick cash flow analysis of both costs and revenue. It is often not practical - and should not be necessary - to define every PROBID operation as a PROPLAN activity and assign it a code, calendar, start date, etc. (An estimate often contains many operations that have to be priced, but would not be included in a project schedule.) However, for costing and revenue and cost cash flow projections it is essential that all costs, etc., are transferred to the PROPLAN network. Each PROBID item is copied to a corresponding PROPLAN hammock. The hammock code, description, measure unit, budget quantity and bill unit rate are taken directly from the item. (If a number of PROBID items have the same code, the hammock codes are made unique by appending sequential lowercase alphabetic characters.) The hammock's start and finish activity codes are taken from the activity codes in the item's operations. The start activity is taken from the operation with the earliest start date, and the finish activity from the operation with the latest finish. This ensures that the hammock spans all of the item's operations. If some item's have no operations - or no operations with activity codes - the export facility will create two dummy "activities" to represent the job start and finish and uses these as pivots for the "unhung" hammocks. (These activities are set up with the arbitrary codes - - - - - - and + + + + + +.) The PROPLAN hammock's budget quantity is set to the PROBID item's actual quantity, and the bill unit rate to the item's submitted rate. PROPLAN's REVENUE CASH FLOW report can then produce an immediate projection of periodic billing amounts and the profile and interest cost/value of the projected revenue stream. This export facility also creates a set of artificial PROPLAN "resources" and allocates these to the PROPLAN hammocks. These resources are dummies for various cost and revenue combinations, so that the hammocks can capture the detailed cost breakdown from the corresponding PROBID item. PROPLAN can then produce RESOURCE LOADING histograms for any of these dummy "resources". These resources are Consumable, are allocated as Fixed Amounts and are measured in thousands of currency units (e.g., $000s). They will be like this:- Code Resource Description Item Equivalent Cu$$$$ TOTAL COST - unassigned Unassigned Item Costs CL$$$$ TOTAL COST - Labour Item Cost-1st cost type CE$$$$ TOTAL COST - Equipment Item Cost-2nd type, etc. ... ... ... Ct$$$$ TOTAL COST Total Item Costs Ta$$$$ TENDER TOTAL Submitted Tender Amount Nr$$$$ NET Net Revenue (Tender - Costs) Hence a PROPLAN hammock, created by the PROBID export facility, might have resource assignments such that it looks like this in the Allocate Resources screen:- =============================================================================== Allocate Resources System date: Mon, 26MAY97 Hammock CA14 Platform A - Steel Erection 18 days Rsc Code Resource Description Rsc Type Allocated Loading MU ÝTa$$$$Ý TENDER TOTAL Consumable Fixed amt Ý 113.592ÝTh ÝNr$$$$Ý NET Consumable Fixed amt Ý 16.452ÝTh ÝCt$$$$Ý TOTAL COST Consumable Fixed amt Ý 97.140ÝTh ÝCu$$$$Ý TOTAL COST - unassigned Consumable Fixed amt Ý 0.000ÝTh ÝCL$$$$Ý TOTAL COST - Labour Consumable Fixed amt Ý 0.000ÝTh ÝCO$$$$Ý TOTAL COST - Own eqpt Consumable Fixed amt Ý 0.000ÝTh ÝCR$$$$Ý TOTAL COST - Rental eqpt Consumable Fixed amt Ý 0.000ÝTh ÝCP$$$$Ý TOTAL COST - Perm. Matl. Consumable Fixed amt Ý 78.208ÝTh ÝCT$$$$Ý TOTAL COST - Temp. Matl. Consumable Fixed amt Ý 0.000ÝTh ÝCS$$$$Ý TOTAL COST - Subcontract Consumable Fixed amt Ý 18.932ÝTh ........ .......................... .......... ..... ... . ......... F2 record F10 cancel F4 bring fwd F3 blank fld ** PgUp top PgDn bottom Alt C for CALC sheet NUM =============================================================================== Each cost type (Labour, Materials, Subcontract, etc.) will typically have a different disbursement lag. This detailed breakdown by cost type provides the PROBID estimator with the option of fine tuning cash flow projections to produce more realistic figures for interest cost. The job cost and revenue detail is thus provided in several different forms. Before working with job totals of budgets or cash flow you must decide which form best suits your needs and disable the presentations that are not required. The hammock resource allocations can be removed by deleting all hammocks, deleting the artificial resources, or just zeroing their unit cost. (See page D-Error! Not a valid filename. of your PROBID manual for more details.) Costing Having broken a project down into tasks for purposes of time control, it seems only logical that we should use that same breakdown for cost control. The resource assessment, required to estimate durations, could be used to generate a budget for each task - and hence a budget or "estimate of cost" for the complete project. Progress assessment for time reporting could be tied in with valuation assessment for cost reporting - avoiding duplication of effort and providing some assurance that the two processes are harmonised. This approach to costing - called PERT COST because of its early association with PERT networks on major defence development projects - is the basis for all the costing systems "built in" to Project Scheduling software, including PROPLAN. Despite this intuitive appeal, attempts to apply PERT COST concepts in the construction industry have been particularly unsuccessful. Some of the reasons for this are:- * A task breakdown is determined by precedence logic-a cost breakdown should be determined by the logic of work similarity. When this is done, cost centres usually cut right across the task breakdown. * The granularity of the breakdown rarely matches. Tasks often include work of many different types-cost centres usually include work from many areas and stages in the project. Things that are important for purposes of time control (approvals, etc.) are not as important for cost control and vice versa. * Reporting frequency, completeness, and required accuracy, differ. Valuation and cost reporting is usually undertaken at the end of fixed periods (daily, weekly, or monthly) while time progress reporting should be an ongoing process with the timing of formal updates determined by project status. * The resource and cost assessment required for a budget-or cost estimate - is vastly more detailed than that required to develop a time plan. When task duration is determined by resource availability/usage (and often the reverse is the case) it is usually dependent upon only one or two "key" resources. In this case it is only necessary to consider these resources in time planning. Estimating and Costing must deal with all resources and costs. PROPLAN has special capabilities that address some of these problems:- * A single costcode can cover any number of tasks - so costs can be allocated to broad aggregates, while valuation is still performed at task level. * Hammocks - as well as activities - can be directly costed. This provides more flexibility in handling overheads, indirects, and "global" costs, by avoiding the need to artificially spread common costs over sets of activities. * Resource based or directly allocated costing - or both - can be used. * Directly set budgets can combine a fixed and quantity related component. * Valuation progress is not rigidly tied to time progress. Nevertheless, PERT COST cannot be recommended as a viable substitute for properly designed construction job costing systems. ======================================================================= For more information contact:- PROCON CONSTRUCTION SYSTEMS 3/5-7 Victoria Parade MANLY NSW 2095 Tel: +61 2 9977.6863, Email: sales@procon.com.au =====================================================================