Proje değerlendirme şebeke analizi ve bir bilgisayar uygulaması

Abstract

Bu tez çalışmasında proje değerlendirme tekniklerinden biri olan şebeke analizi yöntemi ele alınmış ve bu yöntemi kullanarak projenin maliyet analizi ve kaynak dengelemesini yapan bilgisayar programı ha zırlanmıştır. Tezin birinci bölümünde çalışmanın hareket noktasını teşkil eden proje kavramı üzerinde durulmuştur. Daha sonra çalışmaya konu olan şebeke analizi yöntemi ve tarihi gelişimi hakkında kısaca bilgi verilmiştir. İkinci bölümde projenin en alt birimleri olan olay ve faaliyet kavramları üzerinde durulmuş ve şebekenin kurulmasında uyulması gereken kurallar sıralandıktan sonra bu kuralların ışığı altında proje şebekesinin nasıl çizileceği açıklanmıştır. En son olarakta şebeke analizi tekniklerinden PERT ve CPM metodları arasındaki ufak farklılıklar gösterilmiştir. Üçüncü bölümde bu çalışmada üzerinde ağırlıklı olarak durulan CPM metoduyla kritik yörüngenin ve faaliyetlere ait çeşitli bollukların nasıl hesaplandığı gösterilmiştir. Dördüncü bölümde projenin maliyet analizi yapan bilgisayar programının hazırlanmasında büyük kolaylık sağlayan Metin Balaban tarafından geliştirilmiş algoritma tanıtılmış ve bu algoritma bir örnek problem üzerinde denenmiştir. Beşinci bölümde ise Profesör Brooks tarafından geliştirilmiş projenin kaynak dengelemesini yapan algoritma anlatılmış ve bu algoritma örnek bir problem üzerine uygulanmıştır. Altıncı bölümde ise diğer şebeke analizi teknikleri kısa bir biçimde açıklanmaya çalışılmıştır. Yedinci bölümde ise kritik yörünge metodunu kullanarak projenin maliyet analizi ve kaynak dengelemesini yapan bilgisayar programı tanıtılmış, programların kolay anlaşılması amacıyla blok diyagramları çizilmiş ve programa ait printer çıktılarına yer verilmiştir.

This master thesis introduces the evaluation technique termed network analysis and a computer program performed cost scheduling and resource scheduling of a project. The first chapter deals with concept of project, definition of network analysis and its background. Network analysis is a generic term for a family of related tec hniques developed to aid managment in the evaluation, planning and control of projects. These techniques show the inter-relationship of the various job or tasks which make up the overall project and clearly identify the critical parts of the project. They can provide planning and control information on the time, cost and resource as pects of a project. Network analysis has found its value when used in large-scale and complex projects. Network techniques are important because they provide an easily understood diagram, or graphic net work, as well as an analytical analysis of the project. In 1958 the US Naval Special Projects Office set up a team to plan and control the development of Polaris missile. The outcome of the team's efforts was the development of the network technique known as PERT (Program Evaluation and Review Technique). Since 1958 the technique has been developed and nowadays many variants exist. The second chapter deals with basic network terminology, rules for construction of networks, drawing networks and comparision with PERT and CPM. Network comprise activities and events. Activity is a task or job which takes time and resources, e.g build a wall etc. An activity is represented in a network by an arrow. Event is a point in time and indicates the start or finish of an activity, e.g wall built. An event is represented in a network by a circle or a node. Dummy activities are necessary to show logical relationships. They don't consume time and resources. -vııı- Network is the combination of activities, dummy activities and events in logical sequence according to teh rules for drawing net works. The following rules are all logically based and should be thoroughly learned before attempting to draw networks. a. A complete network has only one start event and only one end event. b. Every activity must have one preceding or "tail" event and one succeeding or "head" event. However many activities may use the same tail event and many may use the head event. c. No activity can start until its tail event is reached. d. An event is not complete untill all activities leading in to it are complete. e. A series of activities which lead back to the same event are not allowed because the essence of networks is a progression of ac tivities always moving onwards in time. f. All activities must be tied into the network i.e they must contribute to the progression or be discarded as irrelevant. In addition to the rules for drawing networks above, which must not be violated, certain conventions are usually observed and for the sake of uniformity and easier communication students are recom mended to fallow the normal conventions. a. Networks proceed from left to right. b. Networks are not drawn to scale ie. the length of the arrow does not represent time elapsed. c. Arrows not be drawn in the horizontal plane but unless it is totally unavoidable they should proceed from left to right. d. If there are not already numbered, events or nodes should be progressively numbered from left to right. Simple netforks may have events numbered in simple numeric progression i.e. 0, 1, 2, 3 etc. -IX- Activities may be identified in several ways and students should familiarise themselves with the various methods so that unfamilior presentation does not cause confusion. Typical of the methods to be found include: a. Shortened description of the job e.g. plaster wall, order timble etc. b. Alphabetic or numeric cade. e.g. A, B, C etc. ar 1D0, 101, 108 etc. c. Identification by tail and head event numbers, e.g. 1-2, 3-3, 2-5 etc. PERT requires the use of three time estimates: optimistic, most likely, and pessimistic. By using three time estimates, it is pos sible to determine the variance and to calculate the expected time for each ectivity. Critical path method which is another popular technique similar to PERT uses only one single time estimate instead of hree times as is found in PERT. The third chapter deals with calculating the critical path and floats of activities in a network. The critical path is the longest contiguous series of activities through the network and has no slack time. It is determined by using what is known as the earliest start time and latest finish time for the activities. The early start is the earliest time at which an activity can occur, assuming that all preceding activities have been started and completed as soon as possible. The latest fininsh is the latest date on which an event can occur without creating a delay in the completion of the project. The critical path is the chain of activities where the earliest start times and latest start times are the same. The fourth chapter develops the analysis of networks and deals with the cost aspect of activities and the process of least cost scheduling sometimes known as "crashing" the network. A further important feature of network analysis is concerned with the costs of activities and of the project as a whole. This is somatimes known as PERT/ COST. The primary abjective of network cost analysis is to be able to calculate the cost of various project durations. The normal duration of a project incurs o given cost and by more labour, working overtime, -x- more equipment etc. the duration could be reduced but at the expense ?f higher costs. Some ways of reducing the project duration will be cheaper than others and network csot analysis seeks to select the cheapest way of reducing the overall duration. Following basic definitions ara related to cost scheduling. a. Normal cost: The costs associated with a normal time estimate for an activity. Often the normal time estimate is set at the point where resources are used in the most efficient manner. b. Crash cost: The costs associated with the minimum possible temi for an activity. Crash costs, because of extra wages, overtime premiums, extra facility costs are always higher than normal costs. c. Crash time: The minimum possible time that an activity is planned to take. The minimum time is invariably brought about by the application of extra resources, e.g more labour or machinery. d. Cost slope: This is the average cost of shortening an acti vity by one time unit (day, week etc.). The cost slope is generally assumed to be linear and is calculated as fallows: n,, Crash Cost-Normal Cost Cost slope = Normal Time-Crash Time The fifth chapter deals with the resources aspects of network analysis. The resources (men of varying skills, machines of all types, the required materials, finance, and space) used in a project are sub ject to varying demands and loadings as the project porceeds. Management need to know what activities and what resources are critical to the project duration and if resource limitations (e.g shortage of materials) might delay the project. They also wish to ensure, as far as possible constant work rates to eliminate paving short time working at another stage. To be able to schedule the resource requirments for a project the following details are required. a. The customary activity times, descriptions and sequences as previously described. b. The resource requirements for each activity showing the classifi cation of the resource and the quantity required. -xi- c. The resources in each classification that are available to the project. If variations in availability are likely during the project life, these must also be specified. After calculating the critical path in. the usual manner a Resour ce Aggregation Profile (s) is prepared i.e. the amount of the reso- urcels) required in each time period of the project based on the EST' s of each activity. If the resource aggregation indicates that a const raint is being exceeded, and float is available the resource usage is "smoothed" i.e. the start of activities is delayed. The sixth chapter deals with other network techniques excepting PERT and CPM. Shortest path problem relate to a map, plan or engineering daujing which can be idealised as network of routes joining nodes or vertices. Travelling salesman problem is concerned with finding a circular tour of all the nodes which has the minimum passible length. Minimal spanning tree problem is concerned with finding a routine diagram for laying cable or a pipeline to connect together all the nodes of network in the most economical way. And the last chapter introduces seven computer programs. One of these programs is a batch file which is called Run. Bat. Gwbasic programming language is used to write other programs whose names are Menu. Bas, Yeniveri. Bas, Eskiveri. Bas, Eksikver. Bas, Malana. Bas and Kayden. Bas. The aim of these programs is to perform const scheduling and resource levelling of network.