Binalarda elemanlara dayalı maliyet planlaması ve kontrolu kapsamında mevcut bina eleman sınıflandırmalarının değerlendirilmesi

Abstract

Bu tez çalışmasının amacı, bina üretim sürecinin ihale öncesi evrelerinde bina maliyetinin planlaması ve kontrolünün yapılabilmesi için gerekli alan maliyet tahmin (hesaplama) yöntemlerini tanıtmak, tasarlama evresi içinde maliyetin en etkin bir şekilde planlanmasına ve kontrolüne imkân veren elemanlara dayalı maliyet hesabı yöntemini kapsamlı bir şekilde açıklamak ve elemanlara dayalı maliyet hesabının yapılabilmesi için gerekli olan eleman sınıflandırmalarının hangi temel özelliklere bağlı olarak oluşturulması gerektiğini vurgulamak ve mevcut eleman sınıflandırmalarını incelemek ve irdelemektir. Birinci bölümde tezin kapsamı içinde geçen ilgili kavramlar tanımlanmıştır. İkinci bölümde maliyet planlaması ve kontrolünün önemi vurgulanmış, planlama koşulları belirtilmiş, mali yet tahmin (hesaplama) modelleri tanıtılmış olup son olarakta ihale öncesi evrelerde alınan kararlar ve bu kararların maliyeti nasıl etkilediği ve her bir evrede maliyet planlaması ve kontrolü hangi yöntemlerle yapıldığı açıklanmıştır. Üçüncü bölümde, elemanlara dayalı maliyet hesabı (planlaması) kapsamlı olarak ele alınmış olup, maliyet planlaması süreci açıklanmıştır. Dördüncü bölümde, elemanlara dayalı maliyet hesabının yapılabilmesi için en önemli koşul olan eleman sınıflandırmasının hangi özellikleri içermesi gerektiği belirtildikten sonra, halen çeşitli ülkelerde kullanılan eleman sınıflandırmaları incelenmekte ve irdelenmektedir. Sonuç bölümünde, elemanlara dayalı maliyet planlaması ve kontrolünde elemanların sınıflandırmasının önemi tartışılmaktadır.

Decisions that play important role in building coat estimation are taken into consideration during designing. Following, the planning and control of cost is an imperative in order to achieve the construction with a minimum cast. It has always been, at every stage of history, important to estimate the cost of a building prior to the costruction. Before the industrial revolution, a rough and vague estimation was satisfactory to meet that demand, since the input metarials did not consti tute a great problem then. Along with the development of industry cost esti mation has begun to acquire an ever inceasing importance Factors like making more profit, increase in the scale of projects and complexity of technology, changes in the economical and social systems, ever-increasing demand for housing with the population boom, etc. gave way to a new approach that buildings should be planned within certain cost limits. New systems in construction has been introduced, thanks to the development of the industry. In evalua tion of these systems productivity and economics are two important critaria. Which production system produces the most economical building in the shortest time is the subject of inquaries. To achieve economy and increase productivity in construction it is an imperative to make cost estimation VI designing. So it is high time we definde the term cost. Cost is the value in monatary terms of materials and services consumed in activities organised to achieve o goal. * Cost of building: Cost of building is the sum of expenses that start with the definition of a demand for a building and end when that building becomes out of use. More specifically cost of building is composed of the cost of initial investment+cost of utilization + cost Df demolition. If we define economy * Economy is to achieve a certain amount of product with a given minimum production factor. In other wods, it is to achieve maximum production with a given procduc- tian factor. * Cost estimation: Cost estimation is to predict for a short term the real cost of a building under given circumstances. Cost planning: Cost planning is a method to which the construction planning is adapted to maximize the utility -cost ratio or to keep the cost within certaion standards of limits. * Goals of cost planning are: - to minimize the cost, - to limit the cost, - to maximize the utility-cost ratio, Vll * Costituents af coat planning are: - cast analysis - element classification, - unit price analysis, - project conforming to standards. A. Cost estimation models: We can gather cost estimation models under three groups: * analytic models, * cost estimation on the basis of funtional build ing elements, * cost estimation on the basis of production units, * Analytic models: These methada which are applied to achieve a short cut and realistic cost estimation at the preliminary stage of construction follow a way of calculation which is formed of the total measurable building size multip lied by the unit price. Cost estimation in analytic methods is achieved through four different approaches, which are: - unit method, - cube method, - area method, - storey enclosure metod. Vlll * Cost estimation an the basis of functional build ing elements: It is an estimation that permits the building be divided into its constituing elements and each group of elements be evaluated as separate items, a way which allouis to a comparison of real cost of elements with the aimed costs. The constituents of the cost estima tion an the basis of functional elements are: - functional elements, - amount of elements, - unit price. * Cost estimation on the basis of production units: This method follows a way of calculation in which amounts of elements obtained from the project are mul tiplied with the unit prices fur each element group, and the results are added to obtain a total sum. B. Cost planning and control at the phases before adjudication : When a building design with a limited cost in demanded, cost planning and control is an imperative during the designing. The phases before the adjudica tion can be defined as fallows: * enterprise -feasiblity phase, * designing phase, * Enterprise -feasibility phase: This stage where a decision for building is taken, needs and limits are defined, administrative organisa tion is set-up, a team of architects and designers is appointed, is the most important stage in respect to the economy of construction. IX Designing phase This is the stage where designing is carried out within certain limits for the building which is v/aguely defined an the basis üf information gathered during the enterprise-feasibility phase. * Approaches to the cost planning and control dur ing the designing phase: - cost planning on the basis af elements, - comparative cost planning, C. Proceedures to be followed in cost planning on the basis of elements: - assessment of pre-estimation cost, - preparation of pre-estimation plan, - preparation of cost plan, - cost control, - compromise in adjudication,, - cost control after the contract. D. Basic characteristics to be taken into account in element classification can be defined as follows: 1- Element classification should follow a hierarc hical order. 2- Element classification should allow to a cost estimation in respect to the functional elements of the building, and, planning and designing should take these elements into account. 3- The elements which are brought under a hirerac- hical order should be as little as possible in the first grouping while containing satisfactory information for cost planning. k- The mast important measure to define which elements to be included in which element class is which functions they will perform in the building. 5- Element classification should contain informa tion necessary for the cost planning and control for all phases prior the adjudicaiton. The various element claaaif icatioriB which are developed and in use in various kinds are: - SfB system - CLASP system - AJ system - CPU system - BIC system - BCIS system - BSAB system - IMBRI system - DIN 276 system - YAE system - Bouwcentrum system - A. Plawden system, and etc.