Prefabrike beton bileşenlerle yapımda hata, boyutsal sapma ve toleranslar

Abstract

Bu tez çalışması, hazır bileşenlere dayalı yapılar da yapılacak alan hataları, elemanda oluşan boyutsal sapmaların nedenleri, türleri ve alınabilir önlem öne rileri ile üretim ve montaj aşamalarında oluşan boyutsal kabul edilebilir toleranslarını içermektedir. Saptanmış olan üretim ile ilgili A.C.I 117-81 ve DİN 18203, montaj ile ilgili A.C.I. 117-81 tolerans değerleri örnek olarak verilecektir. Bu çalışma dört ana bölümden oluşmaktadır. Bu bölümlerde aşağıdaki konular ele alınmıştır. Bölüm 1; Giriş bölümü olan bu bölümde, dünyada ve Türkiye'de önüretimli bina gereksinimi hakkında genel bir bilgi verilerek, kullanılacak olan endüstrileşmiş bina yapım yöntemlerinde hata, boyutsal sapma ve tolerans ların önemi vurgulanmaktadır. Bölüm 2;. Bu bölümde, hata ve boyutsal sapma kavram larının tanımları, çeşitli sınıflamalara göre türleri, nedenleri ve oluşan boyutsal sapmanın hesaplanma yöntem leri incelenmektedir. Bölüm 3; Bu bölüm toleransların maliyet ilişkisini, tolerans türlerini, oluşacak sapmaların hangi noktalarda toleranslarının saptanması gerektiğini ve bu konu ile il gili standartları içermektedir. Bölüm h; Bu bölümde, birleşim noktaları ve birleşim aralığının tasarlanmasında dikkat edilecek noktalar ve çeşitli tipik detaylar incelenmiştir. Sonuç olarak, hata, boyutsal sapma ve toleranslar ile ilgili problemlerin en aza indirilebilmesi için, ta sarlama, önüretim, stoklama, ulaştırma ve montaj aşama larında alınabilecek önlemler önerilmiştir.

The raasona, different types and calculation met hods of faults, dimensional deviations and acceptable values of those (tolerances) which may be occur in the phases of production and erection of precast/prestressed products are examined. The considerable parts of A.C.I 117-81 and DIN 182D3 for production tolerances, and A.C. I. 117-81 for erection tolerances, issued by American Concrete Institute, is used as referance of the determi ned and used values of tolerances regarding the compo nents. The thesis has been set as four sections. The fol lowing subjects are examined in the sections: Section 1; After The Second World War, in order to meet the high mass housing demand, new construction systems have to be designed by architects and engineers since it was impossible to reconstruct the cities in a very short time by applying the conventional system which has a li mited production percentage of a year. On the other hand, not anly the houses might be constructed economi cally, but also they might be in a certain production qua-lity. The prefabricated building construction met hods have been developed and they reached to their pur pose. This subject has not been encouraged by the Turkish Government in '^O's (especially in the Recovery Plan For Second Five Years/1968-1972). But, because of the advantages of prefabricated systems, bussinessmen have Vll prefered it in construction of their industrial buildings. Now, these new methods are being used either in construc tion Df industrial buildings or housing projects. It is a new subject in Turkey, and it is the only solution for housing problem. That's why the actual con ditions of the country must be determined in such a way that reflecting the reality is much as possible, and then it must be choosen the best and the most siutable to the conditions. The subj-ects of faults, dimensional deviations and tolerances are some of the important data far comparing the systems. Section 2; Faults and dimensional deviations are examined in this section. Generally, products in a prefabricated construction system are realized in three main pha'ses. These are: * Design, * Manufacturing, - Storage - Transportation, * Erection. These interrelated phases should be considered as a whole structure. In design phase, the designer must arrange the pro ject with the modular and dimensional coordination rules by using a basic module. In this phase, all of the de- cissions, drawings, details about manufacturing and erec tion are completed differently from conventional system. Naturally, there are some differences between nomi nal and actual dimensions of the components. The most important thing is to determine these deviations and decide the mast adequate limits of those. In manufacturing phase, all decissions, details and shop-drawings which are prepared by technical department are sent to the factory as a normal procedure, then the components are manufactured there according to those de cissions and drawings. vm Even just a little fault will cause not getting reasonable results', in the end the building will not be executed as purposal, or it will not be realized. That's why designers should consider the dimensional deviations which will occur. Precast components are transported to the construc tion site in order to fit each other. In erection phase it is possible to erect the components in some deviati ons in the direction of three coordination axles. As a result of these, the limits Df these deviations which are possible being done in erection phase, must be deter mined according to the actual conditions. Faults and dimensional deviations can be classified by their sources. These sources are: * * Design and decissions, Manufacturing, * Application and * Erection. In order to reduce and control the faults in design phase, coordinations must be set among the drawing sheets, codes, lists, etc. in such a way that will not cause to make any mistake. Besides, since the subject of prefab ricated construction is a specific field, having special technical acknowledge and experience is necessary for executing the system successfully. When architects get the decissions about materials, manufacturing, storage, transportation and erection, they should get a conclusion from the analysis of present market alternatives. Gne of the most important unit is "control" in or der to reduce the faults. If it works well, it may pre vent all of the faults at the begining. Well begun is half done. The faults about the source of manufacturing is di vided into two parts: * Dimension, * Surface, IX Dimensional faults can be in length, width and depth of the fabricated components. The inaccuracies in the dimensions of the components are dependent on: * the moulds, * the nominal dimensions, * the nature of the components, * the position during concreting, The manufacturing dimensions are most effected by moulds. It is on the condition of the moulds that the accuracy primarily depends. Besides, uith increasing nominal dimensions, the deviations undergo only an insig nificantly small further increase beyond a certain limit, If the deviations depending on the nature of the components and their position during concreting are also taken into account, then the entire deviations associa ted uiith manufacture can be determined from the indivi dual values in accordance uith Gauss's theorem. Section 3; The subject of tolerances are examined in this sec tion. The dimensions of precast concrete units are never exactly as theoretically specified. The difference bet ween the theoretical dimension and the actual dimension is called the dimensional deviation. If this deviation exceeds the permissible value, damage and/or expense may be incurred on account of the lack of fit and the cost of remedial measures. The term "tolerance" is applied to an acceptable dimensional deviation, i.e., a deviation that is within certain limits and will thus not have adverse effects. If the tolerances are choosen too large, the cost of subsequent adjustment will be higher. On the other hand, if they are choosen too small, manufacture and erection are made more difficult. So it must be adjus ted that it must be the most siutable values at the po- intwiew of economy. The tolerances should be determined on the basis of actual manufacturing and erection analy ses. Tolerances are normally established by economical and practical production considerations of how the mem ber must fit into the overall construction and its rela tionship to adjacent units. It must be noted that the particular selection of casting forms and measuring techniques is often based on economics and functional reasons rather than on the manufacturer's capability to follow the most sophisticated methods. The following are typical items for uhich dimensio nal tolerances have to be established. * Overall Plan Dimensions Generally there are three types of forms. These are: rigid, semi-rigid and flexible. The designer should avoid from the rigid forms because of the necessity of working with a higher degree of accuracy than other form types, in both the length and width directions. Flexible forms shauld be preferred if it is possible. * Blackouts; A tolerance for both the size and location of the blockout should be considered. It also is important that the eventual function of the blockout be properly considered. * Sweep or Horizontal Alignment: Horizontal misalignment usually occurs as a result of form tolerances and member width tolerances. It can also result from prestressing with lateral eccentricity thus causing a sweep in the member. Handling Devices: It is important that handling devices be embedded as soon as possible. However, it is also necessary to recognize the importance of placing handling device locations in different directions, especially in thin and narrow sections. xi * Camber; Some af the factors affecting camber variation are: design, time-dependent effects, tolerance of strand lo cation, curing methods, storage configuration. It is very important to maintain uniformity at the time of cam ber measurement. Squareness of Ends: Squareness of ends will depend greatly on the type of forms used. * Positions of Weld Plates * Tipping and Flushing of Weld Plates * Haunches of Columns and Wall Panels It is more important to control dimensions from haunch to haunch in multitiered columns rather than to maintain tight control of actual haunch location dimen sions from the end of the member. * Reinforcing Steel Tolerance * Warping, Bowing and Local Smoothness of Panels: Especially architectural members demand special consideration. Differential temperature effects and differential moisture absorption between the inside and outside faces of a panel, and possible prestress eccent ricity, should be considered in design to minimize bow ing and warping. The erection tolerances are given in three groups; * Precast element to precast element, * Precast element to cast-in-place concrete of masonry, * Precast element to steel construction. Xll Section k; membe sider area can b far a consi width ans a still width Clea rs a in wher e ab rchi dera mua nd t pre to ranee nd is erecti e erec sarbed tectur tian. t accD he ere vide b allDLd is the space provided between adjacent one of the most important factors to con- on. Clearance should provide a buffer tion and production tolerance variations Exposed joint clearance determination al panels is an especially important In the architectural panel, the joint modate variations in the panel dimensi- ctian tolerances for the panel, and must oth a good visual line and sufficient for effective sealing. The following items should be addressed when deter mining the appropriate clearance to provide in the design: * Product tolerance, * Type of member, * Size of the member, * Location of member, * Member movement, * Function of member, * Erection tolerance. With interfacing tolerances, it is important to note that the tolerances may be very system dependent. Interfacing requirements are: * Structural requirements, * Uolume change, * Weather/corrosion, * Jiaterprodf igg, Drainage, Architectural requirements, Dimensional considerations, Vibration considerations, Fire-rating requirements, Acoustical considerations, Economics, Manufacturing/Erection considerations.