Betonarme endüstri yapılarında beton kalitesinin boyutlara ve maliyetlere etkisi

Abstract

Bu çalışmada, tek katlı iki açıklıklı bir endüstri yapı sisteminin beton kalitesindeki değişime göre optimum çözümü aranmıştır. Bu amaçla boylama kirişleri, kren kirişleri, kren konsolu, çerçeve sistemi ve temeller ayrı ayrı gözönüne alınarak bir inceleme yapılmıştır. Döşeme sisteminde böyle bir irdelemeye gerek duyulmamış, daha önce yayımlanmış olan birtakım literatürler gözönünde tutulduğunda malzeme olarak BSI6, BÇ I kullanılmasının uygun olduğu düşünülmüştür. Boylama ve kren kirişleri, şartnamelerde verilen sınır değerler de gözönünde tutularak değişik beton sınıflan için ayrı ayrı incelenmiş, bu elemanların boyut, donatı ve metrajları çıkarılmıştır. Kren konsolu için bir inceleme yapılırken yine değişik beton sınıfları için ayrı ayrı konsol hesaplan yapılmış ve konsolların boyut, donatı ve metrajları çıkarılmıştır. Çerçeve sisteminde çerçeveyi oluşturan kolon ve kirişler değişik beton sınıflan için şartnamelerde verilen sınır değerler gözönünde tutularak ayrı ayrı incelenmiş, bu elemanların boyut, donatı ve metrajları çıkarılmıştır. Temeller, üzerlerine gelen yükler esas alınarak sürekli temel olarak düşünülmüş, şartnamelerde verilen sınır değerler gözönünde tutularak değişik beton sınıflan için ayrı ayrı incelenmiş, boyut, donatı ve metrajları çıkarılmıştır. Yapılan analizler sonucunda, beton sınıflarındaki değişim esas alınarak yapının her beton sınıfı için toplam maliyeti bulunmuş ve böyle bir yapı sisteminde optimum çözüm için gerekli beton sınıfının saptanmasına çalışılmıştır.

Economic design of structural reinforced concrete systems is still most important problem in design and civil engineering. The experience of the engineers has been mostly used such designing problems but, design problems have become more sensitive and more important subject to be studied for calculating total cost of the system. Alternative solutions can be obtained for a structural system. On the other hand, costs which belong to these solutions can be quite different. That is why the system costs which are the vital component of designing have to be dealt with carefully by designers and civil engineers. The main purpose in the optimization of a structural system is to get appropriate values for optimum solution of the cost function which is defined for certain load conditions. The cost function needs some boundry conditions to obtain optimum solution. These boundry conditions can be defined as limit values or restrictions which are determined for system basic parameters, system behaviour and system geometry. Limit values for system behaviour and system geometry are given in specifications for civil engineering. System basic parameters which can be defined as element dimensions, system form and material caracteristics have to be determined appropriately and cost function has to be minimized. Restrictions about basic parameters are given in specifications and basic parameters have to be determined according to these restrictions. Basic parameters can be taken into consideration together while finding out solution of the cost function in the optimization of the structural system. On the other hand, it will be better to take this parameters into consideration seperately in the optimization. In this way the effects of each basic parameter can be seen easily. In this study, optimum solution of a single-store and double-spanned reinforced concrete industrial structural system shown in Figure 1 is investigated according to the variance of concrete qualities. Sub-systems which are the components of the structural system are studied seperately by using different concrete qualities. For this purpose, purlin-crane beam system, crane bracket, frame system and foundations are studied seperately and costs for these sub-systems are tried to be obtained. xvm In the investigation of slab system; it is thought that there is no need to make an investigation as made for other sub-systems. This is a convenient appproach to use poor concrete and steel when some researches about slab system are taken into consideration. Concrete qualities which are used while optimizing the structural system are considered BS16, BS20, BS25, BS30, BS35, BS40, BS45, BS50 and sub-systems of the structural system are studied seperately by using these cocrete qualities. Quality of the steel is not investigated like concrete qualities in the optimization of the system, but, it is thought that using BÇüIas reinforcement is an appropriate approach for this kind of structral systems (excluding slab system) when some researches about optimization of industrial systems are taken into consideration. E3- E3- *.- E3 e& D3 Dl D4 D2 £3- -6 3- -E3 -E3 -E3- ?3 -E3 -E3 -E3 5İI0 5J0Q 5,30 530 530 5,30 530 52)0 40 4,60 1 4.60 1 4,60 ı 4.60 '4>f".(.? ? 18.35- 4,60 1 4.60 i 4.60 1 4,60. 18,35 00 8.2E 6.84 Figure 1. Industrial structural system xix In the investigation of the slab system of the roof; BS 16, BÇ I are considered as appropriate materials. There are four kind of slabs in structural system according to support conditions. These slabs are shown in Figure 2 below. 5,00 5,00 4,60 5,00 4,60 Figure 2. Different slabs 5,00 4,60 4.60 Slab thicknesses are calculated for each slab and reinforcements are also calculated in x and y direction separately. In addition to this, corner reinforcements which prevent torsion effects are placed at slab corners. Restrictions about reinforcement and slab thickness are taken into consideration while calculating slabs. Slab costs are considered as total of reinforcement, concrete, mould, coating, roof covering and browning coat costs. These costs are calculated separately and whole slab system cost is obtained. In the investigation of purlin beam system; dimensions, reinforcements and costs of beam system are obtained for different concrete qualities by using restrictions given in specifications. Minimum beam section is selected as b/h = 20 cm/3 0cm There are two different purlin types according to load conditions and geometry. One type purlin which exist at the edge of the system. These purlin types are nonsymmetrical T-beam geometry and have half load area in comparison to other purlins. In addition to this, there is breastwork load on edge purlins. Other type purlins are ridge purlin and the rest of purlins which does not exist at the edge of the system. These purlin types have symmetrical T-beam geometry and their load area is twice as big as edge purlins. These purlin types are shown in Figure 3. Since there are symmetry axis in x and y directions, structual design calculations can be made for half of the system. In this case moment diagram will be symmetric and shear diagram will be antimetric. Edge purlins Ridge and other purlin Figure 3. Purlin beam types xx After getting moment and shear values, reinforcement calculations and beam dimensions are obtained according to these values. No bent-up bars as bending reinforcement are used at purlin beams. Additional reinforcements are used at support sections to take negative bending moment. Shear forces are taken by only shear reinforcements. Purlin beam system costs are considered as reinforcement cost, concrete cost, mould cost, coating cost and breastwork wall cost. These costs are calculated separately and whole purlin beam system cost is obtained for every concrete quality. In the investigation of crane beam system; dimensions, reinforcements and costs of beam system are obtained for different concrete qualities by using restrictions given in specifications. Crane beam sections are selected in rectangular shape. Crane type is selected as commanded from module and crane capacity is selected 10 t. According to crane type values, structural design calculations are made for crane beams. Since there are symmetry axis in x and y directions, structural design calculations can be made for half of the system. In this case moment diagram will be symmetric and shear diagram will be antimetric. After getting moment and shear values, reinforcement calculations and beam dimensions are obtained according to these values. No bent-up bars as bending reinforcement are used at crane beams. Additional reinforcements are used at support sections to take negative bending moment. Shear forces are taken by only shear reinforcements. Crane beam system costs are considered as reinforcement cost, concrete cost, mould cost, coating cost. These costs are calculated separately and whole crane beam system cost is tried to be obtained for every concrete quality. In the investigation of crane bracket; dimensions, reinforcements and costs of bracket are obtained for different concrete qualities by using restrictions given in specifications. The type of crane bracket is shown in Figure 4. 4 Figure 4. Crane bracket Since c/d2 <1, the crane bracket shown in Figure 4 has to be calculated as short bracket. According to crane type values, structural design calculations are made for crane brackets. After getting moment and shear force values, reinforcement calculations and bracket dimensions are obtained according to these values. Crane bracket costs are considered as reinforcement cost, concrete cost, mould cost, coating xxi cost. These costs are calculated seperately and whole crane bracket cost is obtained for every concrete quality. In the investigation of frame system; beams and columns which make the frame system as a whole are seperately studied. Dimensions, reinforcement and cost of beams and columns are obtained seperately for different concrete qualities by using restrictions given in specifications. Frame system is taken as a middle frame system and solved for different load cases to get structural design values. These values are added to get combined values of moment, shear force and axial forces. Reinforcement calculations and dimensions are found out seperately for columns and beams. Frame system is shown in Figure 5 below. 1.376 6.Ö4 h -İ8.35- -«.35- Figure 5. Frame system Due to symmetry of the system there are two different columns to be taken into consideration. Column A and Column B are investigated according to their structural design values. Reinforcement calculations and dimensions are obtained by using mo ment and axial forces for each column type. The check of slenderness is made for each column according to specifications and slenderness is taken into consideration in column calculations. Since there is symmetry axis in z direction there are two different beam types to be taken into consideration. Beam K4 and K7 are the same beams and beam K5 and K6 have the same geometry. All beams have symmetrical T-beam geometry. Reinforcement calculations and dimensions are obtained by using moment, shear force and axial forces for each beam type. Reinforcing bars are designed for both straight bar and bend-up bar. Additional reinforcements are used at support sections to accommodate negative bending moment. Shear forces are taken by bent- up bars and shear reinforcements. Frame system costs are considered as reinforcement cost, concrete cost, mould cost, coating cost. These costs are calculated seperately and whole frame system cost is tried to be obtained for every concrete quality. In addition to this, front wall cost and scaffolding cost of the whole structural system are taken into consideration in this part. The foundation system of the structure is considered as continuous footing when thinking of load cases and values. Dimensions, reinforcement and cost of continuous xxii footing are obtained for different concrete qualities by using restrictions given in specifications. Continuous footing is considered as inverted T-beam and calculated as elastically supported continuous beam when soil strength is taken into consideration. For this purpose, some nodes are determined under beam and spring constants are defined at this nodes. Spring constants are stated depending on bed constant and load area of the node. Depending on combined load values, structural design calculations are found out and moment, shear force values are obtained. Continuous footing and nodes are shown in Figure 6 below. 1,00 M "T M' (5) - 1 - (6) (7) (8) I I (9) (11) aroja» (13) (14) (15) (16) (17) ?+? -+- -+- ?+- 1,00 3.00 3.00 3.175 3,175 3,00 3,00 1.00 (19) (15) am at» -fl 1 3.00 3.00 3,175 3,175 3,00 3.00 LOO Figure 6. Continuous footing and nodes Continuous footings are connected with beams which are placed between two footings to prevent different horizantal displacements. These beams are considered as 30cm x 30cm rectangular beams. Reinforcements and dimensions are obtained seperately for TKİ and TK2. Reinforcing bars are designed both straigth bar and bend-up bar. Additional reinforcements are used at support sections to take negative bending moment. Shear forces are accommodated by bent-up bars and shear reinforcements. Continuous footing costs are considered as reinforcement cost, concrete cost, mould cost. These costs are calculated separately and foundation system cost is tried to be obtained for every concrete quality. In addition to this, excavation cost, gravel-sand mixture cost and plain concrete cost are taken into consideration to calculate the total cost of foundations. As a result of these analyses, total cost of the structure is obtained seperately for different concrete qualities and optimum concrete quality is found for the selected industrial structural system.