Çok katlı kirişsiz döşemeli bir yapının boyutlandırılması

Abstract

ÇOK KATLI KİRİŞSİZ DÖŞEMELİ BİR YAPININ BOYUTLANDIRILMASI ÖZET Yüksek Lisans tezi olarak hazırlanan bu çalışmada çok katlı betonarme bir yapının yatay ve düşey yükler altında, statik ve betonarme hesapları yapılmıştır. Yapının statik hesapları SAP90 ( Yapı Analizi Programı ) bilgisayar programı kullanılarak yapılmıştır. Program, sınırlandırılmış eğitim versiyonu olduğu için simetri durumu dikkate alınmıştır. Yapı, altı normal ve iki bodrum kattan oluşmuş bir sistemdir. Yapının bodrum katının çevresi perde duvar ile çevrilmiştir. Döşeme tipi, kullanım açısından kirişsiz döşeme olarak seçilmiştir. Döşeme çevresi boyunca, altına duvar gelen yerlere kenar kiriş kirişler konulmuştur. Yapıda düşey taşıyıcı sistem olarak kolonlar ve perdeler seçilmiştir. Döşemenin süreksizlik gösterdiği merdiven - asansör boşlukları çevresinde perde uygulanmış, perde ve döşeme birleşim bölgelerinde kiriş kullanılmıştır. Döşeme kalınlığı 25 cm seçilmiştir. Normal kat yüksekliği 3.40 m, zemin kat(1.Kat)4.00mdir. Düşey ve yatay yük kombinasyonları için TS50O'de belirlenen uygulamalar takip edilmiş ve en elverişsiz durum dikkate alınarak boyutlandırılmıştır. Yatay yükler altında hesap için Afet Bölgelerinde Yapılacak Yapılar Hakkında Yönetmelik ( 1997 )' te öngörülen hesap metodları ve kısıtlar takip edilmiştir. Yapının temeli için radye temel ön görülmüştür. Radye temelin hesabında «temel döşemeye benzetilmek yolu ile modellenmiş ve SAP90 programı yardımı ile çözülmüştür. Sonuçlar, uygulama çizimlerinde verilmiştir. X1U

DESIGN OF A MULTISTOREY REINFORCED CONCRETE BUILDING SUMMARY Analysis and design of a multi-storey building under vertical and horizontal loads are presented in the thesis, including drawings, prepared for construction. Software, SAP90 (Structural Analysis Program) is used for the analysis of the structural system. The reinforced concrete design of the members including slabs, beams, columns and foundations is carried out by using design tables. The concrete quality is C25 which has 170 kgf/cm2 of design strength. S420 steel is used for reinforced concrete design. According to TS500, all members are checked for minimum and maximum reinforcement ratios. Allowable soil stress, under footing 20 t/m2 and soil stiffness C=6000 t/m3. TS 498 is used for the desing load of the structural system. The building has six normal storeys and two basement storeys. The basement is surrounded by reinforced concrete walls. The structural system of the building is composed of columns, shear walls and beams. However, the beams connect the columns in the outer edge of the building and there are also beams in the middle of the building where stairs and lifts are located. The columns in the inner part of the building supported slabs directly without beams. The advantage of the flat floor is that no beams hanging from the ceiling can be seen. Slab thickness is chosen to be 25cm. The height of normal storeys are 340cm. First floor (Ground floor) has a height of 400 cm because of architectural considerations. Punching control between columns and slabs is carried out according to TS500. Punching is one of the most critical weakness of the flat slabs Therefore, it is checked at the beginning of the design process. Punching controls usually the thickness of the slab. Failure due to the punching causes brittle collapse. To carry a comparison the software results, two axes are analysed by using Equivalent Frame Method. The comparison the software results, and analysis of Equivalent Frame Method' yields that the two results are close to each other. However, Equivalent Frame method gives slightly large values for the column stripe. XIVThe analysis of slab is carried out by using the shell data block of the SAP90 (Structural Analysis Program). Slab is divided in finite elements having dimensions of 137.5cm - 150 cm. Finite element generation of the slab is done by numbering the elements as well as the joint points of the elements. Because the software used can handle only limited joints, the slab of the normal storey is divided into two parts by considering the symmetry of the structural system. The analysis of the slab is carried out by using the following assumptions in relation with the boundary conditions of the slab. 1. The joints of the slab, finite elements on the columns and on the shear walls do not have any vertical displacements. That means the vertical displacements of the columns and shear walls are neglected in comparison of the displacement of the slab. 2. The other joints are not allowed to displace in X and Y directions. 3. Along the the axis dividing the members of the slab do not rotate around the vertical axis. In the analysis, slab elements defined in shell data, beams defined in frame element as its. In this way the analysis of the slab and the beams are done together. According to the loading types of the slab, the slab is analysed in four different ways.. Uniform live load (q=0.500 t/m2), assumed as singular loads applied on nodes. The magnitude of loads depends on the slab area.. Uniform live load, applied as pressure load on the all slab elements.. Pd=1.878 t/m2 Composed load acting as singular loads to joints, depends on their acting area.. Uniform live load defined by including shell specific weight Although the second method represents the real state of the system, the results are found to be close to each other. This analysis is carried out for vertical gravtiy loads. In addition, the system are analysed under the horizontal loads. In the present case, the horizontal loads consists of the earthquake loads only. In order to find horizontal earthquake loads, the new Earthquake Code 1997 is used. For the analysis, according to the new Earthquake Code, the natural period of the first mode of the structure must be determined at the beginning of the analysis. To determine the first natural period, the structural system is analysed under horizantal loads. So that Rayleigh Method can applied for getting the first period of the structure. The building is in the first degree earthquake area according to the Turkish Earthquake Code and the purpose of its usage is given as a residence. Furthermore it is assumed theat light wall material is used in the building wall. TC YÜKÜ?' * * '? ````. ; ' `URULlf DOKÜMâNIASiuN iSSMEZt xvAccording to the Earthquake Code - 1997 : Analysis of the structures having basements surrounded by reinforced concrete walls must be carried out as follows : i. Structure has to be analysed without considering basement storeys. The height, the weight and the periods of the structure are determined by considering the ground floor and the floor on it. In other words, the ground level is assumed as the base level of the structure. Having determined the period, the equivalent forces can be calculated and applied to the structure for calculating the internal forces. ii. Basements has to be analysed alone without considering other storeys. It means that, weight of the basement storeys are considered for the analysis only and all the other steps have to be carried out without considering other storeys. In this part of the analysis, S(T)=1 (The spectrum value has to be assumed 1), and the equivalent eathquake forces can be calculated and divided by a reduction factor of elastic earthquake forces Ra(T)=1.5 iii. Internal forces and displacements have to be superposed for the whole structure. (Internal forces obtained in (i) and in (ii) have to be superposed) The superposition is done by following, the square roots of the sum of the squares of the results obtained for all structure. In the present thesis at first, the structure is considered as a six storey building without basement and analysed. Secondly, the structure is modelled for analysing by using SAP90, including basement storeys and the basement shear walls. For this reason, the structure is defined totally as a three dimensional frame which composed of equivalent beams which connect columns and shear walls. The shear walls defined as columns which have the same rigidity. For the connections of these columns, beams are used which have large rigidity then the frame elements. These beam rigidity, represents the rigid end joints of the shear wall. The reinforced walls which surrounds basements are modelled as horizontal and diagonal beams. The diagonal beams connects the two consecutive stories. The dimensions of that beams defined according to the system geometry. First step is calculation of the building weight : Wi = Gi + n * Qi G: Dead load of the i.th storey, Qi : Live load of the i.th storey n the live load reduction factor is taken as 0.3 because the purpose of usage is a residence Wj : Total weight of the i.th storey Irregularity of the structure according to the Earthquake Code has to be determined before calculating and getting internal forces. XVIF _WxA(T). Ra(T) : Total equivalent earthquake load Forces applied to each floor : F; = F x W;xH; A(T) = Ao I S(T) : Coefficient of spectral acceleration Ao : Effective ground acceleration coefficient 2.5 I : Structure importance factor 1+l.5*(T7Ta) S(T): Spectral value for the structure T, period of the structure Ta.Tb : Characteristic corner periods depending on the local ground classification Ra(T) : Coefficient for reduction of the elastic earthquake load Ti : First period for structure obtained by Rayleigh Method T, =2kx. (ZMixdf.2) (EFfi*dfi) In this formula, fj displacements have to be known, for that reason, there are two steps for getting Ti natural frequency S(T)=2.5 maximum value is assumed and the total lateral force can be calculated. Having applied the forces to the system for evaluating displacements and Ti can be calculated. Having obtanied Ti, the spectral value S and the effective earthquake forces can be calculated. The external earthquake forces usually act on the mass center of the storeys. According to the Earthquake Code the external forces have to be applied minimum 5 percent of eccentricity. These loading cases cause different internal forces in some elements due to asymmetry at the loading and the whole structure are modelled because symmetry could not be used for this analysis. The structural system are analysed under the verticaland horizontal loads for evaluating internal forces which are used for the design of the members. Having obtained the internal forces, the reinforcement can be calculated. XVllThe flat slab, reinforcement are calculated by using the results from the SAP90 shell output data. Reinforcement ratio and spacing for two directions are required to satisfy the followings : Px+py> 0.0035 S420 where Reinfocement spacing bxd ve sy bxd s=1.5hf s < 20cm s < 25 cm Asmin = Asx+Asy = 0.035*1 00*((22+23)/2) = 7.87 cm2 The column strip in the slab are checked carefully, because it is assumed that loads are carried and transferred by these belts to the vertical elements such as columns and shear walls. Columns minimum section is given as 25cmx30cm however thepresent system, columns are chosen as 60cmx60cm for the basements and first floor ; 50cmx50cm for the 2,3 and 4 floors ; 40cmx40cm for 5 and 6 floors because the vertical rigidity is of prime important in flat slab system including the punching effect. N, May ^f/(Mdx)n N0 (Mdy)maxt m^ `7 Mdx the Earthquake Code requires that for columns ; p,,^ =0.010 ard Pmax = °-°4° and a minimum reinforcement 4<j>16 has to be used because the columns are considered to be the most important members of the structural system. The reinforcement bars are satisfacting the following conditions : <t>h > - ands>12(>v,20 cm <)h : The diameter of stirrupts <j)v : The diameter of vertical bar s : Distance between two stirrupts Reinforced concrete design of the shear walls in the building is done as it is in the design of the columns XVUlThe basement reinforced concrete walls are considered as slabs subjected to forces vertical its plane because the columns continuously carry the vertical loads to the footing, so the basement reinforced concrete walls are designed as shear wall and then checked as slab subjected to soil pressure. Beams are design by considering the combination (1.4G+1.6Q), (G+Q+E) The minimum reinforcement ratio for beams pmin= (12/fyd) for shear forces p«, = Ao/(s*bw) > pmjn=0. 1 5*(Wfywd) The footing of the structure waft foundation and are analysed by using Finite Element Method. For modelling footing plate springs used to represent the soil stiffness. According to this in every joint the ground deflection can be easliy obtained. The loads of the footing calculated from the columns. It is of prime importance that punching must be checked for the footing as well. XIX