Çelik yapılarda kompozit kirişlerin hesabı için yardımcı tablolar

Abstract

Bu çal ışmada; BASIC Programlama dili yardımı ile NPI ve NPU profillerden teşkil edilen kompozit kirişlerin bir ve iki açıklıkta maksimum yayılı yük tasıma kapasite leri ve iki acıklı sistemde yeteri i mesnet donatıları he saplanmıst ır. Programın esasını teşkil eden formül ler ( 1 ) nolu kaynaktan al ınmışt ır. Burada, formüller plastik hesap il kelerine dayanmaktadır. Hesaplama esnasında, senim kontrolü yapılmakta ve kaynakta tavsiye edilen L/300 şart sağlanmaya çalışılmış t ır.Ayr ıca iki açıklıklı kirişler için t at onman la yeri i mesnet donat ı sı hesap ed ilmiştir. Hesaplama sonucunda elde edilen tablolarda değişen profiller ve açıklıklar için belli tabla kalınlığı ve be ton dayanımı için kg /m biriminden düzgün yayıl ı yük de ğerleri verilmişt ir.Ayrıca her değerde kullanılan mesnet donat il arı da bir sonraki tablolarda cm2 biriminde ver ilmiştir.

It is impossible to use only steel in the steel structures, generaly we use reinforced concrete elements like slabs, foundations and etc. Except reinforced concrete foundations, the usege of reinforced concrete slabs and steel beams, reinforced concrete slabs and permanent steel formworks, conrete filled steel tubes and concrete covered steel profiles takes us to think about composite elements. For the purpose of high pressure strength of concrete, the composite elements help us to solve project with a light steel structure. In Turkey, we are living on an earthquake zone but because of treaditional reasons and high price of steel we can not use steel. But, i f we use composite elements, we can solve many problems about high earthquake loads on buildings. Especially, the solving projects with plastic solution methods shows us, we can solve the problem in an economic way. In this way, the steel structures can develop in Turkey. There is a great chance for civil engineers now. They can also use these methods and new technology, they can solve the greatest problems of the big buildings and bridges by an economic way. Engineers have been studying on composite beams for along time. And also there are some standards published in the U.S.A. and Europe. Some of these are CP 117, CP 110, AISC, AASHTO, DIN 1078, Richtlinien für Stahl verbundtrager, ECCS Recommendations. Also in I.T.ü. Prof. Dr. T. Seno ARDA and his friends have been studying on this subject since 1977 and have been published " Plastic Solution of Composite Elements in Steel Structure". Because of these reasons, in this study we try to introduce the performance of the composite beams in some examples and to help engineers to select the best profile for the first selection. But tables are not useful to take loads for using in the projects. Because all projects have different properties. Against the general idea, the solution of the composite beams with plastic method is very easy. So this program is written by using BASIC in computer. As we can see in part " EK A ", the flowchart of the program is very easy. Program is solving 3 types of composite beams < Only steel prof ileCNPI ), concrete covered steel prof ile(NPI), and two simetric steel prof iles(NPU) that concrete filled between them ). Program use NPI80 - NPI400 and NPUSO- NPU400 profile group. Beside these properties it can solve with all types of concrete, all thickness of slab in all spans. But as our real pupose is to help engineer for the first selection, we only solve the spans from 2 m. to 21 m. step 1 m. and the thicknesses of slabs are 8 cm., 10 cm., 12 cm. and the types of concrete are C20, C25(,*) C30. Also, marks near then load values are showing us when program solving the problem which stress is the critical stress for the beam. When the program solving the problem, it provide these criterions; The effective slab width is Beff^ Suggested by AISC for buildings. V4 I 6 J +000 * C25 is used only for beam that have one span, VI 1 In positive moment zone, standards suggest different values of parameters for using in the formulas. We choose a= 1 and b= 0.74 from the U.S.A. standards. In plastic method we use rectangular stress diagrams As br, program use characteristic cube strength of concrete is used. So, there are br values on the tables By using (Table 4.1) user can learn the br values of concrete types. In negative moment zone, again we use rectangular stress diagrams. Here, the only difference is, program calculates reinforcement area on the middle support of the beam. While making the calculations, this program uses the below these criterions; 1) The first hing must be on the middle support. 2) The negative support moment must be smaller or equal to 2 x The bending moment strength of steel profiles. 3) Y" «r Hg / 2 Y''= fcCa:A parameter U^:Steel f lowingstress F^:Support reinforcement area ¦io : Thickness of steel profile body 4) Shear stress must be smaller then shear strength of the steel profile. After program calculate pozitive and negative moment strength of the composite beam, it calculates the member loads and then shear stress of this load. If this shear stress is biger then its shear strenght then program reduce reinforcement area. If it is not enough, then it calculates member load from shear strength of steel profile. After shear stress control then program calculates the using load of the composite beam by dividing the first calculated load to 1.7. And then by using this load program controls the displacements of the composite beam. At first, program calculates the moment of inertia. When calculating the moment of inertia it vn divides the slab width of the composite beam to