Asma kablolar ile desteksiz kulelerin hesabı ve tasarımı

Abstract

ÖZET Bu tez çalışmasında, asma kabloların ve kule yapılarının lineer olmayan statik hesabı konuları incelenmiştir. Bu tür yapıların hesabında, denge ve uygunluk denklemle rinde de formasyonlar dikkate alınmakta, yani 2. mertebe teori sine göre çözüm yapılmaktadır. Birinci bölümde, önce konu tanıtılmakta, daha sonra kablo ve kule yapıların yapısal özellikleri anlatılmaktadır. İkinci bölümde kirişler, kolonlar, kiriş-kolonlar, taşıyıcı çerçeveler, kemerler ve asma kabloların ikinci mertebe hesapları için kullanılan Başlangıç Değişkenleri Yöntemi'nin esasları açıklanmıştır. üçüncü bölümde asma kabloların hesabı incelenmiştir. Bu bölümde, sabit yüklerin yanı sıra hareketli yüklerin de gözönüne alınabildiği sabit uzunluklu ve sabit çekme kuvvetli kablolara ilişkin benzer nitelikte iki ayrı bilgisayar programının esasları açıklanmıştır. Ayrıca sayısal örnekler de çözülmüştür. Dördüncü bölümde asma kabloların tasarımında sıcaklık etkilerini ve mesnet fleksibilitelerini dikkate alan kablo hesapları konusu incelenmiştir. Ayrıca sabit kesitli ve sabit gerilmeli kablo hesabına ilişkin bilgisayar programının açıklaması. ve sayısal örnekler de verilmiştir. Beşinci bölümde, yük etkisi altında geometri değişimi ile ilgili lineer olmamanının gözönüne alındığı elastik konsol kule yapılarının basit bir ayrık eleman modelinin tanımı verilmiştir. Ayrıca kule tipi yapıların bilgisayarla statik hesabı anlatılmış ve sayısal örnekler de çözülmüştür. Altıncı bölümde bu çalışmadan elde edilen sonuçlar ve öneriler özetlenmiştir. Ayrıca Ek 1 'de, televizyon kulelerinin modern tasarımında özellikle uygulamada kullanılabilecek özet bilgiler derlenerek sunulmuştur. vi

SUMMARY In this thesis non-linear analysis of suspension cables and tower structures are examined. In this kind of structural analysis, deformations are taken into account in the equilibruim and compatibility equations, namely second-order theory is used. There are five chapters in this thesis. In first chapter, the subject is introduced and properties of cable and tower structures are explained. In second chapter, the bases of initial variables method used in the second-order analysis of beams, columns, beam- columns, portal frames, arches and suspension cables were explained. The method depends upon the subdivision of the structure within the available computer memory into a moderate of discrete elements. Then sufficient assumptions are made at one boundary about displacement or actions for the stresses and deformations to be determinate serially all the way to the other boundary. Analysis may proceed step-wise from node to node with allowence made for self-weight, temperature effects, external loading as well as the deformations already computed. At the second boundary, errors in actions or displacements will be revealed as many there were initial guessed variables. The key to the successful application of the method is the improvement of the initially guessed variables by the Newton methqd with the elements of the associated Jakobian matrix evaluated numerically by successive chain analyses. The principal assumption then is that the behaviour of a continuous elastic member can be simulated by considering a chain of elements. Each element may extend or compress in its axial direction but is assumed to remain straight. All calculated flexural deformations are assumed to take place at the junctions of the elements forming the chain. It is as if the pinned connections between links were to be elastically restrained with the slope change at each Junction set to the mean of the slope changes computed from simple flexural theory for the elements on each side of the junction. In third chapter, the analysis of suspension cables is examined. The discrete element method of analysis (initial venables method) has been explained first to solve the problem of analysing the constant length cable. Subsequently, the treatment is modified to deal with the cable of constant maximum tension. In both instances, the cable area of section is taken as constant. viiIn fourth chapter, the subject of cable analysis which takes into account the effects of temparature changes and support flexibilities in the design is examined. The explanation and flow charts of cable computer program and numerical examples of cable analysis are also given. In these analyses the cables with constant area and constant tension are used. In fifth chapter a description was given of a simple, descrete element model of elastic, cantilevefed tower structures in which non-linearities associated with geometrical changes under lood car. be quite accurately taken into account. With the initial column subdivided into a number of small elements, and guessed values for the initial variables having been assigned, the computation can proceed simply from element-to-element along the chain. The algorithms for producing the thrust, shear and moment at the head of such element involve simple considerations of static equilibrium. For a column of a non-uniform section, the appropriate axial and flexural rigidities can be predetermined for each element and stored in suitable arrays in computer program. In the sixth chapter, the conclusions of this study are outlined. A note on `Modern Design of Television Towers` which is believed to be. useful to p:raact£c&ng «engineers lias been translated and given in an appendix-. viii