Betonarme çerçevelerden oluşan yapıların depremdeki davranışına merdiven taşıyıcıların etkisi
Başlık çevirisi mevcut değil.
- Tez No: 39187
- Danışmanlar: DOÇ.DR. METİN AYDOĞAN
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1993
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 53
Özet
ÖZET Merdivenler bir yapının vazgeçilmez taşıyıcı elemanları olmasına karşın genellikle alışılagelmiş olarak yatay yük hesaplarında gözönüne alınmamaktadır. Oysa merdivenlerin yapının dinamik karakteristiklerini bir miktar değiştirdiği muhakkaktır, özellikle merdiven konstrüks iyonunun bağlı olduğu çerçevelerin davranışı, merdiven konstrüksiyonundan daha çok etkilenmektedir. Bu çalışmada genel amaçlı bilgisayar programları kullanılarak, seçilen tip sistemler, iki ve üç boyutlu şekilde ayrı ayrı merdiven gözönüne alınarak ve merdiven göz önüne alınmayarak çözülmüş, elde edilen sonuçlar diyagramlar halinde sunulmuş, gerekli irdeleme ve öneriler yapılmış tır. iv
Özet (Çeviri)
STAIRCASE STRUCTURE INFLUENCE ON THE SEISMIC BEHAVIOUR OF REINFORCED CONCRETE FRAMED BUILDINGS SUMMARY The stairs are one of the most important and common vertical circulation elements, that provide to connection between different levels of the structure. Stairs also provide to transport of furnitures and materials which are portables, in addition, one of the important functions of stairs is providing to leave to building during the fire or earthquake by connecting to floors that are at different levels. Although, stairs are one of the most important element of the structure, generally, it is not taken into account while the structure is being calculated at the influence of the horizontal forces. However, it is certain that stairs change to dynamic characteristics of the construction. Specially climbing beams are more effected than stairs. Our country is in earthquake zone and because the position of stairs cannot be changed like walls, behaviour of the structure when stairs are taken into account is more important than stairs are ignored. At this investigation; influence of the stair systems that have climbing beams, on the behaviour of the structure is studied, under the horizontal forces. A lot of investigations have done about this subject, one of them has done by V.Colotti and G.Sara [l] and it is given in brief: The influence of the structure of climbing-beam- type staircases on the seismic force absorption in the reinforced concrete-framed buildings is evaluated. Numerical tests referring to simple staircase frames show the inadequacy of analytical schemes which don't take into account of the presence of the climbing-beamwork. With reference to the problem of the force distribution among the stiffening elements, an analytical approximate model is proposed, which, still in the field of the rectangular-grid schemes, provides results which agree closely with more complex models. A correct aseismic design requires, considering the small code safety factors in the case of severe earthquake, a resort to the most reealistic possible analytical models. The models which may be used to represent more or less satisfactorily the real seismicbehaviour of the reinforced concrete buildings may be of varying complexity. The current seismic design criteria for reinforced concrete framed buildings are often based on simplified but not sufficiently reliable assumptions- with dangerous consequences for the safety of the construction - which is confirmed, on the other hand, by the behaviour of several buildings as has been observed in recent earthquakes. Among the above-mentioned assumptions those relative to the staircase structure modelling inside the structural complex are prominent, for their incidence on the general behaviour of the building. Here, the models which are currently adopted and which could be adapted for climbing-beam-system staircase structures in the reinforced concrete-framed buildings under seismic actions are critically discussed A frequent simplification of the traditional design procedures consists in neglecting the climbing-beamwork in the definition of the model for the evaluation of the structural seismic response, and consequently taking into account a system of simple rectangular-grid frames. The above-mentioned model appears, however, not very suitable for a correct and reliable interpretation of the structural complex behaviour since the absorption of the seismic actions is strongly affected, in practice, by the climbing beamwork. An experimental check of the inadequancy of the usual staircase structure modellings is furnished by the observation that the seismic damage suffered by the reinforced concrete framed buildings has been often localized in the staircase zone, which may be thus recognized as one of the most critical in the construction. The weakness of this zone is due essentially to the omitted evaluation, in the design process, of certain effects, both general (the distribution of seismic action) and local (stress distribution), induced by the peculiarity of the behaviour of the staircase frame in the structural complex. It is therefore necessary to consider the employment of ânalitical models more suitable than those usually adopted. The influence of the staircase on the general behaviour of the construction is studied in relation to the problem of distribution of the seismic action; subsequently, a simple but sufficiently accurate analytical model is proposed. In the second part the perturbations induced by the climbing-beamwork on the stress distribution inside the relative frames are analysed. viAnalysis of the beamwork-stif f ened frame subjected to horizontal forces For a preliminary qualitative as well as quantita quantitative survey of the influence of the climbing beamwork of the staircase frame in relation to the absorption of the seismic action, some parametric numerical tests have been performed regarding a single span reinforced concrete frame of five levels. Different structural schemes have been analysed, characterized by the absence or the presence of climbing-beams and by the different values of the ratio a=^ (EI/L), / (EI/L) Qbetween the stiffness modulus of beams, and columns, assumed to be of constant section at each level (Fig. 1). For each scheme, in the elastic linear hypothesis of behaviour by applying three different analytical models, the translational stiffness matrix is evaluated. O 5.00 100 3.00100 a) 5.00 b) İBH*N*r«l Fig.l. Examples of Frame The comparison performed shows that certain traditional simplifying assumptions, such as the member inextensibility or the restrained joint rotations, may lead, in the case of the climbing beamwork frame to errors much larger than those induced by the sane assumptions, in the simple rectangular-grid frame. Analytical scheme of the stiffened frame for the distribution of seismic action. In order to evaluate more correctly the stiffness of the staircase structure in the distribution of the seismic action, an analytical approximate scheme for viistiffened frames is proposed, which allows us, for the sake of simplicity, to stay within the field of the models of low computational effort generally used in the current design procedures in the case of rectangular-grid frame systems. Consequently, the climbing-beam members affect only the elastic characteristics of the connected columns; their influence may be on the whole, floor by floor, evaluated by means of an equivalent pair of elastic springs, extensional and rotational, applied at the climbing beam/column connection. Stress distribution in the staircase frames The influence of the climbing-beamwork inside the staircase frames appears not only in the alternation of the absorption of the seismic forces but also in the re distribution of the stresses in the structural elements. The under-estimated evaluation of the actual column axial forces may be very dengerous considering the brittling effect induced by the same forces. Finally, we should not forget that the large variations of the column forces also modify substantially the distribution of the stress in the foundations. ;ion [1] Conclusions for the investigation done by V.Colotti and G.Sara The investigation undertaken here shows clearly that the modelling of the staircase frames by means of simplified rectangular-grid schemes, by ignoring the climbing beamwork, is scarcely realistic and consequently not suitable for structural safety; it is therefore necessary to adopt more reliable models. Purpose and content of the work The purpose of this work is, to investigate influence of the stairs on the behaviour of the constructions made with reinforced concrete frames. The diagrams of the bending moments, shear and axial forces in the staircase frames and simplified frames, subjected only to the horizontal actions are compared, in addition the mode shapes which are obtained with analysis are presented. viiiThe systems which are analysed At the investigation that is given as a brief; for evaluating morn correctly the stiffness of the staircase slruduto in the distribution of the seismic action, on analytical approximate scheme for stiffened frames is proposed. Tho climbing beam members affect only the elastic characteristics of the connected columns; their influence may be on the whole, floor by floor, evaluated by means of on equivalent pair of elastic springs, extensional and rotational, applied at the climbing beam/column connection. Hut at- this investigation, instead of taking to stiffness matrix and the stiffness of the springs, by menus of using to computer programs, the problem of the seismic force d i stribution for a five storey (Fig. 2) and for n jGn storey reinforced concrete buildings are analysed. At the same time the solution is obtained for two dimensional frames and three dimensional buildings. »00. 400. 780. 400 400. ttso * SOO 400 9.00 SECTION 2-2 SI 3 aoo SECTION 3-3 SECTION 4-4 Fig. 2. Plan and Sections ixAt the two dimensional solutions; the diagrams of the bending moment, shear forces and axial forces are obtained for the five storey building, subjected to vertical design loads and the same diagrams are obtained for the five storey and ten storey buildings, subjected to seismic forces and the mode shapes are also obtained and presented At the three dimensional solutions; the diagrams of the bending moment, shear and axial forces are obtained for five and ten storey buildings subjected to seismic forces and the mod shapes are also obtained and presented. Load cases [2], [3], [4] ; The dead loads are the weight of the cover and the other parts of the stairs, The live loads are calculated by using to TS 498 [2] and DIN 1055 [3] ; a) Vertical Live Loads: 2 - Houses 3.5 kN/m 2 - General buildings 5.0 kN/m 2 - Tribunes 7.5 kN/m b) Horizontal Live Loads: 2 - At the stairs of the houses 0.5 kN/m - Meeting halls, religion buildings, school, theatre, cinema and stairs at tribunes 1.0 kN/m During the calculation, it is supposed that the building is subjected to second class snow region loads and first earthquake zone loads. G is dead, Q is live load and vertical deisgn load (P) is given by: P= 1.4G + 1.6Q (1) Seismic Loads; a) Quasi static seismic loads, [5]; The parameters which are necessary to obtain the seismic loads of the buildings at the first earthquake zone are followings. x- Coefficient for the earthquake zone C = 0.10 - Spectral coefficient of building S = 1.00 - Coefficient of building type K = 0.80 - Importance coefficient of building I = 1.00 In addition, at the ten storey building; H/D > 3 (H, height of the building, D, width of the building), so it is necessary to calculate to concentrated horizontal force F, that is at the top floor of the building and it is calculated with; F = 0.004F (-)2 (2) *? D Here F is summation of horizontal forces b) Dynamic seismic loads NS components of spectrum curves of the Erzincan (1992) earthquake are used as spectral data. Conclusions Reinforced concrete frames that have climbing beams, subjected to the horizontal forces, should be taken into account and the behaviour of the construction should be evaluated according to these reinforced concrete frames. Specially the columns that is neighbour to the climbing beams, should be calculated more carefully. xi
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