Betonarme çerçeve yapılarda dolgu duvarların deprem davranışına etkisi
Başlık çevirisi mevcut değil.
- Tez No: 55803
- Danışmanlar: PROF.DR. HASAN BODUROĞLU
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 38
Özet
ÖZET Uygulamalarda, yapıların yatay yüklere, özellikle deprem yüklerine göre hesabında, dolgu duvarların katkıları ihmal edilir. Gerçekte ise dolgu duvarların yapının rijitliğine katkısı oldukça büyüktür. Hesapta ihmal edilmeleri, daha çok; (1) hesap güçlüğünden, (2) güvenilir bir hesap metodu bulunamamasından kaynaklanmaktadır. Bu çalışma iki bölümden oluşmaktadır. 1. Bölümde, bu konuda, bugüne kadar yapılmış bazı çalışmalar gözden geçirilmiş ve dolgu duvarlı çerçevelerin davranış biçimleri açıklandıktan sonra, dolgu duvarların eşdeğeri olarak hesap modeline eklenebilecek basınç diyagonallerinin kesitleri hakkında Zarnic ve Tomazevic tarafından geliştirilen hesap biçimi sunulmuştur. 2. Bölümde ise ülkemizde çok sık rastlanan bir yapı mimarisi seçilerek, dolgu duvarların dikkate alındığı ve alınmadığı durumda çözümler yapılmış ve her iki durumdaki kesit zorları tablolar halinde karşılaştırılın ıştır. Hesaplar, dolgu duvarların lineer elastik sınırları içinde geçerlidir. Bina çözümlerinde ETABS programı (Three Dimensional Analysis Of Building System - by Ashraf Habibullah) kullanılarak, düşey yükler ve eşdeğer deprem yükleri altında binanın üç boyutlu analizi gerçekleştirilmiştir. vıı
Özet (Çeviri)
EFFECTS OF FILLER WALL ON THE EARTHQUAKE BEHAVIOR OF REINFORCED CONCRETE FRAMES SUMMARY Mixed structural systems constructed of materials which have different mechanical properties should be carefully designed to resist earthquakes. When subjected to earthquake loading, interaction forces develop between different structural system. If not taken into account in proper way, those forces can result into an unexpected behavior of the structure. Reinforced concrete (R/C) frame-work has very wide range of applications on structural system. In practice, however, for structural analysis of buildings under lateral loads, and especially to the earthquake motion, the effect of the infill walls are in most cases neglected. This may be resource of : (1) the design difficulties, (2) absence of a reliable method of computation. Neglecting of effects of filler-wall sometimes, causes severe damage or failure of individual structural elements or even the collapse of whole buildings. However, the filler-wall, although constructed as a secondary structural element, has in general beneficial influence on the behavior of a framed structure. The experiences gained during some important earthquakes show that in many cases filler-walls have prevented the collapse of high buildings. Therefore, the understanding of interaction mechanism between filler-wall and basic R/C frame structure is of relevant importance. The introduction of infill walls into the frames of building changes the overall dynamic characteristics of the building significantly. These changes depends on the (1) mechanical characteristics and thickness of the filler-wall and mortar, (2) quality of contact between the frame and the filler-wall, openings of filler-wall and geometry of filler-wall. Lateral resistance and stiffness of infilled frames are significantly greater than those of bare frame. Due to the relative increase in stiffness, the fundamental period of the structure decreases. On the other hand, the addition of the filler-wall increases the mass of structure and results an increased period of the structure. These two opposing effects make it difficult to derive generalized conclusions regarding the final effects of the infill. However, the net result is usually a decrease in period. VHlUnder the earthquake loading, first cracks occur in the horizontal mortar joints in the middle of the infill and at the vertical contacts between the frame and the filler-wall as well. With the increased lateral deformations, diagonal cracks are developed in the filler-wall and the frame columns start to bend, which results into the yielding of reinforcement and in crushing of concrete in the frame joint zones. For diagonal compression, three modes of failure are possible for filler-walls : (1) crushing of loaded corners ; (2) tension crack along the loaded diagonal ; (3) combined sliding along a mortar joints and diagonal crack. Two different failure mechanism of the infill frame are observed: in the first case, plastic hinges are developed at the bottom and the top of leeward column, whereas windward column fails in shear due to short column effect. In the second case, however, plastic hinges are developed at the bottom and the top of both frame columns. The design of such buildings to resist earthquake forces can be based on the assumption that an infilled frame subjected to lateral loads may be approximately replaced by an equivalent frame in which the infills are replaced by diagonal struts. This study is composed of two parts. In the first section, some available works are reviewed and behavior of masonry infilled frame is explained. Then a method that developed by Zarnic and Tomazevic is presented, which is used to calculate cross sections of equivalent compressive diagonal struts of filler-walls. In the second section, a structure with a frequently used architectural plan in our country is chosen and analyzed for cases of bare and infilled frames. The structure chosen, has six stories; one basement, one entrance and four normal floors. The structure is non-symmetric corner block, which is usually used in our country. An account of this fact, on one side of structure, there exists external filler-walls without window openings. On the normal floors, the structure expands 1.5 m from three sides as cantilever. The basement is surrounded from four sides with reinforced curtain walls. Type of slabs is joist slab. An architectural and form plans are given in figure 2.1, 2.2, 2.3, 2.4. This structure is modelled in two different ways. In first model, the effects of filler-walls are added to beams as their weights only. In second model, the effects of filler-walls are considered as equivalent diagonal struts in addition to their weights. The directions of struts are adjusted according to direction of applied earthquake loads like figure 2.3. In the second model, cross sections of diagonal struts are considered with an approach which is explained in reference [9]. Cross sectional heights of equivalent compressive struts are taken as the half of the floor height and their widths are taken as the filler-wall thickness. On the other hand filler- walls with small openings, are taken in the account as half of their stiffness and filler-walls with big openings like window openings, are not considered. IXBoth in two solutions, the structure is modeled as three dimensional frames and both two models are analized for the vertical loading and equivalent earthquake loading. Calculations are valid for the behavior of filler walls for their linear elastic ranges. Both two results are examined for entrance and first floor that have much different results between them. Some column forces are given in the comparative tables for entrance and first floor. Three dimensional analysis of the building is realized by using ETABS software ( Three Dimensional Analysis Of Building System - by Ashraf Habibullah ). In the second section, first solution refers to the solution in which infill walls are disregarded and second solution refers to the solution in which infill walls are taken into the consideration. It must not be forgotten that the second solution is done by assuming infill walls behave in linear elastic limits. As mentioned in the first part, after structure is subjected to the severe earthquake loads, infill walls may crack and may isolate from frames. So, infill walls will affect the rigidity of structure in a different way. And this causes changes in results of calculation. Compared solutions must be considered in this platform. The results obtained from two different solutions show that infill walls have great effects on structure's behavior. It is observed that the natural periods, floor displacements and internal forces of structures change seriously, parallel to the natural vibration periods of decrease. If natural vibration periods of two solutions are compared, it can be seen that the periods of second one are smaller than the first one. First natural periods of structure given in the first and second solutions are compared in Table 2.3. It shows 30 % decrease in the natural period of structure after infill walls are included into the calculations. TABLE 2.3 First Natural Vibration Periods Of Two Structure Models The relative displacements of structure also show great decrease like natural period when infill walls are taken into consideration. Displacement values are given in Table 2.4 for both solutions in case of vertical loads (loading case 1), earthquake loading in x-direction (loading case 2) and earthquake loading in y-direction (loading case 3). If displacements of fourth floor areexamined, it can be seen that displacement values of the first solution decrease approximately 57 % compared to the second solution. TABLE 2.4 Displacement Values According to Floors for 1. And 2. Solution It is obvious from example that the natural periods and relative displacements of structure decrease since infill walls increase the rigidity of structure decrease since infill walls increase the rigidity of structure. However, it is difficult to make a judgement for the force distribution of structure. When the column forces of first and second solutions are examined, it is seen that the distributions of forces sometimes increase, sometimes decrease and sometimes these changes are extremely important. These increments and decrements of forces change depending on the column sizes, i.e., stiffness, the placement and rigidity of infill walls. Therefore, it is difficult to give a ratio for the changes of structural element forces. For the column forces, some columns of ground floor and first floor that has noticeable change are examined and the force distributions of these columns are presented in the form of tables. XIC/J c o O tn cm c CD E o ?D 03 Ç to *-» O 1_ o o "O C Cö ı_ O.o ü_ T3 C S CD *^ co o 0.O. E z C E O O (A 0 ü m c\i LU _l CO < XIIAs an example, in Table 2.5, for loading case 2 it is observed a noticeable increase in Mx moment of bottom end of ground floor column (column number 1 0). However, this kind of impressive increments in element forces are few compared to small increments. For loading case 3, Mx moment of bottom end of the same column shows great decrease. By looking at column forces generally, it can be said that decreases in element forces are much more than increases. However, especially in earthquake case, changes in some element forces are interesting. As a result, from the information given in first part and comparisons of examples in second part, it is obvious the effect of infill walls into the behavior of structure. Therefore, it can be said that reliability of calculations that disregard the rigidity and strength of infill walls is arguable. To neglect the effect of infill walls, sometimes give the results for the benefit of structural safety, although this does not seem to be solved from the engineering point of view. On the other hand, this solution method may cause unsafe dimensioning of some structural elements because it changes dynamic characteristics of structure and the behaviour of structure also becomes more complex. Depending on the results of this study, for the design of frame systems with infill walls, it is better to make a calculation with and without infill walls. And it is better to give dimensions and to choose reinforcements of structural elements for the worst force case for both two solutions. On the other hand, even this kind of calculation is done, it must not be permitted to build an infill walls which are not shown in architectural plan or to demolish existing infill walls unconsciously. Xlll
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