Deprem yükleri altında yığma duvarların dayanımı ve takviyesi
Başlık çevirisi mevcut değil.
- Tez No: 75329
- Danışmanlar: PROF. DR. HASAN BODUROĞLU
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Yapı Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Yapı Analizi ve Boyutlandırma Bilim Dalı
- Sayfa Sayısı: 69
Özet
ÖZET Ülkemizde yığma konut yapımı yüksek orandadır. Küçük yerleşim merkezlerinde, kırsal alanlarda ve büyük kentlerin yoğun gecekondu bölgelerinde giderek artan bu yapı türü deprem mühendisliği açısından daima önemini korumuştur. Bunun önemli nedenlerden biri dinamik etkiler altında yığma yapıların mekanik özelliklerinin oldukça değişkenlik göstermesidir. Bu çalışmada, ikinci deprem bölgesinde yapılmakta olan yığma yapıların deprem durumundaki davranışları deneysel olarak araştırılmıştır.Deneysel modellemede, yapının deprem kuvvetine karşı en dayanıksız olan boşluktu ( kapı boşluğu ) taşıyıcı cephesi ele alınmıştır. Bunun sebebi yapının deprem durumunda, bu kritik bölgelerden hasar görmesi kapı kenarı, duvar boyutları, modeleme de esas alınmıştır. Buna göre yükseklik / genişlik oram 1 den büyük olan (kapı boşluğun yanındaki duvar boyutlarına göre) yığma duvar numunesinin deprem yükleri altında davranışları incelenmiş ve yükseklik -genişlik oranlarının davranışa etkisi gösterilmiştir. Deney tipi olarak deplasman kontrollü deney yöntemi kullanılmıştır. Bu yöntemin esas uyarınca, sabit düşey yük altında, önceden nümerik hesapla bulunan deplasmanlara karşılık gelen yatay yükler numuneler üzerinde uygulanmıştır. Birinci bölümde problem ortaya konmuş çalışmanın amacı ve kapsamı belirlenmiş, yapılan kabuller açıklanmıştır. Literatürde bu konuda yapılmış, konuyla ilgili çalışmalardan kısaca bahsedilmiştir ve çalışmalarda kullandığımız deney modeli hakkında bilgi verilmiştir. İkinci bölümde yığma ( tuğla ) duvarların malzeme ve mukavemet özellikleri hakkında bilgi verilmiştir. Üçüncü Bölümde deneyin aşamaları, deney düzeneği numunelerin boyutlandınlması, düşey yüklerin hesabı ve deplasmanların nümerik yolla bulunuşu anlatılmıştır. Dördüncü bölümde deneyin sonuçları değerlendirilmiştir. ıx
Özet (Çeviri)
SUMMARY CONCEPT AND PURPOSE OF THE EXPERIMENT Most of the constructions are masonry in our country. Masonry constructions present not only in rural areas but also suburb area of cities. This situation will probably continue in the future because easiness and relatively cheapness of material supply, simple labour demand for constructions makes masonry constructions attractive. In recent years the situation is the same at the locations where earthquake took place. Inefficiency of masonry constructions to the earthquake is revealed in the Erzincan and Dinar earthquakes. Be cause of this reason researches on the masonry constructions, their inefficiency design of the reinforced constructions, their inefficiency, design of the reinforced constructions that can stand up earthquakes, and repair of damaged buildings are still going on. It is impossible to express support of the brick wall which is a composite material in the form of its compounds, brick and mortar, support. There are formulas developed by theoretics and experimental studies. These formulas express the strength of vertical loading of the wall. However it is difficult assume these formulas reliable. Problem is to control the behaviour of the masonry wall affected by lateral and vertical forces. Solutions can be obtained by experiments on the brick wall. In experimental studies the most inconvenient part to the earthquake loads of the structure which characterise the masonry structures is specimen. While designing the experiment specimen earthquake regulations are based upon. As well known weakest part of the masonry constructions under lateral forces are the external walls where window and door gaps are present. The most critical areas on these gapped external walls are the parts of the wall, which is near the gaps. The lateral segment of the wall between the ceiling and beam of the door - window is not included into critical region because, it behaves more rigidly than gapped external walls. ASSUMPTIONS In our studies“earthquake regulations for masonry buildings”due to the second earthquake region are accepted as assumptions. Vertical load applying to the wall specimen is calculated depending on maximum floor number, thickness of the wall etc. which are taken from the assumptions in the regulations of masonry structures.Some of the accepted assumptions are listed bellowed. 1) Maximum floor number and minimum masonry wall thickness (without thickness of vertical mortar) Floor Thickness of the element Basement 1.5 Ground floor 1.5 First floor 1.0 Second floor 1.0 2) The material of masonry building that will be used in masonry walls should be more than 60 kg/cm2. 3) In the walls cement aided by clay mortar (cement, clay, sand, volumetric ratio=l/2/9) Or cement mortar (cement, sand, volumetric ratio =1/4) will be used. 4) The length of entire walls that will be located between the nearest door or window to the corner and building corner will be at least 1.50 m 5) The length of the walls between door and window gaps except corners on the plan should be greater than 1.00 m 6) Length of gaps of the doors or windows will not exceed 3.00m on the plan 7) Each segment length of lento of doors and windows that sits the walls should not be less than 15 % of free lento length and 20cm Construction of masonry buildings has a ratio in our country and will attain this high ratio. These kinds of buildings which are constructed in small towns, rural areas and dense suburb areas of big cities, have always been problems for earthquake engineers. One of the important reasons of this situation is variation of masonry constructions under influence of dynamic forces. QUASI - STATIC TEST Alternated lateral displacement of increasing amplitude have been imposed quasi-statically to a specimen, under vertical force.two cycles are performed at each amplitude, except when a noticeable strength degradation occurred; then three cycles are performed. The walls are fully instrument with in order to large amount of data susceptible to be compared with finite element results (forces and displacements at the top and also deformed shaped of wall). Specimen is observed during the test. Propagation of cracking can be observed easily too. Failure shape of the wall put in evidence about behaviour of the wall. XIIt is recognised that a real seismic excitation is better simulated in dynamic test., but quasi- static test has several advantages with respect to dynamic shaking table test :e.g. the application of large forces to the specimen is easier, the test to collapse of large specimens or structure requires less expensive equipment phenomena like cracking and spreading of damage can be observed more closely and forces and displacement can be measured more accurately. On the other hand masonry exhibit rate-independent behaviour, propagation of cracking at constant load or at constant imposed displacement often observed, so that quasi- static test tend to show more extensive damage and lower strengths. CALCULATING THE DIMENSIONS OF SPECIMEN Conditions described in assumptions are taken into1 consideration in designed of the experiment specimen. Though the wall that is near the door corner that exists in two floored masonry brick building basement's carrier wall in specimen. Width of specimen (D) is taken as 150 m as described minimum in assumptions, height (H) in wall height is calculated as 30 cm as in the regulation width of 1.5 brick. The behaviour of the masonry buildings, which are constructed in second earthquake region, has been analysed in this study. In experimental modelling, the gapped zone, which is the weakest part of the building to the earthquake forces, has been taken into consideration. Reason of this building gets damage from these critical zones, when an earthquake happened. Window and door corner, wall dimensions are taken into consideration such that, seismic behaviours of specimens of masonry walls of which height to width ratio higher than 1 (due to the wall nearby the door gap) are studied on and affects of height, width ratios are shown. As a method; statically experiment method is considered. On the basis of the method; the horizontal loads corresponding to the depletion due to constant horizontal loads that are previously calculated by numerical analysis have been exerted on the specimen. In the first section; problem is stated, purpose and concept of this research is determined and assumptions are explained. Studies on this subject are expressed briefly in literature. In the second; steps of experiment, calculating the dimension of specimen, experimental order, lateral loads and their calculation by numeric analysis have been explained. XllInformation about experiment method we used and other experiment methods are discussed briefly. In the third section information about properties of masonry (brick) walls and properties of walls and construction type of walls are given. In the third section, results of experiment are given. INTRODUCTION: Evaluation of lateral strength in unreinforced masonry buildings is many times clouded because of uncertainties associated whit estimating shear or flexural strength of individual walls of piers. Furthermore, an incomplete depiction of inelastic behaviour, for such elements aggravates the situation since the nature of story shear redistribution to various elements in a building structural system is not well understood. For lack of better information, unreinforced elements are usually assumed to be brittle. Lateral strength is limited by allowable stresses, and no inelastic action is considered. This assumption infers that, upon initial cracking, all lateral force resisted by a particular masonry element is transferred to adjacent elements, which in turn reach their limit when overloaded. This assumption is very severe because the lateral strength of a system is limited to the strength of its weakest element. If masonry elements are actually not brittle than the lateral strength of a system may be thought of as combined strengths of all of its masonry elements. Most seismic codes prescribe an equivalent static lateral base shear for unreinforced masonry buildings on the basis that the structure has no capacity for inelastic deformation. The ultimate limit state for an unreinforced masonry wall of pier is commonly associated with first cracking whether it be a result of flexural tension or diagonal tension. No redistribution of stress within the element is assumed after initial cracking. When an evaluation criterion is based on this limit state, lateral strength may be unreasonably restricted. STRUCTURAL FORM: Unreinforced masonry structures are distinguished from other building types by their structural form and relative stiffness of the elements. In most general terms, typical unreinforced masonry buildings are likely to be composed of several load bearing masonry walls arranged in orthogonal planes, with relatively flexible floor diaphragms. When subjected to the ground motion, the foundation transmits seismic motion from the ground stiffness elements, the in plane structural walls excite the diaphragms with a motion which has now been filtered by wall response, and the diaphragms in turn excite the out-plane wall. When the diaphragms are flexible, the out plane walls are likely to see displacements amplified significantly from those of the in-plane walls. The mechanism of resistance follows the reverse order, with the inertia loads generated by out plane wall motion being reacted by xiiidiaphragms, so on down to the foundation. The lateral load resistance is provided entirely by the in-plane walls. Observed seismic damage in unreinforced masonry structure often includes out-of-plane failures of walls, driven by excessive deflections of diaphragms insufficient connection between them, but in-plane walls provide stability necessary to avoid collapse. The first problem in experimental testing is then to determine the components and subsystem, which most closely represent elastic structural forms, and to determined the appropriate loads, filtered by as they are by adjacent structural components, which should be applied to them. For purposes of discussion, the failure mechanism of masonry piers; rocking, sliding, and diagonal shear can be described very simply. Sacrificing some accuracy to the purpose of emphasising the relative importance of various parameters on the response of piers.The maximum horizontal shear which can be resisted by a rocking may be approximated by: Vr = v|/3(D 23t / H)3(P/2)3(l-P/(0.85 3f m)) Where D is the pier width, H is pier height, t the pier thickness,“p = P/(D*t)”, is the mean vertical stress on the pier due to the axial load P fin is the compressive strength of masonry and i|/ is a parameter which describes the boundary conditions, taking a value of 2 when the pier is fixed at both ends. xiv
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