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Deprem yüklerinin altında yığma binaların davranışı

Başlık çevirisi mevcut değil.

  1. Tez No: 75268
  2. Yazar: MORTEZA SABERİ
  3. Danışmanlar: PROF. DR. HASAN BODUROĞLU
  4. Tez Türü: Yüksek Lisans
  5. Konular: İnşaat Mühendisliği, Civil Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 70

Özet

ÖZET : Ülkemizde yığma konut yapımı yüksek orandadır ve gelecekte de yüksekliğini koruyacaktır. Küçük yerleşim merkezlerinde,kırsal alanlarda ve büyük kentlerin yoğun gecekondu bölgelerinde, giderek artan bu yapı türü deprem mühendisliği açısından her zaman zor yapılar olmuşlardır. Bunun önemli nedenlerden biri dinamik etkiler altında yığma yapıların mekanik özelliklerinin çok değişkenlik göstermesidir. Bu çalışmada ; deprem bölgelerinde yapılmakta olan yığma yapıların deprem durumundaki davranışları deneysel olarak araştırılmıştır. Deneysel modellemede, yapının deprem kuvvetine karşı en dayanıksız olan boşluklu ( kapı boşluğu ) taşıyıcı cephesi ele alınmıştır. Bunun sebebi yapının deprem durumunda, bu kritik bölgelerden hasar görmesi dir.Bu yüzden, kapı kenan, duvar boyutları, modeleme de esas alınmıştır. Buna göre yükseklik / genişlik oranı 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 yan statik deney yöntemi kullanılmıştır. Bu yöntemin esası uyarınca, sabit düşey yük altında, önceden nümerik hesapla yaklaşık olarak bulunan deplasmanlara karşı gelen yatay yükler numuneler üzerinde uygulanmıştır. 1. Bölümde problem ortaya konmuş çalışmasının araacı ve kapsamı belirlenmiş, yapılan kabuller açıklanmıştır. Literatürde bu konuda yapılmış çalışmalardan kısaca bahsedilmiştir ve çalışmalarda kullandığımız deney modeli hakkında bilgi verilmiştir. 2. Bölümde deneyin aşamaları, deney düzeneği numunelerin boyutlandınlması, düşey yüklerin hesabı ve yatay deplasmanların yaklaşık bir hesapla bulunuşu anlatıl mıştır. 3. Bölümde yığma ( tuğla ) duvarların malzeme özellikleri ve duvarın örgü şekli hakkında bilgi verilmiştir. 4. Bölümde deneyin sonuçlan değerlendirilmiştir. IX

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 Inconvenience of masonry constructions to the earthquake is revealed in the Erzincan and Dinar earhquakes. Because of this reason researches on the masonry constructions get importance.Design of the unreinforced 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 theoretic and experimental studies.These formulas express the strength of lateral and 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 under the earthquake loads of the structure has been taken into consideration. While dimensioning 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 lentos of the door or window, is not included into critical region because, it behaves more rigidly than gapped external walls. Wall dimensions are taken into consideraiton such that under lateral loading structural behaviours of specimens of masonry walls of which height to width ratio higher than 1 and affects of height to width rations are shown. Assumptions In our studies the regulations of the second earthquake region“Afet Bölgelerinde Yığma Yapılar Yönetmeliği”are accepted as assumptions.Maximum floor number and load calculations due to worst conditions are done according to regulation and specimens are dimensioned.Some of the accepted assumptions are listed belowed. 1) Maximum floor number and minimum masonry wall thickness (without thickness of vertical mortar) 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= 1 1219) 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 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 lentos of doors and windows that sits the walls should not be less than 15 % of free lento length and 20cm 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 occured ; 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. It is recognized 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 xi: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 strenghts. Dimensioning Of Specimen Conditions described in assumptions are taken into consideration in dimensioning the experiment specimen. Specimen of experiment is taken as the wall that is belonged to the ground floor of two floor masonry brick building. Width of specimen (D) is taken as 150 m as discribed minimum in assumptions, height (H) in wall height is dimensioned as 30 cm that fits the regulation,and width of 1.5 brick. The behaviour of masonry buildings which are constructed in earthquake regions has been analyzed on this study. 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 analisis have been explained.Inforrnation about experiment method we used and other experiment methods are discussed briefly. In the third section information about properties of masonry (bnck)walls and properties of walls and construction type of walls are given. In the third section results of experiment is given. Evaluation of lateral strength in unreinforced masonry buildings is many time clouded because of uncertainties associated whit estimating shear or flexural strength of individual walls of piers.Furthermore, an incomplete depiction of inelastic behavior for such elements aggravates the situation since the nature of story shear redistiribution 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 xnconsidered. 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. Much like buttons on a shirt,when the first one tears follow quite suddenly.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 sesmic codes prescribe an eqivalent 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 diyagonal tension. No redistribution of stress within the element is assumed after initial cracking. When an evaluation criteria 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 stifness of elements.In most general terms, typical unreinforced masonry buildings are likely to be composed of several loadbearing 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 stifness elements,the in plane structural walls excite the diaphragms with amotion 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 diaphragms, 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 stabilitiy necassary to avoid collapse.The first problem in exprimental testingis then to determine the components and subsystems which most closely represent realastic 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 describe very simply, sacrificing some accuracy to the purpose of emphasizing the relative importance of various parameters on the xmresponse of piers.The maximum horizantal shear which can be resisted by a rocking may be approximated by: Vr = i|/*D2*t*P/2H*(l-P/0.85fm) Where D is the pier width,// is pier height, / the pier thickness, p=P/(D*t), is the mean vertical stres on the pier due to the axial load P, fm is the compressive strength of masonry and vj/ is a parameter which describes the boundary conditions, taking a value of 2 when the pier is fixed at both ends. Conclusion At the end of displacement controlled loading,the wall specimen was collapsed under 28.865 KN load and 7.121 mm displacement.By the assumption of brittle behavior of massonry, loading was started from small value of displacement (0.03 mm).At the following step of loading, lateral displacement increased periodically. During the experiment we were able to observe the changing of transducer measurements from Tmonitor software programme. Load - displacement graffic, which was drawn in load control system computer, was controlled in every step of loading. It was found that, the specimen behave elastically from begining to the values 18.05 KN and 0.079 mm displacement. After that values specimen behaved elasto - plastically. First failure cracking was observed at connection with base plate area, in both ends. Following failure occured very near to the first failure and first cracking got wider. A diyagonal cracking was spreading diyagonally from bottom edge to the right. It follows horizantal and vertical mortar. xiv

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