Geri Dön

Küçük titreşim ölçümleri ve dolgu duvarlarının mekanik modele yansıtılması

Başlık çevirisi mevcut değil.

  1. Tez No: 66623
  2. Yazar: UMUT DEVRİM ERSİN
  3. Danışmanlar: PROF. DR. H. FARUK KARADOĞAN
  4. Tez Türü: Yüksek Lisans
  5. Konular: İnşaat Mühendisliği, Civil Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1997
  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: Yapı Analizi ve Boyutlandırma Bilim Dalı
  13. Sayfa Sayısı: 162

Özet

ÖZET Dolgu duvarları, hesaplarda yapısal eleman olarak gözönüne alınmamalarına karşın, hem kütleleri hem de yatay rijitlikleri nedeniyle yapının dinamik karakteristiklerini değiştirmektedirler. Bu değişim, çoğu zaman dolgu duvarlarının yatay rijitliğinin ağır basarak yapının serbest titreşim periyodunun azalması yönünde olmaktadır. Küçük titreşim ölçümleri yardımı ile yapının periyod ve mod şekli gibi temel dinamik karakteristiklerine ulaşılabilmektedir.' Yüksek Lisans Tezi olarak sunulan bu çalışmada, küçük titreşim ölçümleri için dolgu duvarlarının yapının yatay rijitliğine katkısını yansıtacak bir model önerilmektedir. l.Bölüm'de; yapıda hesap sırasında ortaya çıkabilecek belirsizlikler ve çalışmanın amacı ortaya koyulmaktadır. 2.Bölüm'de; daha önce yapılan, dolgu duvarların yapının yatay yükler altındaki davranışına etkisinin anlaşılmasına yönelik çalışmalar özetlenmekte ve dolgu duvarın elastisite modülünü etkileyen faktörler hakkında bilgi verilmektedir. 3.Bölüm'de; küçük titreşim ölçümleri ve oluşturulan tuğla, harç ve dolgu duvarları numuneleri üzerinde yapılan tek eksenli basınç deneyleri anlatılarak, bu numunelere ait basınç dayanımı ve elastisite modülü değerleri verilmektedir. 4.Bölüm'de; dolgu duvarlarının yatay rijitliğini tanımlamak için dolgu duvarlarının bir çift sanal çapraz çubukla temsil edildiği bir yaklaşım önerilmektedir. Bu sanal çubukların eğilme rijitlikleri; sonlu eleman çözümlemeleri yardımı ile, değişen duvar kalınlıkları, duvar uzunlukları için incelenerek tanımlanmaya çalışılmıştır. Ayrıca dolgu duvarlarındaki boşlukların, sanal çapraz çubukların eksenel rijitliğinde neden olduğu azalma da bir yaklaşımla gözönüne alınmıştır. 5.Bölüm'de; deprem sırasında ortaya çıkan kalıcı yerdeğiştirmelerin dolgu duvarlarının rijitliklerinde neden olduğu azalma; bir yapı gözönüne alınarak, bazı kabullerle ve küçük titreşim ölçümlerinin değerlendirilmesi sonucu bulunan periyod ve mod şekilleri yardımıyla belirlenmeye çalışılmıştır. Bölüm 4' de tanımlanan, dolgu duvarlarını temsil eden sanal çapraz pandüllerin eksenel rijitlikleri, örnek olarak alınan 12 Katlı bir yapının mekanik modeline eklenerek ölçüm ve serbest titreşim hesap sonuçlan karşılaştırılmıştır. XIV

Özet (Çeviri)

SUMMARY The skeleton frames are filled in their plane by clay brick masonry walls to meet the architectural and functional requirements like partitioning, enclosing. In such situations, the combinations of frames and filler walls forms a composite structural system called infilled frame. Even though the infill in such frames are often considered as non-structural elements, they tend to interact with the bounding frame when the structure is subjected to lateral loadings. This interaction has a considerable effect on the overall seismic response of the structure. Unless adequately separated from the frame, the structural interaction of the frame and infill must be taken into account in the design or in the evaluation of seismic behavior. Designers usually tend to neglect the structural contribution of the infill to avoid complexity in the analysis, feeling that such an omission is on the safe side. Because the infill walls which are made of brittle material are broken and losing their lateral strength during the early stages of an earthquake. Besides being unrealistic, such an approach is likely to lead less safe designs due to ill distribution of lateral forces among frame members. It is a common misconception that the infill will increase the lateral load capacity of the structure and therefore must be beneficial to seismic performance. Even if they are relatively weak, the infill can alter the intended structural response, attracting forces to parts of the structure that have not been designed to resist them. Added to this, stiffening effect of the infill usually results in increased seismic forces. The beneficial effect due to the increase of strength may or may not counterbalance the negative effect of increased seismic forces due to the stiffness of infill throughout the structure. The infill influence the dynamic characteristics like fundamental period and mode shape of the structure. With the addition of infill, its mass increases the fundamental period. Unlike the effect of mass, the stiffness of infill decreases the fundamental period. This two opposing effects make it difficult to get a generalized conclusion for the influence of the infill on the period of the structure. However, the stiffening effect of the infill mostly overweights and decreases the period of the structure. The infill panels between the frame members also change the free vibrational mode of the structure from shear type to cantilever type. In certain cases, shear type deformation can be kept even though infills are interacting with the surrounding relatively very weak frames. To sum up, the infill basically affects the stiffness, strength, shear distribution and dynamic characteristics of the main structure. The influence of the infill on these characteristics depends on the number of frames that are infilled and the location of the infill in the structure. XVFirst few periods and free vibrational modes are basic dynamic characteristics of a structure for evaluating its dynamic response for a given dynamic load. Although static behavior of the infilled frames has received considerable attention in the past, relatively few studies have been carried out about their dynamic behavior. The basic dynamic characteristics of a present structure can be derived on the site by means of micro tremor measurements which have amplitudes varying between 0.005- 3000 microns. Thus the existing period and free vibrational mode shapes of the structure could be captured precisely. In this study, an investigation is performed to introduce the contribution of the lateral stiffness of the infill on the mechanical model of the main structure which can be utilized for a possible dynamic analysis. Experimental and analytical studies showed that the stiffening effect of the infill on the structure under lateral forces can be represented fairly well by a diagonal strut model. While the amplitudes of the micro tremor displacements are too small as stated above, it can be supposed that the structure trembles in the range of elastic deformations. Hence the stiffness of the infill is represented by two crossing diagonal strut elements,(Figure 1). The study accounts for elastic behavior of the structure and models the infilled frame into frame elements with multiple diagonal struts. In the course of this study, material tests and finite element analysis have been carried out to determine the equivalent stiffness of the infill. Figure 1 Characteristics Of Infilled Frame and Equivalent Braced System The axial rigidity of the equivalent strut is defined as multiplication of modulus of elasticity E and cross section area F. Because of anisotropy of the infill, average of the elasticity moduli of horizontal and vertical directions is taken as the strut modulus. The cross section area is associated with the thickness t and effective width w of the diagonal strut. Previous studies indicates that the width of the strut depends on a number of factor as the relative stiffness of bounding frame and infill, panel height to length ratio and modulus elasticity of the infill material. In this study the width of the strut is associated with a coefficient which is a percentage of the length of diagonal. By means of finite element analysis, a coefficients are proposed for the infill with and XVIwithout cement plaster coatings and several experimental attempts have been carried out to find a. For that purpose, undamaged 4 structures have been investigated both experimentally and theoretically. Namely micro tremor measurements have been taken in those buildings and free vibrational analysis executed as well. It has been concluded that a is around 0.5. The influence of the openings on the stiffness of the infill is also investigated with finite element analysis and introduced to the equation of axial stiffness by P coefficient. The effects of plastic deformations in the damaged frames during earthquakes is reflected by y to the mechanical model. After the mechanical characteristics of the equivalent struts are determined as, EF = EtaLd p-y (1) their stiffness is introduced to the mechanical model of the structure. Uniaxial compression tests are carried out to obtain the mechanic characteristics of the infill and infill material, i.e. brick and mortar. As the brick and mortar quality varies among wide range, the results of these tests can not be generalized for all infill materials. The wall specimens are composed of 8.5cm and 12.5cm thick bricks with and without cement plaster coatings on both sides to understand the effect of thickness and cement plaster on the elasticity modulus of infill. Some imperfections can be encountered in the wall specimen such as the thickness of mortar bed joints, the quality of mortar, workmanship. These are the effects that influence the basic mechanical characteristics of a specimen, also the infill wall. A wall specimen is formed of four courses of brick with holes in the horizontal (weak) direction. Over and under the specimen concrete headings are added to prevent local cracks and to distribute the vertical load uniformly to the specimen. The vertical force is given manually with a hydraulic jack. Applied force values are transmitted by a load cell put under the jack to Digital Data Logger. The displacements are obtained from the transducers located in the concrete headings on both sides of the specimen. The force and the displacements data are kept in a Digital Data Logger. Upper Concrete Heading Lateral Mortar Layer Vertical Mortar Layer Lower Concrete Heading Bricks w^M Figure 1 Wall Specimen xvuStress values is obtained by dividing the applied load by the nominal cross section area of a brick coarse. The measured displacement values are divided by gage lengths on both sides and the average of these strain values is taken to plot the stress-strain diagram. The modulus of elasticity in the perpendicular direction to the holes is evaluated as the inclination of the secant through 5% and 35% of the crushing load in stress-strain diagram. Then a value for the modulus of elasticity in the direction of holes is proposed depending on some assumptions. The stress-strain diagrams of the wall specimens with and without cement plaster coatings are plotted in Figure 1 and 2. Then elasticity modulus in two directions are suggested for the infill with and without cement plaster coatings to be utilized in finite element analysis, (Table 1). (Eper: Elasticity modulus in perpendicular direction to holes, Epar: Elasticity modulus in parallel direction with holes, Eave: Average of Elasticity moduli) 0.0005 0.001 0.0015 0.002 0.0025 0.003 Strain Figure 2 Stress-Strain Diagrams of Wall Specimens Without Cement Plaster Coatings 0.0000 0.0005 0.0010 0.0015 Strain 0.0020 0.0025 Figure 3 Stress-Strain Diagrams of Wall Specimens With Cement Plaster Coatings XVUlTable1 The Elasticity Modulus Of Infill Walls Utilized In Finite Element Analysis The obtained modulus of elasticity of the infill in two directions are used in the finite element analysis to define the width of the diagonal strut. The program so called SAP90 is utilized in the analysis. Being the ASOLID element block the most appropriate type to represent the anisotropic properties of the material, the rotational degrees of freedom about the axis perpendicular to the plane of the element is neglected and rectangular plane stress elements having two translational degrees of freedom at each node are used to idealize the frame members and infill. (Figure 4) However, a relatively fine mesh having 10x1 0cm rectangular elements is selected to take into account the rotational displacements. Figure 4 Degrees of Freedom of Plane Stress Element Three different lengths 2.8m, 4m, 5m for the infill solid panels have been chosen to determine the lateral stiffnesses. Finite Element Analysis are repeated for each infill length with different thicknesses and plaster coatings The infill is removed theoretically from the infilled frame and the frame members are divided into finite elements to define an equivalent frame. The frame is restraint from point 1 and 4 by hinge and roller supports respectively and a unit load has been applied onto points 2 and 3 at the intersections of beams and columns. Then an equivalent frame is defined consisting of beam elements having the same mechanical characteristics i.e. modulus of elasticity, moment of inertia. The length of the beam elements are taken as the distance between the intersection of column and beam axis. Then comparative analysis are performed to resemble the equivalent frame to the one with finite elements. In order to fully simulate the frame members as beam elements, rigid sections at the ends of frame members are introduced to the equivalent frame and an iterative procedure is followed. In the beginning, a random value is given for the length of the rigid section. Then the iteration continued until the lateral displacements of point 2 are equal at each frame. After the length of the rigid sections are determined by iterative procedure, two crossing diagonal struts are introduced to the equivalent frame. Thus the discrete system representing the infilled frame has been formed. The analysis will be fulfilled on discrete system to define the lateral stiffness of the infill. Unit load is applied to the infilled frame in finite elements at point 2 and 3 as stated above. The lateral displacement of point 2 is computed by means of SAP90. In the discrete system, a random value has been given for cross section area of the strut at the beginning. Then unit load is also applied to the discrete XIXsystem at the same points and iteration for cross section area has been made until the lateral displacement of point 2 is equal in each system. The width of the infill is obtained by dividing the provided cross section area by the thickness of the infill. F = tw (2) This width is associated with a percentage, symbolized as a, of the diagonal length, a coefficients are given in Table 2 for different wall thickness and length w = a-Ld a w 17 (3) It has been observed that a coefficient is independent from infill length but infill thickness. Table 2 The Evaluated a values For Different Lengths and Thicknesses of Infill The decreasing effect of the openings on the stiffness of the infill is investigated on the infill walls without having frame elements around. The most frequent/encountered opening types are allowed for in this analysis,(Figure 5). The unit load acting to the infill walls is distributed to each node uniformly on the top. The displacements at the top on the left and right ends are compared to define the degradation in stiffness. The ratio of the displacements of the infill with openings to the one without any opening is accepted as stiffness degradation factor caused by the openings. These ratios are given as coefficient p in Table 3 according to the dimensions of openings. window for toilet /' 7 7 / )' V / /' ) ) /' Typel window for room wall to wall window door window + door r i / i i r ) / v / / r i >' > ; ; ' ; / v > Type 4 Type 5 Type 6 Figure 5 Types of Infill Walls Taken Into Account to Define 3 Coefficients XXThe other effect which influences the axial rigidity of the struts is imperfections in the material and plastic deformations observed in the frame damaged during earthquakes. The coefficient y defining the effect of plastic deformation can be evaluated by means of mode shape and period directly derived from micro tremor measurements and depending on some realistic assumptions done. An advantage of this evaluation is to define y coefficient for each story. The assumption made for the evaluation of this coefficient is that the structure acts as shear frame rather than cantilever frame. This assumption could be considered convenient if the compression strength of the concrete is too low and when the reinforced concrete structure behaves like a masonry structure and if the columns of frame is relatively weak in comparison to the beams. A trial and error procedure has been followed to derive the y coefficients for a 4 story RC structure damaged during 1995 Dinar earthquake. The fundamental mode shape is taken into account as occurred displacements at each story levels under lateral loading of this shear frame by 1 kN on top. A lateral rigidity for each frame is evaluated and the rigidities are normalized. Then the normalized relative rigidities are considered as y coefficient for each stories and used for the modification of EF values at each story. Using the new axial rigidities of bracings, the new period and mode shape is obtained by free vibration analysis. The ratio between square of evaluated period to square of measured period is multiplied by the previous normalized rigidity values. This procedure is continued until the evaluated and measured periods become equal. The micro-tremor measurements are obtained from 12 story residential building without infill walls. After adding the infills to the structure, another micro tremor measurements have been recorded to capture the effects of infill. Using the above mentioned a and P coefficients, the axial stiffnesses of the infill panels are introduced to the mechanical model of the structure. The measured and evaluated periods are given in Table 4 and 5. Table 4 Measured and Evaluated Periods At Bare Frame XXITable 5 Measured and Evaluated Periods At Infilled Frame The effects of infill on the fundamental period of the structure can be obviously seen from Table 5 if it is compared with Table 4. The infill panels will affect the intensity of earthquake loads which will be imparted to the structure. As a conclusion, in this study, an attempt has been made to define the effective axial stiffnesses of the equivalent fictitious struts representing infill walls. For that purpose uniaxial compression tests and comparative finite element analysis have been carried out during the experimental part of the work. More experiments containing different kind of brick and mortar qualities and analysis of infilled frames having varying dimensions need to be performed to improve the proposed model. XXll

Benzer Tezler

  1. Tez No

    142597

    Yeni Cami'nin akustik açıdan performans değerlendirmesi

    Evaluation of the acoustical performance of the New Mosque

    EVREN YILDIRIM

    Yüksek Lisans

    Türkçe

    Türkçe

    2003

    Mimarlıkİstanbul Teknik Üniversitesi

    Mimarlık Ana Bilim Dalı

    PROF. DR. SEVTAP YILMAZ DEMİRKALE

  2. Tez No

    495450

    Orta yükseklikteki betonarme binaların temel periyotlarının çevresel titreşim ölçümleri ile belirlenmesi ve periyot bağıntısı önerilmesi

    Proposal of an empirical equation by means of ambient vibration measurements for fundamental vibration periods of mid-rise rc buildings

    ONUR KAPLAN

    Doktora

    Türkçe

    Türkçe

    2017

    İnşaat MühendisliğiAnadolu Üniversitesi

    İnşaat Mühendisliği Ana Bilim Dalı

    PROF. DR. YÜCEL GÜNEY

    PROF. DR. ADEM DOĞANGÜN

  3. Tez No

    348539

    Yapıların dinamik özelliklerinin mikrotremor ölçümleri ile belirlenmesi

    Determination of dynamic properties of structures with microtremor measurement

    GÖKHAN ÖZCAN

    Yüksek Lisans

    Türkçe

    Türkçe

    2013

    İnşaat MühendisliğiPamukkale Üniversitesi

    İnşaat Mühendisliği Ana Bilim Dalı

    PROF. DR. MEHMET İNEL

  4. Tez No

    783711

    Comparison of experimental and semi-experimental models for predicting solar thermal power plants with artificial neural network

    Solar termal santralların yapay sinir ağlarıyla öngörüsünde deneysel ve yarı-deneysel modellerin karşılaştırılması

    SHABNAM CHOOPANI

    Yüksek Lisans

    İngilizce

    İngilizce

    2023

    Enerjiİstanbul Teknik Üniversitesi

    Enerji Bilimleri ve Teknoloji Mühendisliği Ana Bilim Dalı

    DR. ÖĞR. ÜYESİ BURAK BARUTÇU

  5. Tez No

    677350

    Incremental nonlinear dynamic inversion based trajectory tracking controller for an agile quadrotor

    Çevik bir döner kanat hava aracı artımlı doğrusal olmayan dinamik ters çevirme tabanlı yörünge izleme denetleyicisi

    EMRE SALDIRAN

    Yüksek Lisans

    İngilizce

    İngilizce

    2021

    Havacılık Mühendisliğiİstanbul Teknik Üniversitesi

    Uçak ve Uzay Mühendisliği Ana Bilim Dalı

    DR. ÖĞR. ÜYESİ RAMAZAN YENİÇERİ

Geri Dön