Betonarme binaların patlamalarla planlı yıkımı
Başlık çevirisi mevcut değil.
- Tez No: 75250
- Danışmanlar: PROF. DR. ANTONİO L. TRUPİA
- 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: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Yapı Mühendisliği Bilim Dalı
- Sayfa Sayısı: 191
Özet
ÖZET Bu çalışmada, betonarme binaların patlamalarla planlı yıkımı incelenmiştir. Giriş bölümünde, planlı yıkımda kullanılan patlayıcıların patlaması sonucunda oluşan en yüksek fazla basınç, yansıtılan basınç ve quasi-statik gaz basıncı gibi patlama karakteristiklerine yer verilmiştir. Ayrıca, yapı elemanları üzerinde patlamalar sonucunda oluşan hasarlar incelenmiş ve bu hasarların oluşmasını engellemek amacıyla önerilen koruma elemanları örnekleri verilmiştir. İkinci bölümde, asismik olarak dizayn edilmiş altı katlı betonarme bina üzerinde yapılan patlamalarla planlı yıkım testine yer verilmiştir. Bu testte, planlı yıkım testi için kullanılan binanın yapısal özellikleri, patlama metodları, patlayıcılar, patlayıcıların özellikleri, miktarları ve yerleşim yerleri incelenmiştir. Yıkım sonucunda oluşan hasar sonuçları ve yıkımın oluşturduğu vibrasyon ve etrafa yayılan parçalar gibi çevre etkileri gözlemlenmiştir. Üçüncü bölümde, dört katlı betonarme binanın patlamalarla anti-simetrik yıkımı üzerine bir çalışma yapılmıştır. İlk olarak sabit yükler ve yük dağılımları belirlenerek kirişlere gelen yükler bulunmuştur. Kiriş ve kolonların plastikleşme momentlerinin de hesaplanmasıyla yıkım için gerekli ön hazırlık tamamlanmıştır. Yıkım, her aşamada planlanan yapı elemanlarının patlatılması ve yapıda oluşan plastik mafsalların tanımlanmasıyla üç aşamada gerçekleştirilmiştir. Her aşamadan sonra yapı sisteminin çözümü, SAP90 yapı analiz programı ile yapılmış ve hesaplamalar yapı mekanizma durumuna gelinceye kadar sürdürülmüştür. Planlı yıkımı sağlayacak olan patlayıcı tipi, miktarı ve yıkımın istenilen şekilde gerçekleşmesi için patlamaların zaman adımı seçilmiştir. Sonuç olarak dört katlı betonarme binanın batı yönünde yıkımı sağlanmıştır. Sonuçlar bölümünde, planlı yıkım projelendirilmesinde gözönüne alınması gereken etkenler belirtilmiştir.
Özet (Çeviri)
SUMMARY CONTROLLED DEMOLITION OF CONCRETE STRUCTURES BY EXPLOSIONS Explosion is a type of extraordinary dynamic load to which structures may be subjected in addition to normal loads. In general, an explosion is a phenomenon resulting from a rapid and sudden release of a large amount of energy. Conventional explosives, such as TNT depend on a rearrangement of their atoms for the energy, whereas nuclear explosions result from the release of energy building protons and neutrons within the atomic nuclei. Explosive materials may be classified according to their physical state : solids, liquids and gases. Solid explosives are primarily high explosives for which the blast effects are best known. The shock or blast wave is generated when the atmosphere surrounding the explosion is forcibly pushed back by the hot gases produced from the explosion source. This wave moves outward from the central part only a fraction of a second after the explosion occurs. The front of the wave, called the shock front, is like a wall of highly compressed air and has an overpressure much greater than that in the region behind. This peak overpressure decreases rapidly as the shock is propagated outward. After a short time the pressure behind the front may drop below the ambient pressure. During such a negative phase, a partial vacuum is created and air is sucked in. Over pressure impulse Ambient pressure I Positive phase, Negative pha se. Fig.1 Blast wave pressure-time curve The shock wave leaves the point of explosion and when it strikes some object of density greater, a reflected wave travels back toward the point of explosion. t- 4- Fig.2 Reflected pressure-time curve XIThe overpressure in the reflected wave is greater than the incident shock pressure. At a point some distance from the explosion centre, the reflected wave will catch up the incident wave, producing a single vertical wave front called a Mach Stem which moves horizontally along the surface of the ground. The juction point is known as the triple point. As the pressure wave advances along the ground, the triple point describes a path. Structures below this path will experience a single shock, whereas objects above this path will be subjected to two shocks - the incident and reflected waves. R = reflected wave. I = incident wave I kegton of regular Region of Mach -reflection reflection Fig. 3 Shock wave reflection phenomena At an arrival time of t after the explosion, the pressure at this location suddenly jumps to a peak value of overpressure above the local ambient pressure, (P0). The pressure then decays to ambient in time (ts), to a partial vacuum of very small amplitude, and eventually returns to P. The quantity Ps is usually termed as the peak side-on pressure or the peak overpressure. The decay of the overpressure is usually described as quasi-exponential in character. The following expression to describe the positive phase is the most commonly used. In terms of a dimensionless wave form parameter a and time t measured from the instant the shock front arrives, the relation is established as, Ps(t) = Ps(1-t/ts)e-a,/,s (1) For a blast wave, the impulse per unit of projected area is obtained by the integration of the above equation. is = I Ps(t) dt (2.a) = Psts[1/a-1/a2(1-e-a)] (2.b) The overpressure-time curves can be represented by triangular equivalents. These equivalent triangles have the same initial peak overpressure. For the equivalent triangles the time t, is selected so that the total impulse of the equivalent triangular curve is equal to that of the actual curve. t = 2 is / Ps (3) Recently, the studies on demolishing the structures by explosions was made. Explosives are used in order to demolish structures in a plan. For this purpose, an experiment on six-storey reinforced apartment was carried on. The building is six- xiistorey rigid box-frame reinforced concrete construction. The concrete strength is found as Fc = 296-358 kgf/cm2. Prior to the actual blasting demolition experiment, test blasts were carried out on columns, stair hall walls, frames and other walls forming the structurel body. 10 specimen locations forming part of the structural body of the apartment building were selected for blasting. The formula for calculating the amount of each charge was as follows. L = CXA (4) A blasting coefficient of C=0.6 kg/m was selected since it was necessary to plan for complete collapse Totally 153.8 kg. explosives, No.3KD and Coblac were used in the experiment. © ® o Fig. 4 Plan of typical floor The blasting plan is summarized as follows. a) The fall direction was selected in southwest direction considering the availability of vacant land there. b) The plan was to remove all walls on the 1F to 3F. All columns and wall columns were left to be completely demolished by the blasting. c) Stair hall columns and wall columns on the 4F were expected to be rigid. It was decided to destroy them completely by blasting. All columns on the 5F were to be severed by blasting in the middle aiming to reduce the rigidity of the 4F, 5F and 6F sections. Columns on the 6F were not blasted. d) The plan was to cut off the bases of the 1F, 3F and 5F columns in line 7 by blasting only to weaken them. e) It was decided to pull down the columns on line 7 from the line 6 side using wire rope to prevent them slipping down the slope to the east at the time of demolition. f) To make collapsing the building toward the long side easier, both ends of all beams parallel to the long side on each floor were to be cut off by blasting. g) Stair halls were considered the most rigid sections, it was decided to blast the panel zones at the intersection of C6 column and the G12 beam on the 2F, 3F and 4F. XIIIh) Since the building is especially extensive in the direction of the long side, it was decided to demolish the whole building into three parts. Another demolishing plan was made on a four-storey reinforced concrete building. The building has 23.7 m. length, 13.5 m. width and 12.6 m. height. An anti-symmetric demolishing plan was established an it was decided to demolish the building towards west. The calculations was made only for the dead loads. First of all, the dead loads of the building were calculated and for the floors gf = 0.450 t/m2 and for the walls gw = 0.662 t/m were taken. In the second step, the plastic moment values for beams and columns were calculated. Both concrete and stell show an extra strength when they were loaded rapidly. This property was undertaken as using the characteristic strength values (fyk and t,) in the calculations. As BS 20 and BÇ III were used in the four-storey reinforced concrete building, the values are: BS20 fck = 195kgf/cm2 BÇIII fyk = 4197.5 kgf/cm2 The calculated plastic moment values are as follows: Beams: Section a-a Mp = 15.11 tm. Section b-b Mp = 12.66 tm. Section c-c Mp = 15.79 tm. Section d-d Mp = 1 5.79 tm. Section e-e Mp = 5.67 tm. Columns M, s 12.90 tm. M2= 8.60 tm. The demolition plan was established in three steps by demolishing of chosen columns and beams in each step by explosions with a delay time of 0.50 sec. First, the static solution of the structure was made under dead loads. In the first step, it was decided to demolish 108,109,114 and 115 no. columns by blasting. For modelling the demolition of these columns, their elasticity modulus values were taken zero in the calculations. For this step, the structural system was solved again and the places which the plastic hinges will occur was obtained by analyzing the static solution. The plastic hinges were found on 511, 512, 710, 711, 712, 521, 522, 720, 721, 722, 1004, 1104, 1204, 1304 and 1007 no. beams. After the first step, displacement of the structure towards west which was the planned direction of the demolition was ocurred. In the second step the sections that the plastic hinges occurred was modelled by putting hinges and loading plastic moment values as an external load to these sections. In this step also it was planned to demolish 610, 620, 810, 820, 911 and 921 no. beams which were parallel to the long side of the building. Then the structural system was solved again. The plastic hinges were found on 202, 302, 402, 203, 303, 403, 220, 320, 420. 221, 421, 107, 207. 409, 110, 113, 415, 116, 307, 407, 310, 313, 413 and 316 no. columns and 511, 512, 513, 711, 712, 713, 811, 812, 520, 521, 522, 523, 721, 722, 723, 821, 822, 1003, 1005, 1105, 1205, xiv1006, 1106, 1107, 1207, 1307, 1008, 1108 and 1208 no. beams, The displacement of the structure towards west increased after the second step. In the third step, the sections that the plastic hinges occurred was modelled. And also it was planned to demolish 110,111,116 and 117 no. columns by blasting in order to demolish the structure completely. Then the structural system was solved again. The plastic hinges were found on 102, 202, 302, 402, 103, 203, 303, 403, 104, 204, 304, 404. 205, 305, 405, 107, 207, 307, 407, 208. 308, 408, 309, 409, 210, 310. 410, 211, 311, 411, 112, 412, 113, 213, 313, 413, 214, 314, 414, 215, 315, 415, 216. 316. 416, 217, 317, 417, 118, 418. 120, 220, 320. 420, 121, 221. 321, 421. 122. 222. 322, 422, 223, 323 and 423 no. columns and 510, 511, 512, 513. 611. 612. 613. 711. 713, 811, 812, 910, 912, 913, 520, 523, 621, 622, 623. 721, 722. 723. 821. 822. 920, 922, 923, 1003, 1103. 1203, 1303, 1004, 1104, 1204, 1304. 1005. 1305. 1006. 1106, 1206, 1306, 1007, 1107, 1207, 1307, 1008, 1108. 1208, 1308. 1009. 1109. 1209. 1309, 1010. 1110. 1210, 1310, 1011, 1111, 1211. 1311. 1012, 1112. 1212. 1312. 1013, 1113, 1213, 1313. 1014, 1114, 1214 and 1314 no. beams At the third step with the new plastic hinges the structural system became mechanism. The demolition was completed in three steps. The static solutions of the structural system were obtained by using SAP90 (Structural Analyzing Programme). In the demolition plan it was decided to use TNT explosive in order to demolish the chosen structural elements. Explosives were settled on 108, 109, 110, 111, 114 and 115 no. first floor columns and 610, 620, 810, 820 no. first floor and 911,921 no. second floor beams. As the demolition was completed in three steps, the delay time for each step was chosen 0.50 sec. The amount of explosive for demolishing the structural elements was chosen by the help of the equation, D = 0.23 W1/3. It was planned to settle 3.5 kg TNT at the ends of each column and 2 kg TNT at the ends and in the middle of each beam. The demolition plan was completed by using 56 kg TNT for columns, 36 kg TNT for beams and totally 92 kg TNT. xv
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