Betonarme binaların kontrollü patlamalarla yıkılması /
Yazar: Ç. YÜCEL ÖKER
Danışman: PROF. DR. ANTONİO L. TRUPİA
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 1998
Konu: İnşaat Mühendisliği = Civil Engineering
Dizin: Betonarme binalar = Reinforced concrete buildings ; Patlama = Explosion ; Yıkım = Demolition

Özet:
Çalışmamızın konusu patlayıcı ile bina yıkımıdır. Patlama asıl olarak ani etkiyen bir darbe yüküdür. Bu nedenle, önce genel olarak darbe yüklemesi tariflenmiş, ardından patlama dalgasının tanımlaması yapılmıştır. Patlama yüklemesinin yapı elemanları üzerindeki etkisinin araştırıldığı bir takım teorik ve deneysel çalışmalardan bahsedilmiştir. En son olarak, esas amacımız olan kontrollü patlamalarla betonarme binaların yıkılması üzerinde bahsedilmiştir. Problemin genel bir tanımlaması yapılmış, bir yıkım projesi hazırlanması için gereken çalışmalardan bahsedilmiştir.

Abstract:
The subject of the thesis is demolition of reinforced concrete structures by using controlled explosions. Explosion load is a very extra ordinary kind of load which occurs on a structure near its normal loads. It is a kind of impulsive load. Before we made any explanation about explosive loading, we discussed a little bit about impulsive loading. Nowadays in the civil engineering environments, lots of studies are made about impulsive loads. Impulsive load may be explained as a shock load which strongly acts in a very short period of time. The explosion loads, wave slam effect and the striking of a vehicle to a structure part may be figured under this subject. The calculation methods used until this time depended mostly on experimental results and the engineer's anticipations. But these methods mostly gave non- economic and untrustable results. But the non-linear act of the material and dynamic character of the load makes it hard to derive any formula for calculating the problem. The searches on the effect of explosion loads has started from n. World War. But the search for the physical process started in 1968, when Weibull examined the peak quasi-static pressure from a TNT explosion in a closed area. The most generally accepted definition of an explosive is expressed in the following terms: A solid or liquid substance or mixture of substances, which on the application of a suitable stimulus to a small portion of the mass, is converted in a very short interval of time into other more stable substances, largely or entirely gaseous, with the development of heat and high pressure. The explosive material derives most of its disrupting force from the rapid conversion of the substance into hot gaseous occupying many times the original volume and thereby exerting high pressure over its surroundings. This produces a shock a wave moving as shown in figure S. 1. As a consequence of gas expansion due to heat and inertial effects, the pressure discontinuity at the front is later on followed by negative(Figure S.2) and then once again positive pressure faces. Although, the searches on this subject started with martial reasons, like building explosive stores and strategical places under military threat, it has become a more widespread subject around the world. It has become a need building explosion safe places for industry and banks. Also demolition using explosives is becoming very popular around the world.There are several methods for demolishing a building a building but most of these depend mostly on conventional ways of using machines for breaking and smashing structure's elements. But the need for lots of man work, expense, and the huge amount of time needed for demolition made the most of these methods non-popular nowadays. Trials to accomplish a more economic and less time taking method lasted with the use of explosives. By applying controlled explosions on a building, the structure can fall and break down to pieces in a very short period of time, with no man work at all. The potential danger of explosives and the damage that the explosion may cause to surroundings, if not controlled properly, made people timid to the method. But especially in America this method is successfully used in many kind of places and problems(Figure S.3, Figure S.4). These successful attempts take the attention of the world and the method is rapidly getting wide spread in all over the world. The aim is to weaken the main structure using explosions and let the building fall with its own weight. The structure may be demolished by exploding its bottom, but it is observed in some cases that, when the building is exploded from the bottomapart of the structure may fall down unfragmentedly, and this causes the demolishing job to be unsuccessful. To prevent this problem, the structure must be weekend also in the upper areas. When starting to make a demolition project of a building, the site of the building must be carefully examined. This way, the decision about the mechanism of the building's collapse can be made. The collapse may be limited around the buildings original borders while the building may also fall on one side to increase the area of collapse. Increasing the area of collapse, will increase the workability over the heap. The amount of explosive used is also very important. Increasing the amount will cause the crushing of building to smaller pieces and increase workability over the crashed heap. But this will also lead to increasing amount of noise, vibration, and distance, and distance and amount of the particles that fling with the effect of explosion. For a successful demolition project, all of these situations must be considered. Also protecting people around the site is a very important aspect. The openings, like doors and windows of the building must be closed with things like mats, wires for stopping the particles to scatter around the building. In our study, we tried to make a demolition project of a six storey reinforced concrete building. The building was 19.2m in height and 20*36m in area. Because of its usage style it had walls only around its periphery. First the structural calculations and drawings of the building was examined. The building was made with the materials of C20 and STlII/STI(stirrups). The failure forces of all critical sections was calculated. We tried to arrange the collapse mechanism from outside to center. To be able to do that, we sequenced the explosions to occur from outwards to center. This would also cause a destructive shearing to fragment the floor slabs to pieces. We used step by step method for finding out the nature of the collapse mechanism. In every step of explosions we tried to figure out the changes that occur in the building. After every step, all of the element forces were checked out and each section that went into failure or plastic hinge occurred were noted. Before the second step of explosions started, every change that occurred on the structure after first step were applied on the structure and the places for locating explosives and further calculations were accomplished after that. This process of calculations were continued until the building went into a collapse mechanism. In our study we sequenced three steps of explosions. At the first step, we exploded only the central four columns at the first and fourth storeys. This would give the structure the first impulse to central collapsing movement. Also we decided on making small scaled explosions in the middle of every floor slab at every storey for reducing the rigidity of the building that resists central movement.In second step we decided to destroy other inner four columns and some beams at the first and fourth storeys. After finishing the calculations of this step it was seen that it was examined that the building was mostly demolished. But for giving a last shot; at the third step, we destroyed the beams on every floors center. In the start we didn't want to make any explosion at the buildings periphery; because that, this way we could control the noise and the particles that fling around with explosions. After we have decided the elements to demolish, we calculated the explosive needed to demolish the section. We used the formula:L = Ca * A where L : Amount of explosive needed(kg) Ca: Coefficient(kg/m2) A : Cross sectional area We prepared the drawings showing the placements of explosives. We think that this study of ours is a simple but important study for it is one the first studies in Turkey about this subject. Lot's of further studies about this subject and reliant ones can be made later. We see it a need for Turkey developing technology on this subject; for this method will save lots of money to our economy.