Publication: Global response of 2D reinforced concrete structures under blast loads and progressive collapse
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Mahad, Mohamed Abdullahi Adan
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Abstract
Patlama, evrendeki terör grupları tarafından yapılan terör saldırılarının artması nedeniyle son yıllarda yapı mühendislerinin ilgisini çekti; Bu tür saldırılara bir örnek, 1993 yılında Dünya Ticaret Merkezi'ne yapılan bombalı saldırıdır. Aşamalı çöküş, bu tür olayları takip eder ve yapıların tamamen çökmesine neden olur. Bu kitapta, 2B betonarme bir yapının patlama ve aşamalı çökme altındaki küresel tepkisi üzerinde durulmuştur. Bu çalışmanın amacı, gerinim oranlarının RC yapılarının genel tepkisi üzerindeki etkisini araştırmak, iki özdeş yapının direnç kapasitesini değerlendirmek ve karşılaştırmak; biri düşük dayanımlı beton (Çerçeve B) ile tasarlanırken, diğeri yükleri patlatmak ve kademeli olarak çökmek için nispeten yüksek dayanımlı beton (Çerçeve A) ile tasarlanmıştır. Farklı gerinim hızları altında ikinci mertebeden itme analizi yapılarak, yapıların tepkisi üzerindeki gerinim hızı etkisi incelenmiş, ardından itme eğrileri karşılaştırılmıştır. Yapıların patlama direnci kapasitesini değerlendirmek için yapılar, her ikisi de yapılardan 10 m uzaklıkta iki yüzey patlaması senaryosuna (100 ve 300 kg) tabi tutuldu, her bir eklemin patlama basıncı-zaman geçmişi UFC_3_340_02'ye göre hesaplandı ve üç yükleme kalıpları karşılaştırılmıştır. İki yapının aşamalı çökme direnci kapasiteleri, GSA yönergelerine göre çeşitli kolon kaldırma konumlarında karşılaştırıldı. Patlama ve aşamalı çökme analizleri, Newmark'ın ortalama yöntemi kullanılarak adım adım entegrasyonla doğrusal olmayan dinamik analizle yapıldı. Analizlerde kütle ve sertlik orantılı Rayleigh sönümü dikkate alınmıştır. Sonuçlardan, gerinim hızının artmasıyla yapısal mukavemetin arttığı gözlemlenmiş, ayrıca patlatma analizinden, olay açıları dikkate alınarak basitleştirilmiş patlama yükü modelleme yöntemlerinin kabul edilebilir doğruluk sağladığı fark edilmiştir. B Çerçevesi, aşamalı çöküşün tüm durumlarında başarısız olurken, iki dahili sütunun çıkarılması durumunda Çerçeve A başarısız oldu.
Explosion gained the interest of structural engineers in the last decades due to the increase of the terrorist attacks done by terrorism groups around the universe; an example of such attacks is the bombing attack at the World Trade Center in 1993. The progressive collapse follows such events and leads the structures to total collapse. In this book, the global response of a 2D reinforced concrete structure under the blast and progressive collapse was focused. The aim of this study is to investigate the effect of the strain-rates on the overall response of RC structures, assess and compare the resistance capacity of two identical structures; one is designed with low strength concrete (Frame B) while the other is designed with relatively high strength concrete (Frame A) to blast loads and progressive collapse. The strain-rate effect on the response of structures is examined by performing second-order pushover analysis under different strain-rates then the pushover curves were compared. To assess the blast resistance capacity of the structures, the structures were subjected to two surface-burst scenarios (100 and 300kg) both at 10m away from the structures, the blast pressure-time history of each joint is calculated as per UFC_3_340_02, and three loading patterns were compared. The progressive collapse resistance capacities of the two structures were compared in various column removal locations as per GSA guidelines. The blast and progressive collapse analyses were done by nonlinear dynamic analysis by step-by-step integration using Newmark's average method. Mass and stiffness proportional Rayleigh damping was taken into account in the analyses. From the results it was observed that the structural strength increases with the increase of the strain-rate, also from the blast analysis, it was noticed that the simplified methods of blast load modeling with considering the incident angles give acceptable accuracy. Frame B failed in all cases of the progressive collapse while Frame A failed in the case of two internal columns removal.
Explosion gained the interest of structural engineers in the last decades due to the increase of the terrorist attacks done by terrorism groups around the universe; an example of such attacks is the bombing attack at the World Trade Center in 1993. The progressive collapse follows such events and leads the structures to total collapse. In this book, the global response of a 2D reinforced concrete structure under the blast and progressive collapse was focused. The aim of this study is to investigate the effect of the strain-rates on the overall response of RC structures, assess and compare the resistance capacity of two identical structures; one is designed with low strength concrete (Frame B) while the other is designed with relatively high strength concrete (Frame A) to blast loads and progressive collapse. The strain-rate effect on the response of structures is examined by performing second-order pushover analysis under different strain-rates then the pushover curves were compared. To assess the blast resistance capacity of the structures, the structures were subjected to two surface-burst scenarios (100 and 300kg) both at 10m away from the structures, the blast pressure-time history of each joint is calculated as per UFC_3_340_02, and three loading patterns were compared. The progressive collapse resistance capacities of the two structures were compared in various column removal locations as per GSA guidelines. The blast and progressive collapse analyses were done by nonlinear dynamic analysis by step-by-step integration using Newmark's average method. Mass and stiffness proportional Rayleigh damping was taken into account in the analyses. From the results it was observed that the structural strength increases with the increase of the strain-rate, also from the blast analysis, it was noticed that the simplified methods of blast load modeling with considering the incident angles give acceptable accuracy. Frame B failed in all cases of the progressive collapse while Frame A failed in the case of two internal columns removal.