International Journal of Scientific & Engineering Research, Volume 8, Issue 3, March-2017 976 ISSN 2229-5518 IJSER © 2017 http://www.ijser.org Mitigation of progressive collapse of buildings resulting from accidental explosions Atef Eraky 1 , Tharwat A. Sakr 1 , and Riham Khalifa 2 Abstract— Accidental explosions are frequently encountered nowadays due to several reasons as gas vehicles, military works and terrorist attacks. This paper introduces a study of the effects of accidental explosions in front of façade columns of RC buildings and their mitigation. Nonlinear finite ele- ment analysis is carried out on space frame due to the rapid release of energy in the form of light, heat, sound, and a shock wave resulting from explo- sion. The spherical free-air bursts of TNT detonation and expansion of the spherical charges are developed using a one dimensional Euler wedge through the ANSYS AUTODYN software. Different cases of charge weights (500 and 1000 kg TNT) and stand-off distances (3, 5 and 10 m) are used in the study. Overpressure, displacements, stresses, and damage index are the common response parameters investigated. Interior shear walls are ap- plied as common mitigation techniques and their effects on the building damage are investigated. Index Terms— Explosive load- Reinforced concrete frames - Numerical analysis – AUTODYN - Mitigation. ——————————  —————————— 1 INTRODUCTION Progressive collapse as major field of study has been attracting researchers and code writers during recent decades. Progres- sive collapse is defined as the failure of one or a group of key structure load-carrying elements that gives rise to a more widespread failure of the surrounding structural elements and partial or complete structure collapse or the spread of an ini- tial local failure from member to member resulting in the col- lapse of an entire structure or a disproportionately large part of it [2]. Loss of lives and economic losses encountered in pre- vious events and accidents verified the importance of studying progressive collapse. The famous Ronan Point apartment building partial collapse, the disproportionate collapse of the Alfred P.Murrah Federal Building [3], the damage of Al- Khobar building [4], and the catastrophic collapse of the twin World Trade Center towers [5], all except the first caused by terrorist attacks. Regulations and standards were developed to consider the probability of accidental or terrorist explosions into account in designing new buildings or evaluating existing buildings to avoid progressive collapse [6]. Research related to progressive collapse includes too many branches as exprimental investigations, loss of support analy- sis and the direct effect of explosions in addition to mitigation techniques. Luccioni, et al. [7] tested concrete slabs under ex- plosive loads and concerned with the behavior using a non- linear dynamic analysis. A novel simplified framework for the progressive collapse assessment of multi-story buildings, con- sidering the sudden column loss as a design scenario was also investigated [8]. A case study was proposed to learn the pro- gressive collapse process of a typical steel-framed composite building. It was concluded that steel-framed composite build- ings with typical structural configurations could be prone to progressive collapse initiated by local failure of a vertical sup- porting member. ———————————————— • Atef Eraky: Prof. of Structural Engineering, Zagazig University – Faculty of Engineering, Egypt. • Tharwat Sakr: Prof. of Structural Engineering, Zagazig University – Faculty of Engineering, Egypt. • Riham Khalifa: Master Student, Egypt. E-mail: e_reham2009@yahoo.com A large number of applications using the finite elements were also developed for the detailed 3D model structure, and the main modelling parameters affecting the numerical results were estimated [8]. ANSYS AUTODYN is used to calculate TNT equivalencies for three different explosives at varying distances from the explosive charge, using both peak pressure and impulse methods. The TNT equivalency curves were dif- ferent depending on whether the equivalency was based on peak pressure or impulse. When TNT equivalencies are used, an understanding of how they are determined and when they are valid is essential for engineers designing against blast loads [9]. Experimental results about the behavior of steel fiber rein- forced concrete panels subjected to blast loads were also car- ried out [10]. Nonlinear static and nonlinear dynamic analyses to estimate the progressive collapse resistance of a building subjected to column failure are carried out by Tsai and Lin [11]. Mohamed [12] proposed a new mitigation scheme to res- ist the progressive collapse of reinforced concrete buildings that resulted from potential column failure by installing steel cables parallel to the columns either externally connected the ends of the beams for retrofitting existing buildings or em- bedded in the columns for upgrading new buildings. Also, the proposed scheme included placing a hat braced steel frame on the top of the buildings by which the vertical cables are hanged and supported. When a column failure occurs, the vertical cables will transfer the floor loads upward to the hat braced frame which in turn redistributes these transferred loads to the adjacent columns. Kwasniewski [13] carried out the progressive collapse analysis of an existing eight-story steel framed structure built for fire tests using nonlinear dy- namic finite element simulations according to the GSA guide- lines. Adding fibers to reinforced concrete enhanced the dura- bility and ductility of concrete. For fiber-reinforced concrete, fiber types, and properties of fiber length, and concrete strength were discussed. Adding steel fibers to concrete had been shown to enhance the concrete’s post-crack behavior IJSER