الفهرس | Only 14 pages are availabe for public view |
Abstract The main objective of this thesis is to study hfferent levels of damage due to close explosion on reinforced concrete panels. One of challenges in close blast loading is that when tests are replicate using equal charge size and standoff distance, significantly different values of impulse positive phase duration, and the response of a structural element are produced. This is because such loading is rather sensitive to my small change in clmge or specimens. This is achieved by studying documented experimental work where reinforced concrete panels were subjected to close explosion, and comparing observed readings with predicted results using numerical solution Implicit and explicit analysis scheme are used to study cracks propagation of remforced concrete panels subjected to blast load. Predicted central deflection and failure patterns xe compared with published experimental work The stress-strain plots in concrete and reinforcement elements were selected as the application of the local failure that lead to structural progressive collapse. For implicit analysis, the effect of considering cracking of concrete ~naterial and nonlineasity is investigated, by compari~ig stress and strain trends for linear and nonlinear models. For explicit analysis, the strain rate effect is studied by studying the response of models with and without strain rate effect, and compxes their results with expelimental readings. A comparison between the results of the analysis using implicit and explicit analysis schemes is presented. The study includes using UFC 3-340-2014 technical manual to predict damage level and central deflection, which is based on simple approaches for the problem. The response of implicit analysis model due to adding strain rate effect to steel and concrete materials is investigated, and pasametric study to provide recommendations for the safe design of the slab using simplified calculations according to UFC 3-340- 2014 manual is conducted. The discussion also includes a parametsic study on two parameters used in the explicit analysis. The first parameter is concerned with the effect of changing fractuse energy for concrete material by changing maximum aggregate size. The second parameter is conceined with the effect of using scalar damage parameter, d equal to one, and ignoring the co~iditiono f maximum principle stsain to initiate cracking of the element The study shows that tlie ovelpressuse blast load on test panels is much higher than the resistance of the reinforced concrete panel. This results in heavy damage for the panel. For this reason, the implicit solution using ANSYS program stops before the time to reach maximum deflection. For explicit analysis using Ls-Dyna program, the solution continues even if early failure occuned for the panel. This is because explicit integration method does not require a factorization of tlie stiffness matsix in the step by step solution. Good agreement is noted between predicted crack patterns of explicit nonlinear cracked model, and observed cracks patterns for field test slabs. The study shows that the response of the panel is affected by damage in concrete material more than nodineaity in the concrete and reinforcement. It was found that stsain rate effect is vital to get good presentation for the response of the panel under blast load. Recommendations for the safe design of reinforced concrete panels under blast load are included in the study. Recommendations are also presented for the implicit and explicit solutio~isin cluding material types and parameters used in material modeling. |