تحليل و بررسي بار ناشي از انفجار سطحي روي سازه زيرزميني

پديده انفجار از نوع مسائل با نرخ كرنش بالا است كه براي حل آن نياز به تحليل ديناميكي هست. همچنين با توجه به اندركنش بين سازههاي زيرزميني و خاك تحليل اين سازهها تحت اثر هر نوع بار از نوع تحليل غيرخطي است. بهاينترتيب تحليل سازههاي زيرزميني تحت اثر انفجار از نوع م سائل با نرخ كرنش بالا ا ست كه براي حل آن نياز به تحليل ديناميكي غيرخطي ميبا شد. دو روش حل ضمني و صريح براي تحليل ديناميكي وجود دارد كه با توجه به شرايط مسائل انفجار تحليل آنها بهصورت حل انتگرالي صريح است. روشهاي شبيهسازي عددي به عنوان يك روش نوين در محاسبه بارهاي ديناميكي غيرخطي كاربرد وسيعي يافتهاند. بر اساس نتايج پژوهشگران از ميان نرمافزارهاي صريح موجود نرمافزار اتوداين به دليل قدرت زياد در حل مسائل با نرخ كرنش بسيار بالا نتايج مناسبي از شبيهسازي و تحليل مسائل انفجار بهدست ميدهد. از طرفي بارگذاري انفجاري سازههاي زيرزميني غالباً بر اساس رابطههاي حاصل از پژوهشهاي نظري و تجربي انجام ميشود. در اين پژوهش از روش شبيهسازي عددي براي تحليل و شبيهسازي اثر انفجار سطحي روي سازه زيرزميني استفاده شده است. همچنين كليه مراحل انجام شده است. به منظور تحليل چگونگي بارگذاري، پاسخ سازه زيرزميني در اعماق متفاوت AUTODYN شبيهسازي با استفاده از هيدروكد بررسي شده و نتايج عددي با روابط ارائه شده در دستورالعمل ارتش آمريكا و نيز منابع معتبر علمي مقايسه شده است. در نهايت پيشنهاداتي در راستاي بهبود بارگذاري سازههاي مذكور در طراحيها ارائه شده است.

Most of underground structures are designed and built to withstand the effects of precision penetrating weapons and heavy bombs in the soil. Usually the depth of the structures is high and there is no possibility of missiles to the main structure. Accordingly, the design of these structures is performed for blast loads. The explosion phenomenon is a type of high strain rate problem that requires dynamic analysis to solve. Also,due to the interaction between underground structures and soil, the analysis of these structures is affected by any type of nonlinear analysis. Thus, the analysis of underground structures in simulations affected by the explosion is a high strain rate problem that requires nonlinear dynamic analysis. There are two implicit and explicit solutions to dynamic analysis that, given the explosion problems, their analysis is explicitly integral. The loading of underground structures is often based on the relationships obtained from theoretical and experimental research. Currently, the most important reference for explosive loading in the field of underground structures is the US code (TM5-855-1) provided by the US army. The numerical simulation methods have recently been widely used as a novel method in the calculation of nonlinear dynamic loads. According to the researchers, among the explicit software available in AUTODYN software, due to its ability to solve very high strain rate problems, it yields good results from simulation and explosion problem analysis. On the other hand, the explosive loading of underground structures is often based on theoretical and empirical research. In this study, a numerical simulation method was used to analyze and simulate the effect of the surface explosion on the underground structure. Also, all the simulation steps were performed using AUTODYN hydrocode. In order to analyze the loading and response of underground structures, the effect of the explosive charge weight and the depth of burial of the structure has been studied and the numerical results have been compared with the relationships presented in reliable US scientific and guidance sources. Finally, suggestions are made to improve the loading of these structures. Also, considering the results of the load on the roof of the structure, it was observed that the values of the US code are conservative compared to the other two methods. Therefore, it is recommended not to apply 1.5 incremental coeficient load to the structure in accordance with this instruction. The numerical simulation results including a comparison of maximum pressure and the velocity values with the values provided in the by code (TM5-855-1) showed that the predicted values for the maximum pressure values larger than of instructions America's Army. The reason for this is that the code assumes that the investigations take place in the full explosion range (mating coefficient f = 1), while in the numerical model under consideration, the explosion is formed at the joint surface of air and soil. Hence the coupling coefficient is equal to (f = 0.4). In other words, the depth of the explosive charge is almost zero and there is little difference between the results.