جستجوی مقالات مرتبط با کلیدواژه "abaqus software" در نشریات گروه "پدافند غیرعامل"

Due to the emergence of terrorist threats in recent years, in the form of air attacks, sudden explosions of ammunition and suicide bombers around special and strategically important structures such as arched concrete dams that have a very high capacity for storing surface water, the performance and design of this The threatened structures are mandatory and their possible failure can cause a huge flood, which can cause huge financial and human losses downstream. Therefore, the purpose of this research is to identify the nature of the explosion along with investigating the vulnerability of concrete dams. arching and investigating the parameters affecting the non-linear response of the structure by comparing the location change of the dam crest and the amount of compressive and tensile damage for dam-piling and dam-piling-reservoir systems due to explosion. The results of the sensitivity analysis for the linear and non-linear behavior of concrete showed that it is necessary to model the non-linear behavior of concrete in order to investigate the behavior of arched concrete dams against dynamic loads, especially loads of an impact nature such as explosion. In the linear mode, the changes in the amount of the explosive material in the time history of the location change are not noticeable and the permanent location change of the crown is very close to each other for all the explosive loading conditions and finally returns to the final value of the static condition. Also, comparing the outputs of linear and non-linear analysis showed that the difference between the answers from the explosion of 500 kg of TNT at a distance of 8 meters to 1500 kg of TNT at a distance of 2 meters has an increasing trend, so that the difference between the response of the change of location The background values for the linear and non-linear states are 18.7% and 25.2%, respectively, which emphasized the necessity of considering the non-linear behavior of concrete, especially for explosion in the near field. By comparing the maximum displacement responses of the full tank state, it was concluded that the presence of the tank reduces the influence of the reference point position and the amount of explosive charge on the crown response, compared to the empty tank state. Also, the results showed that in the full tank state The extent of pressure vulnerability is greater for the downstream, which indicates the application of hydrodynamic pressure of reservoir water to the downstream elements of the dam, and this happened due to the shape of the arch, but in the case of an empty reservoir, due to the absence of hydrodynamic pressure, the extent of this The damage was less.

 At the present age, the increasing possibility of offensive attacks against residential areas has drawn much attention to the matter of safety and resistance in constructions subjected to blast loads. Given the widespread use of reinforced concrete slabs in many structures, the present study intends to investigate the impact of blast loads on hollow-core slabs. The paper discusses the numerical analysis carried out using the finite element software Abaqus, since experimental research would be costly, time-consuming and limited. The investigation focuses on a hollow-core slab with dissimilar hole diameters dealing with five different amounts of TNT charge mass. The results indicate that with charge mass having increased, the deflection experienced by the samples goes up as well. In terms of structural performance, the effect of pore size on slab deflection is nearly independent of the charge mass, nonetheless it should also be assessed as a variable parameter when making a precise evaluation. Considering the fact that air explosion is the most efficient energy absorbing, practically in all samples the presence of holes would make reduced the slab deflection in buildings undergoing blast loading. Moreover, the study concludes that by comparison with a hollow-core slab, the damage on conventional slab could be more severe.

Among the most important factors that influence the decision making and planning in passive defense such as structural hardening and especially underground structures such as tunnels and subways are situation estimate and their response to dynamic loading (caused by an explosion). In this regard, one of the effective factors influencing the amount and distribution of load blasting on an underground structure, is burial depth of the structure and condition of soil reinforcement. Therefore, considering the depths of the tunnel of interest (9 and 12m from the tunnel) and four layers of reinforcement (the distance of one meter from each other), computer simulations using ABAQUS software and comparing the obtained results was implemented. In fact, in many cases structural design (e.g a section of tunnel structures) the geometry and depth of the tunnel as a certain value to the project designer were considered necessary in order to achieve the specific goals of the project, while there are no restrictions in terms of soil reinforcement. In this mode, the best conditions for soil reinforcement can be selected. Simulation results show that by increasing the depth of the tunnel from the depth of 12 meters downward, the impact of blast wave on the behavior of underground structures will be depreciated and for explosive charge, depth of 12m can be introduced as the safe depth for tunnel construction with the soil characteristics and an explosion equivalent to 1000 kg TNT. Moreover, by increasing the reinforcing layers of geogrid to three layers, the reduction of possible damage to the underground structure is observable.