جستجوی مقالات مرتبط با کلیدواژه « Blast Load » در نشریات گروه « عمران »

The performance evaluation of structures, particularly steel structures against blast loads, is of great importance. One important prediction for dealing with destructive lateral forces in structures is the application of structural steel framing systems. In this study, seven samples of lateral load-resisting systems were developed in a five-story steel structure, considering the provisions of Standard 2800. Using ABAQUS and SAP2000 software, numerical analysis was performed on these systems under blast loads. An aerial explosion was considered, with an explosive material quantity of 200 kg in terms of T.N.T, located at a distance of 2 meters from the centerline of the beam-column connection, in a height of 2.8 meters from the ground level. The results showed that in all models, the adjacent column to the explosion source experienced severe deformation, and plastic damage occurred in the connection region. Additionally, the stresses in the beam web and connection plates at the base of the column reached their maximum values. This occurrence was less observed in moment frame models, while special moment frames and intermediate moment frames demonstrated better performance. In various shear wall models, no plastic damage was observed at the base of the adjacent column to the explosion source, and the energy absorption per unit weight of the structure was obtained. Consequently, the special moment frame had the highest energy absorption capacity, and the lowest was associated with the concentric moment frame.

Earthen dams have a significant impact on the lives of surrounding communities, so the need for continuous monitoring during the construction and safe operation of these structures when applying dynamic loads, especially explosive loads due to possible sabotage and firefighting has always been considered. The effects of explosive loading, assuming the conditions affecting the performance of earth dams, can be measured using several parameters, the most important of which are the dimensions of the pit caused by the explosion and the stability coefficient of the slopes of the structure. Therefore, in the present study, according to the researches done in the field of dynamic loading of earth dams, while selecting the model and its characteristics, in order to validate the simulation process and apply dynamic loading, the results of numerical solution with the article A reference is compared that provides acceptable consistency. Then the dynamic loading of the explosion in the form of finite element software is simulated in certain parts of the structure and after analysis, the results show that by increasing the explosive charge and increasing the water level of the dam reservoir and also reducing the density of constituents Of the body; The depth and dimensions of the hole created by the explosion in the crown of the dam will increase, which will also indicate local damage. Finally, to investigate the dynamic stability of the slopes, the results are transferred from finite element software to the slope stability analysis software, and the model under pseudo-analysis Static and dynamic, and finally stability analysis. The results indicate that under an explosive charge of 800 kg , the reliability coefficient of slope stability is higher than the reliability coefficient introduced by the publication 624, which indicates no serious damage and instability of the dam structure

Nowadays terrorist attacks on civilian facilities have increased.Paying attention to the design of construction sites against the impact loads due to the explosion is important. Identifying the nature of explosive loads and their impact on the structure is one of the important issues to be studied. The explosion is one of the complex phenomena including high strain rate which highly affects the structural elements behavior. Regarding the fact that existing steel structures are typically designed based on conventional gravity and seismic loads, it is required that the performance of these structures be investigated under the explosion load. In this study, the evaluation of simple steel frame behavior with different dampers against explosive load and earthquake is investigated. Nonlinear dynamics analysis is performed on models with 3, 5 and 10 floor structures and in accordance with UFC 3-340-02 at two different levels of explosive charge, in the SAP 2000 software. The results show that between XADAS, friction dampers, Viscose in diagonal system, in the seesaw system, U-shaped with flexural and shear performance and proposed pipe dampers, The displacement dampers have the greatest impact in reducing the structure response. From this Friction damper and pipe and U-shaped with flexural function is more effective.

High-performance reinforcement concrete due to its ductility and higher energy absorption has many applications in the field of passive defence than the normal concrete. These high-performance materials can be used in many cases, such as seismic improvement of building members. In some cases the structural capacity is increased, which is called strengthening. Strengthening can be carried out by increasing the toughness and increase of resistance. In this study, the use of Explosion Proof concrete in order to protect the structural components (in this study: Weak-one Slabs). In this paper, four weak-one way slab that were strangled in various zones have been studied. The numerical modelling is proceeding in Abaqus / explicit. For modelling the behaviour of concrete, CDMP method has been used. The results of this study show that the energy absorption in the strengthened slab in the tense region has increased to seven times compare to other zone of strengthening. The use of fiber reinforced concrete has a significant effect on the increase of bearing capacity and the ductility of a one-way slab. In other words, the use of high-performance fiber reinforced concrete as a method for the strengthening of structural elements such as slabs will be effective in improving the behaviour of them, especially in the field of passive defence. Also, the maximum tolerable explosive load in compression, tensile and compression-tensile strengthed zone specimens was 1.3, 0.85 and 1.21 times compare with the reference specimen. The results of this study show that the use of high-performance fiber concrete laminates in all zones of the slab simultaneously, increase stiffness and reduce the deflection of the specimen.

one of the most important structural members that greatly affects the overall performance of the structure is the beam-to-column connection. Undesirable performance and failure of these connections can lead to local failure in the first step, and in the next step,a progressive collapse in the structure and falling. Therefore in this paper, the performance of two prequalified moment connections in the tenth chapter of the national building regulations of Iran against the external blast loads at a distance of 10 meters from a 1-story building in the Abaqus finite element software has been investigated. Thus, we first designed the structure with the seismic criteria, and then we designed the connections manually. Finally, we analyzed the connections in Abaqus finite element software against the blast loading. Results indicate a good response to the BFP connection compared to the WFP welded connection. As well as the percentage of failure of the WFP connection components relative to the percentage failure of the BFP connection components was more than triple. The results of this investigation show that the dominant failure mode is the failure of the joints due to the twisting of the column, consequently the screw connection due to better shapeability,gives a better response under the blast loading.

The increasing risks resulted by blast loads in current broad and thin plates necessitate the studies and evaluation of these challenges. Practical and cost-effective solutions such as plates enforcement with stiffener are suggested due to high displacement of structure as a result of applied loads. Moreover, application issues and the possibility of developing opening in plates and thus their change of behavior are considered important issues, for which solutions are suggested in this study. Functionally graded plates (FGM) with a power distribution in the direction of thickness are suggested as a solution to this challenge. Accordingly, the present study assesses parameters related to plates with opening including kind, percentage and the position of opening, the mass amount of explosive material, and the parameters related to plates with stiffener including type, count, arrangement of stiffeners, boundary condition and also the joint effect of stiffener and opening using Abaqus Software. The results indicate that opening decreases the plate hardness which consequently increases the amount of displacement. Plate displacement constantly reduces as a result of increase in opening percentage and hence decrease in the surface on which load is applied. On the other hand, the rectangle shape of stiffener has a better performance due to higher moment of inertia and easier application compared to other shapes. By studying the joint effects of these factors, it can be suggested that developing opening and application of an appropriate stiffener can significantly reduce the amount of plate displacement compared to other types.

Today, with the increasing damages of explosion, it is of great significance to assess the performance of structures against such damages that established by explosive load. Accidental explosions exert great and intense dynamic forces to surrounding structures. Recently, composite shells have been used in structures to protect them against explosion which is due to its high resistance to volume ratio, flexibility and resistance to shock forces. Thus, it is essential to assess how structures protected by such materials behave against these forces. In this paper, we have used Abaqus software to analyze data pertaining the behavior of composite shells against explosive loads. We assessed the various parameters affecting the behavior of CRFP and E-Glass Epoxy and how they were affected by explosive load. Some of the parameters assessed include loading, curving rate, number of layers and size of interior angle. In practice, it is necessary to include openings in the composite shell, thus it is important to evaluate the effect of these openings on the behavior of the composite shell. The survey showed that use of the opening has fallen down shift. The reason for this phenomenon is reduction of area that effected by explosive load in composite shell

Nowadays explosion in city centers and residential building areas is a dangerous threat to all buildings. Bomb explosion within or nearby a building can cause catastrophic damage to the buildings external and internal structural frames. The analysis and design of structures subjected to blast loads require a detailed understanding of blast phenomenon and the dynamic response of various structural elements subjected to blast loads. Comparison between response and behavior of reinforced concrete frame and shear wall systems under blast loading is rare in literature. In this paper, response of the RC frames subjected to lateral blast loads is investigated using explicit finite element (ABAQUS). This paper also examines the response of RC moment frames subjected to lateral blast loads and compares it with concrete shear wall system. A nonlinear finite element program is used to model 1 to 3 stories RC moment frames and concrete shear walls. In this study, displacement, stress, damage type and strain energy in the models under blast loading are compared. According to the main results, damage pattern of moment frames is concentrated in base columns and beam to column joints. In the shear wall models damage is distributed through beams, columns, joints and shear walls. Also, energy absorption in shear wall system is much more than moment frame.

Terrorist attacks and explosions in the vicinity of buildings and vital areas are happening in different countries repetitively. Most of these incidents lead to global and local failure in the main elements of the buildings and in some cases due to intensity of explosions can occur entire structure collapses. Columns are the key bearing elements in the building, and between all columns, the exterior of them are more vulnerable to terrorist attacks. Usually blast resistant design of structure is carried out by simplifying the models and considering a single column with nonlinear behavior under blast loading. Explosion is a complex phenomenon with high strain rate, which affects strongly on behavior and material property of structural elements. Operation of experimental test on structures under blast load is very expensive, difficult and dangerous. Hence, simulation of experimental models using nonlinear finite element software is very useful. In this paper, to achieve better performance of columns under blast loading, the response of steel columns with different cross-sections has been investigated. In addition, effects of blast wave incidence angle, blast distance and different boundary conditions are considered. For this purpose, wide flange steel column of experimental test has been simulated under axial force and blast load using LS-DYNA software. Numerical model is simulated using shell elements and its result has been validated with the full scale blast experimental data. In the finite element analysis the effects of high strain rate and material nonlinearity are considered. The columns with different cross sections of wide flange, cross-IPE and box sections are simulated under two angles of blast waves extensive, zero and 45 degree. Also, two support conditions of fixed-fixed end and pinned-pinned end have been considered. The results show in the both boundary conditions for blast with zero angle, the dynamic response of column with wide flange section subject to blast load has been less than the other cross sections. Also, the box section has better performance than cross-IPE. In 45 degree blast angle and fixed end boundary conditions, the displacement time history of box column is less than two other sections and it shows better performance respect to other sections. But, under pined end boundary conditions, cross-IPE section has better and stronger behavior respect to wide flange and box sections. In addition, the displacement of wide flange section (section with non-identical strong axes) in 45 degree blast angle has more than zero degree. However, in the columns of box and cross-IPE section under the same explosion situation in 45 degree blast angle, the dynamic response is less than zero degree, because they have two identical strong axes. Then for corner columns of buildings that direction of blast wave propagation may be 45 degree the best section (based on minimum deflection criteria) is column section with two strong axes such as box and cross-IPE, however for peripheral middle column of building that bending moment of explosion may be accrued about strong axis, the wide flange section with only one strong axis is better. Various distances of explosion from column cause different nonlinear behavior, therefore investigation of optimum column cross section under blast loading depends to distance of explosion from the column. Then displacement criteria may be not enough and use of additional criteria such as residual load bearing capacity can be appropriate.

Nowadays, many old buildings are destroyed by explosive material and replaced by new structures. During explosion, some of the concrete structures experience kind of unexpected loads which lead to localized destruction on one or more structural members and then finally the whole structure will be modified under the new distribution loading. This study will examine the behavior of reinforced concrete members when some of its members will be suffered local damage under different loading and will predict the primary performance of structure under these loading conditions. In this regard, the equivalent section method is used for the modeling of reinforced concrete elements under static and dynamic loads. In this research, finite element software “Abaqus will be used. Analysis results show that the method of equivalent section will indicate the behavior of structures with high accuracy and will reduce the analysis time due to declining of members and constraints in the modeling. This modeling approach also can be related to the mechanical failure such as crack growth and behavior of matter in the formation of cracks.