جستجوی مقالات مرتبط با کلیدواژه « نرم افزار abaqus » در نشریات گروه « عمران »

With the advancement of the construction industry, the use of high-strength steel has gradually increased. High-strength steels can withstand higher stresses compared to conventional steels, yet they exhibit less ductility. Currently, due to their high cost, they are primarily utilized in specialized industries. Connecting two steel pieces requires the use of welding or bolts. Fillet welding is the simplest and most commonly used type of welding. Therefore, investigating this type of weld in high-strength steel is of great importance. Fillet welds can also have different angles in the direction of applied force, which itself affects their strength. In this study, the influence of the welding angle on the axis of the applied force has been examined. First, an experimental model, considering the effect of defects in the weld, was modeled and validated using ABAQUS software. Subsequently, specimens were analyzed at various angles. The maximum strength of the weld and its ductility were investigated. Additionally, the recommended strength of the American steel code for welds at different angles was examined. The results showed a 14% average difference from the code. Unlike mild steels, an increase in the welding axis angle with the direction of the applied force increased the ductility of the fillet weld.

For the first time in January 1991, the issue of studies and construction of urban trains was proposed by the esteemed representatives of the city of Tabriz in the Islamic Consultative Assembly. Due to the increasing growth of intercity travel in Tabriz and the need to use a 2-rail transportation system in order to reduce traffic problems, studies of Tabriz city train lines were conducted and Tabriz city train network including 4 routes, a total of 60km and 63 stations were designed.The analysis of underground structures is very complex due to the interaction with the surrounding environment in a dynamic state. For this reason, less research has been done. One of the first people who investigated the effect of earthquakes on underground structures is Newmark, in 1968 he presented an easy method to calculate the relative strains of underground pipe structures and long tunnels (Bozorgnia et al., 1995). In 1969, Kuesel established a simple method for calculating earthquake forces on linear tunnels, which in most cases is the basic of later works. Douglas and Warshaw in 1971 presented the results of tunnel design analysis under the influence of earthquakes. Lee and Trifunac in 1979 investigated the response of the lined tunnel under the shear wave effect. In 1981, Owen and Scholl's studied three types of deformations, including compressive-tensile, longitudinal bending, and rhomboidal and elliptical deformations as the result of seismic vibrations in underground structures.

Steel slit damper is a replaceable and repairable tool that is made of a standard section with a number of slits in its core. The mechanism of this type of damper is such that before the bracing member buckles, the slit damper yields and the buckling instability of the brace is removed from the frame. In this study, the cyclic performance of the seesaw energy dissipation system with a slit damper with fixed and ellipse cavity in ABAQUS software has been investigated. The fundamental concept of the seesaw system is the quasi-linear motion mechanism, which enables the bracing members to remain in tension during vibration. In The following, the assessing and comparing the stiffness, the final strength and the amount of energy absorption of the samples are conducted. The results showed that by reducing the distance between the cavities of damper, the position of maximum stress occurs in the web plate of damper between slits and close to the sides and part of it near the flange plates. Further increase in the curvature of the holes reduced the amount and yield range of the damper so that the yielding range tended to the boundary of the slit walls. Also, by increasing the thickness by 40%, a similar result was obtained with the increase in the curvature of the holes, so that the entire distance is yielded between the cavities of damper on the sides.

The use of asphalt in paving BRT lines in Tehran, due to heavy axial loads of passing vehicles and heavy braking force caused by these vehicles, has led to various pavement failures such as reflective cracks, grooves, shrinkage, longitudinal and transverse cracks. In this paper, a model of conventional concrete pavements is compared with models of new materials such as fibrous concrete, permeable concrete and fiber permeable concrete using Abaqus and Kenpave software in paving BRT lines in Tehran. Laboratory results have been used to calibrate the modeling parameters. At the end of the article, the effect of repetitive loading on tensile fatigue behavior in concrete models is discussed. To generalize the results, light cargo and A380 aircraft were also used. Compressive, tensile, deformation, and von Mises stress diagrams were obtained by applying these loads to models with a thickness of 5, 10, 15, 20, and 25 cm. The results showed that by controlling the tensile and compressive stresses applied on the surface and also applying one million loading cycles on it, all the mentioned materials can be used in road pavement and fiber concrete in airport pavement.

In this study, RBS connections behavior reinforced by horizontal and vertical stiffeners are assessed under cyclic loading and the effect of stiffeners is studied in order to improve the cyclic behavior of connections. The finite element ABAQUS software has been used to verify and simulate reduced beam section (RBS) connection behavior. Parametric study have been conducted by changing the stiffeners number, material and arrangement in connection area. The finite element analyses results showed that when using a combination of two horizontal and two vertical stiffeners, the initial and ultimate strength of the connection have been increased by 6.2% and 26.1%, respectively, compared to that of the connections without stiffeners. When using horizontal and vertical stiffeners in a rectangular arrangement with a length equals to 75% of the section reduction area length and its height equals to 75% beam height, the initial and ultimate strength of the connection has been increased by 6% and 20%, respectively in comparison the state without stiffeners. By comparing the use of ST37 and ST52 in stiffeners, it has been observed that both used steels have the same effect on the connection strength. Meanwhile, the effect of steel material of stiffeners could be ignored on improving the connection strength.

The present study investigates the influence of the number, material and configuration of bolts on rigid bolted connections under fire. In this study, 6 steel rigid bolted connection specimens with end-plate were modeled as A490 and A300 in ABAQUS software and they are assessed under fire by nonlinear dynamic analysis. By examining the results, the highest stress in the bolt is occurred with material A300. This is due to the lower yield stress of the A300 bolts than to the A490 because the A300 bolts yield at lower stresses and, as they enter the plastic deformations, cause the steel plates to become more involved and the values Increase the stress, especially around the bolt holes. Sample stresses CON.M22 8B A490 and CON.M18 12B A490 T2 are different about 4%. This displacement value for specimens with A300 bolt materials increses to 240 MPa which is equivalent to the yield stress of material A300. The strain with material A490 for CON.M22 8B A490 and CON.M18 12B A490 T2 samples is about 59% and for CON.M18 12B A490 and CON.M22 8B A490 T2 samples is about 67%. The strain with materials A490 for CON.M22 8B A490 and CON.M18 12B A490 T2 samples is about 38% and for CON.M22 8B A490 and CON.M18 12B A490 samples is about 20%. Specimen displacement for bolts with materials A490 whereas this value for specimens with A300 bolts for CON.M22 8B A300 and CON.M18 12B A300 T2 specimens had the highest and lowest vertical displacements, respectively, which is about 25% difference. In the CON.M22 8B, CON.M18 12B and CON.M18 12B T2 samples with different bolt materials, the percentages are 15, 24 and 44%, respectively. The use of materials with lower yield and rupture stresses caused yielding in the lower temperature and reducing the resilance of structure under fire.

Since unreinforced structures have the highest potential for earthquake damage and have multiple failure mechanisms, due to the lack of many uncertainties in the parameters of this type of structures, their vulnerability should be studied with proper knowledge of this and considering the parameters and the most probable modes for its failure. Also, most of the structures that are of historical importance are made of building materials and bricks. These types of structures usually have major weaknesses against earthquakes. Recognition of these weaknesses is a prelude to choosing the appropriate method to strengthen them. In recent decades, researchers have used various methods to enhance the seismic behavior of brick walls. Common methods for this work are coating and reinforcement with plaster and sprayed concrete, which is the most common method of using sprayed concrete. In this study, the micro method is used for finite element modeling in ABAQUS software. In modeling, three methods of reinforcement are used, which include reinforcement with steel sheet, FRP sheet and mortar. The results of this study showed that the sequential arrangement of FRP strips, compared to other methods, had a greater effect on improving the flexibility and the diagonal arrangement of the mentioned strips had a tangible effect on increasing the final strength of masonry walls.

Nowadays, with the spread of terrorist attacks in many parts of the world, the design approach to abnormal loadings, such as a blast load, has also become noted of design regulations. In recent years, the dual moment-resisting frame system with steel plate shear wall has been used in the design of structures as a load-bearing system and has several advantages such as low construction cost, rapid installation, high energy absorption potential, suitable ductility, Increasing stiffness and decreasing displacement have made the steel plate shear wall as a proper system for retrofing existing structures, so it is necessary to investigate the behavior of this system against blast loads. In this study, moment-resisting frame structures with and without steel plate shear wall (3, 6 and 9-story) were designed in 3D by ETABS software based on code guidelines and then two-dimensional side frame was extracted in order to be analyzed under the effect of blast loading in 2 scenario such as in-plane and out-plane frame with finite element ABAQUS software and finally the possibility of occurrence progressive collapse were investigated and compared. The results of the present study showed that steel plate shear wall dual system has a suitable performance in comparison to moment-resisting frame in the scenario "in-plane blast loading". It restricted the progressive collapse potential while in the scenario "out-of-plane blast loading" because of the blast load wave propagation in steel plate shear wall, then the moment frame has a better performance. Also, according to the Robustness Index (RI) comparison, with regarding to the in-plane and out-of-plane blast loadings, the steel plate shear wall and moment-resisting frame structures had the best performance, respectively.

Nowadays, using FRP materials as reinforcing rebars in concrete structures, bridge decks and roads is common to prevent rusting of steel rebars. The purpose of this study was to strengthen the flexural strength of the concrete beams with FRP rebars and also to improve the weak beams that were reinforced with these rebars and reinforced by attaching the CFRP Laminates in the lower part of the beam along its length. For this purpose, two main parameters of ductility and flexural strength of sections reinforced with FRP rebars, designed in 12 models and subjected to nonlinear static analysis (pushover) in ABAQUS software and then the GFRP sample is also subjected to cyclic loading. The results show that to reinforce the beams if these rebars are used in the absence of steel bars, it is better to use the AFRP rebar because it provides flexural strength of beam sections about 8 to 18% more than the sections reinforced with CFRP and GFRP rebars and if the ductility is considered, It is advisable to use GFRP rebar which has about 7-15% more ductility than AFRP and CFRP sections, and if the weak section is strengthened with CFRP Laminates under cyclic loading, the flexural capacity can be more than 2.28 times to the nonlinear static analysis (pushover).

The elastic behavior analysis of post-buckling of the frames is complex. When a frame is exerted force over critical load, it begins large deformations. In this case, the theory of small deformations is not valid for the structure, and it must be used the theory of large deformations. Post-buckling analysis of the elastic structures always requires solving method with a set of nonlinear differential equations based on equilibrium equations. In designing the members under the axial force or the axial force and the bending moment in the structure, in addition to the yielding criterion, the buckling criterion is important too. However, if the length of the member is too much or the member is slender, before yielding, buckling occurs in the member, which requires the member to be checked for possible buckling. In this research, the post-buckling behavior of the lateral unbraced frame is analyzed with the help of Elastica theory. For this purpose, the first step is to analyses a cantilever column by the Maclaurin Series method. By examining the results of the post-buckling behavior of this column with the previous research, the verification of this method has been evaluated. In the following, due to the verification of the method, the large deformations and post-buckling behavior L-shaped frame are investigated. To analyses the frame, it is necessary to solve a nonlinear equation system. The Maclaurin Series method has been used to obtain nonlinear equations. With the help of the equations, the frame deformations diagrams have been plotted. Mathematica software is used to draw charts and solve nonlinear equations. In the following, with the modelling of the frame in Finite Element ABAQUS software, the comparison of the accuracy of the software results with this analysis has been checked and the convergence of the responses has been examined.

Due to the seismic dangers in the buildings, it is necessary that engineers consider newer and more suitable ways to resist against the seismic forces regularly. The Buckling Restrained Brace (BRB) are almost the new systems against the seismic forces that generally have more ductility in comparison with other lateral loading systems. In this study, the building 5 story with eccentric buckling restrained braces are designed by ETABS software and then two dimensional side frame is modelled by ABAQUS software in order to investigate the effect of material and specifications of link beam variations on the cyclic performance of eccentric buckling restrained brace. Therefore, first its link beam was modeled with soft steel ST37, then with high strength steel ST52 and finally with hardening bond and reduced surface area by 20%, 40% and 60% (6 models totally). The results show that the highest resistance is related to the sample whose link beam is with the stiffener. Also, the highest plasticity belongs to the model whose link beam is modeled with ST52.

Reinforcement of weak concrete structures against lateral loads is essential. Rehabilitation of existing structures is one of the important issues of the day in the construction industry in Iran and even in other countries. Due to the fact that many structures are almost impossible to use due to reasons, type of use, the presence of important equipment, the importance of building and many other things, the need for retrofitting is felt more and more. Today, there are many varied methods in rehabilitating structures around the world, which is used in the field of knowledge and technology and the needs of the region. In our country, some methods are used, such as the use of concrete armored and steel armored vehicles, the use of polymer fibers, seismic separators, the addition of concrete and steel shear walls and the addition of braces and so on. Each of the above methods may be suggested for reasons such as structural weakness, time and economic efficiency, user continuity during retrofitting, maintaining architecture, and most importantly, answering technical and computational design. Each of the above methods may be suggested for reasons such as structural weakness, time and economic efficiency, user continuity during retrofitting, maintaining architecture, and most importantly, answering technical and computational design. Among the existing methods, the use of unbreakable steel bracelets is one of the main recommendations. In this study, 6 samples of braided curtain braced frame were made by a bulking resistant brace and analyzed using ABAQUS software.

Today, the use of high strength concrete in large projects around the world has become very common. It is almost impossible to build the world's largest and tallest structures without using high strength concrete technology. On the other hand, due to the wide range of concrete structures in our country, the regulations for the design of concrete structures do not mention the effects of concrete strength on the dynamic performance of the structure; Therefore, the aim of this study is to investigate the seismic performance of concrete structure with common and high strength concrete by using nonlinear dynamic time history analysis, so that the effect of parameters such as roof displacement, base shear, and axial force of the columns is compared. Therefore, at first, 2-storey concrete moment frame structure with intermediate ductility was designed in three-dimensional mode, according to the available regulations, then the real details were modeled in ABAQUS software. In order to perform nonlinear analysis, nonlinear model is used for structural elements and seismic analysis of the system is performed using three near-fault pairs of accelograms. The results show that increasing the strength of the concrete increasing the base shear as well as the stiffness of the stories, and the axial force values of the columns is almost ineffective.

In Iran reinforced concrete are extensively used in construction. using rebar joint in this buildings is an unavoidable issue. mechanical splices is the common joint which used in constructions an the most important disadvantages of this joint is using big amount of rebar. Steel is a valuable material hence the optimum usage of it could be profitable for the next man kind generation an environment. One of the best approaches to use the optimum amount of rebar is to use mechanical splice in spite of overlap method. It has been recommended that to use mechanical splice in ACI 318 and the ninth issue of national building regulations. According to the problems of the operation issue in heavy concrete buildings due to thick rebar. Mechanical splices are the safe joints which could compensate other problems regarding to rebar density. In every concrete building 15% of used rebar will remains as overlap joint in concrete, therefore using mechanical splice could reduce the amount of rebar and it wastes. In this thesis Abaques software had been employed to analyze the reinforced concrete bar. The non-overlapped bars , mechanical splice equipped bars, and overlapped bars had been investigated in this study. To validate this research the problem had been analyzed experimentally by quick wedge method and straight sample.
In conclusion mechanical splice operation under stress is in good agreement with non-overlapped bars and will increase the load endurance as much as 15% in comparison with overlapped rebars.

Pipelines are considered as lifelines, because they are used for transportation of different fluids such as natural gas, oil and water, which the human life depends on their existence. The damages to the pipelines are usually associated with human fatalities, financial losses and also environmental pollution. Earthquake wave propagation and permanent ground displacement (PGD) caused by surface faulting are potentially devastating natural events which threaten buried pipelines. Although small regions within the pipeline network are affected by faulting hazards, the rate of the damage is very high since fault movement imposes large deformation on pipelines. On the contrary, the whole of pipeline network is influenced by the wave propagation hazards, but the damage rates is lower which leads to lower pipe breaks and leaks per unit length of the pipe. On the other hand, buried pipelines due to their long length, have to pass through active faults which their large movements may lead to failure and rupture of the buried pipes. It is, therefore, essential to investigate the behavior of buried pipelines against fault displacements in order to mitigate the losses caused by these natural events and to try to keep them in service under various situations. Over the years, many researchers have attempted to analyze pipeline behavior via numerical, analytical an experimental modeling, but most of these works were designed to assess pipe response to strike-slip faulting and some were implemented to recognize the behavior of pipelines under normal faulting with right deformation angles. In the present study, In order to understand the behavior of the pipelines under reverse fault movements, the effects of different geotechnical and geometric conditions on the response of the pipes is examined. Numerical simulations have been conducted using the software ABAQUS based on finite element method. In most of the previous studies, a simplified beam-spring model was used to simulate the behavior of the pipes, but in this study a 3-D continuum model is employed to simulate the behavior of the buried pipes against reverse fault movements. In order to increase the accuracy of the analysis, it is tried to use the elements that best match with reality of the nature of soil and pipe behavior and the interaction between them. The results of the numerical study confirmed that the compressive strains in pipe caused by reverse faulting are larger than the tensile strains, thus compressive strains are considered as the main cause of the failure of the buried pipes in the reverse fault motions. Investigating the pipes behavior in different soil types demonstrated that the buried pipelines in loose and soft soils experience less amount of strain in comparison with those which are bureid in other types of the soils. This is due to the fact that the displacement of the pipeline in loose and soft soils is easier and there are less soil resistance forces against pipe displacement. The assessment of effect of soil dilatation angle illustrated that in large fault displacements, the amounts of pipe strain decline with the reduction of the dilation angle, while changing the modulus of elasticity of the soil has no impact on the response of the pipes. The results also showed that by reducing the burial depth, the level of strain induced in the buried pipes decreases.

Local buckling of steel plates, buckling of hollow columns and lateral-torsional buckling of I-shaped beams are some of the vulnerabilities of steel members against buckling. In this study, the effect of GFRP plates on improvement of stability behavior of steel plates and sections was evaluated using ABAQUS finite element software. The results indicate that using GFRP plates for strengthening steel plates leads to an enhancement in their buckling capacity, particularly for plates with higher slenderness ratio. Also, strengthening columns with GFRP plates leads to enhancement in their load carrying capacity and for retrofitting of I-shaped beams by increasing critical buckling load can be effective to delay lateral-torsional buckling, specially when the flange and web have a higher width-to-thickness ratio.