mehdi vajdian

In steel structures, joints play an important role in the behavior of the structure. In this paper, using numerical modeling with Abacus finite element software, several different models of connection to steel columns, modeling and placement cases have been taken. This paper investigates the effect of beam-to-column connection with two types of t-bar and corner joints. Therefore, 20 models with different conditions of different thickness and different types of hardeners, as well as 6 models with columns have been studied. Abacus finite element software has been used for modeling. All models are modeled in this software. Used to load cyclic loads.The results show that the model with t-bar hardener has a higher and has 12 to 28% higher bending capacity in the joint than the corner hardener. With increasing the thickness of the corner or spray, the connection of the beam to the column has increased to about 12 to 25% of the capacity, in the thickness of 18 mm, the anchor capacity has increased by 12% and in the thickness of 20 mm, it has increased by 25%. Is. The model of columns with concrete is about 15 to 25% different from the similar model without concrete, and the model of columns with concrete has more bearing capacity.

In previous earthquakes, many steel frames suffered damage to their ordinary rigid moment beam-to-column connections. As a result, the use of multi-level control systems in structures has gained attention from engineers in recent years. The main idea in this system is to combine two separate control systems with different stiffness and strength, thus creating dual seismic behaviors. In this study, a two-level friction-yielding damper passive control system is presented for beam-to-column connections, and its cyclic behavior is evaluated using nonlinear static analysis with the finite element method using ABAQUS software. The evaluation results demonstrate that the performance of the samples improves with an optimal ratio of length to thickness. This improvement is reflected in increased stability and area of the hysteresis curves, ultimately leading to higher energy absorption. Additionally, the hysteresis curves indicate a ductile behavior for the proposed damper in the moment connection. Moreover, the obtained hysteresis curves show that the system reliably dissipates energy at different earthquake levels, satisfying the seismic criteria for special moment resistant connections based on the AISC code. The proposed damper serves as an energy dissipating device, effectively dissipating energy at different levels of earthquakes by facilitating slip and yielding, thereby controlling the seismic response of the structure.

The moment frame system is used as a lateral load resisting system against seismic loads. So far, a large body of research has been conducted on steel connections and various types of connections including Reduced Beam Section (RBS) and Drilled Flange Connection (DFC). Using RBS results in the formation of inelastic deformation in a part of the beam far from the column flange. They have studied the seismic performance of the recently developed DFC as a simple and efficient alternative to mostly used conventional RBS. In this research, the beam flange is drilled in different patterns in terms of the hole diameter. After simulating the models in Abaqus, the moment-rotation curves are extracted and analyzed numerically. Having obtained the results of the current research regarding the moment connection where beam flanges are drilled, it is evident that drilling holes in the beam flange with a clock pattern can better satisfy the flexibility expectations. Moreover, this pattern has the higher capability for plastic hinge transfer from the column face compared to the direct pattern. Additionally, this pattern can reduce the bending stress in the penetration weld of the direct beam to column connection. Thus, the clock pattern of beam flange holes performs better than the straight one.

The destruction of concrete depends on the formation of cracks and cracks in the cracks. As the load increases, the cracks are connected together, forming the cracks. In order to overcome this problem as well as the creation of homogeneous conditions, in the last few decades, a series of thin strands used in all the volume of concrete are used, which are called fibers. Fibers concrete is actually a composite that increases the tensile strength by applying the reinforcing fibers inside the concrete mixture. This composite combination has the proper integration and continuity and the possibility of using concrete as a possible material to produce wiggly - resistant surfaces. Fibers concrete is also highly capable of absorbing high energy and is not easily break down under the impact of impact loads. The historical witness of this technology is the great use of building buildings. As a matter of fact, fibers concrete is the advanced form of this technology, which is replaced by natural and synthetic fibres, replacement of straw, and cement replacement in the thatch. The fibers used in this study is of the type of polyolefin fiber and polyolefine. In this research, the reason for the necessity of using fibers, construction method, mechanical propeties and applications of fiber concrete and obtaining conversion coefficients of standard cubic samples of fiber concrete to standard cylindrical sample of fiber concrete according to the results of applications and research has been discussed.

The use of fiber concrete can have a significant change in the quantity and quality of running structures or future plans of the country. Fiber concrete is actually a composite that increases the tensile strength by applying the reinforcing fiber inside the concrete mixture and is not easily break down under the impact of impact loads. This composite combination has the proper integration and continuity and the possibility of using concrete as a possible material to produce wiggly-resistant surfaces. The use of macrosynthetic fibers increased the physical and chemical properties of concrete and reduced shrinkage of fresh and hardened concrete. Macrosynthetic fiber can be a suitable replacement for metal fiber and thermal rebars, so the use of this type of fiber has spread in recent years. Fiber concrete is currently widely used in various applications such as highways, foundations, military industries, protection walls, and other cases. In this research, the reason for the necessity of using kortta fiber, construction method, mechanical properties of fiber concrete samples according to the results of applications and research has been discussed.