The high ductile of steel moment-resisting frames (SMRFs) during earthquakes has been challenged due to the brittle fractures of their welded (rigid) beam to column connections. Consequently, SMRFs have suffered severe damages and have produced collapse in main structural members (such as beams and columns). During previous years, energy dissipative devices in the connections of SMRFs have been developed by some researchers to resolve the ductility problem in the connection of rigid beam to column in SMRFs. Circular pipe steel damper (CPSD) proposed as a type of steel damper can indicate and mainly dissipate the seismic energy through its inelastic deformation. Among steel dampers such as shear panel damper, the advantage of CPSD is to resiste applied load in all directions. Under cyclic loading, the Circular shape of CPSD can change to elliptical shape which causes an extra energy in its absorption capacity. The previous studies indicated that the stress concentration was high at both ends in the loading direction. The maximum stress was also observed at lower ends in the direction of loading. Henec, finding the best shape of the cross section can enhance the behaviour of pipe steel damper (PSD). In this study, the ellipse PSD (EPSD) (or the ellips of cross section) was proposed for improving the performance of rigid beam to column connections of steel structures. For investigating the performance of the proposed EPSD, the behavior of a rigid connection with the common slit steel damper (SSD) was assessed subjected to cyclic loading in the ABAQUS software. It is noted that the proposed EPSD has the same weight in comparison with that of the common CPSD. The results of the assessment shown that the energy dissipation of the proposed EPSD and CPSD subjected to cyclic load is equal to 11. 11 kJ and 9. 11 kJ, respectively. Thus, the proposed damper in comparison with CPSD can effectively contribute to about 22% of the total dissipated energy. The distribution of stress in the proposed EPSD in comparison with that of CPSD was also uniformly caused in the hight of EPSD. Furthermore, the performance of a rigid beam to column connection equipped with the proposed EPSD and SSD subjected to cyclic loading was compared. The results of the comparison revealed that the EPSD in the rigid connection increased to about 63% of the total dissipated energy. Due to the distribution of stresses in more area of the EPSD, the strength of the proposed damper increased. Finally, the performance of a rigid beam to column connection equipped with the proposed EPSD and the welded connection subjected to cyclic loading was compared. The results of this study demonstrated that the rigid connection equipped with the proposed EPSD colud withstand a large number of cycles of loading until the failure. Therefore, the proposed EPSD can be used instead of welded connection in SMRFs. In the future studies, it is proposed that the best geometry shape of the PSD subjected cyclic loading can be found in the framework of an optimization problem.

In this paper, a new kind of ring damper composed of three rings is introduced and investigated numerically and experimentally. The proposed damper combined three steel ring damper in order to dissipate energy of two different level of predefined excitation such as moderate and severe one. first fuse (outer pipe) and second fuse (inner pipes) can absorb energy in moderate and severe earthquakes respectively. To evaluate the introduced damper, numerical finite element models are developed to clarify the effect of thickness and diameter variation of main fuse. Results of force-displacement curves obtained from cyclic loading confirmed the two level performance of models. Stiffness and fore increase improved the energy dissipation capacity after the predefined displacement gap. Also, damping ratio are calculated for all samples and results showed that equivalent damping ratio have been improved when main fuse was engaged. Two experimental samples have been constructed based on numerical models and examined under cyclic loading. Defined results of experiments showed that samples could tolerate 20 cycles of 10 times of yield displacement amplitude. Good agreement between numerical model and experimental samples results have been achieved.

By studying steel buildings, civil engineers are always looking to design joints that, in addition to increasing the rotational capacity of the joint, prevent the brittle failure of the structure and allow the structure to be repaired after an earthquake. steel dampers are suitable elements to achieve this goal and simple construction and use, has given them a relatively high advantage over other dampers. These dampers also provide the possibility of reconstruction and low cost of the building by preventing the severe destruction of steel beams and columns during an earthquake. In this study, by comparing several samples of these dampers, their energy dissipation, damping and effective stiffness have been investigated by modeling in ABAQUS software. According to the results, SPD and DPD type dampers have better seismic behaviors and with increasing height, the seismic performance of all dampers have improved. Also, by simulating the behavior of dampers in SAP software, two-dimensional frames of 3, 7 and 15 story with and without dampers have been investigated under the acceleration of 5 earthquakes. The frame response does not give the same results at different accelerometers. However, by adding dampers and creating suitable conditions for the steel beam rotation, an increase in frame energy absorption has been observed in all models with dampers.

Usage of yielding dampers, through an effective guidance of damages to some restricted and predefined special areas of the structure. In addition to the energy dissipation of earthquake, leads to the simplicity and cost reduction of the repairs for the damaged structure after an earthquake. In this paper, a new connection detail with pipe dampers is proposed in which entrance energy is dissipated by the plastic behavior of steel material. The suggested dampers are quickly replaceable, which is a great advantage for serviceability of the structure after an earthquake. In this research, behavior of the suggested connection is compared with other moment resisting steel connections, such as conventional welded connections and moment connections with slit dampers. Results show that by using pipe dampers in beam in column connections, development of undesirable inelastic deflections in the main members, such as beams and columns, is prohibited. Moreover, stiffness, strength, and ductility of these connections stay in a suitable range are compared to the conventional moment-resisting connections. Stiffness, energy absorption, and strength of the connections with pipe dampers vary in the ratios of the capacity of the pipe damper to the plastic capacity of steel beam. This is a controllable parameter in the design of the dampers. Investigations on the effect of the capacity of the dampers show that using pipe dampers with capacity ratios more than 70% will cause plastic deflections in the main members, such as beams and columns. Based on these results, in order to take the optimized usage of the beam bending capacity and prevent the development of unsuitable plastic deflections in beams and columns, it seems that suggested pipe dampers should be designed so that their ultimate bending capacity can be about 50% of the beam plastic bending capacity.

Soil type of building site is one the most effective parameters on the buildings seismic behavior. Site effect, which occurs mostly is softer soils fortifies the influence of earthquakes and apply greater seismic forces to the buildings. Therefore, the buildings in soft soils should be designed for greater lateral seismic forces, based on the codes such as Iranian Standard 2800. In the present research, performance of viscous dampers in buildings is investigated in all soil types from very stiff, type I to very soft soil, type IV. The main purpose of this paper is to find where viscous dampers have the most performance regarding different soil types. For this, some building frames having 5, 10 or 15 stories are designed on different soil types. It is assumed that the buildings have steel moment resisting structures. Each building on every soil type is designed twice: with and without viscous dampers, and their seismic behaviors are calculated under some earthquake records and compared. ASCE7-16 is based for designing the buildings having viscous dampers. The assumed buildings were analyzed for earthquake acceleration records of the corresponding soil type, with return period of 475 years, having PGA of 0.35g.. Nonlinear time history analyses of the buildings under 24 far-field records and 10 near-field records show that: regular buildings, without viscous dampers, on softer soils are more vulnerable, and equipping them with viscous dampers is a good method to protect them in earthquakes and decreasing their responses and damages. Viscouse dampers are more effective in buildings on softer soils. In summary, viscous dampers are always effective in decreasing the structural seismic responses and damages, and they are more effective in buildings on soft soils.

Most of the steel moment resisting frames, damage at the beam-to-column connections during seismic loads. Application of passive dampers in order to prevent damages to the main components of structure has been an interesting subject for many researchers recently. In this present study, performance of the metallic yield damper is slit steel damper (SSD) on the steel beam-to-column connection is carried out using finite element model. Thus, first this damper and its connection is simulated. After validation of results, the effect of various dimensional parameters including radius slot, of damper on the performance of damper and its connection was investigated. Then various forms of this damper simulated and their effect on the performance of damper and the steel beam-to-column connection is studied. Moment-rotation, Hysteresis curves and plastic strains for each size of radius slot and different shapes extracted from the analysis were compared. Furthermore base shear force for steel frames with and without slit dampers in term of energy absorption and deformation are compared together. Findings indicated seismic behavior fitted to such dampers. The results indicate that the slit damper shows a proper function in absorbing energy. Recommendation for appropriate size and shape of slit steel dampers proposed.

Double-pipe heat exchangers are commonly used in various industries, including power plants, solar cells, refineries, and automotive. The double-pipe heat exchanger is one of the most used simple exchangers in the industry. In this study, we employ computational fluid dynamics to investigate the flow characteristics of nanofluids within a double-pipe heat exchanger featuring a square inner tube and a Circular outer tube (SC). The simulations are conducted under constant heat flux conditions, exploring laminar and turbulent flow regimes. Numerical results for water flow under forced convection are compared with reference results for validation. The results indicate that as the Reynolds number increases, particularly in turbulent flow regimes, the Nusselt number in nanofluid flow increases more than in water flow. For instance, in the case of aluminum oxide nanofluid flow at a Reynolds number of 500, the Nusselt number demonstrates a nearly 5% enhancement over water flow. In contrast, at a Reynolds number of 20000, this enhancement escalates to approximately 20%. Three types of nanoparticles are considered to investigate the effect of nanoparticle type on heat transfer and pressure drop. The results show that the use of nanoparticles has a slight effect on the friction factor while significantly enhancing heat transfer.

pipe racks or pipe bridges are one of the most important refinery structures which are used to maintain pipes and other equipment at the required levels and are usually made of concrete, steel or a combination of these two. Measures should be taken to reduce the damage of piping system due to separation of pipe-racks, the separate behavior of each of these parts during the earthquake, and also the large force involved in the separation of the pipe supports. dampers are one of the most powerful earthquake engineering tools as a passive control system. Although the use of dampers in pipe-rack structures is unusual, it can be very useful in some cases. In this study, the function of dampers in a four-part pipe-rack under the influence of faults near faults and earthquakes was investigated. Our Findings revealed that when dampers placed in a longitudinal braces, the use of dampers in the pipe-rack has a very good performance and reduces the damage to the structures and piping system after the earthquake. Adding dampers to these structures can dramatically reduce the inter-levels drainage and acceleration of floors, and thus protect the pipes. In this way, these structures can fully maintain their usability during the earthquake and can be exploited immediately after the earthquake, which is very important in refineries.

The present article seek to investigate the function of elliptical steel damper function in steel frames seismic resisting. The elliptical damper is a kind of earthquake energy dissipater in structure which acts based on the steel yielding feature. Thus, this damper in frame lateral displacement mechanism is expected to have a satisfying hysteretic behavior in terms of energy absorption is on acceptable level. To study the EADAS (elliptical added damping and stiffness) elliptical damper function Abaqus software was used in seismic resisting of steel frames. To do the analysis one span- one floor which was modeled with eight kinds of suggested damper was used. The basis of the analysis method is based on the finite element method and a cyclic loading curve was used and the frame will be pushed to the failure of the dampers. The results of the present study indicates that through the addition of this damper with the damage focus in damper the structure elements remain in elastic zone and without any damage bear the lateral load. The damper causes an increase in ductility and the frame energy absorption hysteretic and it can be used for seismic resisting of steel frames.