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In order to facilitate the release of floods from the dams and to prevent their damage or collapse, a structure called a spillway is used. Due to the natural and variable flow of the input to the reservoirs of the dams, there are times when the river inflow exceeds the consumption amount in the downstream agricultural lands. In these cases, excess water is discharged over the crest of the weir and flows towards the spillway, which causes high velocities. This high velocity creates low pressure areas on the spillway concrete surface, which can cause major damage to the spillway or even endanger the integrity of the dam structure. Therefore, the dam spillway must safely dissipate the kinetic energy. One of the types of weirs is the stepped spillway to facilitate the passage of the flow over the dams. One of the most obvious practical features of stepped spillways compared to other spillways is the considerable energy dissipation along the spillway. Care should be taken in designing and selecting the type of spillway to prevent potential erosion and reduce kinetic energy as the water flow passes over the spillway. One possible solution is to use a stepped spillway instead of a smooth spillway. In this study, a numeral model of a stepped spillway with different steps and slopes is used. For this purpose, ANSYS software is used for modeling free surface with application of k-ε turbulence model. In the present study, numerical simulation using the Volume of Fluid (VOF) model was used to investigate the mixing phenomenon of two phases of air and water of the free surface flow. The flow field was continued until the residuals reached 10^-7. Compared to simpler models such as Mixture, which operates solely on the basis of averaging the properties of two phases, the VOF model, is separating the phases and considering the effects of the interface. The VOF model, is capable of more accurate simulation of phenomena such as fluid mixing, turbulent flows, and heat transfer in multiphase flows. A number of hydraulic specifications which are considered in designing the stepped spillways are the pressure on the surface of the steps, velocity distribution and energy dissipation. The results from the numerical models were compared with experimental studies. They showed acceptable agreement with physical simulations. Results show that discharge and spillway slope increment reduces the amount of energy loss. In the spillway with 5 steps, for a discharge of 0.063 m³/s, the amount of energy dissipation at a slope of 26.6 degrees changes from 85 to 82% at a slope of 45 degrees, which shows a decrease of 3%. With the increase in discharge, the flow depth increases and reduces the effect of the roughness of the steps on the upper layers of the flow. Increasing the height of the steps increases the rate of energy dissipation and also increases the occurrence of negative pressures in stepped spillway. In this case, the contact surface between the main flow and the eddy currents increases. With the increase in the height of the steps, the dimensions of the rotating vortices also increase and cause a larger radius of rotation on the steps. The presence of these large rotating vortices separates the flow from the bottom of the steps and reduces the pressure on the surfaces. The number and dimensions of steps can alter the energy dissipation rate. Increase in the number of steps in a spillway with constant height, reduces the energy loss as the result of steps dimensions being shrunk

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Recent damaging earthquakes in Iran and around the world have induced great death and damage providing serious reminders of seismic vulnerability of existing structures. It is more crucial in Iran, where many structures have been built when seismic codes were not effective enough, specially considering the fact that construction is not perfectly consistent with design specifications and drawings Many of existing building, therefore, have inadequate strength when subjected to earthquake. To prevent such damage and tragic event, efficient ways are necessary for retrofitting these buildings. One of useful extensively used methods is passive control. By reducing seismic demand and increasing ductility, these control ways can reduce rate of seismic damage. Seismic resisting structures are expected to maintain adequate stiffness during frequent but moderate excitations on one hand, and to dissipate a large amount of energy under damaging earthquake on the other hand. The conventional framing systems, i.e., concentrically braced frames, and moment frames are not able to satisfy two aforementioned requirements instantaneously. The concentrically braced frames usually possess high stiffness, but poor ductility owing to the buckling of the compression diagonal braces. On the contrary, the steel moment frames can show acceptable ductility and energy dissipation capacity through flexural yielding in beams, while their stiffness is limited. A combination of these two systems can make a balance between requirements concerning stiffness and energy dissipation capacity. One of the most effective mechanisms available for dissipating seismic energy through inelastic deformations of metallic substances is use of shear panels. Use of yielding dampers has been increased recently for their high capability in energy dissipation. Due to recent advances in passive control methods specifically significant improvements in earthquake energy dissipation and prevention of damage in the main parts of the structures, this paper provides a new hysteretic damping system, especially beneficial to retrofitting steel structures having Eccentrically Braced Frames, EBFs. Despite eccentrically braced frames, EBFs, these pieces are not embedded in floor and can be exchanged easily with little cost after earthquakes. The basic role of shear panel system is to absorb a major portion of input seismic energy, thus reducing energy dissipation demand on structural members and minimizing probable structural damage. This research studies the seismic performance of EBFs with double shear panels. Five specimens have been evaluated using nonlinear finite element analysis under cyclic and monotonic loading. The findings present the proper performance of proposed revision for EBFs, the rise in energy dissipation and the elimination of damage to the main parts of structure (column, bracing, main beam) and its concentration in shear panels reducing displacement of horizontal link (main beam) of EBFs. The analytical results showed the shear panel shear distortion capacity of 0.08 - 0.15rad (displacement of horizontal link of 0.5 - 1.25cm). The response modification factor of this system was also obtained in the range of 8.7-9.8.

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Abstract: Recent damaging earthquakes in Iran and around the world have induced great death and damage providing serious reminders of seismic vulnerability of existing structures. It is more crucial in Iran, where many structures have been built when seismic codes were not effective enough, especially considering the fact that construction has not been perfectly consistent with design specifications and drawings. Many of existing building, therefore, have inadequate strength when subjected to earthquake. To prevent such damage and tragic event, efficient ways are necessary for seismic upgrading of these buildings. One of useful extensively used methods is passive control. By reducing seismic demand and increasing ductility, these control ways can reduce rate of seismic damage. One of the most effective mechanisms available for dissipating seismic energy through inelastic deformations of metallic substances is use of shear panels. Use of such yielding dampers has been increased recently for their high capability in energy dissipation. Despite eccentrically braced frames, EBFs, these pieces are not embedded in floor and can be exchanged easily with little cost after earthquakes. The basic role of shear panel system is to absorb a major portion of input seismic energy, thus reducing energy dissipation demand on structural members and minimizing probable structural damage. Due to recent advances in these passive control methods specifically significant improvements in earthquake energy dissipation and prevention of damage in the main parts of the structures, this paper provides a new hysteretic damping system, especially beneficial to retrofitting steel structures having Eccentrically Braced Frames, EBFs. This research studies the seismic performance of EBFs with double shear panels. Five specimens have been evaluated using nonlinear finite element analysis under cyclic and monotonic loading. The findings present the proper performance of proposed revision for EBFs, the rise in energy dissipation and the elimination of damage to the main parts of structure (column, bracing, main beam) and its concentration in shear panels reducing displacement of horizontal link (main beam) of EBFs. The analytical results showed the shear panel shear distortion capacity of 0.08 - 0.15rad (displacement of horizontal link of 0.5 - 1.25cm). The response modification factor of this system was also obtained in the range of 8.7-9.8. Based on the results obtained in this paper, using double SPS in addition to dissipating more than 70% of imposed energy and increasing the structural ductility, can reduce lateral displacements due to decreasing seismic demand. Finally, using shear panel is highly recommended as an effective and efficient way for seismic design of new steel building structure and also for seismic retrofit of existing steel buildings.  

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Hydraulic jumps occur in natural systems like streams and rivers as well as manufactured systems. Samples of the latter occurance are jumps in water distribution and irrigation networks formed downstream of hydraulic structures such as spillways, sluice gates, and drops. These structures are usually designed for a specific tailwater depth. Stilling basins with baffle blocks are frequently used as energy dissipators downstream of hydraulic structures. Baffle blocks are often used to stabilize the jump, decrease its length and increase the energy dissipation. If the flow rates become more than the design discharge, the tail water depth will be greater than the one required for a free jump. These situations are common in low head hydraulic structures including low diversion dam spillways and gates. Under such conditions the hydraulic jump will be submerged.  The performance of the blocks in submerged jump (SJ) condition differs from the free jump (FJ) case. According to some factors such as Froude number, block shape and location and submergence factor, flow regimes on baffle blocks in condition of submerged hydraulic jumps which occurs in stilling basins, are classified into two regimes, the deflected surface jet (DSJ) and reattaching wall jet (RWJ). In this article a numerical study was conducted to investigate flow pattern, vortexes and the magnitude of vorticity in submerged hydraulic jumps with baffle blocks downstream of a sluice gate. The results were compared to ones in same conditions without blocks. 3D RANS simulations have been applied by Fluent software. RSM turbulence model were used which illustrated much precise results in verification. Three numerical models have been created; Submerged wall jet without blocks, submerged hydraulic jumps with baffle blocks in the condition of deflected surface jet flow regime and submerged hydraulic jumps with baffle blocks in the condition of reattaching wall jet flow regime. Flow pattern has been exhibited for each model and results were compared with each other. Vortexes formed in such situations classified into three groups according to axis which they whirl around. It was observed that deflected surface jet regime has more vortexes in comparison to the two other conditions. In addition, by measuring the average magnitude of vorticity in cross-sections it has been concluded that z-vortexes –vortexes which rotate around z axis– much more powerful than x- and y-vortexes as they determine the kind of flow regime. Furthermore, this magnitude is about two times larger in deflected surface regime than two other situations. This fact leads to more turbulence in the flow that makes deflected  surface jet  regime the desirable condition in which baffle blocks perform more efficiently as energy dissipators in comparison to two other investigated models. In order that, from energy vantage point, conditions should be provided in a way to form submerged hydraulic jump as deflected surface jet regime.

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One of the common bracing systems in our country is Y-shaped bracing system. Because of architectural advantages, it attracts more attention in comparison to x shape concentric braced frame (CBF). But, its stiffness is less and it has more potential for out of plane buckling. One of the extensively used methods for improving the seismic behavior of the structural systems is using the passive control systems. By reducing seismic demand and increasing ductility, this control way can reduce the rate of seismic damage. Yielding dampers are one of the elements to achieve this kind of control in the structures. Because of good ability of yielding dampers in earthquake energy dissipation, the use of these dampers is increased through recent decade in passive control of structures. Due to development of passive control methods for earthquake energy dissipation and for preventing the structures from earthquake losses, this paper proposes a new improved dissipating element for Y shape bracing systems which could be used for structural rehabilitation of steel structures. The basis of the proposed element operation is its operation as a fuse element to improve the bracing elements behavior. The operation of the proposed element is in such a way that before formation of a hinge in bracing element, the presented element is yielded and by absorbing appropriate energy, prevents the bracing elements from inappropriate performance. Before inserting the proposed element in the bracing frames, using the ANSYS software, the element performance is studied for different dimensions and appropriate dimensions are determined. The energy absorbing element is inserted into two different positions in the bracing systems of interest. 2D steel frames with three different number of stories (4, 6 and 8 story frames) are modeled in SAP 2000 software, using conventional braced frames and their behavior is compared to braced frames with the proposed energy absorbing element. The frames are analyzed through nonlinear time history analysis, using appropriate time history records from near source and far source locations. The results show the appropriate ductility of the proposed element, the improvement of bracing elements behavior and also, the higher energy dissipation of the new bracing system, which can be shown through comparison of the hysteresis loops of the bracing frames, solely and those with proposed elements. It could be shown that the ductility of the system is affected by the position of the proposed element. Reducing the base shear due to earthquake records and also decreasing the permanent displacement of the structural stories after earthquake occurrence are some of other advantageous of the presented element. Inserting the new proposed elements in bracing system can also reduce the input energy of the system, during the earthquake. In general view, it can be concluded that by appropriate design of the proposed element, the other structural elements behave elastically and the inelastic behavior is happened in the presented elements, which is resulted in improving the seismic structural performance of the new system.The results of this study can be used in seismic design of earthquake resistant structures

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Passive energy dissipation devices have been widely used in structures in the last decades, as effective and relatively low-cost systems to reduce the earthquake damage. Inelastic deformation of ductile metals in metallic dampers is a mechanism which may be used to dissipate seismic energy. The research on yielding metallic dampers was started by the pioneering works of Kelly et al. (1972), which was continuously followed by other researchers. These dampers, if used effectively, can dissipate significant portion of seismic energy through inelastic deformation of ductile metals. Generally, depending on the yielding mechanism, metallic dampers can be divided into four groups of flexural, axial, shear, and torsional. The most wide spread yielding dampers are Added Damping and Stiffness, ADAS, Triangular-ADAS. Yielding shear panels and slit dampers are other types of yielding dampers that are studied more recently. Slit dampers are known as a special type of metallic dampers, in which plates with a number of slits or openings are subjected to in-plane shear deformations. The slits/openings divide the steel plate to a series of links acting in flexure under the global in-plane shear deformation of damper. Based on the concept of slit dampers, researchers have proposed and tested various types of dampers. In addition some attempts have been made to find out the optimum geometry of openings and usually, rhombus-like openings have found to be more suitable than others. Considering the results and observations of previous studies on slit dampers, this paper presents a new yielding metallic damper called comb-teeth damper, CTD, which consists of a series of steel links/teeth acting in parallel and dissipating energy through in-plane flexural yielding deformation. Special attention is paid to the geometric design of links in order to generate uniform stress distribution along their length and to prevent strain localization and premature failure. The design is then checked out through a set of nonlinear finite element analyses and finally, experimental specimens are fabricated and tested under cyclic loads. Experimental studies have confirmed very stable hysteretic behavior of CTDs under cyclic loading with large displacement amplitudes. For example, a specimen was loaded under twenty fully reversed cycles at amplitude of 40 mm and even after these cycles, hysteretic curves were quite stable and thus displacement amplitude was increased to 60 mm. It should be noted that 40 and 60 mm in amplitude respectively correspond to more than 20 and 30 times the yield displacement of outer fiber of links. After numerical and experimental investigation of the behavior of CTD specimens, the behavior of three simple steel frames equipped with such dampers is studied under cyclic loading. In this regard, CTDs are installed between beams and Chevron bracing. The results of experiments show that the dampers can reproduce the satisfactory performance observed in the tests on individual devices and as a result the hysteretic behavior of frames is very stable. Therefore this type of dampers has a potential for application in building frames. The experimental set up and results will be reported in detail in the paper.

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One of the most frequently encountered cases of rapid varied flow is the hydraulic jump. Stilling basins are used to dissipate the excess kinetic energy of flow to ensure the safety of overflow spillway, chutes, sluices, pipe outlets etc. in this study the topic of block in stilling basins is investigation in a general approach and it’s effect on energy dissipation and downstream scouring are analyzed. In the present research, the energy dissipation and scouring phenomenon were studied in different hydraulic and geometric conditions. Moreover, the present paper was focused on the effect of presence of blocks as an effective parameter on energy dissipation on stilling basin performance. To analyze and assessment of formed hydraulic jump in the stilling basins, the experimental data of many recent researches were achieved and compared. It was concluded that presence of blocks has significant effect on energy dissipation from 1% to 34%. It is also shown that with increasing the Fr Number, the secondary depth increases and the using a rough bed causes reducing the secondary depth between 18% to 37% in comparison with smooth one. Moreover, installing a rough bed also reduced the length of hydraulic jump between 27% to 67%. Using block in the stilling basins, reduces the scouring depth from USBR standard recommendation. Finally, it was concluded that using blocks increased the efficiency of the stilling basin performance.

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Abstract: Seismic Behavior of Concentric brace frames has been one of popular topics in earthquake engineering. Relatively low cost and the ease and speed of implementation has led to the widespread use of these braced frames but past earthquakes experiences show inappropriate behavior, inability to dissipate high energy and the lack of ductility. This paper presents a new mechanism by combining the steel angle and slot in brace member to improve the seismic performance and postponing the buckle. Stresses and displacement of structures using nonlinear static and dynamic analysis by finite element software "ABAQUS" are evaluated. At first In order to verify the results and ensure the implementation details and parameters used in the numerical model, results of laboratory test under cyclic loading were compared. Evaluation hysteresis loop obtained from numerical analysis and experimental results show suitable match. then, for nonlinear static analysis, seven diagonal brace model were created and tested. In the first specimen, the normal braces with no particular change, modeled and evaluated. in the second to fourth models, slot were created near the gusset plate with various dimension to reduce the axial load capacity of brace to less than it's buckling load. In the fifth model to evaluate the performance of steel angles in cyclic loading, brace section was perfectly cut and double angle used to connect two parts of brace for transfering axial load. Finally, in the sixth and seventh models, in the hope that achieving suitable seismic behavior, combination of steel angle and reduced brace section were used. Results indicate improved seismic performance and ductility of CBF systems. Concentration of inelastic response in steel angle results in high energy dissipation and prevents from nonlinear behavior in other elements. In addition, comparing the hysteresis loop of proposed model with that of normal braces shows symmetric and stable rational behavior where strength and stiffness degredation is not seen in the displacement up to about 2 cm while the normal brace buckles in about 1 cm. After that, In order to investigate the behavior of the system under seismic loading, dynamic time history analyses using the horizontal component accelerograms of the Imperial Valley, Loma Perieta and Kobe earthquakes were performed. According to the results of the nonlinear static analysis, proposed sample was chosen as a specimen with acceptable behavior and suitable ductility. Therefore, in this section regarding the long time duration on dynamic analysis, its seismic behavior was compared with the normal brace. Comparison of results obtained from three seismic records, demonstrates less input energy and base shear and appropriate seismic behavior of proposed model due to sensible stiffness reduction of proposed brace. It should be noted that due to the appropriate results obtained in numerical analysis, specimen fabrication and experimental work to verify the results in the next stage of research should be on the agenda. Keywords: Slit brace, steel angles, nonlinear static and dynamic analysis, energy dissipation, ductility. Keywords: Slit brace, steel angles, nonlinear static and dynamic analysis, energy dissipation, ductility. Keywords: Slit brace, steel angles, nonlinear static and dynamic analysis, energy dissipation, ductility.

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Energy dissipation downstream of large dams is one of the most important concerns in the design procedure of dams. Flip buckets are employed whenever the velocity of flow at the downstream of the spillway is in excess of typically 20 m/s because of problems with stilling basins in terms of cavitation, abrasion and uplift. One of the most important issues in flip buckets is determining their optimal dimensions in order to increase the energy dissipation and reduce the maximum pressure on the surface of the flip bucket, simultaneously. Nowadays, the increasing computational power of computers to analyze complex problems, development of numerical modeling techniques and artificial intelligence models have caused them popular, in contrast with physical models which are often very time consuming and expensive. Hence, most of the researchers use these methods to analyze the complex engineering problems. In this research, by developing a new simulation-optimization methodology, the optimum dimensions of the flip bucket were determined based on the FLOW-3D model, artificial neural network (ANN) model and Genetic Algorithm (GA) models. The aim of determining the optimum dimensions is to calculate the radius of curvature and also the deflection angle of the flip bucket such that the maximum pressure on the surface of the bucket be minimum and the relative energy dissipation be maximum. Based on this methodology, in the first, the flip bucket of the Jareh dam was simulated for different radii and deflection angles using Flow-3D software. The calibration process was done in the basis of the experimental results which were obtained from the laboratory model. This laboratory model was built in the Water Research Institute of Tehran. Then, an artificial neural network (ANN) as a meta-model was trained using the maximum pressure on the surface of the bucket and the amount of energy dissipation after the impact of trajectory jet with the downstream channel bed. Then it was evaluated by the data that were not used during the training phase. The ability of this meta-model is to predict the values of the maximum pressure on the surface of the flip bucket and the amount of energy dissipation after the impact of trajectory jet with the downstream channel bed for different dimensions of flip bucket. Then by combining this neural network meta-model, with the genetic algorithm (GA) optimization model, the optimum dimensions of the mentioned flip bucket were determined. The optimum dimensions of flip bucket based on the mentioned objectives were found to be equal to the radius of 14 meters (0.28 m at physical model) and angle of 44.5 degrees. The results showed that despite the reduction of dimensions compared to the original size of flip bucket, the rate of energy dissipation has been increased (about 14% for the PMF flow).

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Based on ASTM E1823 standard, fatigue phenomenon is the process of permanent, progressive and localized structural change which occurs to a material point subjected to strains and stresses of variable amplitudes which produce cracks which lead to total failure after a certain number of cycles.
During an earthquake fatigue failure can occur at loads much lower than tensile or yield strengths of material. Therefore material behavior under cyclic loading is an important design criterion.
Fatigue data are obtained from the experiments and are shown in S-N curves which represent stress or strain amplitude versus number of cycles. All fatigue ranges can be included generally in three categories. Ultra Low Cycle Fatigue (ULCF), Low Cycle Fatigue (LCF), and High Cycle Fatigue (HCF). HCF is recognized with low strain amplitude and high frequency, and LCF is a material deterioration which is described as high plastic strain amplitude and low frequency. ULCF involves a few cycles (less than 20) of large plastic strains. ULCF is of great importance for structural and earthquake engineers, because fatigue failure in structural members occurs generally in less than 10 cycles during a seismic event. Fatigue fracture in moment connections, or gusset plates and brace members are examples for ULCF or ductile fracture.
Fatigue life is expressed as the total number of stress cycles required for a fatigue crack to initiate and grow large enough to produce fatigue failure. Currently, two major methods are available for fatigue life prediction of structures. One type is based on material fatigue life curves (e.g., S–N curves or ε–N curves) and a damage accumulation rule. The other is based on fracture mechanics and crack growth analysis.
The Manson–Coffin law is the most widely used procedure to predict material failure under LCF and ULCF. But last researches showed that Manson–Coffin relation overestimates fatigue life in ULCF domain.
Miner’s rule is one of the most widely used cumulative damage models for failures caused by fatigue.
The rainflow method is a method for counting fatigue cycles from a time history. The counting of each load cycle and the relative damage produced must be done with extreme accuracy and care. Rainflow counting has been shown to be most effective. The rainflow method allows the application of Miner's rule in order to assess the fatigue life of a structure.
In this paper low cycle fatigue performance of restrained buckling braced frames with diagonal, V-shaped and chevron configurations are investigated. Last researches and experimental tests results of BRBs usually show very stable hysteresis behavior with an excellent low cycle fatigue life.
In this study For modeling the low cycle fatigue phenomenon, the “fatigue material” model in OpenSees is used. The fatigue material uses a modified rainflow cycle counting algorithm to accumulate damage in a material using Miner’s Rule. Once the Fatigue material model reaches a damage level of 1.0, the force (or stress) of the material becomes zero and the material is destructed completely.
By obtaining the hysteretic loops and also the cumulative damage charts of diagonal, V-shaped and chevron buckling restrained braced frames, the hysteretic behavior and fatigue life of them are evaluated. Buckling restrained braces in three configurations of concentrically braced frames, exhibited stable hysteretic behavior up to failure. Considering area of the hysteretic loops and low cycle fatigue life, V-shaped buckling restrained braced frame showed better low cycle fatigue performance.

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Walls convergence of stilling basins is one of the ways to improve hydraulic jump to increase tailwater depth and energy dissipation at downstream of spillways of high head dams. On the other hand, occurrence of hydraulic jump in converged sections is accompanied with formation of shock waves. Technically, production and development of the mentioned waves are undesirable due to amplification of mixture of water and air and resulting, disturbance outbreak on occurrence of stable hydraulic jump. Many studies have been conducted on the characteristics of hydraulic jump over gradually expanding cross sections, but comparatively few have been carried out on basins with convergent wall. In this research, occurrence of hydraulic jump in stilling basin with convergent wall was studied using experimental model for three different geometry and initial Froude number equal to 3.17 and 4.46. Experiments were conducted in a flume with a length of 6m, width of 1m and depth of 0.7m. Angels of convergence (7.7º and 19.5º) and type of stilling basins walls (straight and curved) were intended as geometric variables. In all experiments, widths of upstream and downstream channels were considered 80 and 40 cm, respectively (contraction ratio=0.5). The flow discharges were measured by an ultrasonic flow-meter having the accuracy of 0.02 lit/s. Values of instantaneous velocity were measured in 10 vertical sections in centerline of the convergent stilling basins using an electromagnetic 2-D velocity meter having the accuracy of 0.5 cm/s. Maximum height of produced shock waves in the contraction sections and conjugate depths of hydraulic jump were measured by a point gauge having the accuracy of 0.1 mm. The measured values of conjugate depths ratio and energy dissipation were compared with the obtained results of analytical equations presented by Sturm (1985) and Montes and Chanson (1998). The average relative errors of calculation of the mentioned parameters were respectively achieved 9.75% and 17.15%. It should be mentioned that the equations tended to underestimate the conjugate depths ratio and energy dissipation values. The velocity and turbulence intensity profiles were demonstrated and analyzed based on the mean values of instantaneous velocity and minor fluctuation of instantaneous velocity. The effects of convergence angle and curvature of basin wall were investigated on changes trend of the profiles. The results showed that changes of the convergence angle has a considerable impact on the conjugate depths ratio, energy dissipation and length of hydraulic jump. As for a constant Froude number, increasing of the convergence angle to approximately 12º was averagely accompanied with decrease of the conjugate depths ratio and hydraulic jump length to the 34.4% and 35.5%, respectively and increment of the energy dissipation to the 33.2%. It should be mentioned that increasing of the convergence angle caused intensification of the shock waves. Moreover, effects of curvature of basin wall were investigated for an equal convergence angle. As regards it had insignificant impact on improvement of hydraulic jump characteristics and difficulty of its implement, so it is not economical. The obtained results of the present research can be very useful for designer engineers.

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In an open channel, A hydraulic jump is the rapid varied flow which results water surface level increment and energy suppression. In most cases, by this phenomenon energy dissipation process is accomplished in downstream of hydraulic structures such as weirs, sluice gates and so on. The hydraulic jump is controlled by utilizing a structure called stilling basin. Building such structure can be very costly. Several approaches, such as bed roughness, chute blocks, baffle blocks and end sill, have been proposed to reduce the construction cost. For the first time, it is recommended to use the suspended anchored spherical energy dissipator blocks. From a practical point of view, this structure is very similar to baffle blocks but due to having less drag coefficient compared to the baffle blocks, they will suffer less force. Therefore, the slab thickness of basin decreases to a certain extent. Furthermore, due to fluctuations, using such dissipators leads to an increase in energy dissipation. These blocks have a relative density lower than water and are anchored by a thin resistant plastic to the floor of stilling basin. To the best of our knowledge, there are no studies on using these structures in the basin and analysis of their influences on the hydraulic jump characteristics. There are several interesting questions about the effect of such structures on the conjugate depth, jump length, and optimization of the design of the stilling basin as well. The main goal of our study is to answer these queries. In this work, 30 experiments were conducted in the range of froud numbers of 5-8 and in the form of four types of arrangement. It should be noted that, five experiments are concerned with testing the designed bed without any blocks. The Experiments were carried out in a flume with glass walls, 8 m length, 35 cm width and 40 cm heights. In order to form the hydraulic jump, the height of the walls were extended up to 80 cm in the beginning part of the flume and a chute with 30 degree angle and the height of 40 cm was set up. Next, in order to modeling such structures the obstacles diameter was set to 4 cm i.e. 1.2 times more than highest initial depth in classical hydraulic jump of present study. The size of the anchor length was chosen in such a way that the blocks do not enter into the roller environment and remain in front of impinging jet stream into the stilling basin, since no energy dissipation will occur if they enter into the roller ambient. The results showed that the arrangements decrease the jump length and conjugate depth respectively, in average to 31% and 21%. Additionally, the energy dissipation using the suspended blocks in average is around 68% that is approximately 11% greater than smooth bed. In all arrangements for experiments, conjugate depth reduction and energy dissipation increment is not impressive compared to each other, but even so the most and lowest effective arrangement respectively, was type 4 and type 3.

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Abstract
Scope and Background: Dissipating high kinetic energy of supercritical flows for the purpose of protecting downstream structures has always been a concern of hydraulic structure engineers. One of the approaches to tackle this problem is the utilization of hydraulic jump phenomena in which a great amount of kinetic energy is dissipated through turbulence which is more pronounce in roller part and conversion to potential energy in term of depth increase at downstream end and turbulence. A hydraulic jump may occur in prismatic or non-prismatic, converged or diverged and horizontal or inclined channels. However, there are oblique shock waves initiating at the start of a contracted channel, interact with each other and sidewalls and may create a complex flow pattern which is detrimental to the channel itself and downstream facilities. The present research aims at studying hydraulic jumps taken place in a converging inclined channel. The main parameters of a hydraulic jump such as its location, initial depth, ratio of conjugate depths, jump length and energy dissipation are studied for various inclination and convergence ratios and inflow conditions.
Methodology: The experiments were conducted in a channel with different bed slopes of 0, 5, 10, and 15 percent, and convergence angles of 3.66 and 5.4 degrees. The end sills of 0.75 to 11 cm high were installed at the end, depending on the bed slope, to fix the jump location in the channel. The entrance was set carefully to produce the least disturbance due to sharp edges and protruding elements appeared in the flow; hence, a symmetric hydraulic jump may be observed all over a cross section. In order to double-check the accuracy of measurements, clips of various hydraulic jump were shot through sidewalls, converted into the images and digitized using Grapher^TM.
Discussion and Conclusion: The length of a hydraulic jump, was mainly a function of bed slope, such that by increasing the slope to 15%, the increase in the jump length was about 37.5% in average. Specifying a unique initial depth in a converging channel was challenging. There were oblique waves originated from the concave corners and coincided at the center line of the channel. In cases where the hydraulic jump occurred before the coincidence of the oblique waves there were three different depths at the start of the jump. In this work, the centerline depth was selected as depth of reference in the development of equations. By enhancing the bed slope, the mean initial depth decreased and the conjugate depth ratio increased. The energy dissipation increased by both the bed slope and convergence ratio. However, the effect of bed slope was more significant such that the average growth of dissipation in a horizontal bed was about 30% compared to a sloping bed. By increase of initial Froude number the difference between energy dissipation in various bed slopes approached to that of a horizontal bed. Using regression models, empirical relationships were developed for the estimation of length, conjugate depths ratio and energy dissipation of a hydraulic jump in an inclined converging channel. 
 

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Nowadays, building structures encounter with challenges such as construction speed and cost, especially in high seismicity zones. To accomplish this, steel structures was developed to accelerate the construction process and other economic issues. According to high strength ductility and energy dissipation, steel structure systems have been used widely in active seismic regions. The idea of application of shear panels has been using from many years ago as systems with high energy dissipation capability in EBFs as link beams and steel shear walls. The purpose of the EBFs design is the yielding of link beam and remaining the adjacent member at elastic region. According to the available criteria in design codes, shear in beams is a force-controlled action that exceeding the specified value as nominal strength is not permissible and the capacity design theory should be considered. Increasing the web thickness is the main effective factor achieving the needed shear strength and leads to the enhancement of plastic flexural capacity. The result of this action is more seismic demands in other structural members to keep in desirable operational level. So the shear plastic hinges is introduced instead of flexural plastic hinges at both ends. At this case because of uniform shear yielding through the web, energy dissipation capability is much better than the flexural yielding which begins from the outer face of the beam located on flanges. The web panels of built-up sections restrained by top and bottom flanges and two-sided transverse stiffeners have the ability to carry further loading beyond the web buckling load. The small lateral web displacements produced by excessive loading are not substantial because of available components to supply more resistance. Using adequate stiff transverse to resist against the out-of-plane deformation resulted from post-buckling; tension field actions are developed in shear panels before reaching the maximum shear strength by forming a truss with tension diagonals and compression verticals fixed by stiffeners.
The concept of shear resisting frames with non-prismatic beams were presented with the scope of reduction in link beam rotation, elimination of architectural limitations, restrictions on the ratio of span free length to beam total depth and high energy  dissipation capacity. Shear yielding and out of plane deformations caused by tension action field mainly control the frame behavior and energy dissipation. The proposed system is made up two strong side columns connected to the link element with weaker section in the middle of the frame as shear fuse with non-prismatic beams. Tendency to use haunched beams makes it feasible to achieve any link length ratio especially less than 1.0. This paper presents the introducing, design and performance of 1-story-shear resisting frames with different link length ratios (ranges from 0.5 to 1.6 with 0.1 variations) and shear-controlled behavior. The goal is achieved by implementing pushover and cyclic analyses numerically with ABAQUS software. But at first a verification analysis is done to validate the modeling procedure and reach a good conformity between numerical and experimental results. The outputs are presented in the form of response modification factor, displacement ductility and overstrength factor for pushover analyses and hysteresis behavior, backbone curve, energy dissipation capability and overstrength factor for cyclic analysis. Also at the end, 3, 5 and 7-story-frames were studied through pushover analysis and values of response modification factor and overstrength factor of the total frames presented. The results indicate desirable behavior of 1-story-shear resisting frames from the point of stiffness and strength degradation with high values of response modification factor equal to 9.18.

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Structural vibration control has become a controversial topic among researchers today.In recent years passive dampers have been proposed as an effective and reliable method against these vibrations. In this paper, an innovative configuration for steel braced frames using energy dissipaters is presented. The proposed bracing system includes two-level slotted bolted connection (SBC) dampers with slipping performance and a horizontal shear panel system (H-SPS) or eccentrically braced frames (EBF) which is called CS+EBF.The proposed model consists of four structural parts, including horizontal shear link beam, beam, bracing and columns, which other structural components were designed based on the shear capacity of horizontal shear link beam. The brace provides the rigidity of the frame and remains elastic until the end of the loading, like columns and beam. The SBC fuse with frictional movement of the end of the brace in the slot hole and the H-SPS fuse with shear yield can dissipate energy at low, medium and severe earthquake levels, respectively, and prevent or delaying the bracing member from buckling. Past experience has shown that dampers designed for an earthquake energy level also start working in low level earthquakes than that level, which has hampered the ability of these dampers to dissipate energy in more severe earthquakes. Therefore, the SBC fuse is considered as an auxiliary fuse in this innovative two-level system to prevent the main fuse from operating in mild earthquakes. Also, the SBC fuse, unlike the yielding fuses after the earthquake, does not need to be replaced and is repaired by applying prestressed load to the connection screws, which distinguishes the proposed two-level system from other similar systems. The samples are modeled with 1/2 scale and solid elements to achieve accurate results.
The proposed configuration and other similar samples, in addition to push over loading, were also subjected to cyclic SAC loading protocol to compare the behavior of the proposed sample and other samples properly. The results obtained in this study indicate that in the push over analysis, in addition to maintaining the strength and stiffness of the proposed sample (CS+EBF), the ductility of this sample compared to other similar single-level systems, SCBF and EBF has increased. In addition based on cyclic loading, it was found that two-level proposed system has more ductility and energy dissipation than similar single- level systems and also shows that with increasing shear thickness of shear panel beam, energy dissipation and final strength of braced frame increases. The energy dissipation of the proposed configuration is 88% and 33% higher than that of SCBF and EBF single-level systems, respectively, and the share of energy dissipation of the first fuse (SBC) and second fuse (H-SPS) is 33% and 30% of the total energy dissipated by the CS+EBF2 braced frame respectively.

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