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The equilibrium moisture content is an important parameter for several post-harvesting operations for pistachio nuts, such as drying processes and storage. In this re-search the adsorption and desorption equilibrium moisture content were determined for two major varieties of Iranian pistachios at 11 to 85 percent relative humidities and a con-stant temperature of 50°C. A significant hysteresis effect between the adsorption and de-sorption processes was observed statistically. For predicting the adsorption and desorp-tion EMC, the Halsey model was found the most proper equation for adsorption processes for two varieties (Ohadi and Kalehghochi), whereas the Oswin and Smith models were most appropriate for Ohadi and Kalehghochi for desorption processes, respectively, at constant a temperature of 50°C.

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Contact interfaces are known as the main source of energy dissipation in the structural joints. Therefore it is important in structural dynamic analysis to use predictive joint models which are capable to simulate the structural response and energy dissipation with an acceptable accuracy. In this paper an analytical model is proposed for energy dissipation evaluation due to micro slip mechanism in a beam structure with frictional-free boundary condition. The bending response governing equations are derived under harmonic external excitation and are solved in order to detect transition from stick to slip at the contact interface. The resultant hysteresis loops are obtained and parametric study is done for a numerical case study.

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In this article, the influences of different effective parameters on sensitivity of a magnetostrictive force sensor are investigated and then, a high sensitive magnetostrictive force sensor is designed and fabricated. Initially, the operational principles related to magnetostrictive force sensors are presented. Then, conceptual design of the sensor is illustrated and sensors geometry and applied materials are determined. In the next step, measurement of magnetic hysteresis and optimization of the magnetic properties through heat treatment are presented. To this end, magnetic hysteresis curves of not-annealed low carbon iron and annealed low carbon iron under different currents and magnetic hysteresis curve of bulk TERFENOL-D under different preloads and currents are obtained. Then, through numerical simulations using finite element method software, parameters affecting sensor sensitivity were identified and designed. Finally magnetostrictive force sensor is fabricated and its sensitivity and functional specifications are tested under different conditions. The magnetostrictive force sensor sensitivity and linearity error are found as 0.51mV/N and 2.8% FSO respectively, which is a higher value compared to similar magnetostrictive force sensors.

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The Prandtl-Ishlinskii (P-I) model is one of the powerful models which is used in modeling complex hysteretic nonlinear behavior in systems. The initial form of this model, called the Classical Prandtl-Ishlinskii model, cannot describe systems with output saturation and also results have considerable error when there is an asymmetric in hysteresis loops. In order to eliminate these defects, some modifications are applied to the Classical Prandtl-Ishlinskii model and these models are called the generalized or modified Prandtl-Ishlinskii models. This model is usually utilized in modeling complex hysteresis nonlinear behavior in piezoceramic, piezoelectric, magnetostrictive and shape memory alloy actuators, but in this work, the model is used for identification hysteresis behavior of hydraulic proportional relief valve consist of asymmetric hysteresis loops. This model is trained by the experimental data which are obtained of hydraulic proportional relief valve and then the parameters of the model are identified in order to adapt the model response to the real hysteretic behavior. The data consist of the descending reversal curves of major loop. Then the accuracy of the obtained model in predicting nonlinear hysteresis behavior of the valve is validated with some different experimental data. The results show this model has well accurate and good ability in behavior prediction of proportional relief valve.

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This paper briefly reviews Fiber Reinforced Elastomeric Isolators (FREIs) as a relatively new type of elastomeric bearings. In comparison with conventional Steel Reinforced Elastomeric Isolators (SREIs) that are reinforced with steel plates, FREIs utilize fiber fabric layers as the reinforcement material. The fiber reinforcement is employed to prevent the lateral bulging of elastomer layers when the bearing is subjected to vertical compression. Fiber reinforced isolators are categorized in two groups, namely, “bonded-“ and “unbonded-“ FREIs, depending on the boundary conditions at top and bottom surfaces of the bearing. The main objective of this paper is to simulate the lateral load-displacement hysteresis loops of unbonded-FREIs. In an unbonded-FREI, no bonding is provided between the bearing and its top and bottom contact supports. As such, shear forces are transferred via friction at the contact surfaces. When an unbonded-FREI is deformed laterally, portion of its contact surfaces roll off the contact supports, and the bearing exhibits a specific deformation called “rollover deformation”. As a result of rollover deformation, the effective lateral stiffness of the bearing is decreased significantly. This in turn improves the seismic isolation efficiency due to the increased base isolated period of bearing. The ultimate lateral displacement in an unbonded-FREI may achieve when the originally vertical faces of the bearing contact top and bottom supports. Lateral load-displacement response in an unbonded-FREI is characterized with a gradual softening (due to rollover deformation) that is followed by a stiffening behavior at the ultimate stage of lateral bearing displacement. Under a cyclic excitation, the response characteristics of the bearing during the first load-cycle are different than the subsequent cycles of the same load amplitude. This phenomenon that is specific to elastomeric materials is known as Mullins’ effect. In this paper an extended Bouc-Wen model is developed to simulate the lateral load-displacement hysteresis loops of unbonded-FREIs. The model captures the gradual softening and ultimate stiffening behavior in the load-displacement curve of the bearing, and addresses the Mullins’ effect in the simulation of hysteresis loops. The proposed model comprises two simultaneous coupled equations which employ six constant coefficients altogether. To determine these coefficients, the model is fitted to experimentally-evaluated load-displacement hysteresis loops of prototype bearings. The experimental loops are obtained from cyclic shear tests that are conducted on the bearing while it is subjected to constant vertical compression. In order to account for Mullins’ effect, an individual set of coefficients corresponding to unscragged loops (the first cycle of each displacement amplitude) are evaluated. The second set of coefficients is attributed to scragged response (subsequent cycles of each displacement amplitude) of the bearing. To simulate the load-displacement hysteresis loops, the proposed model switches between the first and the second set of coefficients depending on the unscragged or scragged state of the elastomer, respectively. A constraint is imposed on the model to assure its continuity when the model coefficients are alternated. Comparison between analytical and experimental results (shake-table test data) indicates that the proposed model is accurate in dynamic response simulation of the unbonded-FREIs studied in this paper.

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Today, due to ever-increasing demand for fast and precise movements and changes, along with small-scale actuations in many engineering fields, the use and efficiency of smart materials has increased in importance. Magnetic Shape Memory Alloy (MSMA) is one of the latest smart materials having both shape memory and magnetic properties. As a matter of fact, in normal room temperatures, it has magnetic field-induced strains far more than any other smart materials such as magnetostrictive, piezoelectric or electrostrictive materials and its frequency response is greater than thermal shape memory alloy. However, on the downside, asymmetric hysteresis is a property that constrains its widespread applications. Prandtl-Ishlinskii model is one of the powerful phenomenological models for simulating asymmetric, non-linear hysteresis used to simulate smart material behavior. In the present study, MSMA hysteresis behavior simulation has been investigated through a new approach using generalized Prandtl-Ishlinskii model. After identifying the model parameters, the study compares the predicted output with the experimental results. For validation the model, using different data, model accuracy has been checked and prediction error has been compared. The experimental results have approved the capability of the model in predicting the hysteresis behavior. Thanks to invertible and simplicity potential of the generalized Prandtl-Ishlinskii model, the inverse of model can be applied as a feedforward controller for compensating the hysteresis behavior. It should also be noted that all the experimental results have been yielded through using experimental set-up.

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Piezoelectric actuators (PA) are widely used in electromechanical system thank to interesting properties such as: high resolution, fast response, wide bandwidth, mechanical simplicity, high stiffness. Despite these unique desirable properties, they suffer from nonlinear behaviors which adversely affect the positioning accuracy. Among them, hysteresis between applied voltage , actuator position is the most important nonlinearity which can lead to significant error if not compensated. In this study, a sliding mode controller associated with an unknown input observer, which uses the position feedback provided by a selfsensing circuit, is suggested to use in micro positioning applications. The selfsensing technique is based on the linear relation between position , charge, which is measured by an active charge measurement circuit. The advantages of proposed scheme could be summarized as follows. It is a sensorless method which does not need an external position sensor. It does not need any operators to model hysteresis or its inverse. It has improved performance in comparison to traditional controllers like proportional integral (PI) controller. Obtained experimental results demonstrate the effectiveness of proposed method to use in micro-positioning applications.

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The hysteresis nonlinearity of the Magnetic Shape Memory Alloy (MSMA) actuator limits its control applications. To tackle the problems, usually the hysteresis behavior of these materials is models. Prandtl-Ishlinskii (PI) model is more practical in this area, because of its simplicity and having analytical inverse. Two versions of this model, entitled: rate-independent model and rate-dependent model, have been developed. Experimental results show that with increasing input frequency, the shape of hysteresis loops is amplified. In this study, by using experimental test setup the input voltage is applied to the MSMA actuator at the frequencies 0.05- 0.4 Hz and the displacement output captured by proximity position sensor, also the MSMA is modeled by generalized rate-dependent Prandtl-Ishlinskii (GRDPI) model and modified generalized rate-dependent Prandtl-Ishlinskii (MGRDPI) model. The modified version of the model are presented by the authors to enhance the ability of the GRDPI model for describing the asymmetric and saturated hysteresis behavior in MSMAs by hyperbolic tangent function in the model output. For training of the mentioned models, the actuation frequencies 0.05 and 0.2 Hz are selected and the model parameters of each model are also obtained by using genetic algorithm (GA). For validation of the models the hysteresis loop at frequency 0.1, 0.3 and 0.4 Hz is selected. The result shows that, due to using hyperbolic tangent function in the model output, the modified version of the GRDPI model can describe the hysteresis behavior in MSMAs more accurately.

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In this study, the batch equilibrium method was used to conduct metribuzin adsorption/desorption experiments with eight soils from different regions of Iran. The results indicated that the organic carbon (OC) content, clay content, cation exchange capacity (CEC), and pH had a combined effect on the metribuzin adsorption on soil. Under the experimental conditions, the adsorption amount of metribuzin on soils was positively correlated with the content of soil organic carbon. Freundlich adsorption isotherm provided the best fit for all adsorption and desorption data. The values of K_f-ads, Freundlich adsorption capacity, ranged from 0.16 to 2.53 L kg^-1. Soil organic carbon content and pH were the main factors influencing adsorption. Adsorption was positively correlated with OC and negatively correlated with pH. Metribuzin desorption showed that almost all of the adsorbed metribuzin was desorbed in all soils, except soil 1 and 8. However, adsorption was not completely reversible.

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In this study a novel solution method for dynamic analysis of clamped-free shape memory alloy beams is presented. It is assumed that the beam is entirely made of shape memory alloy. Based on Euler-Bernoulli beam theory the governing equations of motion and corresponding boundary conditions are derived by using extended Hamilton principle. In the derived PDEs the transformation strain is behaved as external force that changes with time and position. The Galrkin approach is employed to convert PDEs to ODE system equations of motion. The derived equations of motion are solved by using Newmark integration method. The shape memory alloy constitutive model that presented by Souza is applied for specifying the phase of material all over beam. The transformation strain as internal variable that is coupled with states of equations of motion is identified in every time and every position of beam by using return map algorithm. A parametric study on the control variables has been adopted and the results of parametric study are discussed. The results show that the hysteresis damping is increased by increasing the operating temperature. Moreover the damping of system is faster by increasing the initial displacement in free vibration.

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In this research, an analytical method is presented for predicting the viscoelastic and dynamic behavior of polymer nanocomposite. The analytical model is achieved by coupling the SUC micromechanical model with standard linear solid model. Boltzmann superposition principle is used to develop the constitutive equations. First, the strain associated with a relaxation experiment is considered, and then by using the idea of linearity as embodied in the Boltzmann superposition principle, the resulting stress history is predicted. Eventually, the creep function corresponding to the relaxation modulus is obtained and the hysteresis loop for nanocomposite material is represented. Creep response is sinusoidal in time and a function of stress history. Loss and storage modulus and material behavior in Laplace domain are obtained using standard linear solid model and SUC micromechanical model, respectively. Standard linear solid model is achieved by paralleling the Kelvin model with Maxwell model. The model is validated with experimental results. Effects of different interphase thickness, CNT volume fraction and phase angle on hysteresis loop is studied. Obtained results reveal that increasing the CNT volume fraction and phase angle leads to decreasing and increasing the nanocomposite hysteresis loop area, respectively. Also, Interphase thickness contains considerable effects on the nanocomposite dynamic behavior.

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In this study, numerically investigated effect of magnetic heat sources (residual and hysteresis) that can be useful in hyperthermia and their effects on cancerous tissue. The governing equations of continuty, momentum, concentration, energy and Arrhenius tissue destruction equation in the form of couplings are defined, solved and investigated in the finite-element COMSOL software. For blood flow inside the cancerous capillary, non-newtonian and temperature dependent model is used. The geometric model is simulated in three dimensions, including the capillary and cancerous tissue. Thermophysical properties of blood and tissue are also temperature dependent. Results indicated that the residual heat source plays a major role in increasing the temperature of the blood and tissue and can be ignored the effect of hysteresis heat source. The residual heat source has an inverse relation to the particle size and is ineffective in the particle size above 100 nm but hysteresis heat source is directly related to the size of the nanoparticles, and for particles with a size of 150 nm, it will result in a 1 degree increase in temperature for the tissue. The increase in blood temperature for 25 nm magnetic nanoparticles with the residual heat source can lead to the most destruction in cancerous tissue. Also, the viscosity of blood has an inverse relation with the concentration of magnetic nanoparticles in the capillary wall and blood temperature.

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Abstract:
   As a passive control system, braces have an effective role in creating structural resistance to lateral forces such as earthquakes and winds. One of the ways to make the braces more economical is to use their inelastic capacity. Ordinary braces perform well in tension; however they buckle under pressure and exhibit undesirable behavior. This problem can reduce dissipated energy due to lack of plasticity, which plays an important role in cyclic loading such as earthquakes. For this reason, buckling-restrained brace (BRB) have become increasingly popular in different countries. BRBs include yielding steel core and an outer steel hollow section. Although the yielding steel core has a low compressive capacity, its capacity in pressure can be increased by limiting its buckling due to the outer steel hollow section. So far BRBs introduced as mentioned have a single yielding core, however
In this paper, in order to improve the seismic behavior of BRBs, buckling-restrained brace with three parallel cores with different yield stress have been suggested and introduced. The buckling braces were made in one and three steel core with the same tensile and compressive capacity. These braces were subjected to cyclic tensile and compressive loads in the laboratory under the ATC-24 loading protocol. Hysteresis cyclic performances of each brace were obtained and examined. The experimental results show that: 1) the hysteresis loop of the 3-core brace is thicker and higher than the 1-core brace, 2) indicating that the three core brace has 16.3% and 8.8% higher energy absorption and damping capacity, respectively compared to that of the single core brace. Furthermore, it has better seismic performance.
 
 

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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 connections have been developed by researchers to resolve the ductility problem in rigid beam to column connections of SMRFs. Slit steel damper (SSD) as one of these devices contains a plate or a standard section with a number of slits in its web. The damper can dissipate the seismic input energy with inelastic deformation absorption and also prevent seismic energy transmission to the main structural members (such as beam and column). Due to the uniform strut width of SSD, stress concentration at the end parts of the damper struts is produced and unbalanced distribution of von-Mises stresses along the struts is shown. Furthermore, slit dampers are commonly fractured in the end parts of its struts. The low participation of the middle parts of struts in the energy dissipation is caused. Henec, finding the best shape of slits has been attracted by researchers. In this study, new geometry shape of SSD was proposed for improving rigid beam to column connections of steel structures. For investigating the performance of the proposed damper, the behavior of a rigid connection with the common and proposed SSD was assessed subjected to monotonic and cyclic loads in ABAQUS software. The proposed SSD has the same weight in comparison with that of the common SSD. The results of assessment was shown that in the proposed SSD reducing the width of damper slits in two its ends and increasing its middle parts improved its seismic performance in comparison with that of the common SSD. The proposed damper in comparison with common one subjected to shear load can effectively contribute to about 41% of the total dissipated energy. Furthermore, using the proposed damper in a rigid beam to column connection subjected to cyclic loading can effectively contribute to about 51.8% of the total dissipated energy. The performance of the proposed SSD shows that first, the middle part of strip treat like fuse and the suitable ductility provide. Then, the maximum stresses transfers to the top and bottom of strips. Due to the distribution of stresses in more area, the strength of the proposed damper increases. Therefore, withstanding a large number of loading cycles until the failure in this proposed damper, it can be used instead of welded connection in SMRFs.

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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 connections have been developed by researchers to resolve the ductility problem in rigid beam to column connections of SMRFs. Circular pipe steel damper (CPSD) proposed as a type of steel damper can indicate and dissipate seismic energy mainly through inelastic deformation. Among steel dampers such as shear panel damper, the advantage of CPSD is to resiste applied load in all direction. Under cyclic loading the circular shape of CPSD can change to elliptical shape which causes an extra energy in its absorption capacity. The previous study 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 cross section can enhance the behaviour of pipe steel damper (PSD). In this study, ellipse PSD (EPSD) was proposed for improving 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) SSD was assessed subjected to cyclic load in ABAQUS software. The proposed EPSD has the same weight in comparison with that of the common CPSD. The results of assessment were shown that in 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 in subjected to cyclic loading was compared. The results revealed that EPSD in the rigid connection increased to about 63% of the total dissipated energy. Due to the distribution of stresses in more area, the strength of the proposed damper increases. Finally, the performance of a rigid beam to column connection equipped with the proposed EPSD and the welded connection in subjected to cyclic loading effectively was compared. The results demonstrated that the connection equipped with the proposed EPSD colud withstand a large number of loading cycles until the failure. Therefore, the proposed EPSD can be used instead of welded connection in SMRFs.

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Abstract

Rotational friction dampers are a specific type of friction dampers which have several advantages. Dampers are used to improve the cyclic behavior of structures against forces caused by wind and earthquake. These types of dampers will cause energy dissipation by its rotating and rerotating. However, complete and comprehensive researches have not been performed on the effect of rotational friction dampers and their effect on the bearing capacity of steel frames. In this research, the behavior of concrete-filled steel tube (CFT)  in two cases frame braced with rotational friction dampers and frame braced without rotational friction dampers is investigated. For verification, the results obtained from finite element method software, ABAQUS, were compared with that of experimental studies for test samples used in a building with a height of 300m in Osaka, Japan. The hysteresis curves of the modeled samples are in good agreement with the experimental results.

In order to investigate the performance of steel composite frame (with CFTs) braced with rotational friction dampers towards to steel composite frame (with CFTs) braced without rotational friction dampers  under the effect of three earthquake Far-field records, the structure was modeled, designed and analyzed in ETABS software. The use of bracing with rotational friction dampers has caused a decrease in the displacement of the roof’s center of mass for each record mentioned above which modeled in ETABS software. It decreased by 13 to 49 % for 9 records and increased by 2 to 17 % for 2 records. The use of bracing along with rotational friction damper modeled in ABAQUS software under the effect of each record has caused a decrease in base shear. The extent of these reductions was different for each record mentioned above. In each record modeled in ETABS software, the base shear of the structure has not reduced similarly; however, in some cases, the base shear has increased. It had a decrease of 11 to 37% for 7 records and an increase of 3 to 26% for 4 records.

 Then a Single-storey frame with single-span With the same materials and specifications introduced in ETABS software in ABAQUS software Has been modeled. For lateral loading of columns, the lateral loading protocol based on ATC-24 and the instructions for using dampers in the design and reinforcement of buildings have been used.
 According to Regulation No. 766 of the Program and Budget Organization, the loading cycles introduced in ETABS software with a frequency of 1.15T have been used in the ABAQUS Limited Components Software to move. The use of rotary braces and crankshafts in the ABAQUS limited component software under the influence of each of the discussed records has reduced the displacement of the structure relative to the structure without braces and without rotational friction dampers of the structure mentioned above was exerted under the record effect of the same earthquake in ABAQUS software The use of bracing along with rotational friction damper modeled in ABAQUS software under the effect of each record has caused a decrease in base shear. The amount of energy reduction for records understudy was not equal and varied from 8% to 34.7%. The hysteresis curves of base shear of braced structures with and without dampers are well presented.

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Reduced Beam Section (RBS) connections are extensively used within seismic resistant steel moment frames in order to deal with the risk of brittle fractures in the connections, absorbing seismic energy through yielding and protect columns from damage. In this connection, at specific locations the beams flanges are trimmed back to provide weakened sections, in order to shift the plastic deformations away from beam-column connections and into the beam. Consequently, adequate ductility is provided by the frame to absorb the seismic energy and avoid the risk of brittle fractures occurring. The seismic performance of steel structures has been studied widely by many researchers. In general, the results of these studies indicate the good capability of RBS connections achieving these targets. In a reduced beam section (RBS) moment connection, in the region adjacent to the beam-to-column connection, a part of the beam flanges is trimmed selectively. Yielding and hinge formation are intended to take place primarily in the reduced section of the beam. Currently, in the design of RBS connections, the effect of RBS cutting parameters on the cyclic performance of the beam elements are not taken into account. However, using different RBS geometries for any beam with different sections can have different results in cyclic performance of the connections. In order to evaluate the effects of geometric parameters of RBS connection on the cyclic behavior of these connections, a parametric study is carried out on forty different European I-shaped steel cross-section specimens. These specimens are analyzed using ABAQUS finite element software under cyclic loading and the moment-rotation hysteresis curve was extracted for each of the specimens. In order to validate the FE model, a full-scale beam–column sub-assemblies were modelled in the general finite element (FE) software ABAQUS. An ideal curve was extracted from each of the hysteresis curves and using the curves, five parameters including Yield Moment (My), Peak Moment (Mc), Ultimate Rotation (θu), Ductility (μ) and Energy Dissipated Capacity (EDC) were extracted as the key design parameters for each sample. variation of the above-mentioned seismic design parameters in respect to the changes of RBS dimensions are analyzed. The results clearly illustrate that geometric features c do have most effect on the moment parameters. the parameters a and b have very little influence on moments which can be considered negligible, whereas these parameters have a small effect on the ultimate rotation, ductility and energy dissipated capacity. Increasing the value of c between its lower and upper limits, reduces the My more than 20% and Mc more than 17%. The effect of the distance of the cut area from the column face (a) and the length of the cut area (b) on the moment is close to zero and can be ignored. The effect of a and b on the ultimate rotation, ductility and energy dissipated capacity is less than five percent. However, the parameter c has significant influence over all the five seismic design parameters considered. Investigating the graphs of the variation of the key seismic design parameters respect to the changes of RBS dimensions shows that there is not enough correlation between the RBS parameters and the key seismic design parameters to propose a single equation between the key seismic design parameters and RBS parameters. Investigating the relationship between RBS dimensions, moment of inertia of RBS and full section characteristics showed that a relationship can be established between these parameters and the key seismic design parameters. At the end, the results of the investigation and relationships for calculating the key seismic design parameters were presented. This relationship was presented as a single equation, which includes the effect of all the above parameters. Using the obtained equation, the value of each of the key seismic design parameters can be calculated based on the dimensions and geometric characteristics of the section and the beam cutting dimensions.