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This paper aims to carry out sensitivity analyses to study how the effect of each design variable on the performance of self-centering buckling restrained brace (SC-BRB) and the corresponding buckling restrained brace (BRB) without shape memory alloy (SMA) rods. Furthermore, the reliability analyses of BRB and SC-BRB are performed in this study. Considering the high computational cost of the simulation methods, three Meta-models including the Kriging, radial basis function (RBF), and polynomial response surface (PRSM) are utilized to construct the surrogate models. For this aim, the nonlinear dynamic analyses are conducted on both BRB and SC-BRB by using OpenSees software. The results showed that the SMA area, SMA length ratio, and BRB core area have the most effect on the failure probability of SC-BRB. It is concluded that Kriging-based Monte Carlo Simulation (MCS) gives the best performance to estimate the limit state function (LSF) of BRB and SC-BRB in the reliability analysis procedures. Considering the effects of changing the maximum cyclic loading on the failure probability computation and comparison of the failure probability for different LSFs, it is also found that the reliability indices of SC-BRB were always higher than the corresponding reliability indices determined for BRB which confirms the performance superiority of SC-BRB than BRB.

In this study, coarse aggregates extracted from waste concrete were used as recycled coarse aggregates in a concrete mixture. Such durability properties of concrete samples as water absorpt...

This paper presents an experimental study on the durability of both sound and cracked reinforced concrete (RC) beam specimens. Using nano-silica (NS) can improve the durability properties of reinforced concrete. So, RC beams with three nano-silica percentages of 0 %, 1.5 %, and 3 % were prepared. In addition, to consider the effect of cracking on corrosion, crack widths between 0.1 mm and 0.5 mm, and cover depths of 30 mm and 45 mm were considered. All beam specimens were subjected to 5 % NaCl solution and monitored weekly for half-cell potentials (HCP). The presented results include the HCP evaluation and diffusion factor values in sound and cracked concrete beams exposed to chloride attack. The experimental results indicated that the chloride diffusion coefficient increases with extending crack width. Nano-silica improved the permeability characteristics of concrete, HCP and also diffusion factor values. Regressive models of the chloride diffusion factor and HCP values were proposed for influencing parameters, i.e., nano-silica and crack width with two different cover depths.

Chloride ion penetration is an important parameter influencing the service life of a concrete structure, especially in aggressive environments. Severe chloride-induced corrosion of reinforced concretes has been reported in the southern part of Iran in the region of Oman Sea. In this paper, the effect of different environmental conditions of the Oman Sea on chloride penetration and mechanical properties of self-compacting concrete (SCC) and normal concrete (NC) is investigated. For this purpose, a number of prismatic specimens were exposed to various environmental conditions such as tide, submersion and atmospheric conditions. Surface chloride concentration and diffusion coefficient of SCC in these zones were calculated based on Fick’s second law, at 28, 90 and 150 days and compared with NC. Based on the values obtained in this study, relationships are proposed for concrete permeability and surface chloride of self-compacting concrete (SCC) at different ages in different aggressive environments. By determining the corrosion time based on these relations, it is observed that for a given water-to-cement ratio, the self-compacting concrete (SCC) has higher durability compared to normal concrete (NC).

In the present study, two new simulation-based frameworks are proposed for multi-objective reliability-based design optimization (MORBDO). The first is based on hybrid non-dominated sorting weighted simulation method (NSWSM) in conjunction with iterative local searches that is efficient for continuous MORBDO problems. According to NSWSM, uniform samples are generated within the design space and, then, the set of feasible samples are separated. Thereafter, the non-dominated sorting operator is employed to extract the approximated Pareto front. The iterative local sample generation is then performed in order to enhance the accuracy, diversity, and increase the extent of non-dominated solutions. In the second framework, a pseudo-double loop algorithm is presented based on hybrid weighted simulation method (WSM) and the Non-dominated Sorting Genetic Algorithm II (NSGA-II) that is efficient for problems including both discrete and continuous variables. According to hybrid WSM-NSGA-II, proper non-dominated solutions are produced in each generation of NSGA-II and, subsequently, WSM evaluates the reliability level of each candidate solution until the algorithm converges to the true Pareto solutions. The valuable characteristic of presented approaches is that only one simulation run is required for WSM during entire optimization process, even if solutions for different levels of reliability be desired. Illustrative examples indicate that NSWSM with the proposed local search strategy is more efficient for small dimension continuous problems. However, WSM-NSGA-II outperforms NSWSM in terms of solutions quality and computational efficiency, specifically for discrete MORBDOs. Employing global optimizer in WSM-NSGA-II provided more accurate results with lower samples than NSWSM.

Purpose Reliability-based design optimizations (RBDOs) of engineering structures involve complex non-linear/non-differentiable performance functions, including both continuous and discrete variables. The gradient-based RBDO algorithms are less than satisfactory for these cases. The simulation-based approaches could also be computationally inefficient, especially when the double-loop strategy is used. This paper aims to present a pseudo-double loop flexible RBDO, which is efficient for solving problems, including both discrete/continuous variables. Design/methodology/approach The method is based on the hybrid improved binary bat algorithm (BBA) and weighed simulation method (WSM). According to this method, each BBA’s movement generates proper candidate solutions, and subsequently, WSM evaluates the reliability levels for design candidates to conduct swarm in a low-cost safe-region. Findings The accuracy of the proposed enhanced BBA and also the hybrid WSM-BBA are examined for ten benchmark deterministic optimizations and also four RBDO problems of truss structures, respectively. The solved examples reveal computational efficiency and superiority of the method to conventional RBDO approaches for solving complex problems including discrete variables. Originality/value Unlike other RBDO approaches, the proposed method is such organized that only one simulation run suffices during the optimization process. The flexibility future of the proposed RBDO framework enables a designer to present multi-level design solutions for different arrangements of the problem by using the results of the only one simulation for WSM, which is very helpful to decrease computational burden of the RBDO. In addition, a new suitable transfer function that enhanced convergence rate and search ability of the original BBA is introduced.

Lumachelle stones, which are produced by marine sediments widely available in most coastal areas, can be considered as one of the aggregates replacements in roller compacted concrete (RCC). This study aims to evaluate the applicability of Lumachelle as fine aggregates in RCC that contains pozzolan. Three series of mixtures A, B, and C were designed based on the “dimension reduction prediction method” (DRPM). Mixes contained different water/cement ratios (W/C), varied quantities of pozzolan, and different amounts of Lumachelle fine aggregates as a replacement for the standard fine aggregate. Compressive strength, water absorption, under-pressure water penetration depth, and elasticity modulus tests were done on the specimens. Probabilistic performance evaluation and sensitivity analysis were also carried out based on the Monte Carlo simulation, the score function approach, and the DRPM. Experimental results have revealed that if optimum moisture content is calculated and used, specimens with different percentages of Lumachelle fine aggregates will have strengths close to those prepared with standard aggregates. It can be concluded, therefore, that Lumachelle fine aggregates can be used in the RCC through appropriate control of the W/C-Pozzolan ratio; Pozzolan reduces water penetration in mixes effectively causing the enhancement of concrete durability. The probabilistic evaluation results also show that the structure will have an appropriate degree of safety if an optimum moisture content is used and the construction process is controlled. Reliability sensitivity result confirms that among different random variables considered in the analysis, Lumachelle fine aggregates had the least effects on the failure of this type of concrete.

In this study, the reliability-based design optimization (RBDO) of rotating functionally graded cylindrical shells (FGCSs) subjected to temperature dependent probabilistic frequency constraints is investigated. The uncertain parameters such as FG material properties and the shell thermo-mechanical loads are considered as random variable in RBDO. To decrease model uncertainty, the effect of initial thermal stresses are efficiently included in elasticity-based vibration equations of the shell and the powerful differential quadrature method (DQM) is employed to accurately determine the shell frequency parameters. An efficient RBDO framework based on the hybrid weighted average simulation method (WASM) and DQM together with the particle swarm optimization (PSO) method is then presented for design optimization of the FGCSs. A key feature of proposed hybrid DQ-WASM-PSO is that only one simulation run is required for WASM during entire optimization process of the FGCS, even if the distribution type of input variables and/or the system target reliability level be changed. The influence of temperature rise, temperature-dependence of FGM properties, annular velocity, PDFs of the random variables, and convection heat transfer coefficient of the shell inside fluid on the RBDO results are carried out. Parametric study indicates that exact evaluation of the initial thermal stresses, temperature-dependence of the FGM properties and convection heat transfer coefficient have considerable effect on optimization results.

In this paper, a new algorithm is introduced for reliability analysis of structures using response surface method based on a group method of data handling-type neural networks with general structure (GS-GMDH-type NN). A multilayer network of quadratic neurons, GMDH, offers an effective solution to modeling nonlinear systems without an explicit limit state function. In the proposed method, the response surface function is determined using GMDH-type neural networks. This is then connected to a reliability method, such as first-order or second-order reliability methods (FORM or SORM) or Monte Carlo simulation method to predict the failure probability (Pf). In the proposed method, the use of the GMDH-type neural network with general structure, where all neurons from previous layers are used to produce neurons in the new layer, can improve the limit state function. In addition, the structure of the neural network and its weight are simultaneously optimized by genetic algorithm and singular value decomposition. As a result, the obtained model has no significant error, despite its simplicity. Moreover, the obtained limit state function is explicit and allows direct use of FORM and SORM methods. To determine the accuracy and efficiency of the proposed method, four numerical examples are solved and their results are compared to other conventional methods. The results show that the proposed method is simply applicable to analyzing the reliability of large complex and sophisticated structures without an explicit limit state function. The proposed approach is a high accurate method that can significantly reduce computing time compared with direct Monte Carlo method.

Meta-models or surrogate models are convenient tools for reliability assessment of problems with time-consuming numerical models. Recently, an adaptive method called AK-MCS has been widely used for reliability analysis by combining Mont-Carlo simulation method and Kriging surrogate model. The AK-MCS method usually uses constant regression as a Kriging trend. However, other regression trends may have better performance for some problems. So, a method is proposed by combining multiple Kriging meta-models with various trends. The proposed method is based on the maximum entropy of predictions to select training samples. Using multiple Kriging models can reduce the sensitivity to the regression trend. So, the propped method can have better performance for different problems. The proposed method is applied to some examples to show its efficiency.

The use of waste materials in the concrete industry has been a topic of interest for researchers around the world in recent decades. In this research, the fracture toughness (Kc) of edge-notched disc bend (ENDB) specimens of self-compacting mortars containing 0%, 20%, 40%, 60%, 80% and 100% waste glass aggregates (WG) under the pure mode 1, mixed mode 1/3, mixed mode 3/1, and pure mode 3 in ages of 14, 28 and 56 days have been studied. The results show that the use of 20% and 40% of WG will improve the fracture toughness of the mortars. On the other hand, increasing the curing age from 14 to 28 days, with and without WG, improves the fracture toughness of samples significantly. Increasing the curing age has the highest impact on the results of pure mode 3. In addition, due to the effective fracture toughness results, pure mode 3 is introduced as critical loading condition for self-compacting mortars containing WG.

In this study, a combination of Kriging surrogate method with U-learning function and K-means clustering were used to predict the concrete fracture energy (as an output parameter) based on previous experimental data sets including compressive strength, maximum aggregate size and the water to cement ratio (as the input parameters). Therefore a collection of 246 data series obtained from previous studies was collected. The strength, accuracy, and efficiency of the proposed models were examined by selecting 10%, 30%, and 50% of the data for learning, and the results were compared with the previous equations. The results show that combining the Kriging method with the U-learning function in the work of fracture method (WFM) will increase the predictive power of fracture energy compared to basic Kriging and K-means clustering methods, and the previous relationships. However, the size effect method (SEM), the models created using K-means and 50% of the data has led to better forecasting results than other models. The value of the correlation coefficient (R2) of the proposed Kriging combination models and previous existing relationships are in the range of 0.59–0.95 and 0.14–0.69, respectively. The results show that the combination of the Kriging method, the U-learning function, and K-means clustering will reduce the time and cost of the experiments, as well as increasing the accuracy of concrete fracture energy prediction results using a small number of previous experimental data.

In this study, a methodology to determine the response modification factor is presented. The main goals are to achieve a given probabilistic performance objective and to bring economy to the resultant design. The proposed methodology allows to determine the maximum value of the response modification factor of a building for a desired probabilistic performance objective. A probabilistic performance objective is expressed in terms of an allowable non-performance probability for a given performance level conditioned on the seismic intensity corresponding to a specific hazard level. The methodology is used to determine the response modification factors of special moment resisting perimeter frames for three probabilistic performance objectives. By using both parametric and regression analyses, for each of three objectives, a new analytical expression for calculation of the response modification factor is proposed. To evaluate the proposed response modification factor expressions, four example buildings are employed. The example buildings are optimally designed for the response modification factor obtained from the expressions. The results reveal that the proposed response modification factor expressions can efficiently convert the force-based design method to a direct probabilistic performance-based design procedure.

The enhanced weighted simulation-based design method in conjunction with particle swarm optimization (PSO) is developed as a pseudo double-loop algorithm for accurate reliability-based design optimization (RBDO). According to this hybrid method, generated samples of weighed simulation method (WSM) are considered as initial population of the PSO. The proposed population is then employed to evaluate the safety level of each PSO swarm (design candidates) during movement. Using this strategy, there is no required to conduct new sampling for reliability assessment of design candidates (PSO swarms). Employing PSO as the search engine of RBDO and WSM as the reliability analyzer provide more accurate results with few samples and also increase the application range of traditional WSM. Besides, a shift strategy is also introduced to increase the capability of the WSM to investigate general RBDO problems including both deterministic and random design variables. Several examples are investigated to demonstrate the accuracy and robustness of the method. Results demonstrate the computational efficiency and superiority of the proposed method for practical engineering problems with highly nonlinear and implicit probabilistic constrains.

The effects of six drying schedules on physical and mechanical properties of Paulownia wood (Paulownia fortune Seem.) were studied. Three schedules were based on the recommendations by Forest Product Laboratory (FPL), while the other three were established based on diffusion theory. FPL schedules consisted of a mild (T6E3), a moderate (T6E4), and a severe (T7E4) drying schedule; diffusion schedules consisted of three initial moisture contents (MC) of 113% (Dif-1), 75.5% (Dif-2), and 53.5% (Dif-3). Boards with a commercial thickness of 5 cm were randomly dried to the final moisture content of 8 ± 2% in all six schedules. Results indicated that drying under diffusion schedules had the most improved properties due to the beneficial effect of heat upon wood plasticity. However, lower plasticity effect in FPL schedules, due to lower temperatures, resulted in lower properties in most cases.

In this paper, an algorithm with a new sensitivity vector for reliability analysis is presented in reliability analysis. The sensitivity vector is computed using the conjugate gradient vector of limit state function based on Hasofer-Lind and Rackwitz-Fiessler (HL–RF) method (CHL–RF algorithm). An appropriate probabilistic model which is included model error and burst model of corroded pipe that is defined based on burst pressure of intact pipes and remaining strength due to corrosion defect, is developed using the average shear stress criterion. The best burst pressure model of the corroded pipeline was chosen based on the confidence index which was a statistical comparison for efficiency goodness-of-fit measure between experimental burst of corroded pipes and predicted pressure by burst model of pipe. Finally, effects of the mean and standard deviation of random variables have been investigated using the CHL–RF algorithm for pipeline with time-depended corrosion defect. Results indicate that the CHL–RF algorithm is more robust than the HL–RF scheme and small error is achieved using the probabilistic model for predicting burst of corroded pipe. Failure probability of corroded pipe is more sensitive to defect depth.

Purpose– Generally, iterative methods which have some instability solutions in complex structural and non-linear mechanical problems are used to compute reliability index. The purpose of this paper is to establish a non-linear conjugate gradient (NCG) optimization algorithm to overcome instability solution of the Hasofer-Lind and Rackwitz-Fiessler (HL-RF) method in first-order reliability analysis. The NCG algorithms such as the Conjugate-Descent (CD) and the Liu-Storey (LS) are used for determining the safety index. An algorithm is found based on the new line search in the reliability analysis.Design/methodology/approach– In the proposed line search for calculating the safety index, search direction is computed by using the conjugate gradient approach and the HL-RF method based on the new and pervious gradient vector of the reliability function. A simple step size is presented for the line search in the proposed algorithm, which is formulated by the Wolfe conditions based on the new and previous safety index results in the reliability analysis.Findings– From the current work, it is concluded that the proposed NCG algorithm has more efficient, robust and appropriate convergence in comparison with the HL-RF method. The proposed methods can eliminate numerical instabilities of the HL-RF iterative algorithm in highly non-linear performance function and complicated structural limit state function. The NGC optimization is applicable to reliability analysis and it is correctly converged on the reliability index. In the NCG method, the CD algorithm is slightly more efficient than the LS algorithm.Originality/value– This paper usefully shows how the HL-RF algorithm and the NCG scheme are formulated in first-order reliability analysis. The proposed algorithm is validated from six numerical and structural examples taken from the literature. The HL-RF method is not converged on several non-linear mathematic and complex structural examples, while the two proposed conjugate gradient methods are appropriately converged for all examples. The CD algorithm is converged about twice faster than the LS algorithm in most of the problems. Therefore, application of the NCG method is possible in reliability analysis.

Effects of three drying schedules on fluid flow were studied in the sapwood and heartwood of Paulownia wood (Paulownia fortunei). Boards with a commercial thickness of 5 cm were randomly dried to a final moisture content of 8 ± 2% using a mild (T6E3), a moderate (T6E4), and a severe (T7E4) drying schedule. Permeability measurement was carried out when specimens reached the final moisture content. Results showed a significant difference in the specific gas permeability as well as liquid permeability of the boards dried under the three drying schedules. Furthermore, a significant difference was observed in the gas permeability of sapwood and heartwood, dried under the different schedules, but not much significant difference was seen in the liquid permeability between sapwood and heartwood. T6E3 had the highest liquid permeability; furthermore, it was reported to have resulted in the lowest warping and most homogeneous moisture profile. This mild schedule is therefore recommended for commercial drying of Pau...

The computation of structural failure probability is vital importance in the reliability analysis and may be carried out on the basis of the first-order reliability method using various mathematical iterative approaches such as Hasofer-Lind and Rackwitz-Fiessler (HL-RF). This method may not converge in complicated problems and nonlinear limit state functions, which usually shows itself in the form of periodic, bifurcation and chaos solution. In this paper, the HL-RF method has been improved based on the relaxed method to overcome these numerical instabilities. An appropriate relaxed coefficient has been defined, ranging between 0 and 1, to enhance the HL-RF method. This coefficient can be computed using the information from the new and previous iterations of the HL-RF algorithm based on second-order fitting. Capability, robustness and efficiency of the proposed algorithm have been studied by results of several examples compared to the HL-RF. Results illustrated that the proposed method is more efficient and robust in the computation of the failure probability compared to the HL-RF method.

In this paper, a new simulation method for approximating the probability of failure and the most probable point of failure is proposed. The method works by generating uniformly distributed samples in a design space for all random variables and applying the probability density value as a weight index at any sample. The result is a simple approximation of the probability of failure without any limitation becoming feasible. The probability of failure is defined as the ratio of the sum of the weight indices in the failure domain over the sum of the indices in the entire domain. High accuracy in estimating small values of the probability of failure as well as the need for few samples are advantages of this method. Moreover, the possibility of estimating the point and the region with the highest failure probability for different types of limit state functions can be considered as another important advantage of the proposed method. The efficiency and robustness of the method are investigated by solving several examples. The results are compared with the results of common reliability methods, and they demonstrate the efficiency and robustness of the proposed method.

In this paper, the application of artificial neural network (ANN) in predicting seismic response of reinforced concrete (RC) frames with masonry infilled walls is investigated. The objective of this research is to predict roof displacement and base shear (ANN outputs) in the target displacement. The total of 855 database were prepared for modeling neural network using finite element method (FEM) by changing six parameters (the input parameters of ANN) including the number of bays, the number of stories, thickness of masonry infill, infilled wall ratio, existence of soft story and design spectral acceleration. A training set of 513 prepared database were used as training data and the validation set of 342 database were used as validation data in the next step. In the present study, two ANNs were trained; a multilayer perseptron (MLP) with Levenberg–Marquardt (LM) back propagation algorithms and a Radial Basis function (RBF), both with different structures and the best structure for each of them was obtained. The performance of ANNs was evaluated using mean square error (MSE) and correlation coefficient (R2) criteria. Results indicate that using both MLP and RBF ANNs for predicting target displacement have been appropriate and have low error as well as high speed. Furthermore, RBF network has a higher speed in training process of data compared to MLP network.

For vulnerability assessment of structures, different damage indexes have been established by researchers that estimate the structural damage level. In these indexes different parameters have been used for calculating structural damage level. In this paper, damage indexes based on deformation, energy and cycle hysteretic behavior are investigated in order to find a correlation between their numerical values. The selected damage indexes are calculated and compared by applying them in nonlinear time history analysis of low and intermediate rise knee braced steel frames subjected to a set of seven earthquake accelerograms. Correlations between various indexes have been presented graphically and approximate conversion formulas are also provided.

Space mapping is a powerful technique to optimize such complex models by efficiently substituting accurate but expensive electromagnetic models, fine models, with fast and approximate models, coarse models. In this paper, we apply space mapping, an explicit space mapping techniques to Design, a microstrip passband filter. The filter configuration is made of a perfect conductor on the top of a substrate (RT_DURROID_5880) with a relative dielectric constant of 2.21 and a height of 20mil, backed with a perfect conductor ground plane. The proposed passband filter 9GHz to 10GHz is designed and simulated with Advanced Design System (ADS 2010) and was implemented with good compactness and low insertion loss.

As to the importance of permeability in the preservation process of solid woods, the effects of diffusion drying schedule with three different initial moisture contents (MC) on fluid flow in the sapwood and heartwood of paulownia wood (Paulownia fortunei) were studied here. Boards with initial MCs of 113 % (D-1), 75.5 % (D-2) and 53.5 % (D-3) were dried to the final moisture content of 8 ± 2 %. Results showed a significant difference in the specific gas and liquid permeability of paulownia wood dried with these different initial MCs. Although gas permeability of sapwood and heartwood specimens was significantly different, no significant difference was seen in liquid permeability between these two parts. D-2 and D-1 showed the highest specific gas and liquid permeability, respectively. It was therefore concluded that the initial MC has a significant effect on the gas and liquid permeability of paulownia boards dried under diffusion schedule with different MCs. Furthermore, the presence of tyloses plays a more important role in permeability than vessel size and frequency by forming an impermeable barrier, resulting in a significant decrease in gas and liquid permeability in paulownia wood., En cuanto a la importancia de la permeabilidad en el proceso de preservación de maderas macizas, se estudiaron los efectos del programa de secado de difusión con tres diferentes contenidos de humedad (MC) iniciales en el flujo de fluido en la albura y el duramen de la madera de paulonia (Paulownia fortunei). Los tableros con MC iniciales de 113 % (D-1), 75,5 % (D-2) y 53,5 % (D-3) fueron secados al contenido de humedad final de 8 ± 2 %. Los resultados mostraron una diferencia significativa en la permeabilidad específica del gas y del líquido de madera de paulonia secada con estos diferentes MC iniciales. Aunque la permeabilidad al gas de la albura y duramen fue significativamente diferente, no se observó ninguna diferencia significativa en la permeabilidad a los líquidos entre estas dos partes. D-2 y D-1 mostraron la mayor permeabilidad al gas y a los líquidos, respectivamente. Por tanto, se concluyó que el MC inicial de paulonia tiene un efecto significativo sobre la permeabilidad al gas y al líquido de la madera secada con programas de difusión con diferentes MC. Además, la presencia de tilosis juega un papel más importante en la permeabilidad que el tamaño y la frecuencia de los vasos mediante la formación de una barrera impermeable, lo que resulta en una disminución significativa en la permeabilidad de gas y líquido en madera de paulonia.

A new simulation method presented by authors to approximate the failure probability and most probable point. In a discussion, it is claimed that the presented failure probability approximation method is exactly the classical Monte Carlo integration (MC). Here we prove that the discussion is just a proof of trustworthy of main formula of subject paper by using the classical MC integration. For clarification, an example is also presented.

The unanticipated destruct of more of the steel moment frames in Northridge earthquake, altered class of regard to the beamto- column connections in moment frames. Panel zone is one the significant part of joints which, it-s stiffness and rigidity has an important effect on the behavior and ductility of the frame. Specifically that behavior of panel zone has a very significant effect on the special moment frames. In this paper , meanwhile the relations for modeling of panel zone in frames are expressed , special moment frames with different spans and stories were studied in the way of performance-based design. The frames designed in according with Iranian steel building code. The effect of panel zone is also considered and in the case of non-existence of performance level, by changing in intimacies and parameter of panel zone, performance level is considered., {"references":["Federal Emergency Management Agency, FEMA-355d,\nSeptember, 2000, State of the art report on connection\nperformance.","J.M.Castro, A.Y.Elghazouli, and B.A Izzuddin. \"Modeling\nof the Steel and Composite Moment Frames\", Journal of\nEngineering Structures, 27(2005) 129-144","William M.Downs, Simpson Strong Tie, \"Modeling\nProcedures for Panel Zone Deformation-s in Moment\nResisting Frames\", International Conferences of Connection-s\nin Steel Moment Frame-s, V, Amsterdam, June 3-4 , 2004","FEMA 451, NEHRP Recommended Provisions: Design\nExamples, Chapter 3, Structural Analysis, 49-144","Kee Dong Kim, Michael D. Engelhardt. \"Monotonic and\nCyclic Loading Models for Panel Zones in Steel Moment\nFrames\" Journal of Constructional Steel Research; No. 58\n(2002) 605-635","PERFORM-3D, Nonlinear Analysis and Performance\nAssessment for 3D Structures, User Guide, version4, August\n2006","Building & Housing Research Center , Iranian Code of\nPractice for Seismic Resistant Design of Buildings , Standard\nNo.2800 2nd.Edition-2005","Ministry of Housing and Urban Development, Iranian\nNational Building Code , part:10 , Steel Structures , 2004","Islamic Republic of Iran , Management and Planning\nOrganization , Instruction for Seismic Rehabilitation of\nExisting Buildings ,No. 360, 2007\n[10] 1997 Uniform Building Code, UBC97\n[11] Federal Emergency Management Agency, FEMA 356,\nNovember 2000, Prestandard and Commentary for the Seismic\nRehabilitation of Buildings.\n[12] Applied Technology Council, ATC 55: Evaluation and\nImprovement of Inelastic Seismic Analysis Procedures,\nDecember 2001\n[13] Federal Emergency Management Agency, FEMA 356f,\nState of the Art Report on Performance Prediction and\nEvaluation of Steel Moment-Frame Buildings."]}

Because of architectural condition and structure application, sometimes mass source and stiffness source are not coincidence, and the structure is irregular. The structure is also might be asymmetric as an asymmetric bracing in plan which leads to unbalance distribution of stiffness or because of unbalance distribution of the mass. Both condition lead to eccentricity and torsion in the structure. The deficiency of ordinary code to evaluate the performance of steel structures against earthquake has been caused designing based on performance level or capacity spectrum be used. By using the mentioned methods it is possible to design a structure that its behavior against different earthquakes be predictive. In this article 5- story buildings with different percentage of asymmetric which is because of stiffness changes have been designed. The static and dynamic nonlinear analysis under three acceleration recording has been done. Finally performance level of the structure has been evaluated., {"references":["Ghobarah Ahmed, \"Performance - based design in earthquake\nengineering, state development\", structures, vol. 23, pp878- 884, 2001.","Federal Emergency Management Agency. Guideline for the seismic\nrehabilitation of building. FEMA273. 1998.","International research center of seismology and seismic engineering,\n\"Guidelines for seismic improvement of existing buildings\". Sep. 2002.","Iranian Code of practice for seismic resistant design of building,\nBuilding and housing research center publications, Standard No.2800.\n3rd Edition. 2006.","Sixth subject of building national provisions: \"incoming loads to the\nbuilding, the office of gathering and promotion of building\" national\nprovisions, 2006."]}

Because of architectural condition and structure application, sometimes mass source and stiffness source are not coincidence, and the structure is irregular. The structure is also might be asymmetric as an asymmetric bracing in plan which leads to unbalance distribution of stiffness or because of unbalance distribution of the mass. Both condition lead to eccentricity and torsion in the structure. The deficiency of ordinary code to evaluate the performance of steel structures against earthquake has been caused designing based on performance level or capacity spectrum be used. By using the mentioned methods it is possible to design a structure that its behavior against different earthquakes be predictive. In this article 5- story buildings with different percentage of asymmetric which is because of stiffness changes and kind of bracing (x and chevron bracing) have been designed. The static and dynamic nonlinear analysis under three acceleration recording has been done. Finally performance level of the structure has been evaluated., {"references":["Ghobarah Ahmed, \"Performance - based design in\nearthquake engineering, state development\", structures,\nvol. 23, pp878- 884, 2001.","Federal Emergency Management Agency. Guideline for\nthe seismic rehabilitation of building. FEMA273. 1998.","International research center of seismology and seismic\nengineering, \"Guidelines for seismic improvement of\nexisting buildings\". Sep. 2002.","Iranian Code of practice for seismic resistant design of\nbuilding, Building and housing research center\npublications, Standard No.2800. 3rd Edition. 2006.","Sixth subject of building national provisions: \"incoming\nloads to the building, the office of gathering and\npromotion of building\" national provisions, 2006.","Tenth subject of building national provisions: \"designing\nand performing the steel constructions, the office of\ngathering and promotion of building\" national provisions,\n2006."]}