Enhanced Jaya Algorithm for design optimization of planar steel frames S. O. Degertekinοͺ1 I. B. Ugur2, Department of Civil Engineering, Dicle University, 21100, DiyarbakΔ±r,Turkey 1 2 Department of Civil Engineering, Dicle University, 21100, DiyarbakΔ±r,Turkey Abstract. An efficient meta-heuristic optimization method called Jaya Algorithm (JA) has gained wide acceptance among optimization researchers in various engineering problems. The characteristic feature of JA is that does not use algorithm-specific parameters and has a very simple formulation based on the concept of approaching the best solution and moving away from the worst solution. This study presents an enhanced JA formulation for design optimization of planar steel frames under strength, displacement and geometric-size constraints. The enhanced Jaya Algorithm (EJA) accelerates the convergence to global optima and obtains better designs by randomizing a specific number of best and worst solutions in each iteration in order to strengthen the exploitation behavior of the method. The validity of EJA for planar steel frames is investigated by solving well-known five benchmark problems up to 32 design variables. The results demonstrate the superiority of EJA over standard JA and other state-of-the-art metaheuristic optimization methods in terms of optimized weight, number of structural analyses and several statistical indices like standard deviation. Keywords: algorithm design optimization; planar steel frames; meta-heuristic optimization methods; enhanced Jaya 1. Introduction The emergence of meta-heuristic optimization methods that mimic natural phenomena has increased considerably over the past three decades. A meta-heuristic could be defined as the process of an iterative generation which sheds light on a heuristic by incorporating smartly different concepts for exploration and exploitation of the search space and achieving strategies in order to find near-optimum solutions [1]. Exploration and exploitation are the most significant concepts of finding the best solution in all metaheuristic optimization methods. Exploration provides generating diverse solutions in order to explore search space on a global scale whereas exploitation focuses on the search in a local region by exploiting the information. The balance between these two concepts allows to identify regions containing high-quality solutions and move away from previously explored regions that are far from global optimum. In the last two decades, the bio-inspired approaches (Genetic Algorithm (GA) [2], Particle Swarm (PSO) [3], Ant Colony (ACO) [4], Honey Bee Mating (HBMO) [5], Enhanced Honey Bee Mating (EHBMO) [6], Whale Optimization Algorithm (WOA) [7], Enhanced Whale Optimization Algorithm (EWOA) [8] etc.) and physic-inspired approaches (Simulating Annealing (SA) [9], Harmony Search (HS) [10], Big-bang big-crunch [11], Colliding Bodies (CBO) [12] etc.) have been proposed for the optimization problems and extended by enhancing their capabilities in optimization procedures such as the convergence, time consumption and achieving the near-global optima. Constructions must be designed as safely bearing the specified design loads constrained to the structural provisions as well as the least amount of material is to be used. Meanwhile, resource and time management are some of the most challenging problems in structural engineering, however, structural designers can overcome these problems using meta-heuristics to obtain the best design in terms of cost and safety. Since frame structures constitute the vast majority of the skeletal systems in structural engineering, the optimum design of planar steel frames is a common selected issue as a benchmark problem to investigate the efficiency of meta-heuristics. Hence, various optimization methods have been proposed for the minimization weight of steel frames under strength and stability circumstances specified in design codes. Just to overview the literature published in the past two decades, Camp et. al. [13] used the Ant Colony algorithm (ACO) that is to simulate the ant behavior to structural optimization of steel frames. Degertekin [14] utilized the Harmony Search (HS) based on the concept of searching for the best harmony in musical improvisation. The efficiency of HS was tested in the optimization of planar steel frames using three steel frames in comparison to the genetic algorithm and ant colony optimization methods. In the study proposed by Saka [15], structural optimization algorithms including GA, SA and HS were reviewed and assessed comparing the optimization results of a steel frame design example for each method. Hasancebi et. al. [16] applied these techniques genetic algorithms, simulated annealing, evolution strategies, particle swarm optimizer, tabu search, ant colony optimization and harmony search to the real size rigidly connected steel frames including a planar example. Dogan and Saka [17] developed an optimum design algorithm based on particle swarm optimizer for planar steel frames. The superiority of the proposed algorithm was verified by optimizing three steel frames in comparison to SA and GA. An enhanced honey bee mating optimization method (EHBMA) for the optimum design of side sway steel frames was proposed by Maheri and Nerimani [6] in order to overcome trapping local optima and extend the search space of HBMO. The performance of the new method was evaluated with four design examples. Kaveh and Gaazan [8] proposed a new method called EWOA aimed to enhance the convergence speed and solution accuracy of the standard method by modifying the formulation of WOA. The efficiency of the new method was tested with four benchmark skeletal structures involved steel frames and the results were compared to WOA and other optimization methods. Carrero et. al. [18] implemented a search group algorithm (SGA) to three steel frame examples in order to investigate the efficiency of the method in the structural design field. The method has worked on the feasible domain only that leads to avoiding numerous structural analyses. The results demonstrated that the proposed method achieved competitive performance. Farshchin et. al. [19] applied a school-based optimization (SBO) algorithm that is an extended version of teaching-learning based optimization (TLBO) including multiple classrooms and multiple teachers for the optimum design of planar steel frames Most evolutionary and swarm-based intelligence algorithms require algorithm-specific parameters for tuning the optimization process. However, inappropriate tuning of these parameters affects the computational cost or convergence rate of the method negatively. In order to overcome these issues, Rao [20] proposed a parameter-less evolutionary algorithm that has a powerful search engine and can be easily implemented for any optimization problem. The JA and its enhanced versions with various strategies have been utilized in large-scale real-life urban traffic light scheduling problems [21], parameter estimating of battery models [22], cost minimization of underground cable systems [23], structural damage detection [24] and medical imaging problems. Besides, the JA was used also for the optimum design of truss structures with both discrete and continuous variables [25,26]. The satisfactory performance of the JA in optimum sizing of truss structures encouraged the authors to use JA in the structural optimization of planar steel frames. The main objective of this study is to minimize the weight of planar steel frames with limitations of LRFD-AISC [27] and ASD-AISC [28] provisions using the JA and enhance the standard JA in terms of faster convergence and stronger search capability. For this purpose, JA is applied to sizing optimization of the well-known planar frame structures include up to 32 design variables utilized as the benchmark problems in the literature. In particular, the 244member planar frame is selected as an optimization problem since it has multiple search spaces that vary according to the element type. The remaining parts of the study are organized as follows. Section 2 recalls the discrete sizing optimization of planar steel frames according to LRFD-AISC [27] and ASD-AISC [28]. Section 3 outlines the main steps for the implementation of the JA and EJA. Section 4 describes the test problems and discusses optimization results. Section 5 provides a brief conclusion of the study. 2. Sizing optimization of planar steel frames To design an economical structure, the weight should be minimized within feasible conditions. The weight of a steel structure depends on the material density, lengths and crosssectional areas of the elements. Cross-sectional areas are selected as design variables in the optimization problem since material density and lengths are constant. The objective of the optimization problem is to minimize the weight of structures under stress, displacement and geometrical constraints by searching best cross-sectional areas in a pre-defined section list. It can be stated as; Find π΄ ∈ π = {π΄1 , π΄2 , . . . . . , π΄πππ } ng nm k ο½1 i ο½1 To minimize W ( A) ο½ ο₯ Ak ο₯ ο§ i Li k=1,2,….,ng i=1,2,...,nm (1) j=1,2….nc Subject to gj(A) ≤ 0 where A is the vector including the design variables (i.e. member groups), S is a set of discrete cross-sectional areas, W(A) is the total weight of structure defined as a object function, γi and Li are the material density and the length of member I , Ai is the cross-sectional area of the member i., gj(A) denotes the design constraints including stress, displacement and geometric constraints, n is number of constraints, ng is number of member group (i.e. design variables), nm is the number of members, nd is the number of degrees of freedom, ncs is the number of discrete cross-sectional areas in the section list. In order to convert a constrained optimization problem to an unconstrained one, a penalty approach is utilized to take into account the constraint violations. Accordingly, the objective function is redefined as: ππ (π΄) = (1 + π1 β π)π2 × π(π΄) (2) π = ∑ππ=1 maxβ‘[0, ππ (π΄)β‘] (3) where n is the number of constraints for each design, π represents the sum of the violated constraints. π1 is the penalty constant set to 1, π2 is the exponent of the penalty function taken as 2. The penalty parameters allow the objective function to approach in a feasible direction. 2.1 Constraints of frame structures The optimum design of steel frame structures is subjected to displacement, stress and geometrical constraints specified in the design codes. In this study, LRFD-AISC [27] requirements are utilized for the first four examples whereas ASD-AISC [28] limitations are selected as design constraints for the last example. Strength constraints are described as following equations indicated in ASD-AISC for different cases of fa/Fa: π π π π ππ ,π (π΄) = [πΉπ + πΉππ₯ + πΉππ¦ ] − 1 ≤ 0β‘β‘β‘β‘β‘β‘β‘ππβ‘β‘ πΉπ ≤ 0.15β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘π = 1,2 … ππ π π ππ ,π (π΄) = [πΉπ + π ππ₯ π ππ¦ πΆππ₯ πππ₯ π (1− π )πΉππ₯ πΉ′ππ₯ + πΆππ¦ πππ¦ π (1− π )πΉππ¦ πΉ′ππ¦ π β‘] − 1β‘ ≤ 0β‘β‘β‘β‘β‘ππβ‘β‘ πΉπ > 0.15 π (4) (5) π π π π ππ ,π (π΄) = [0.6πΉ + πΉππ₯ + πΉππ¦ β‘] − 1 ≤ 0β‘β‘β‘β‘ π¦ ππ₯ (6) ππ¦ Fy is the yield stress of the material, fa is the required axial stress computed as P/A where A is the cross-sectional area. Fa denotes the allowable axial stress depending on the elastic or inelastic buckling behavior of the member. fbx and fby are required flexural stresses about the major and minor axis. Fbx and Fby represent nominal flexural stress about the major and minor axis. Fex and Fey stand for Euler stress on the -x and -y axis, respectively. Cmx and Cmy are described as reduction factors that are used for the distribution of moments along the member length depending on the sway behavior. Strength constraints are described as following equations indicated in LRFD-AISC against both bending and axial forces: π 8 ππ’π₯ β‘β‘ππ ,π (π΄) = π π’π + 9 (π π πππ₯ π π π ππ’π₯ β‘β‘β‘ππ ,π (π΄) = 2π π’π + (π π πππ₯ π π ππ’π¦ +π π πππ¦ ππ’π¦ +π π ) − 1 ≤ 0β‘β‘β‘ππβ‘ π π’π ≥ 0.2β‘ π πππ¦ π π π ) − 1 ≤ 0β‘β‘β‘ππβ‘ π π’π < 0.2 π π (7) (8) Pu and Pn represent the required axial strength and the nominal axial strength for both compression and tension; Mux and Mnx denote required flexural strength and nominal flexural strength about the x-direction (major axis); Muy and Mny are the required flexural strength and nominal flexural strength about the y-direction (minor axis). It should be noted that Mny=0 for planar frame structures. ππ is the axial resistance factor and taken as 0.90 for tension and 0.85 for compression; ππ is the flexural resistance reduction factor and taken as 0.90. Lateral displacement and inter-story drifts are considered as displacement constraints and restricted to be less than the limit values described below: β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘ππ (π΄) = βπ π» − π ≤ 0β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘ π πππ ,π (π΄) = βπ − π πΌ ≤ 0β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘β‘π = 1,2 … ππ β‘ π (9) (10) where β π represents the lateral displacement of the top story, H is the total height of the frame structure, R denotes the maximum displacement limit taken as 1/300, dn is the inter-story drift of the n-th floor, hn is the story height of the n-th floor. Ns is the number of stories. RΔ± denotes the inter-story limit value specified as 1/300. Apart from strength and displacement constraints, geometrical constraints are considered so as to restrict the flange width of the beam section at each beam-column connection to be less than or equal to the flange width of the column section. The equations of geometrical constraints are shown below: Figure 1. Beam-column connection ππ (π΄) = πππ πππ ππ (π΄) = (π − 1 ≤ 0β‘β‘ π′ππ π −2π‘π ) −1 ≤0 (11) (12) bf, π′ππ and bfc represent the flange width of the beam B1, the beam B2 and the column, respectively, tf is the flange thickness of the column. 3. Enhanced Jaya Algorithm (EJA) The JA quite recently developed optimization method is firstly proposed by Rao [20]. The word “Jaya” originally means “victory” in Sanskrit. The algorithm is based on the concept that the solution obtained for a given optimization problem should move toward the best solution and must avoid the worst solution. The algorithm always tries to get closer to success (i.e., reaching the best design) and then tries to avoid failure (i.e., moving away from the worst design) [20]. The most important feature of JA is that the JA has not any algorithm-specific parameters whereas the other metaheuristic optimization algorithms have algorithm-specific parameters. The JA only requires two standard control parameters which are the population size (i.e., number of solutions in the population) and maximum iteration number. The implementation of JA is very simple and has only one equation for modifying the designs. Ak,l,it denotes the value of the k-th design variable for the l-th design during the it-th iteration, the JA modifies the Ak,l,it as follows: ο¨ ο© ο¨ Aknew ,l ,it ο½ Ak ,l ,it ο« r1, k ,it Ak ,best,it ο Ak ,l ,it ο r2, k ,it Ak , worst ,it ο Ak ,l ,it ο© (13) where Aknew ,l ,it is the new design variable for the Ak ,l ,it , r1,k ,it and r2 ,k ,it are the randomly generated real numbers in the range [0,1] for the k-th design variable at the it-th iteration. Ak ,best ,it is the k-th design variable of the best design at the it-th iteration and Ak ,worst,it is the k-th design variable of the worst ο¨ ο© design at the it-th iteration. The term r1,k ,it Ak ,best,it ο Ak ,l ,it indicates the tendency of the solution to ο¨ ο© move closer to the best solution, and the term ο r2,k ,it Ak ,worst,it ο Ak ,l ,it indicates the tendency of the solution to avoid the worst solution. It is worth pointing out that the random numbers r1 and r2 ensure good exploration of the search space and the absolute value of the candidate solution (|Ak,l,it|) considered in Eq (13) further enhances the exploration ability of the algorithm [20]. The flowchart diagram of JA is shown in Fig.1. There are many concepts are used in metaheuristic algorithms in order to strengthen the searching process, converge the better global optima or accelerate the optimization. One of these concepts is the elitism which is used during every generation in which elite (best) solutions replaced with the worst solutions. In Enhanced Jaya Algorithm, unlike the elitism concept, worst solutions are not duplicated by the elite ones. The specified number of best and worst solutions are identified. Afterward, one of the identified solutions for each best and worst solutions is selected randomly then used in the modification equation of JA. This process allows the algorithm to avoid the local trapping and enhance the exploration capability. As mentioned earlier, standard JA has no algorithm-specific parameter and only needs common control parameters as population size (np) and maximum iteration number (itmax). The optimization is terminated when the maximum iteration number is exceeded. However, each optimization run could find the best solution for a different value of itmax. Instead, the following formulation is implemented to terminate the search process when it is satisfied. πππ·[ππ (π΄1 ),ππ (π΄2 ),…ππ (π΄ππ )] ππ ∑ ( π=1 1 ≤ ππππ (14) ) ππ (π΄π ) In Eq. (14), ππ (π΄π ) represents the penalized objective function of i-th design in the population, ns is the population size, ππππ is the coefficient of convergence tolerance taken as 10-4. As a consequence of considering a dynamic itmax value, the needed common control parameters reduced to only one which is population size. 4. Implementation of EJA for frame structures In frame optimization, the EJA is initialized by randomly generated frame designs as the population size np (number of frame designs) and the penalty functions for each design are calculated by the results of structural analysis. The penalized functions are calculated at the rate of constraint violation. After that, the frame design with a certain number of lower penalized function values ππ (π΄πππ π‘ ) π and a certain number of higher penalized function values ππ (β‘π΄π€πππ π‘ ) are assigned to the best design and the worst design vectors, respectively. The π size of the best and worst vectors is set to 3. In order to modify the design variables by using Eq.(13), the best and worst design is randomly selected from the best and worst vectors. The new frame design is generated with modified design variables. The new penalized objective function ππ,πππ€ (π΄) is calculated. If the new penalized objective function value is smaller than the previous one, ( ππ,πππ€ (π΄) < ππ,πππ (π΄) ), the new design is replaced with the previous one. Otherwise, the previous design remains unchanged. This process is repeated for each frame design in the population then an iteration is completed. The optimization is terminated when the Eq. (14) is satisfied which depends on the standard derivation of penalized objective function values in the population The Eq. (14) was defined as a termination criterion depends on the standard deviation of penalized objective function values in the population and when the criterion is satisfied, the optimization process is terminated. The best design without constraint violation is reported as the optimum design. The implementation of enhanced JA for optimum design of frame structures is summarized below. Step 1: Generate the initial population (i.e., frame designs) using random integers between 1 and the number of discrete values for each design variable. Calculate the penalized objective function values ππ (π΄) for all frame designs in the population using Eq. (1-12). Set the iteration counter as it=0. Step 2: Increase the iteration counter, it=it+1 Step 3: Determine the best and worst three designs of the population. π΄ππππ π‘ , π΄ππ€πππ π‘ β‘β‘π = 1,2,3. Select one of them as the best and worst design randomly. Step 4: Modify discrete design variables by using Eq. (13) for each frame design in the πππ€ population. Obtain the new designs with modified design variablesβ‘π΄ πππ€ the penalized function values ππ (π΄ and calculate ) with modified design variables. Step 5: If ππ (π΄πππ€ )<β‘ππ (π΄πππ π π ) , replace the i-th new design with the previous one otherwise; keep the previous design. Repeat this process for each frame designs stored in the population. Step 6: Terminate the optimization process if Eq. (14) is satisfied. Store the feasible design corresponding to the lowest value of the objective function as the final optimum design. Otherwise, go to Step 2 5. Design Examples To demonstrate the performance the Enhanced Jaya Algorithm, five classical benchmark frame examples as follows: Two-bay three-story steel frame, one-bay ten-story steel frame, three-bay fifteen-story steel frame, a three-bay twenty four-story steel frame and 224-member braced planar steel frame are optimized according to provisions of LRFD-AISC [27] and ASDAISC [28] specifications and the results are compared with standard Jaya Algorithm and other metaheuristic methods in the literature. The EJA and JA were executed ten times and the initial population of each run was generated randomly. The population size was set to 20 for all examples. The statistical performance and robustness of algorithms used in benchmark examples are assessed and reported in related tables in terms of the best, mean, worst weighed designs, the standard deviation of best designs obtained in each run and number of structural analyses. The optimum design of each example reported in other studies was analyzed using the given optimum sections in order to check constraint violation. If detected, the violation rates of both strength and displacement constraints are reported in the tables. EJA was coded in the MATLAB R2017a [29] programming language and automated to interact with OPENSEES [30] structural analysis program for controlling design and displacement constraints during the optimization process. The proposed program was executed on a standard PC equipped with a single 2.2 GHz Intel® Pentium i7-4702MQ CPU. 5.1. Two-bay three story frame The first design example to test the validity of EJA is two-bay three story frame as shown in Fig. 2. The frame example has 15 members divided into 2 groups: beams and columns. The column members are restricted to be selected from W10 sections and beams are selected from all W shaped standard sections. The Young modulus of steel E is 29000 ksi and yield stress is Fy is 36 ksi. For each column, the effective length factor is calculated according to equations proposed by Dumonteil [31] for sway-permitted frames. The effective length factor of the out-of-plane columns (Ky) is considered as 1.0. The unbraced length ratio of beams is set to 0.167. Displacement constraints are not taken into account for this design. Figure 2. Two-bay three story frame This frame example was optimized by Camp et al. [13] using ACO, Degertekin [14] using HS, Carraro et al. [18] using SGA, by Maheri and Nerimani [6] using HBMO and Farshchin et al. [19] using SBO, JA and EJA from this study. The best design obtained by each algorithm is reported as well as the statistical performance of these methods in terms of average weight and standard deviation in Table 1. The JA and EJA obtained the same design weighing 18792 lb as ACO, SGA and SBO methods. While other methods required at least 420 structural analyses to converge the optimum, JA and EJA required 155 and 72 structural analyses, respectively. It is evident that the enhanced Jaya Algorithm converges the best design in much less structural analysis than the others as shown in Fig 2. In ten independent runs, the mean weight and standard deviation values of EJA are 18814 lb and 32.34 lb less than other methods except SBO. The results reported by HS and HBMO methods are not feasible due to the constraint violations as demonstrated in Table 1. Table 1. Comparison of optimum designs for two bay three story frame Optimal cross section area (in2) Design variables ACO [13] HS [14] SGA [18] HBMO [6] SBO [19] JA This study EJA This study Column W24×62 W21×62 W24×62 W10×77 W24×62 W24×62 W24×62 Beam W10×60 W10×54 W10×60 W10×77 W10×60 W10×60 W10×60 18792 18292 18792 18000 18792 18792 18792 3000 1853 420 463 502 155 75 19163 18784 19011 N/A 18792 18851 18814 1693 411 385.09 N/A 0 36.68 32.34 Max IR 0.946 1.02 0.946 1.39 0.946 0.946 0.946 IRlimit Max CV (%) 1 1 1 1 1 1 1 None 2 None 39 None None None Best weight (lb) NSA Mean weight (lb) SD Convergence curves are compared by plotting the structural weight versus number of structural analyses in Fig 2. It is obvious that the EJA has the most powerful convergence ability among all methods shown in Fig 2. Figure 3. Comparison of convergence curves for the one-bay three story frame 5.2 One-bay ten story frame A further design example commonly used in literature is one bay ten story plane as given in Fig 4. with configuration, member grouping and load conditions. The frame has 30 members which are gathered in 9 design groups and grouped in a way that the columns of two consecutive stories and the beams of three consecutive stories except roof beams form a group distinctively. Beam groups are selected from any 267 standard W-sections, column groups are restricted to W12 and W14 sections. The material density, yield stress and the effective length factor of members are considered as in the previous example. The columns are considered unbraced along their length and the unbraced length for each beam member is specified as 1/5 of the span length. Figure 4. Two-bay three story frame Two different optimization cases are considered in terms of displacement limitations. In case 1, the inter-story drift for all stories is limited to story height/300; while in case 2, only the displacement of top story is limited to total frame height/300. Both optimization cases are considered in this study and the results are compared with other related methods in the literature. Table 2. Comparison of optimum designs for one bay ten storey frame Optimal cross section (area. in2) Case 1 Sizing variables Case 2 GA [34 ] SBO [19] HBMO [6] EHBMO [6] 1 2 3 4 5 6 7 8 W14×233 W14×176 W14×159 W14×99 W12×79 W33×118 W30×90 W27×84 W14×233 W14×176 W14×159 W14×99 W14×61 W33×118 W30×90 W27×84 W14×159 W14×159 W14×159 W14×159 W14×145 W21×73 W21×73 W24×76 W14×159 W14×159 W14×132 W14×109 W14×90 W24×94 W24×94 W18×76 JA This Study W14x233 W14x176 W14x159 W14x99 W14x68 W33x118 W30x90 W24x84 EJA This Study W14x233 W14x176 W14x159 W14x99 W12x65 W33x118 W30x90 W24x84 ACO [13] HS [14] SGA [18] SBO [19] W14×233 W14×176 W14×145 W14×99 W14×61 W30×108 W30×90 W27×84 JA This Study W14x233 W14x176 W14x145 W14x99 W12x65 W30x108 W30x90 W27x84 EJA This Study W14x233 W14x176 W14x145 W14x99 W12x65 W30x108 W30x90 W24x84 W14×233 W14×176 W14×145 W14×99 W12×65 W30×108 W30×90 W27×84 W14×211 W14×176 W14×145 W14×90 W14×61 W33×118 W30×99 W24×76 W14×233 W14×176 W14×132 W14×99 W14×68 W30×108 W30×90 W27×84 9 W24×55 W18×46 W24×76 W24×62 W21x44 W21x44 W21×44 W18×46 W21×50 W18×46 W21x44 W21x44 Best weight (lb) 65136 64002 61014 57714 64298 64151 62610 61864 62262 62430 62610 62579 NSA N/A 12691 1823 1340 18541 11857 8300 3690 7980 11677 7688 6933 Mean weight (lb) N/A 65880 N/A N/A 66992.8 64469.5 63308 62923 65257 63244 62943 62684 Worst weight (lb) N/A N/A N/A N/A 68785 65027.08 N/A N/A N/A N/A 63518 63150 SD Max ISD N/A 0.0033 832 0.0033 N/A 0.00851 N/A 0.00596 1614 0.0033 294 0.0033 684 4.23 1.74 4.125 7027 4.224 706.84 4.217 340 4.23 252 4.32 ISDlimit 0.00333 0.0033 0.00333 0.00333 0.00333 0.00333 4.92 4.92 4.92 4.92 4.92 4.92 Max IR 0.967 1 1.91 1.438 0.968 0.998 0.986 1.0502 1.0148 0.999 0.986 0.998 IRlimit 1 1 1 1 1 1 1 1 1 1 1 1 Max CV (%) None None 155.1 78.9 None None None 5.02 1.48 None None None The optimization performance of GA [34], SBO [19], HBMO [6], EHBMO [6] for case 1 and ACO [13], HS [14], SGA, [18], and SBO [19] for case 2 is summarized in Table 2. Although the best design of EJA is % 0.23 heavier than the SBO, EJA requires 834 less structural analysis than SBO in case 1. Besides, EJA has the least standard deviation value that indicates the robustness of the method. As detailed in the Table 2, best designs of HBMO and EHBMO are extremely violated both strength and displacement constraints while EJA, JA, GA [34] and SBO [19] strictly satisfy the limitations. In case 2, SBO [19] has the best design with the weighing of 62430 lb that is % 0.24 lighter than EJA. It is clear that the best results of both methods are rather close. In terms of required analysis number and statistical values, EJA has the most satisfying performance with a standard deviation of 252 lb, a mean weight of 62684 lb and structural analysis number of 6933. Figure 5.a. Comparison of convergence curves for the two-bay three story frame (Case 1) Figure 5.b. Comparison of convergence curves for the two-bay three story frame (Case 2) The convergence history of EJA and JA is indicated and compared with other methods for both cases in Fig. 5. The convergence rate of the EJA is significantly higher than the others as seen in the figure. In comparison to JA, the trend of achieving the near-optimum region is faster by far. 5.3. Three Bay Fifteen Story Frame Three bay fifteen-story planar frame was optimized firstly by Saka [15] using SA and GA according to both LRFD [27] and ASD [28] provisions. The geometry and load conditions of the frame are shown in Figure 6. The frame consists of 105 members divided into 12 design groups. Grouping is considered as consecutive three-story inner and outer columns form a distinct group, roof and intermediate story beams constitute a distinct group. The frame is subjected to gravity loading as well as wind loading which computed according to The British Code considering 45 m/s wind speed and 6 m frame spacing [15]. The modulus of elasticity is 200 kN/mm2. In this example, both inter-story drift and lateral displacement of the top story are considered as displacement constraints and restricted to be smaller than 1.17 cm and 17. 67 cm, respectively. In this example, the strength capacities of members are calculated with the formulations specified in LRFD-AISC [27]. Figure 6. Three bay fifteen story frame The optimum design results of EJA and other methods are reported in Table 4. The EJA obtained the best design weighing of 33896 kg which is %9.27 lighter than the best design obtained using PSO [17], %13.7 lighter than the SA and %17.22 lighter than GA [15]. In addition, EJA has found better a design with less structural analysis with less standard deviation than standard JA. The design of PSO [17] violated displacement constraint at a high rate as seen in Table 3. Table 3. Comparison of optimum designs for three bay fifteen storey frame Sizing variables GA [15] SA [15] PSO [17] JA This Study EJA This Study 1 W21×50 W21×50 W6×9 W8×18 W8×18 2 W24×55 W21×57 W21×44 W21×44 W21×44 3 W10×39 W10×33 W10×33 W12×35 W10×54 4 W14×53 W10×39 W10×33 W16×40 W16×36 5 W14×53 W12×53 W14×53 W21×55 W21×48 6 W14×68 W16×67 W21×111 W24×84 W21×68 7 W24×117 W24×104 W21×111 W30×90 W30×90 8 W14×43 W10×39 W14×61 W12×35 W8×24 9 W14×48 W14×48 W14×61 W16×40 W16×40 10 W14×68 W14×61 W24×76 W21×55 W24×62 11 W14×109 W14×99 W27×94 W30×90 W30×90 12 W16×100 W14×99 W27×102 W33×118 W30×108 40949 39262 37360 34103 33896 Best (kg) weight NSA 25000 15500 7000 7870 7165* Mean weight (lb) N/A N/A N/A 35381 34664 Worst weight (lb) N/A N/A N/A 37395 36752 SD N/A N/A N/A 1366 1199 Max ISD 1.12 1.17 1.07 1.16 1.16 ISDlimit 1.17 1.17 1.17 1.17 1.17 Max IR 0.95 0.91 0.87 0.99 0.99 1 1 1 1 1 None None 116 None None IRlimit Max CV (%) The design history graph of optimization using PSO [17], JA and EJA is plotted in Fig. 8. The convergence of EJA is rather satisfying in comparison to PSO [17] by far. JA has similar convergence behavior with EJA as illustrated in Fig 7. Figure 7. Comparison of convergence curves for the three-bay fifteen story frame 5.4 Three-Bay Twenty-Four Story Frame The fourth, commonly used benchmark example is three-bay twenty-four story frame consisting of 168 members that are collected in 20 groups shown in Fig. 8. with configuration and loading conditions. The frame was originally designed by Davison and Adams [32] later optimized by Camp et. al using PSO [13] , Degertekin using HS [14], Carraro et. al. using SGA [18], Mahari and Nerimani using HBMO and EHBMO [6], Kaveh and Ghazaan using WOA and EWOA [8] and Farshchin et. al. using SBO [19]. The material modulus of elasticity is 29782 ksi and the yield stress is taken as 33.4 ksi. All members are considered unbraced along their lengths. For each column, the effective length factor is calculated according to equations proposed by Dumonteil [31] for sway-permitted frames. The effective length factor of the out-of-plane columns (Ky) is considered as 1.0. The beam member groups could be selected from W-shaped sections in AISC standard list while the column members are limited to W14 sections. The grouping scheme is demonstrated in Fig. 8. Figure 8. Three-bay twenty-four story frame Table 4 lists results of optimum designs including EJA and other optimization methods. The EJA has the best design weighing of 201193 lb in comparison to all techniques reported in the table. It should be noted that the EJA is overall the most efficient optimizer with the lightest feasible design and the lowest standard deviation value. Much as SGA [18] and EHBMO [6] found lighter designs weighing of 194508 and 188640 lb respectively, these designs violate constraints at high rates as %34 and %1766. Table 4. Comparison of optimum designs for three bay twenty four story frame Optimal cross section (area. in2) Sizing variables W30×90 JA This Study W30×90 EJA This Study W30×90 W10×30 W8×18 W16×26 W12×19 W21×62 W24×55 W21×48 W24×55 W24×55 W14×26 W6×8.5 W6×8.5 W6×8.5 W6×8.5 ACO [13] HS [14] SGA [18] HBMO [6] EHBMO [6] WOA [8] EWOA [8] SBO [19] 1 W30×90 W30×90 W24×68 W10×22 W10×15 W30×90 W30×90 2 W8×18 W10×22 W21×55 W27×539 W36×256 W10×17 3 W24×55 W18×40 W24×62 4 W8×21 W12×16 W12×87 W8×21 W6×16 W33×221 W27×146 5 W14×145 W14×176 W14×159 W14×145 W14×145 W14×109 W14×159 W14×152 W14×120 W14×159 6 W14×132 W14×176 W14×145 W14×145 W14×120 W14×145 7 W14×132 W14×132 W14×120 W14×68 W14×26 W14×109 W14×120 W14×109 W14×90 W14×109 8 W14×132 W14×109 W14×99 W14×22 W14×26 W14×99 W14×74 W14×74 W14×90 W14×74 9 W14×68 W14×82 W14×68 W14×48 W14×53 W14×53 W14×74 W14×82 W14×74 W14×61 10 W14×53 W14×74 W14×48 W14×68 W14×99 W14×43 W14×43 W14×43 W14×34 W14×38 11 W14×43 W14×34 W14×48 W14×132 W14×159 W14×34 W14×30 W14×34 W14×30 W14×34 12 W14×43 W14×22 W14×34 W14×342 W14×22 W14×22 W12×19 W14×22 W14×22 13 W14×145 W14×145 W14×109 W14×159 W14×145 W14×120 W14×90 W14×109 14×109 W14×90 14 W14×145 W14×132 14×109 W14×99 15 16 W14×30 W14×99 W14×120 W14×120 W14×132 W14×82 W14×109 W14×26 W14×99 W14×120 W14×109 W14×120 W14×109 W14×99 W14×99 W14×74 W14×109 W14×90 W14×99 W14×109 W14×90 W14×90 W14×82 W14×109 W14×48 W14×26 W14×82 W14×99 W14×99 W14×90 W14×90 17 W14×90 W14×61 W14×90 W14×43 W14×26 W14×90 W14×68 W14×68 W14×74 W14×74 18 W14×61 W14×48 W14×74 W14×53 W14×26 W14×61 W14×61 W14×61 W14×74 W14×61 19 W14×30 W14×30 W14×43 W14×176 W14×370 W14×38 W14×43 W14×34 W14×43 W14×34 20 W14×26 W14×22 W14×43 W14×211 W14×109 W14×22 W14×22 W14×22 W14×22 W14×22 220465 214860 194508 214848 188640 206520 203490 202422 203069 201193* 15500 13924 8010 2074 1826 19640 18820 14572 13097 16306 229555 222620 213545 N/A N/A 216475 208648 209560 207949.2 203612.9 N/A N/A N/A N/A N/A 243143 226019 N/A 216308.9 207178.9 4561 N/A 7027 N/A N/A N/A N/A 7052 4204 1966 0.00307 0.0329 0.00447 0.0331 0.0622 0.00332 0.00332 0.0032 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.0033 0.00333 0.00333 Max IR 0.779 0.0774 0.949 4.69 10.75 0.974 0.817 0.998 0.991 0.952 IRlimit Max CV (%) 1 1 1 1 1 1 1 1 1 1 None None 34 893 1766 None None None None None Best weight (lb) NSA Mean weight (lb) Worst weight (lb) SD Max ISD ISDlimit Fig. 9 illustrates the convergence history of EJA and other algorithms to the optimum design. In this example, number of structural analyses required by EJA in order to find the optimum design is 16306. Despite the fact that the convergence rate of EJA is slightly slower than the others, it reaches the best feasible design. It can be explained as comparing the convergence behavior of the unfeasible designs with feasible ones is pointless. Figure 9. Comparison of convergence curves for the three-bay twenty-four story frame 5.5. 224 Member Braced Frame The last comparison example is 224 member braced frame which was firstly optimized by Hasancebi et. al. [16] using seven different algorithms: SA, ESs, TS, ACO, PSO, SGA and HS. (a) Side view (b) Plan view Figure 10. 224 member braced frame Fig 10. demonstrates side and plan views of the example which represents one of the interior frameworks of the structure along the short side direction. The height is 276 ft and the frame has three bays that each one has a span of 30 ft. The non-swaying concept is provided by bracing the frame with X-type system placed within the middle bays. The further trusses are also placed at the twelfth and the top story in order to increase lateral rigidity and hence the large displacements are prevented. The members are collected in 32 groups that specified as interior columns, exterior columns, beams and diagonals of successive three stories as shown in Fig 10.(a). The material properties of the steel are as follows: modulus of elasticity (E) is 29000 ksi and yield strength (Fy) is 36 ksi. The column members are selected from the wide-flange profile list consisting of 297 sections while beams and diagonals are restricted to be selected from discrete sets of 171 and 147 economical sections classified according to the properties of area, inertia and radii of gyration. The single loading condition is the combination of the gravity, live, snow and wind load that are calculated as to ASCE7-05 [33]: a design dead load of 60.13 lb/ft2, a design live load of lb/ft2 a ground snow load of 25 lb/ft2 and a basic wind speed of 91 mph resulting in a uniformly distributed gravity load of 1001.62 lb/ft on top story beams, and of 1453.72 lb/ft on other story beams. Wind loads applying at each floor level on windward and leeward faces of the frame are tabulated in Table 5. The strength, stability and displacement constraints are considered according to the provisions of ASD-AISC [28]. Table 5. Wind loads acting on 224-member braced frame Windward Leeward Floor (kips) (kips) 1 1.69 2.454 2 1.933 2.454 3 2.17 2.454 4 2.356 2.454 5 2.512 2.454 6 2.646 2.454 7 2.765 2.454 8 2.872 2.454 9 2.971 2.454 10 3.062 2.454 11 3.146 2.454 12 3.225 2.454 13 3.3 2.454 14 3.371 2.454 15 3.438 2.454 16 3.502 2.454 17 3.563 2.454 18 3.621 2.454 19 3.678 2.454 20 3.732 2.454 21 3.784 2.454 22 3.835 2.454 23 3.884 2.454 24 1.966 1.227 The optimum results of 224 member braced frame using JA, EJA and other methods are tabulated in Table 6. The EJA obtained the best design weighing of 219845.9 lb that is %11 lighter than the SA which has the best design among seven methods in the study of Hasancebi [16]. In addition, EJA obtained %7.2 lighter design with 1491 less number of structural analyses and with 7206 less standard deviation value than JA. Table 6. Comparison of optimum designs for 224 member braced frame Sizing variables Optimal cross section (area. in2) SA [16] ESs [16] TS [16] ACO [16] PSO [16] SGA [16] HS [16] JA EJA This Study This Study 1 W14×109 W14×109 W12×120 W14×120 W27×146 W18×143 W24×146 W14×145 W14×120 2 W40×277 W40×277 W36×280 W40×268 W36×260 W40×328 W14×233 W14×257 W36×280 3 W8×40 W10×39 W8×40 W10×45 W10×39 W10×39 W10×49 W10×33 W8×24 4 W16×40 W16×40 W16×45 W16×40 W16×40 W16×40 W16×40 W18×40 W16×36 5 W14×99 W30×108 W18×106 W33×118 W18×130 W18×119 W14×109 W18×119 W14×99 6 W12×190 W12×210 W30×191 W40×221 W14×176 W21×201 W21×201 W30×191 W24×192 7 W10×39 W8×35 W8×35 W8×35 W8×35 W8×35 W10×39 W8×24 W6×20 8 W16×45 W14×43 W16×45 W14×43 W16×40 W16×40 W16×40 W16×40 W21×44 9 W14×90 W27×94 W18×97 W14×90 W21×101 W14×99 W21×101 W10×100 W14×90 10 W14×145 W14×145 W40×167 W33×152 W21×182 W12×152 W14×132 W36×150 W36×150 11 W8×31 W8×35 W10×33 W14×43 W8×401 W10×39 W12×45 W6×20 W8×24 12 W16×45 W14×43 W16×45 W18×50 W16×45 W16×45 W16×50 W21×44 W18×40 13 W30×90 W30×90 W27×94 W30×90 W21×101 W30×99 W21×147 W24×104 W14×90 14 W27×114 W30×116 W10×112 W27×129 W10×112 W30×235 W21×147 W27×129 W10×112 15 W8×40 W8×40 W10×39 W8×35 W8×35 W8×31 W14×61 W8×24 W10×22 16 W18×50 W18×50 W16×50 W18×60 W18×50 W24×76 W24×68 W16×40 W21×44 17 W10×68 W21×73 W24×76 W21×83 W12×87 W16×67 W14×82 W14×82 W24×94 18 W24×104 W24×104 W18×97 W24×104 W18×86 W14×99 W14×109 W30×124 W27×102 19 W8×31 W8×31 W8×31 W8×31 W8×31 W10×33 W10×33 W5×19 W6×15 20 W16×45 W14×43 W16×50 W16×40 W16×40 W14×43 W16×40 W18×46 W21×44 21 W14×53 W24×76 W14×53 W21×62 W24×84 W10×60 W18×71 W10×68 W16×57 22 W12×72 W8×31 W14×68 W21×73 W12×53 W14×74 W14×90 W12×72 W12×65 23 W8×31 W8×31 W8×31 W8×31 W8×31 W8×35 W8×48 W8×21 W6×15 24 W16×40 W16×40 W16×40 W16×40 W24×68 W18×50 W16×45 W14×38 W18×40 25 W16×40 W16×40 W14×43 W16×67 W21×68 W16×45 W14×74 W16×57 W18×50 26 W10×54 W10×49 W12×45 W12×53 W10×39 W12×53 W27×129 W10×54 W16×57 27 W8×31 W8×31 W8×31 W10×33 W8×31 W8×40 W12×40 W6×20 W6×15 28 W16×40 W16×40 W16×40 W16×40 W16×40 W16×45 W16×40 W18×35 W18×35 29 W8×31 W8×31 W8×35 W14×53 W24×76 W10×60 W21×83 W8×40 W12×35 30 W8×35 W8×35 W10×33 W12×45 W14×61 W16×67 W14×61 W10×100 W8×28 31 W8×31 W8×31 W10×33 W10×33 W8×31 W8×31 W10×49 W6×20 W6×15 32 W14×43 W14×43 W18×55 W18×55 W24×68 W24×68 W18×65 W16×31 W18×35 247053.34 248226.5 255486.55 264471.82 270204.24 285261.62 300092.65 236959.5 219845.9 50000 50000 50000 50000 50000 50000 50000 29427 27932 Mean weight (lb) N/A N/A N/A N/A N/A N/A N/A 257403.46 236434.7 Worst weight (lb) N/A N/A N/A N/A N/A N/A N/A 286639.9 258593.1 SD N/A N/A N/A N/A N/A N/A N/A 21222.31 14016.71 Max ISD 0.00166 0.001715 0.001625 0.001582 0.001556 0.001503 0.001436 0.001786 0.001831 ISDlimit 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 0.00333 Best weight (kg) NSA Max IR 0.9979 1.81 0.9885 0.9647 0.9982 0.9726 0.9887 0.9947 0.9986 IRlimit Max CV (%) 1 1 1 1 1 1 1 1 1 None 81 None None None None None None None The convergence history curves of all algorithms are plotted in Fig. 9. It should be noted that the number of structural analyses for the EJA is almost half of other methods and this is a shred of strict evidence that EJA has a great convergence performance compared to all methods given in Fig 9. Although JA does not converge as fast as ESs [16] and TS [16] methods, it eventually obtains lighter designs than both. Figure 11. Comparison of convergence curves for the 224-member braced frame 6. Conclusions JA is one of the most efficient optimization algorithms using only one simple modification equation without specific parameters based on approaching the best solution meanwhile getting away from the worst ones. In this study, the standard formulation of JA was modified in order to enhance the exploration capacity with less structural analyses and avoid trapping in local optima also applying a dynamic termination criterion for preventing useless iterations which do not affect the optimization process. Frame structures are relatively more complex optimization problems since involving more parameters and formulations unlike truss structures. In order to tackle the complexity and attain better solutions, the enhanced Jaya algorithm (EJA) was proposed for the weight minimization of planar steel frames by size tuning of structural members. To test the validity of the algorithm, five planar steel frame structures were optimized and the results were compared with those of optimization methods. Remarkably, EJA found the best design compared to all methods in every single example and strictly satisfied the constraints. The statistical results indicate that EJA has better performance than the standard JA and other algorithms in terms of robustness, convergence speed and feasibility. The competitive performance of EJA allows the researchers to apply the method to other engineering problems. Further studies are currently conducted for using EJA in the optimization of large-scale 3D steel frames with a large number of design variables. REFERENCES [1] Henderson, D., Jacobson, S. H., Johnson, A. W., Glover, F., & Kochenberger, G. A. (2003). Handbook of metaheuristics. Chapter The Theory and Practice of Simulated Annealing, 57, 287-319. [2] Holland JH . Adaptation in natural and artificial systems. Ann Arbor, MI: Uni- versity of Michigan Press; 1975 [3] Kennedy J, Eberhart R (1995) Particle swarm optimization. In: Proceedings of IEEE international conference on neural networks.Perth, Australia, pp 1942–1948 [4] Dorigo M , Maniezzo V , Colorni A . The ant system: optimization by a colony cooperating agents. IEEE Trans Syst Man Cybern B 1996;1(26):29–41 . [5] Bozorg Haddad O , Afshar A , Marino MA . Honey bees mating optimization algorithm (HBMO); a new heuristic approach for engineering optimization. In: Proc. 1st int. conf. on modeling, simulation and applied optimization (ICMSA0/05), Sharjah, UAE; 2005 February . [6] Maheri, M. R., Shokrian, H., & Narimani, M. M. (2017). An enhanced honey bee mating optimization algorithm for design of side sway steel frames. Advances in Engineering Software, 109, 62-72. [7] Mirjalili, S., & Lewis, A. (2016). The whale optimization algorithm. Advances in engineering software, 95, 51-67. [8] Kaveh, A., & Ghazaan, M. I. (2017). Enhanced whale optimization algorithm for sizing optimization of skeletal structures. Mechanics Based Design of Structures and Machines, 45(3), 345-362. [9] Van Laarhoven, P. J., & Aarts, E. H. (1987). Simulated annealing. In Simulated annealing: Theory and applications (pp. 7-15). Springer, Dordrecht. [10] Geem, Z. W., Kim, J. H., & Loganathan, G. V. (2001). A new heuristic optimization algorithm: harmony search. simulation, 76(2), 60-68. [11] Erol, O. K., & Eksin, I. (2006). A new optimization method: big bang–big crunch. Advances in Engineering Software, 37(2), 106-111. [12] Kaveh, A., & Mahdavi, V. R. (2014). Colliding bodies optimization: a novel meta-heuristic method. Computers & Structures, 139, 18-27. [13] Camp, C. V., Bichon, B. J., & Stovall, S. P. (2005). Design of steel frames using ant colony optimization. Journal of Structural Engineering, 131(3), 369-379. [14] Degertekin, S. O. (2008). Optimum design of steel frames using harmony search algorithm. Structural and multidisciplinary optimization, 36(4), 393-401. [15] Saka, M. P. (2007). Optimum design of steel frames using stochastic search techniques based on natural phenomena: a review. Civil computations: tools and techniques, Saxe-Coburg Publications, Stirlingshire, UK, 105-147. [16] Hasançebi, O., ÇarbaΕ, S., DoΔan, E., Erdal, F., & Saka, M. P. (2010). Comparison of nondeterministic search techniques in the optimum design of real size steel frames. Computers & structures, 88(17-18), 1033-1048.2 [17] DoΔan, E., & Saka, M. P. (2012). Optimum design of unbraced steel frames to LRFD–AISC using particle swarm optimization. Advances in Engineering Software, 46(1), 27-34. [18] Carraro, F., Lopez, R. H., & Miguel, L. F. F. (2017). Optimum design of planar steel frames using the Search Group Algorithm. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 39(4), 1405-1418. [19] Farshchin, M., Maniat, M., Camp, C. V., & Pezeshk, S. (2018). School based optimization algorithm for design of steel frames. Engineering Structures, 171, 326-335. [20] Rao, R. (2016). Jaya: A simple and new optimization algorithm for solving constrained and unconstrained optimization problems. International Journal of Industrial Engineering Computations, 7(1), 19-34. [21] Gao, K., Zhang, Y., Sadollah, A., & Su, R. (2016). Jaya algorithm for solving urban traffic signal control problem. In 2016 14th International Conference on Control, Automation, Robotics and Vision (ICARCV) (pp. 1-6). IEEE. [22] Wang, L., Zhang, Z., Huang, C., & Tsui, K. L. (2018). A GPU-accelerated parallel Jaya algorithm for efficiently estimating Li-ion battery model parameters. Applied Soft Computing, 65, 12-20. [23] OcΕoΕ, P., Cisek, P., Rerak, M., Taler, D., Rao, R. V., Vallati, A., & Pilarczyk, M. (2018). Thermal performance optimization of the underground power cable system by using a modified Jaya algorithm. International Journal of Thermal Sciences, 123, 162-180. [24] Ding, Z., Li, J., & Hao, H. (2019). Structural damage identification using improved Jaya algorithm based on sparse regularization and Bayesian inference. Mechanical Systems and Signal Processing, 132, 211-231. [25] Degertekin, S. O., Lamberti, L., & Ugur, I. B. (2018). Sizing, layout and topology design optimization of truss structures using the Jaya algorithm. Applied soft computing, 70, 903-928. [26] Degertekin, S. O., Lamberti, L., & Ugur, I. B. (2019). Discrete sizing/layout/topology optimization of truss structures with an advanced Jaya algorithm. Applied Soft Computing, 79, 363-390. [27] LRFD–AISC, Manual of steel construction. Load and resistance factor design. Metric conversion of the second edition, vol. I & II. AISC; 1999. [28] ASD-AISC, Manual of steel construction-allowable stress design, 9th ed.,Chicago, Illinois, USA; 1989. [29] The MathWorks, MATLAB®Version R2017a, 2017, Austin (TX) USA. [30] Mazzoni, S., McKenna, F., Scott, M. H., & Fenves, G. L. (2006). OpenSees command language manual. Pacific Earthquake Engineering Research (PEER) Center, 264. [31] Dumonteil P, Moore, W. Simple Equations for Effective Length Factors-Discussion. Eng J-Am Inst Steel Constr INC 1993; 30:37–37. [32] Davison, J. H., & Adams, P. F. (1974). Stability of braced and unbraced frames. Journal of the Structural Division, 100(2), 319-334. [33] ASCE 7-05. Minimum design loads for building and other structures; 2005. [34] Pezeshk S, Camp CV, Chen D. Design of nonlinear framed structures using genetic optimization. J Struct Eng 2000;126:382–8.