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Composite beams consisting of precast concrete slabs and steel beams connected by deconstructable high-strength friction-grip bolts (HSFGB) have recently attracted much research attention due to their compatibility with sustainable construction. However, studies on the behavior of these composite beams have been entirely deterministic, with no consideration for uncertainty in the governing parameters, especially for the bolted shear connector varieties. In this paper, a three-dimensional finite element model is developed to investigate the behavior of this type composite beam considering the nonlinearities of the geometry, materials, and component interfaces. Nonlinear springs with zero length are utilized to model the HSFGB shear connectors, and then the complete beam model is embedded in a Monte Carlo-based probabilistic assessment approach. The results show that the simplified spring model is reliable in predicting the behavior of composite beams while being efficient in terms of computational efficiency and time savings for conducting probabilistic analyses. The probabilistic analysis finds that Monte Carlo simulation is a useful method for identifying probabilistic trend behaviors with acceptable accuracy to quantify the effect of structural parameter uncertainties. The composite beam with a partial shear connection shows a greater variety of beam responses than the composite beam with a full shear connection. © 2025 Institution of Structural Engineers
Eccentrically braced frames (EBFs) are widely recognized as effective seismic resisting systems for buildings and other structures due to their high ductility and stiffness. The performance of EBFs heavily relies on the behaviour of the critical component known as the link, which governs the system's ductility, strength, and overall response. While the link is typically subjected to high shear force and bending moment, the significance of axial force in certain EBF configurations has received limited attention in previous studies and design codes. This research aims to investigate the effects of high axial load on the reliability and performance of EBF links using the finite element method. Experimental data is utilized to validate numerical models, ensuring the accuracy of the subsequent reliability analysis. The assessment of link reliability under high axial force is conducted within the framework of Eurocode 8 (EC8), employing the first-order reliability method (FORM). The results demonstrate that EBF links with very short lengths exhibit acceptable levels of reliability. However, as the link length increases, the target reliability index is not met. To address this challenge, a modification factor is proposed based on the Rackwitz–Fiessler iterative procedure, enabling adjustments to the link shear design. Furthermore, a sensitivity analysis is performed to evaluate the influence of random variables on the reliability analysis. © 2025 Institution of Structural Engineers
Steel and Composite Structures (15986233) 56(1)pp. 49-65
The combination of precast concrete slabs and steel beams connected by deconstructable high-strength friction-grip bolts has emerged as a promising solution for sustainable construction. However, the lack of design guidelines and r egulations has restricted its widespread use. This study aims to conduct a reliability analysis to evaluate the flexural resistance factor (φ) for composite beams with HSFGB shear connectors, as the AISC Specifications incorporate the shear connector resistance factor as part of the overall resistance factor of the composite beam. To analyze the behavior of the composite beam, a three-dimensional finite element model was developed and validated. Additionally, a sensitivity analysis was performed to investigate the impact of various parameters on the flexural strength of the composite beam. The flexural resistance factor for this type of composite beam with varying degrees of connection was evaluated providing an acceptable level of safety. The variability and uncertainty in connectors were determined based on existing push-out tests using statistical analysis. A reliability study found that the reduction factor of flexural resistance for this type of composite beam is dependent on the degree of shear connection. Additionally, using the flexural resistance factor recommended for conventional composite beams with welded shear connectors in the AISC code is unconservative for deconstructable composite beams. © 2025 Techno-Press, Ltd.
Mechanics Based Design of Structures and Machines (15397742) 52(2)pp. 628-649
Due to the low thickness of cold-formed steel (CFS) sections, welding of traditional studs on them is not recommended; and there is a need to use shear connectors suitable for this type of sections. In this paper, the behavior of U-shaped shear connectors as connectors compatible with CFS composite beams has been investigated, to offer practical relationships for predicting the ultimate strength of this type of connectors. Accordingly, after the development of finite element (FE) models with the ability to predict the ultimate strength of U-shaped connectors, their performance against experimental results was validated. Then, an extensive parametric study, consisting of 216 numerical samples, was accomplished to provide a reliable database. As the main and most important of this study, two methods of artificial neural networks and stepwise regression were developed, and practical formulations were proposed to predict the ultimate strength of U-shaped shear connectors in CFS composite beams. Finally, in addition to evaluating the accuracy of the proposed formulas, a comparison was made between them and the relationships proposed by AISI, AS/NZS and EC3 codes for CFS screw connections. The relationships presented in this paper can be used by practical engineers in the design process of CFS composite beams. © 2022 Taylor & Francis Group, LLC.
Mechanics Based Design of Structures and Machines (15397742) 52(7)pp. 4284-4311
In recent years, the high-strength friction-grip bolt (HSFGB) shear connectors in steel-concrete composite beams as deconstructable connectors are of great research interest since they are aligned with sustainable construction. However, the design strength equation for this type of connector has not yet been provided by the design codes such as AISC and Eurocode 4. In this paper, with regard to the reliability aspect, the design strength equation of HSFGB shear connectors is investigated which is projected into a partial safety factor according to Eurocode 4. Accordingly, the three-dimension finite element (FE) push-out model of the composite connection is developed and verified via experimental results to predict the load-slip behavior and failure modes in this type of bolted shear connector. Then One-Factor-at-a-Time (OFAT) method as a sensitivity analysis and Plackett-Burman (PB) design method as a screening analysis are utilized to identify the effective factors of the ultimate strength of HSFGB connectors. Finally, based on a complete database of all existing experimental findings, the results obtained from 55 three-dimension finite element models conducted in this paper, and appropriate statistical analysis, a high-precision equation for predicting ultimate strength is provided. Then the value of the partial safety factor is determined through a reliability study in accordance with EN1990, which provides an acceptable level of safety for the proposed design equation based on Eurocodes. Reliability analysis found that a partial factor of 1.52 was justified for the design strength of HSFGB connectors, which differed from the partial factor of 1.25 stated in the EC for welded stud shear connectors. © 2023 Taylor & Francis Group, LLC.
A new type of steel reduced beam section connection using longitudinal slots in the beam flanges is introduced. The effect of different parameters has been studied by the non-linear three-dimensional finite element method. Parameters have been the distance between the slot and column face, the length and width of the slot, the distance between the slot and the edge of the beam flange, the number of slots, the distance between slots, and the dimensions of the beam. The displacement controlled cyclic loading protocol recommended by SAC has been imposed. The von Mises yield criterion has been used. Obtained results show that creating the slots in the beam flange improves considerably the performance of the connection. The bending moment at the column face and plastic strains in the weld decrease by 32% and 94%, respectively, by increasing the slot length by 264%. The bending moment and dissipated energy reduce by 59% and 66%, respectively, when the slot width is increased by 430%. By increasing the length and width of the slot from a specific value and by moving the slot towards the beam web, the behaviour of the connection becomes unsatisfactory. The effect of the beam height is more than that of other dimensions of the beam. Based on the results obtained, recommendations for the design implications related to the geometric dimensions of the slots have been formulated. © 2023 Institution of Structural Engineers
Eccentrically braced frame (EBF) is considered a suitable seismic resisting system in terms of its high ductility, and stiffness simultaneously. In this frame, nonlinear behavior and energy dissipation are limited to link beam, and other members (capacity-designed members) are designed in proportion to maximum link shear force. Despite the significance of capacity-designed members, their reliability evaluation and the effect of their failure on the overall behavior of EBF have not been studied in prior research. The aim of this paper is to evaluate the effect of brace failure on the probability of collapse by considering system overstrength, varied ratios of the capacity to demand factors (ϕ/γ) in brace design, and seismic hazard curve. To achieve this aim, Incremental Dynamic Analysis (IDA) was used to study nonlinear structural models of EBF, evaluate the force demands on the braces, and the effects of brace failure on the system collapse. The reliability analysis was performed by integrating the viewpoint of LRDF component design with the FEMA P695 system reliability methodology. The results indicate that the probability of total collapse increases significantly at low spectral acceleration due to brace failure. Additionally, the appropriate value of ϕ/γ in brace design can be calculated for different seismic areas and system overstrength to ensure an acceptable margin of collapse safety. © 2023 Institution of Structural Engineers
Engineering Applications of Artificial Intelligence (09521976) 118
In recent years, the use of artificial intelligence-based methods in engineering problems has been expanded. In the current study, the method of artificial neural networks (ANN) has been employed to predict the ultimate strength of bolted shear connectors in cold-formed steel (CFS) composite beams. For this purpose, multilayer perceptron (MLP) networks with a hidden layer were used. Three parameters affecting the performance of these networks, including the training algorithm, the activation function in the hidden layer, and the number of neurons in the hidden layer, were examined and the most accurate network was selected. The input and target data for training the network were provided by conducting an extensive numerical study on the behavior of bolted shear connectors in CFS composite beams. Consequently, using ABAQUS software, finite element (FE) models validated with experimental results were first developed. Then, 216 models with different characteristics were analyzed and a reliable database was provided for the development of neural networks. Moreover, in order to prove the high accuracy of the ANN method, the stepwise regression (SR) method was also developed as one of the powerful regression-based methods, and the performances of these two methods were compared. Finally, the most important purpose of this study is to propose an accurate ANN-based formulation in order to predict the ultimate strength of bolted shear connectors in CFS composite beams. Due to the fact that so far no relationship has been proposed to predict the resistance of shear connectors in CFS composite beams, the formula presented in this paper can be helpful in the design process of this type of beams. © 2022 Elsevier Ltd
Structural And Multidisciplinary Optimization (16151488) 66(12)
This paper proposes a novel two-stage optimization method for the design of reinforced concrete (RC) frames that aims to overcome the limitations of existing optimization methods. The proposed method combines a section-based database schema (SBDBS) and a non-revisiting genetic algorithm (NrGA) to enhance the efficiency and effectiveness of the optimization process. In the first stage, the SBDBS utilizes a multi-objective brute force search technique based on non-dominated sorting to generate an optimal pre-determined section list for RC frame members, considering design constraints and cost-effectiveness. In the second stage, the NrGA optimizes the overall structural design by considering the total cost of the structure. To demonstrate the effectiveness of the proposed method, four design examples with 4 to 16 stories are presented, and the method is developed based on ASCE 7-16 and ACI 318-19. The results show that the proposed method outperforms the traditional method that uses non-optimal pre-determined lists. The proposed method is shown to converge faster, up to 75% for a 16-story frame, and attain optimal solutions with fewer evaluations of the objective function, resulting in more efficient and effective optimization. It is also shown that the presented method is more stable in obtaining optimal solutions by improving the standard deviation of results for independent optimizations by 67 to 100%. By using an optimal pre-determined section list tailored to the specific design problem, the proposed method can increase the probability of finding high-performing solutions, reduce the likelihood of getting stuck in local optima, and result in significant improvements in optimization performance. This method has broad potential for impact in the field of structural optimization, improving the efficiency and accuracy of design optimization while also enhancing safety and cost-effectiveness. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Structures (23520124) 43pp. 271-284
Calculation of reliability index is still a significant challenge in reliability problems. The Monte Carlo simulation technique is beneficial for calculating failure probability, but given the need to generate many random samples, it has a high computational cost. Additionally, it cannot calculate the design point, while it can be important to determine the design point in large-scale practical problems. This paper develops an algorithm for calculating the design point using the modified importance-sampling method. In the proposed method, the standard deviation (SD) of sampling density-function is improved in each step. This enables the proposed algorithm to calculate the reliability index and design point using a small number of random samples. The examples are presented in this paper indicate the high efficiency of the proposed algorithm to calculate the reliability index and design point, even for nonlinear problems with correlated random variables. © 2022 Institution of Structural Engineers
Thin-Walled Structures (02638231) 177
The use of concrete slab in cold-formed steel (CFS) beams can not only increase the ultimate resistance, but also can prevent their lateral buckling. Since the formation of composite action in this type of beams requires the use of appropriate shear connectors, in this paper, an extensive numerical study was conducted to investigate the behavior of 8.8 grade bolted connectors in CFS composite beams. For this purpose, at the first, advanced numerical models of concrete-CFS section connections were developed. Geometric details, material nonlinearities, material damage models and loading protocols were carefully simulated. Next, the results obtained from the numerical models were validated in detail against the experimental results. It was proved that the developed models have the ability to simulate the behavior of the 8.8 grade bolted connectors in these connections. At the end, an extensive parametric numerical study consisting of 216 connections was conducted. The examined parameters included CFS thickness, CFS ultimate strength, concrete compressive strength, embedded bolt's height and bolt diameter. Consequently, the effect of each of these parameters on the ultimate strength, ductility as well as the failure modes of the bolted shear connectors was carefully investigated. © 2022 Elsevier Ltd
Structures (23520124) 44pp. 323-342
The direct displacement-based design (DDBD) procedure is well established for designing reinforced concrete and steel moment-resisting frames (SMRFs). However, a limited number of researches is available on optimum DDBD of SMRFs. Furthermore, the nonlinear time-history analysis response of structures designed based on this procedure is inconsistent with its initial assumptions. Design displacement profile is one of the most essential and influential parameters in the DDBD method because it can impress other design parameters. In this paper, an optimum displacement profile is proposed to improve the results of the DDBD procedure via using the particle swarm optimization (PSO) algorithm. In this regard, nine SMRFs with a different number of stories have been designed using the DDBD procedure. Nonlinear time history analyses are performed for these frames using OpenSees software. The models are subjected to a set of 20 ground motion records. Then, PSO algorithm has been used to optimize the displacement profile of the DDBD procedure to achieve uniform drift distribution along with the height of the frames. Finally, based on regression analysis, the optimum design displacement profile for SMRFs with a different number of stories is formulated. The proposed equations show an average reduction of about 20% and 40% in steel usage and design base shear of the frames, respectively, while they have uniform drift along their heights. © 2022 Institution of Structural Engineers
Engineering Structures (18737323) 249
Since few studies have focused on the shear connectors in the composite cold-formed steel beams so far, this paper studies the behavior of the U-shaped shear connectors which can be used in the composite beams comprising cold-formed steel beam and concrete slab. Accordingly, ten full scale push-out tests were conducted to investigate the ultimate load, failure modes, ductility and stiffness of the U-shaped shear connectors. For this purpose, four types of shear connectors by different screw diameters and orientation of U-shaped shear connectors with respect to the direction of the load were considered; and utilized by two types of cold-formed steel beams with thickness of 1 and 2 mm. The results have shown that change of the screws’ diameter from 4.8 to 6.3 mm, leads to an increase of the ultimate load about 25% and 40% for 1 mm and 2 mm thick specimens, respectively. It is also concluded that transverse shear connectors have a better performance than longitudinal ones considering both ultimate load and ductility. The main observed failure mode of all specimens was tilting and bearing in shear connectors except for two specimens which was incorporated with pull-over mode. Moreover, ductility of the shear connectors was examined according to EC4 code. The results show that except for two specimens, the other U-shaped shear connectors used in this study can be accounted ductile. © 2021 Elsevier Ltd
Thin-Walled Structures (02638231) 164
Pull-out failures are one of the common failures in load bearing cold-formed steel clip angles causing catastrophic damages, where plate and screw fastener are dislocated. Thus, a detailed experimental study was first conducted to investigate the pull-out failures in cold-formed steel clip angles under tensile loading conditions. Then, since experimental tests are time-consuming and expensive, the ability of finite element modeling in the ABAQUS software environment was used to predict the pull-out behavior of the clip angles. The force–displacement behavior, ultimate strengths, and failure modes were compared with those obtained from experimental tests to validate the finite element models. The results were compared with those obtained from current design equations. Then, new design equations associated with numerical and both numerical and experimental results were provided by considering all geometrical and mechanical parameters to accurately predict the pull-out failure loads of the clip angles. © 2021 Elsevier Ltd
Structures (23520124) 34pp. 1710-1719
In this paper, the best geometrical shapes of Persian brick masonry single-shell domes under uniform pressure have been obtained and then the failure concentrated load has been determined. Seven different cross-sectional shapes with three different spans were considered. Three-dimensional finite element analysis was performed with the assumption of non-linear behaviour for materials. The minimum ratio of the apex thickness to base thickness (k) for which the failure load to dome weight ratio was a maximum was taken as the index for the best shape. For uniform pressure, k = 0.2, k = 0.08 to 0.3, and k = 0.144 to 0.54 were the best ratios for semi-circular, pointed and four-centred domes, respectively. The failure load of domes with best shapes under concentrated loads was more than that of other shapes. © 2021 Institution of Structural Engineers
Thin-Walled Structures (02638231) 164
Composite beams comprised of steel sections and concrete slabs, are one of the most widely used beams due to their advantages such as improving stiffness and strength compared to bare steel or reinforced concrete beams. Moreover, another important advantage of such beams is to prevent buckling of steel section by placing it under tension, which is especially important for low-thickness steel sections such as cold-formed steel (CFS) sections. Although the use of CFS sections in combination with concrete slabs can increase the efficiency of such sections, their low thickness makes it difficult to weld traditional studs as shear connectors on their top flanges. The current paper presents an experimental investigation about the behavior of bolted shear connectors in the composite cold-formed steel beams as a suitable alternative to welded shear studs. To do so, three main parameters including thickness of CFS sections, and size and strength of bolts were taken into account. Fifteen full-scale push-out specimens were constructed and tested. The ultimate load, ductility, stiffness and failure mode of all specimens were then assessed; and their results were reported and precisely discussed. Based on the results, depending on the size and strength of bolts, the ultimate load per shear connector for 1 mm thick CFS sections’ specimens is found between 6.2 and 8.6 KN, while this value for specimens by 2 mm thick CFS sections, is found between 15.6 and 26.8 KN. Moreover, based on EC4, the ductility of shear connectors was examined; the results indicate that all bolted shear connectors in this study can be assumed ductile and can be used in partial shear connections. © 2021 Elsevier Ltd
International Journal of Steel Structures (20936311) 20(5)pp. 1465-1481
On the structural analysis, connection effects should be evaluated in terms of rotational stiffness and ultimate strength; this makes it possible to obtain realistic behavior of the structure. In this research, a simple analytical evaluation is carried out to predict the behaviors of the connections as a bi-linear curve. Mechanical properties of the initial and the second parts of this curve are obtained by component-based method and a suggested classification method, respectively. The component-based method represents a joint by using a combination of rigid and flexible components. Each of the components is modeled by means of specific stiffness and strength values and they are assembled together to obtain the initial mechanical properties of the joint. The suggested classification method classifies all the components in a connection into three groups based on comparing the ultimate and the design moment strength of each component with those of the connection. By considering this procedure, a new equation is proposed to determine joint post-limit rotational stiffness. This simple and fast method is applicable to any type of joints regardless of profile type and applied loading. The proposed method is applied to a bolted angle, an end-plate to rectangular hollow section column and two bolted end-plate beam-to-column connections. The results are compared with those obtained from some other analytical, numerical and experimental methods. The outputs confirm that the proposed method is simpler, more accurate and less time consume than the other methods. © 2020, Korean Society of Steel Construction.
Journal of Constructional Steel Research (0143974X) 166
Load bearing cold-formed steel clip angles are one of the commonly used connectors in lightweight cold-formed steel structures. These connectors may fail at their screw connections due to pull-out failure when the screw pulls out of the plate under tension loading conditions. These localized connection failures can cause undesirable failures by dislocating both clip angle and sub-plates. Therefore, a detailed experimental study was carried out to investigate the pull-out failures of load bearing cold-formed steel clip angles considering different parameters such as clip angle configuration, clip angle thickness, screw diameter size, screw thread pitch, number of screws and screw location. This paper presents the test results conducted in this study and compares them with existing pull-out design standard equations. Also, a design equation with a resistance reduction factor is developed and suggested in order to accurately determine the pull-out strength of the cold-formed steel clip angles. © 2020
Applied Soft Computing (15684946) 92
It is still a big challenge to calculate the structural reliability index. Although first order reliability method (FORM) is effective in calculating the reliability index, it encounters many obstacles due to the need for differentiation of the limit state function (LSF) and using an optimization method, particularly when the LSF is nonlinear and non-differentiable. On the other hand, although simulation methods do not suffer from none of these problems, they require a large number of random samples. Moreover, simulation methods can only calculate the failure probability (ρf) directly, and they are not capable of calculating the design point. In the present paper, a new hybrid FORM-sampling simulation algorithm has been proposed to calculate the reliability index, design point, and importance vector. The proposed algorithm is viable to analysis the structural reliability with few random samples by using superior capabilities of importance sampling and step-by-step correction of the standard deviation (SD) of variables associated with the sampling density function. Furthermore, the LSF has been well approximated using the artificial neural network (ANN), leading to a significant reduction in the computation time. The efficiency of the present algorithm is illustrated through some examples in comparison to conventional methods. © 2020 Elsevier B.V.
Structures (23520124) 24pp. 791-803
In this paper, a numerical and analytical study was carried out in order to develop a new initial stiffness equation for thin-walled steel plate in bearing component. In this regard, effects of different design variables and curling occurrence on initial stiffness of this component were investigated. A set of parametric studies was performed on experimentally validated finite element models restraining curling occurrence to investigate the effect of geometrical parameters on initial stiffness of thin-walled steel plates. These design parameters included plate thickness, end distance, and edge distance and number of bolts. Effect of curling occurrence on initial stiffness was also considered using an analytical study. Finally, a new initial stiffness equation was proposed and compared with Eurocode3 design standard equation of hot-rolled steel plates. This new equation can be used in component-based modeling to calculate initial stiffness of thin-walled steel plate in bearing component. The outputs obtained by new equation showed better agreement with validated finite element results than those of old equation. © 2020 Institution of Structural Engineers
International Journal of Steel Structures (20936311) 20(5)pp. 1765-1782
In eccentrically braced frames (EBFs), the link beam is the main factor determining the behavior of this type of system. In order to enhance the ductility and delaying the web and flange buckling, the link beam is reinforced using intermediate web stiffeners to improve its performance and energy dissipation capacity. The web stiffeners spacing criteria is based on short links under pure shear, which have been applied without considering the bending effect on intermediate links. In this paper, first the effects of stiffener details and section geometry on the link behavior are investigated using finite element modeling, and then by proposing an optimization model, new spacing is proposed for stiffeners of intermediate links that is also consistent with bending distribution, and enhances the performance of intermediate links significantly. To further investigate the results of the optimization model and sensitivity analyses results, the behavior of a total of 52 short, intermediate and long links with different lengths and sections is simulated and investigated under cyclic loading based on ANSI/AISC 341-10 (Seismic provisions for structural steel buildings, Chicago, American Institute of Steel Construction, 2010) using ABAQUS. The results show that the section geometry in W-beams affects the stiffeners spacing and thereby, the behavior of intermediate and long links. According to the obtained results in short links, stiffeners spacing are very conservative and can be increased, and for intermediate links, adjusting the stiffeners spacing based on the proposed optimization model can significantly enhance the performance of the link beam. © 2020, Korean Society of Steel Construction.
Thin-Walled Structures (02638231) 150
Load bearing cold-formed steel clip angles are commonly used in various connections, subjected to different loading conditions. This numerical parametric study was performed in order to investigate the effect of various parameters on pull-through strength of fasteners on the anchored leg of cold-formed steel clip angles. In this regard, a finite element analysis is conducted, using ABAQUS program, to model the specimens subjected to tension forces. The finite element modeling is verified, using the existing tested clip angles and the ability of the validated finite element models in predicting the pull-through strength of other clip angle cases is evaluated, by comparing the obtained results with the experimental results. This parametric study provides a detailed information on the effect of any effective parameters, such as clip angle geometry, basic mechanical properties, and screw fastener head or washer sizes on the pull-through failures of bearing clip angles. According to the results, although the effects of parameters, such as screw fastener head or washer sizes and mechanical properties, on the pull-through strength are significant, the effect of clip angle geometry can be neglected. Finally, a suitable design equation is proposed to calculate the pull-through failure of load bearing clip angles. Moreover, a new equation is presented to calculate elastic stiffness of cold-formed steel clip angles, using a simple analytical model. The results obtained from this equation are in a proper agreement with the initial slope of force-displacement curves. © 2020 Elsevier Ltd
Intelligent Buildings International (17566932) 9(4)pp. 222-236
In this article, an intelligent method to detect, locate and quantify structural damages is presented via an optimization model. To predict the damage location and severity, the theory of pseudo-residual force vector (RFV) is applied. The proposed method can identify damages based on only a few mode shapes of the structure that can be easily obtained by a dynamic test. The objective function is defined as a minimum difference between the numerical and experimental variables in the RFV and the gravitational search algorithm is employed as a meta-heuristic technique for solving this optimization problem. The efficiency of the proposed method is investigated through the numerical examples with different damage scenarios. In the examples, the experimental data were simulated numerically using a finite element model of the structure and as demonstrated, it is possible to identify the damages with a reasonable level of accuracy while considering noise effects. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Engineering Applications of Artificial Intelligence (09521976) 62pp. 222-233
The gravitational search algorithm (GSA) is used in this paper to solve large scale reservoir operation optimization problem. Here, two constrained versions of GSA are proposed to solve this problem in which masses may be forced to satisfy problem constraints during solution building. This approach is very useful when attempting to solve large scale optimization problem as it will lead to a considerable reduction of the search space size. Here, in the second version of GSA, the storage volume bounds of the reservoir are modified prior to the main search to recognize the infeasible components of the search space and exclude from the search process before the main search starts. Two formulations are also proposed here for each proposed algorithm considering water releases or storage volumes at each operation time period as decision variable of the problem. Proposed algorithms are used to solve the simple and hydropower operation problem of “Dez” reservoir in Iran and the results are presented and compared with using original form of the GSA and any available results. The results indicate the ability of the proposed algorithm and especially the second constrained version of GSA to optimally solve the reservoir operation optimization problem. © 2017 Elsevier Ltd
Engineering Computations (02644401) 34(2)pp. 447-470
Purpose: The efficiency of the finite element analysis via force method depends on the overall flexibility matrix of the structure, while this matrix is directly affected from null bases vectors. As the null bases for an indeterminate structure are not unique, for an optimal analysis, the selected null bases should be sparse and banded corresponding to sparse, banded and well-conditioned flexibility matrix. This paper aims to present an efficient method for the formation of optimal flexibility matrix of finite element models comprising tetrahedron elements via mathematical optimization technique. Design/methodology/approach: For this purpose, a linear mixed integer programming model is presented for finding sparse solution of underdetermined linear system, which is correspond to sparse null vector. The charged system search algorithm is improved and used to find the best generator for formation of null bases. Findings: The efficiency of the present method is illustrated through some examples. The proposed method leads to highly sparse, banded and accurate null basis matrices. It makes an efficient force method feasible for the analysis of finite element model comprising tetrahedron elements. Originality/value: The force method, in which the member forces are used as unknowns, can be appealing to engineers. The main problem in the application of the force method is the formation of a self-stress matrix corresponding to a sparse flexibility matrix. In this paper, the highly sparse, banded and accurate null basis matrices gains by using mathematical optimization technique. © Emerald Publishing Limited.
Journal of Performance of Constructed Facilities (19435509) 30(2)
In this paper, the structural behavior of nine historical brick masonry minarets in Isfahan, which were built in the eleventh and twelfth centuries A.D., against weight, temperature, wind, and earthquakes is studied. A nonlinear three-dimensional FEM has been used. To investigate the effect of the central column and spiral staircase on the structural behavior, analyses have been performed for two cases: (1) the complete minaret, and (2) only the outer shell. The structural analysis of minarets under temperature changes shows that for certain inner and outer temperature differences, the minarets fail. Minarets do not fail because of the maximum wind velocity of Isfahan. All minarets fail when subjected to imposed earthquakes. By decreasing the minaret height or increasing the material strength, failure is delayed. Changing the failure criterion or damping ratio has little effect on the failure of the minarets. © 2015 American Society of Civil Engineers.
Multidiscipline Modeling in Materials and Structures (15736105) 11(2)pp. 186-201
Purpose - The interest in the ability to detect damage at the earliest possible stage is pervasive throughout the civil engineering over the last two decades. In general, the experimental techniques for damage detection are expensive and require that the vicinity of the damage is known and readily accessible; therefore several methods intend to detect damage based on numerical model and by means of minimum experimental data about dynamic properties or response of damaged structures. The paper aims to discuss these issues. Design/methodology/approach - In this paper, the damage detection problem is formulated as an optimization problem such as to obtain the minimum difference between the numerical and experimental variables, and then a modified ant colony optimization (ACO) algorithm is proposed for solving this optimization problem. In the proposed algorithm, the structural damage is detected by using dynamically measured flexibility matrix, since the flexibility matrix of the structure can be estimated from only the first few modes. The continuous version of ACO is employed as a probabilistic technique for solving this computational problem. Findings - Compared to classical methods, one of the main strengths of this meta-heuristic method is the generally better robustness in achieving global optimum. The efficiency of the proposed algorithm is illustrated by numerical examples. The proposed method enables the deduction of the extent and location of structural damage, while using short computational time and resulting good accuracy. Originality/value - Finding accurate results by means of minimum experimental data, while using short computational time is the final goal of all researches in the structural damage detection methods. In this paper, it gains by applying flexibility matrix in the definition of objective function, and also via using continuous ant colony algorithm as a powerful meta-heuristic techniques in the constrained nonlinear optimization problem. © Emerald Group Publishing Limited.
In this paper an efficient method is developed for the formation of null bases of finite element models (FEMs) composed of tetrahedron elements, corresponding to highly sparse and banded flexibility matrices. This is achieved by applying a modified ant colony system (ACS). The efficiency of the present method is illustrated through some examples. © 2010 Taylor & Francis Group, London.
Engineering Computations (02644401) 27(4)pp. 485-494
Purpose - Cycle bases of graphs have many applications in science and engineering. For an efficient force method of structural analysis, a special cycle basis corresponding to sparse cycle adjacency matrix is required. The purpose of this paper is to develop an ant colony system (ACS) algorithm for the generation of a cycle basis, leading to suboptimal cycle bases. Design/methodology/approach - In this paper, an ACS algorithm is developed for the generation of a cycle basis, leading to suboptimal cycle basis corresponding to highly sparse flexibility matrices. Examples are included to illustrate the efficiency of the developed algorithm. Findings - A new approach is developed which uses the recently developed ACS algorithm for the optimization. Originality/value - Previously, graph theoretical method had been used for the formation of suboptimal cycle bases. Here, optimization is performed using ACS algorithm for the first time. © Emerald Group Publishing Limited.
Finite Elements in Analysis and Design (0168874X) 45(10)pp. 710-720
An efficient algorithm is presented for the formation of null basis of triangular plane stress and plane strain finite element models, corresponding to highly sparse flexibility matrices. This is achieved by applying a modified ant colony system (ACS). An integer linear programming formulation is also presented to evaluate the quality of the results obtained by the proposed ant colony system algorithm. The efficiency of the present algorithm is illustrated through some examples. © 2009 Elsevier B.V. All rights reserved.
Asian Journal Of Civil Engineering (15630854) 10(1)pp. 113-130
An efficient algorithm is presented for the formation of statical basis, corresponding to highly sparse flexibility matrices for structures. This is achieved by applying a modified ant colony optimization algorithm for the formation of localized self-equilibrating systems. The efficiency of the present algorithm is illustrated through simple truss examples.
