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S. Dehghani

Bio: S. Dehghani is an academic researcher from Shiraz University. The author has contributed to research in topics: Damper & Truss. The author has an hindex of 4, co-authored 5 publications receiving 28 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a cluster-based non-dominated sorting genetic algorithm (NSGA) was used to investigate the effects of rehabilitation objectives on multi-objective design optimization of two-dimensional (2D) steel X-braced frames in the presence of soil-structure interaction.
Abstract: A cluster-based non-dominated sorting genetic algorithm (NSGA) II has been considered to investigate the effects of rehabilitation objectives on multi-objective design optimization of two-dimensional (2D) steel X-braced frames in the presence of soil-structure interaction. The substructure elasto-perfect plastic model has been adopted for modeling of the soil-structure interaction and the nonlinear pushover analysis is used to evaluate the performance level of the frames for a specified hazard level. Cross-sections of grouped elements of the frames are considered to be discontinuous design variables of the problem. Via implementing some of the constraints, which are independent of doing the time-consuming nonlinear analysis, input population of the optimization technique has been clustered. By using the nonlinear analysis technique in conjunction with the cluster-based NSGA II, near optimal trade-off relation between minimum weight and maximum story drifts of the frames are obtained. The allowable rotations, geometry, and resistance constraints of the structural elements are considered in the optimization design of the frames. The effects of the enhanced basic safety and limited selective rehabilitation objectives on optimum design of the frame are studied. The results show differences between the optimum results of the three mentioned rehabilitation objectives and effects of soil types.

10 citations

Journal ArticleDOI
TL;DR: The results show that the addition of the curved damper has significantly improved the stiffness, strengths and energy dissipation of the CDSRMFs.

10 citations

Journal ArticleDOI
TL;DR: The proposed TBCD system can be considered as an efficient alternative to conventional seismic force–resisting systems for both newly built structures and the seismic retrofitting of existing structures.
Abstract: Curve-shaped laser-cut steel plate dampers named curved damper have been recently introduced, and their performance has been experimentally investigated through cyclic loading tests. Using the same concept, this study aims to propose a novel cost-effective toggle brace–curved damper (TBCD) system, which combines the toggle braces and curved dampers to provide a practical passive control device. The seismic performance of three-, six-, and nine-story steel moment–resisting structures utilized with TBCD is analyzed using nonlinear time history analysis (NTHA). For better comparison, the TBCD system is optimized using the multi-objective nondominated sorting genetic algorithm (NSGA-II). The seismic performance of the proposed system is then compared against the optimized viscous dampers (VDs), viscoelastic dampers (VEDs), and buckling-restrained braces (BRBs). The results of the optimization process show that the TBCD has comparable performance to the other passive control devices presented, while it leads to more cost-effective design solutions by reducing the constructional, installation, life cycle maintenance and repair cost, and downtime. Hence, the proposed TBCD system can be considered as an efficient alternative to conventional seismic force–resisting systems for both newly built structures and the seismic retrofitting of existing structures.

9 citations

Journal ArticleDOI
TL;DR: The results of the nonlinear dynamic analysis indicated that the newly proposed CDTMF system can control the roof displacement, story drift, and roof acceleration during an earthquake excitation more efficiently than the recent buckling restrained knee braced truss moment frame systems.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: The results demonstrate that the topologically optimal SCBFs not only have the least structural weight, but also they are of considerable collapse safety in comparison to optimalSCBFs with fixed topology of braces.

33 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-level performance-based optimisation method of nonlinear viscous dampers (NVDs) for seismic retrofit of existing substandard steel frames is presented.
Abstract: This paper presents a practical multi-level performance-based optimisation method of nonlinear viscous dampers (NVDs) for seismic retrofit of existing substandard steel frames. A Maxwell model is adopted to simulate the behaviour of the combined damper-supporting brace system, with a fractional power-law force–velocity relationship for the NVDs, while a distributed-plasticity fibre-based section approach is used to model the beam-column members thus incorporating the nonlinearity of the parent steel frame in the design process. The optimum height-wise distribution of the damping coefficients of NVDs satisfying given performance requirements is identified via a uniform damage distribution (UDD) design philosophy. The efficiency of the proposed multi-level performance-based design optimisation is illustrated through nonlinear time-history analysis of 3-, 7- and 12-storey steel frames under both artificial and natural spectrum-compatible earthquakes. Sensitivity analysis is performed to investigate the effects of initial height-wise damping distribution, convergence factor and uncertainty in design ground-motion prediction on the optimisation strategy. The efficiency of the final optimum design solution is also investigated by using drift-based, velocity-based, and energy-based UDD approaches to identify the most efficient performance index parameter for optimisation purposes. It is found that regardless of the selected performance parameter, the optimum damping distribution identified by the proposed methodology leads to frames exhibiting lower maximum inter-storey drift, local damage (maximum plastic rotation) and global damage index compared to an equal-cost uniform damping distribution. However, using drift-based UDD approach generally results in a better seismic performance. It is shown that the proposed UDD optimisation method can be efficiently used to satisfy multiple performance objectives at different intensity levels of the earthquake excitation, in line with performance-based design recommendations of current seismic codes. The proposed method is easy to implement for practical design purposes and represents a simple yet efficient tool for optimum seismic retrofit of steel frames with NVDs.

29 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of an inducer is optimized by considering the inlet tip blade angle, the outlet tip blades angle, and the ratio of the outlet hub radius to inlet hub radius as design variables and the head coefficient, the hydraulic efficiency, and required net positive suction head (NPSHR) as objective functions.
Abstract: Inducer is an important device which is mounted upstream of the inlet to the main impeller of the centrifugal pump and rotates at the same rotational speed as the impeller. The main purpose of the inducer is to improve the suction performance of the pump, but this improvement is dependent on the geometrical parameters of the inducer. Therefore, it is essential to optimize these parameters. In the present study, the performance of an inducer is optimized by considering the inlet tip blade angle, the outlet tip blade angle, and the ratio of the outlet hub radius to inlet hub radius as design variables and the head coefficient, the hydraulic efficiency, and the required net positive suction head (NPSHR) as objective functions. The inducer performance is simulated using 3-D computational fluid dynamics (CFD) and compared with experimental data, which shows the validity of the used method and assumptions. Then the group method of data handling (GMDH) algorithm is used to model the objective functions with respect to design variables. Using the modified non-dominated sorting genetic algorithm II (NSGA-II) approach, Pareto fronts are then plotted and trade-off optimum points are obtained using the technique for order of preference by similarity to ideal solution (TOPSIS). Using multi-objective optimization, the head coefficient, the hydraulic efficiency, and NPSHR are improved 14.3%, 0.3%, and 30.2%, respectively. Recommended design points unveil significant optimum design principles that can be obtained only by using a multi-objective optimization approach.

21 citations

Journal ArticleDOI
TL;DR: In this paper, an improved multi-objective particle swarm optimization with genetic algorithm (MOPSOGA) was used to design a moderately thick hexagonal honeycomb sandwich plate.

19 citations

Journal ArticleDOI
TL;DR: In this paper, a hysteretic damper is proposed for beam-column steel connections to dissipate seismic energy, which helps all structural members including beams and columns to maintain in the elastic region, and will improve the ductility and seismic resilience of the whole building structure.
Abstract: In this study, a novel hysteretic damper is proposed for beam-column steel connections to dissipate seismic energy. The proposed system is classified as a low-damage device and the energy dissipation in the connection is provided through the bending deformations in hourglass shape steel pins inside the hysteretic damper. At the first stage, full-scale experimental prototypes have been fabricated and tested in the dynamic testing laboratory. In the next stage, micro- and macro-modelings of the proposed device calibrated through the experimental testing have been investigated using ABAQUS and OpenSees platforms, respectively. Both experimental and finite element simulations indicated that the proposed damper has a high capacity of energy dissipation without a significant decline in the resistance through loading cycles. Applying this damper to the connection helps all structural members including beams and columns to maintain in the elastic region, and will improve the ductility and seismic resilience of the whole building structure. The proposed damper has the easiness of fabrication, installation, and replacement.

18 citations