Browsing by Author "Hu, Jong Wan"

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    Effect of flexural and shear stresses simultaneously for optimized design of butterfly-shaped dampers: Computational study
    Farzampour, Alireza; Eatherton, Matthew R.; Mansouri, Iman; Hu, Jong Wan (Techno-Press, 2019-02)
    Structural fuses are made up from oriented steel plates to be used to resist seismic force with shear loading resistance capabilities. The damage and excessive inelastic deformations are concentrated in structural fuses to avoid any issues for the rest of the surrounding elements. Recently developed fuse plates are designed with engineered cutouts leaving flexural or shear links with controlled yielding features. A promising type of link is proposed to align better bending strength along the length of the link with the demand moment diagram is a butterfly-shaped link. Previously, the design methodologies are purely based on the flexural stresses, or shear stresses only, which overestimate the dampers capability for resisting against the applied loadings. This study is specifically focused on the optimized design methodologies for commonly used butterfly-shaped dampers. Numerous studies have shown that the stresses are not uniformly distributed along the length of the dampers; hence, the design methodology and the effective implementation of the steel need revisions and improvements. In this study, the effect of shear and flexural stresses on the behavior of butterfly-shaped links are computationally investigated. The mathematical models based on von-Mises yielding criteria are initially developed and the optimized design methodology is proposed based on the yielding criterion. The optimized design is refined and investigated with the aid of computational investigations in the next step. The proposed design methodology meets the needs of optimized design concepts for butterfly-shaped dampers considering the uniform stress distribution and efficient use of steel.
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    Experimental study on the optimized design of butterfly-shaped dampers
    Hu, Jong Wan; Wook Cha, Young; Farzampour, Alireza; Mirzai, Nadia; Mansouri, Iman (2021-01)
    Structural fuses are manufactured from oriented steel plates for use in seismic protective systems to withstand significant lateral shear loads. These systems are designed and detailed for concentrating the damage and excessive inelastic deformations in the desired location along the length of the fuse to prevent the crack propagation and structural issues for the surrounding elements. Among a number of structural systems with engineered - cut-outs, a recently developed butterfly-shaped structural fuses are proposed to better align the bending strength along the length of the fuse with the demand moment, enhancing controlled yielding features over the brittle behavior. Previously, the design methodologies were developed purely based on the flexural stresses’ or shear stresses’ behavior leading to underestimate or overestimate the structural capacity of the fuses. The aim of this study is to optimize the design methodologies for commonly used butterfly-shaped dampers through experimental investigations considering the stresses are not uniformly distributed stresses along the length of the fuse system. The effect of shear and flexural stresses on the behavior of butterfly-shaped are initially formulated based on the Von-Mises criterion, and the optimized geometry is specified. Subsequently, experimental tests are developed for evaluating the optimized design concepts for butterfly-shaped dampers considering the uniform stress distribution and efficient use of steel. It is shown that butterfly-shaped dampers are capable of full cyclic hysteric behavior without any major signs of strength or stiffness degradations.
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    Force-displacement behavior of a beam with butterfly-shaped dampers implementing GE programming
    Farzampour, Alireza; Mansouri, Iman; Mortazavi, Seyed Javad; Hu, Jong Wan (Springer, 2020)
    Structural steel plates having engineered cut-outs to exhibit controlled yielding is recently proposed for desirable performance compared to conventional systems. Butterfly-shaped beams with hexagonal cut-outs inside of the beam’s web is studied to better align the bending strength diagram along the link length with the corresponding demand shape of the applied moment diagram. In previous studies, it has been reported that these links have a substantial energy dissipation capability and sufficient ductility which necessities further investigations. In this study, a set of 240 nonlinear finite element models are developed for creation of a database and subsequently calibrated with finite element software packages. The capability of the gene expression programming (GEP) is explored for prediction of force-displacement relationship of a butterfly-shaped beam. Two new models are developed based on the reliable generated database. Subsequently, the proposed models are validated with several conducted analysis and statistical parameters, for which the comparisons are shown in details. The results represent that the proposed models are able to predict the force-displacement relationship of a butterfly-shaped beam with satisfactory accuracy.
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    Force-displacement relationship of a butterfly-shaped beams based on gene expression programming [conference proceeding]
    Farzampour, Alireza; Mansouri, Iman; Mortazavi, Seyed Javad; Hu, Jong Wan (2019-11)
    Structural steel plates having engineered cut-outs to exhibit controlled yielding is recently proposed for desirable performance compared to conventional systems. Butterfly-shaped beams with hexagonal cut-outs inside of the beam’s web is studied to better align the bending strength diagram along the link length with the corresponding demand shape of the applied moment diagram. In previous studies, it has been reported that these links have substantial energy dissipation capability and sufficient ductility which necessities further investigations. In this study, a set of 240 nonlinear finite element models are developed for creation of a database and subsequently calibrated with finite element software packages. The capability of the gene expression programming (GEP) is explored for prediction of force-displacement relationship of a butterfly-shaped beam. Two new models are developed based on the reliable generated database. Subsequently, the proposed models are validated with several conducted analysis and statistical parameters, for which the comparisons are shown in detail. The results represent that the proposed models are able to predict the force-displacement relationship of a butterfly-shaped beam with satisfactory accuracy.
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    Force-displacement relationship of the butterfly-shaped beams based on gene expression programming
    Farzampour, Alireza; Mansouri, Iman; Mortazavi, Seyed Javad; Hu, Jong Wan (Springer, 2020-09)
    Structural steel plates with engineered cut-outs to exhibit controlled yielding mechanism is recently proposed for desirable structural performance compared to conventional systems. Butterfly-shaped beams with hexagonal cut-outs inside of the beam’s web is implemented to better align the bending strength diagram along the link length with the corresponding demand shape of the applied moment diagram. In previous studies, it has been reported that these links have a substantial energy dissipation capability and sufficient ductility which necessities further investigations and structural behavior prediction studies. In this study, a set of 240 nonlinear finite element models are developed for creation of a database and subsequently calibrated with finite element software packages. The capability of the gene expression programming (GEP) is explored for prediction of force-displacement relationship of a butterfly-shaped beam. Two new models are developed based on the reliable generated database. Subsequently, the proposed models are validated with several conducted analysis and statistical parameters, for which the comparisons are shown in details. The results represent that the proposed models are able to predict the force-displacement relationship of a butterfly-shaped beam with satisfactory accuracy.
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    Improved Homotopy Perturbation Method for Geometrically Nonlinear Analysis of Space Trusses
    Dehghani, Hamzeh; Mansouri, Iman; Farzampour, Alireza; Hu, Jong Wan (MDPI, 2020-04-24)
    The objective of this study is to explore a noble application of the improved homotopy perturbation procedure bases in structural engineering by applying it to the geometrically nonlinear analysis of the space trusses. The improved perturbation algorithm is proposed to refine the classical methods in numerical computing techniques such as the Newton–Raphson method. A linear of sub-problems is generated by transferring the nonlinear problem with perturbation quantities and then approximated by summation of the solutions related to several sub-problems. In this study, a nonlinear load control procedure is generated and implemented for structures. Several numerical examples of known trusses are given to show the applicability of the proposed perturbation procedure without considering the passing limit points. The results reveal that perturbation modeling methodology for investigating the structural performance of various applications has high accuracy and low computational cost of convergence analysis, compared with the Newton–Raphson method.
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    Innovative Lateral Resisting Systems with Seismic Protective Dampers and Guideline Design Procedures
    Farzampour, Alireza; Mansouri, Iman; Hu, Jong Wan (2022-01-01)
    Several conventional structures are in need of proper design and construction to resist seismic loads without experiencing a significant amount of damages. Sufficient strength and stiffness of seismic protective devices would eventually reduce the structural vulnerabilities due to the serious damage under seismic loading. There are variations of structural elements with adequate ductility and energy dissipating capability, which could be implemented as structural fuses to reduce the seismic effects, especially for high-rise buildings. For this purpose, dampers are typically used for improving the seismic energy dissipation, the concentration of the damages in a specific part of the system, proving more ductility, and reducing the unpredictable high plastic strains within the structures. In this study, the widely used conventional eccentrically braced systems are considered for further investigations, and the effects of the implementation of the seismic links in multi-story structures are analyzed for multi-story prototype structures by using verified computational models. Subsequently, innovative seismic protective dampers consist of several butterfly-shaped shear links with a linearly varying width between larger ends, and a smaller middle section is introduced. Ultimately, guideline design procedures are developed for redesigning the conventional eccentrically braced frame (EBF) systems with innovative seismic protective dampers, and backbone curves are derived and compared accordingly.
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    Optimization of the Curved Metal Damper to Improve Structural Energy Dissipation Capacity
    Kim, Young-Chan; Mortazavi, Seyed Javad; Farzampour, Alireza; Hu, Jong Wan; Mansouri, Iman; Awoyera, Paul Oluwaseun (MDPI, 2022-01-11)
    Structural curved metal dampers are implemented in various applications to mitigate the damages at a specific area efficiently. A stable and saturated hysteretic behavior for the in-plane direction is dependent on the shape of a curved-shaped damper. However, it has been experimentally shown that the hysteretic behavior in the conventional curved-shaped damper is unstable, mainly as a result of bi-directional deformations. Therefore, it is necessary to conduct shape optimization for curved dampers to enhance their hysteretic behavior and energy dissipation capability. In this study, the finite element (FE) model built in ABAQUS, is utilized to obtain optimal shape for the curved-shaped damper. The effectiveness of the model is checked by comparisons of the FE model and experimental results. The parameters for the optimization include the curved length and shape of the damper, and the improved approach is conducted by investigating the curved sections. In addition, the design parameters are represented by B-spline curves (to ensure enhanced system performance), regression analysis is implemented to derive optimization formulations considering energy dissipation, constitutive material model, and cumulative plastic strain. Results determine that the energy dissipation capacity of the curved steel damper could be improved by 32% using shape optimization techniques compared to the conventional dampers. Ultimately, the study proposes simple optimal shapes for further implementations in practical designs.
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    Optimization of the curved metal damper to improve structural energy dissipation capacity
    Kim, Young-Chan; Mortazavi, Seyed Javad; Farzampour, Alireza; Hu, Jong Wan; Mansouri, Iman; Awoyera, Paul Oluwaseun (MDPI, 2022-01-15)
    Structural curved metal dampers are implemented in various applications to mitigate the damages at a specific area efficiently. A stable and saturated hysteretic behavior for the in-plane direction is dependent on the shape of a curved-shaped damper. However, it has been experi-mentally shown that the hysteretic behavior in the conventional curved-shaped damper is un-stable, mainly as a result of bi-directional deformations. Therefore, it is necessary to conduct shape optimization for curved dampers to enhance their hysteretic behavior and energy dissipa-tion capability. In this study, the finite element (FE) model built in ABAQUS, is utilized to obtain optimal shape for the curved-shaped damper. The effectiveness of the model is checked by com-parisons of the FE model and experimental results. The parameters for the optimization include the curved length and shape of the damper, and the improved approach is conducted by investi-gating the curved sections. In addition, the design parameters are represented by B-spline curves (to ensure enhanced system performance), regression analysis is implemented to derive optimi-zation formulations considering energy dissipation, constitutive material model, and cumula-tive plastic strain. Results determine that the energy dissipation capacity of the curved steel damper could be improved by 32% using shape optimization techniques compared to the con-ventional dampers. Ultimately, the study proposes simple optimal shapes for further imple-mentations in practical designs.
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    Seismic behavior investigation of the steel multi-story moment frames with steel plate shear walls
    Mansouri, Iman; Arabzadeh, Ali; Farzampour, Alireza; Hu, Jong Wan (Techno Press, 2020-10)
    Steel plate shear walls are recently used as efficient seismic lateral resisting systems. These lateral resistant structures are implemented to provide more strength, stiffness and ductility in limited space areas. In this study, the seismic behavior of the multi-story steel frames with steel plate shear walls are investigated for buildings with 4, 8, 12 and 16 stories using verified computational modeling platforms. Different number of steel moment bays with distinctive lengths are investigated to effectively determine the deflection amplification factor for low-rise and high-rise structures. Results showed that the dissipated energy in moment frames with steel plates are significantly related to the inside panel. It is shown that more than 50% of the dissipated energy under various ground motions is dissipated by the panel itself, and increasing the steel plate length leads to higher energy dissipation capability. The deflection amplification factor is studied in details for various verified parametric cases, and it is concluded that for a typical multi-story moment frame with steel plate shear walls, the amplification factor is 4.93 which is less than the recommended conservative values in the design codes. It is shown that the deflection amplification factor decreases if the height of the building increases, for which the frames with more than six stories would have less recommended deflection amplification factor. In addition, increasing the number of bays or decreasing the steel plate shear wall length leads to a reduction of the deflection amplification factor.
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    Symposium: Butterfly-Shaped Beams Relationship with GEP
    Farzampour, Alireza; Mansouri, Iman; Mortazavi, Seyed Javad; Hu, Jong Wan (2019)
    Structural steel plates having engineered cut-outs to exhibit controlled yielding is recently proposed for desirable performance compared to conventional systems. Butterfly-shaped beams with hexagonal cut-outs inside of the beam’s web is studied to better align the bending strength diagram along the link length with the corresponding demand shape of the applied moment diagram. In previous studies, it has been reported that these links have a substantial energy dissipation capability and sufficient ductility which necessities further investigations. In this study, a set of 240 nonlinear finite element models are developed for creation of a database and subsequently calibrated with finite element software packages. The capability of the gene expression programming (GEP) is explored for prediction of force-displacement relationship of a butterfly-shaped beam. Two new models are developed based on the reliable generated database. Subsequently, the proposed models are validated with several conducted analysis and statistical parameters, for which the comparisons are shown in details. The results represent that the proposed models are able to predict the force-displacement relationship of a butterfly-shaped beam with satisfactory accuracy.
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    Unsupervised Identification of Arbitrarily-damped Structures using Time-Scale ICA: Experimental Investigations
    Farzampour, Alireza; Kamali-Asl, Arash; Hu, Jong Wan (2018-09-14)
    To identify the dynamic parameters of the structures with sufficient accuracy, a new method is developed and used in this study. In this method, the wavelet-transformed (WT) representation of system responses is conducted on the measured responses, and then the independent component analysis (ICA) is implemented to obtain the modal features. Effectiveness of the proposed method under ap-plied loading condition is shown by applying the white noise, and extracting the simulation results of a multi-degree-of-freedom sys-tem to illustrate the applicability of the proposed methodology for both lightly- and highly-damped structures. In this study, it is deter-mined that continuous wavelet transform (CWT) is indicated to have a better efficiency due to its higher adaptive resolution in time-frequency to be incorporated into independent component analysis compared to other conventional methodologies. The applicability of the proposed method for assessing the natural modal frequencies and mode shapes of the existent structures is investigated by study-ing the IASC-ASCE structural health monitoring benchmark. It is shown that in all the cases the modal properties along with the mod-al assurance criterion (MAC) values are in satisfactory agreement with their exact values and the proposed method is sufficiently ro-bust in accurate extraction of higher modes of vibration.