Browsing by Author "Mansouri, Iman"
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- Development of Innovative Lateral Resistance Systems Featuring Earthquake-Protective DampersFarzampour, Alireza; Mansouri, Iman; Mortazavi, Seyed Javad; Retzepis, Eleni; Kaloop, Mosbeh R.; Hu, Jong-Wan (MDPI, 2023-03-17)Several conventional structural systems require sufficient retrofitting design procedures, improvements, and reconstructions to withstand lateral loads and to decrease the occurrence of damage. High strength capacity and ductility for seismic lateral resisting systems improve the structural vulnerabilities and limit damage concentrations in areas subject to seismic conditions. Several types and shapes of structural systems with appropriate ductility and energy dissipation features are currently established as structural fuses to enhance the general performance of the structures and decrease seismic ramifications. To enhance the energy dissipation performance and concentration of the inelasticity, improving the ductile behavior and limiting the unpredictable accumulation of plastic strains is essential. The conventional eccentrically braced systems are examined and reestablished, and the effects of shear fuses used in high-rise buildings are investigated for prototype buildings by implementing the verified simulations. Next, seismic protective fuse systems with innovative dampers consisting of several butterfly-shaped shear links are established. Ultimately, the design guidelines are established based on the conventional eccentrically braced frames (EBFs), which are redesigned with the use of noble seismic protective fuses, and the hysteretic behavior is obtained and compared accordingly.
- Effect of flexural and shear stresses simultaneously for optimized design of butterfly-shaped dampers: Computational studyFarzampour, 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.
- Experimental study on the optimized design of butterfly-shaped dampersHu, 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.
- Force-displacement behavior of a beam with butterfly-shaped dampers implementing GE programmingFarzampour, 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.
- 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.
- Force-displacement relationship of the butterfly-shaped beams based on gene expression programmingFarzampour, 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.
- Improved Homotopy Perturbation Method for Geometrically Nonlinear Analysis of Space TrussesDehghani, 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.
- Incremental Dynamic Analysis for Estimating Seismic Performance of Multi-Story Buildings with Butterfly-Shaped Structural DampersFarzampour, Alireza; Mansouri, Iman; Dehghani, Hamzeh (MDPI, 2019-04-08)Structural strength and stiffness were previously investigated to sufficiently improve the lateral load resistance against major events. Many buildings require appropriate design to effectively withstand the lateral seismic loads and reduce the corresponding damages. Design methodologies and structural elements were recently introduced to improve the energy dissipation capability and limit the high force demands under seismic loadings. The new systems are designed to protect the structural integrity and concentrate the inelasticity in a specific area, while the remaining parts are kept undamaged and intact. This study introduces a new structural system with dampers having strategic cutouts, leaving butterfly-shaped shear dampers for dominating the yielding mechanism over other brittle limit states. The new system is designed for re-establishing the conventional eccentrically braced frame system with simple linking beams. The system with strategic cutouts is subsequently used and compared with the eccentrically braced frames (EBF) system for seismic performance investigation and incremental dynamic analysis (IDA), using the OpenSees program, which is used to indicate the collapse behavior under forty-four selected ground motions. Results show that the butterfly-shaped multi-story buildings, compared to the corresponding conventional systems, are capable of enhancing the system resistance against lateral seismic loads by postponing the collapse state to the larger drift ratio values.
- Innovative Lateral Resisting Systems with Seismic Protective Dampers and Guideline Design ProceduresFarzampour, 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.
- Investigations on The Structural Behavior of Steel Plate Shear Walls with Partially Interconnected Infill PlatesPaslar, Nima; Farzampour, Alireza; Chalangaran, Navid; Mansouri, Iman; Wan Hu, Jong (2023-07-08)Steel plate shear walls are considered an effective lateral load-resisting system widely used in space-constrained high-rise buildings. Steel plate shear walls could improve several structural parameters such as strength, energy absorption, and stiffness. Recently, there is a tendency to have limited connection between the infill plate and boundary elements to prevent significant direct demands on columns, and possible brittle modes of behavior leading to the economical design of various structural elements. However, previous studies showed that the absence of the interconnection between infill plate and columns in steel plate shear walls with beam-connected systems could reduce the performance of the system significantly. In the present study, procedures to improve the performance of the steel plate shear walls with limited infill plate interconnections with the boundary elements are provided. Subsequently, computational steel plate shear wall models, with and without boundary infill plate stiffeners and different widths of the infill plate have been investigated after fully validating the computational modeling methodology to find efficient procedures for eliminating the lack of interconnections. The results show that utilizing boundary stiffeners increased ultimate strength, energy dissipation and stiffness by 15%, 20%, and 24% on average. Although boundary stiffeners cannot fully control the out-of-plane displacements of the infill plate, they would be useful in improving the formation of tension field actions. Furthermore, it is shown that the width of the infill plate and boundary stiffeners are the key factors in the performance of the system.
- Multi-Story Buildings Equipped with Innovative Structural Seismic Shear Fuse SystemsFarzampour, Alireza; Mortazavi, Seyed Javad; Mansouri, Iman; Awoyera, Paul Oluwaseun; Wan Hu, Jong (Elsevier, 2022-03-29)Infrastructures could be designed and constructed to resist seismic lateral loads without experiencing a significant amount of damage concentrations in specific area. Having sufficient strength and stiffness to reduce the structural vulnerabilities against serious damages under seismic loading, requires structural elements to have adequate ductility and energy dissipating capability, which could be provided with the use structural dampers. These elements are typically replaceable, and designed to yield and protect the surrounding members from damages, and then be accessible after a major event. In this study, butterfly-shaped links with linearly varying width between larger ends and a smaller middle section are used for redesigning the prototype structures due to substantial ductility and stable energy dissipation capability. The effect of implementation of innovative seismic dampers in multi-story structures is investigated by analyzing multi-story prototype structures with structural seismic shear dampers, and subsequently compared with simple conventional linking beams. The results of the nonlinear response history analysis are summarized for 44 ground motions under maximum considered earthquake (MCE) and designed based earthquake (DBE) hazard levels. It is shown that implementation of the butterfly-shaped dampers in buildings with similar stiffness and strength leads to higher dissipated energy and less pinched curves compared to typical eccentrically braced frame systems. It is determined that the general stiffness and strength of the system with the butterfly-shaped link is close to conventional models; however, the demands on the surrounding boundary elements are lower than the corresponding conventional model, which could be beneficent for improving the seismic performance of the structural systems.
- Optimization of the Curved Metal Damper to Improve Structural Energy Dissipation CapacityKim, 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.
- Optimization of the curved metal damper to improve structural energy dissipation capacityKim, 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.
- Seismic behavior investigation of the steel multi-story moment frames with steel plate shear wallsMansouri, 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.
- Shape optimization of butterfly-shaped shear links using grey wolf algorithmFarzampour, Alireza; Khatibinia, Mohsen; Mansouri, Iman (2019-03)The shear loading applied to structures is resisted by implementation of hysteric dampers as structural seismic force resisting system. Recently, steel plates with engineered cut-outs are introduced to have controlled yielding. These structural elements behave as shear links are able to post pone brittle limit states, leading to resistance against early fracture. Among which, a promising type of link is butterfly-shaped link, for which the demand moment diagram aligns with capacity moment diagram to efficiently implement the steel. Previous studies show that these elements are used as appropriate choice for structural seismic fuse system since they are able to experience large drifts with sufficient ductility and full hysteric behavior. Therefore, the appropriate geometrical properties for these links are in need of further investigations. In this study, the finite element methodology is initially validated with experimental test. Then optimization criteria is introduced for set of 300 models to investigate the desired geometrical properties for having most energy dissipation with less fracture potential. This paper represents optimization process with which the geometrical properties of butterfly shaped link is improved to have sufficient energy dissipation performance and less potential for fracture. The pushover curves and equivalent plastic strains are obtained from ABAQUS through an iterative process. The Grey Wolf Optimizer method is adopted for optimization methodology due to having strong capability in non-linear system. It can be found that by implementation of optimization methodology the links are designed to have a mode switch from flexural yielding limit state to shear yielding and are able to dissipate energy over a less equivalent plastic strain value.
- Symposium: Butterfly-Shaped Beams Relationship with GEPFarzampour, 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.