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Browsing by Author "Farzampour, Alireza"

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    Compressive Behavior of Concrete under Environmental Effects
    Farzampour, Alireza (IntechOpen, 2019)
    Concrete strength is fairly sensitive to environmental effects. Extreme weather conditions and changes in humidity rates significantly affect the concrete compressive strength development. Concrete as one of the substantial material used in residential buildings and infrastructures is subjected to a massive strength change under extreme weather conditions. For understanding, the different concrete’s behavioral aspects, various commercial cement types under different temperatures, and humidity rates are investigated in this chapter. The experiments are aimed to investigate the concrete strength development over time when the material is cast at lower to mild temperatures and different humidity index rates. Results show that reducing the curing temperature more than 15° could result in 20% reduction in total compressive strength, while decreasing humidity rates by 50% leads to less than 10% drop in ultimate strength. To understand the strength developing process, maturity tests are conducted. It is shown that concrete is not able to reach to the expected ultimate strength if the temperature is significantly low regardless of curing time. The effect of temperature change during the curing process is more tangible on strength development compared to cement type and humidity rate values.
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    Development of Innovative Lateral Resistance Systems Featuring Earthquake-Protective Dampers
    Farzampour, 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.
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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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    Effects of Infill Plate’s Interconnection and Boundary Element Stiffness on Steel Plate Shear Walls’ Seismic Performance
    Paslar, Nima; Farzampour, Alireza (Materials, 2023-01-15)
    Steel plate shear walls (SPSWs) are among the most desirable load-bearing systems, which have been used wildly in various structures. Recently, designers have tended to SPSWs with only beam connections showing several problems. In the present research, several SPSWs with vari-ous types of connection conditions between infill plate and boundary elements, and various stiffness of boundary elements have been studied. The result illustrates that by having the full connection between infill plate and boundary elements, at least a 33% interconnected infill plate to columns could eliminate the significant loss of fundamental factors in SPSWs connected to beam only. Furthermore, increasing the stiffness of columns has more effect on the performance of SPSWs in comparison with beams.
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    Evaluating Shear links for Use in Seismic Structural Fuses
    Farzampour, Alireza (Virginia Tech, 2019-01-28)
    Advances in structural systems that resist extreme loading such as earthquake forces are important in their ability to reduce damages, improve performance, increase resilience, and improve the reliability of structures. Buckling resistant shear panels can be used to form new structural systems, which have been shown in preliminary analysis to have improved hysteretic behavior including increased stiffness and energy dissipating ability. Both of these characteristics lead to reduced drifts during earthquakes, which in turn leads to a reduction of drift related structural and nonstructural damage. Shear links are being used for seismic energy dissipation in some structures. A promising type of fuse implemented in structures for seismic energy dissipation, and seismic load resistance consists of a steel plate with cutouts leaving various shaped shear links. During a severe earthquake, inelastic deformation and damage would be concentrated in the shear links that are part of replaceable structural fuses, while the other elements of the building remain in the elastic state. In this study, by identifying the issues associated with general fuses previously used in structures, the behavior of the links is investigated and procedures to improve the behavior of the links are explained. In this study, a promising type of hysteretic damper used for seismic energy dissipation of a steel plate with cutouts leaving butterfly-shaped links subjected to shear deformations. These links have been proposed more recently to better align bending capacity with the shape of the moment diagram by using a linearly varying width between larger ends and a smaller middle section. Butterfly-shaped links have been shown in previous tests to be capable of substantial ductility and energy dissipation, but can also be prone to lateral torsional buckling. The mathematical investigations are conducted to predict, explain and analyze the butterfly-shaped shear links behavior for use in seismic structural fuses. The ductile and brittle limit states identified based on the previous studies, are mathematically explained and prediction equations are proposed accordingly. Design methodologies are subsequently conceptualized for structural shear links to address shear yielding, flexural yielding and buckling limit states for a typical link subjected to shear loading to promote ductile deformation modes. The buckling resistant design of the links is described with the aid of differential equations governing the links' buckling behavior. The differential equations solution procedures are developed for a useful range of link geometries and the statistical analysis is conducted to propose an equation for critical buckling moment. Computational studies on the fuses are conducted with finite element analysis software. The computational modeling methodology is initially verified with laboratory tests. Two parametric computational studies were completed on butterfly-shaped links to study the effect of varying geometries on the shear yielding and flexural yielding limit states as well as the buckling behavior of the different butterfly-shaped link geometries. It is shown that the proposed critical moment for brittle limit state has 98% accuracy, while the prediction equations for ductile limit states have more than 97% accuracy as well. Strategies for controlling lateral torsional buckling in butterfly links are recommended and are validated through comparison with finite element models. The backbone behavior of the seismic butterfly-shaped link is formulized and compared with computational models. In the second parametric study, the geometrical properties effects on a set of output parameters are investigated for a 112 computational models considering initial imperfection, and it is indicated that the narrower mid-width would reach to their limit states in lower displacement as compared to wider mid-width ones. The work culminates in a system-level validation of the proposed structural fuses with the design and analysis of shear link structural fuses for application in three buildings with different seismic force resisting systems. Six options for shear link geometry are designed for each building application using the design methodologies and predictive equations developed in this work and as guided by the results of the parametric studies. Subsequently, the results obtained for each group is compared to the conventional systems. The effect of implementation of the seismic links in multi-story structures is investigated by analyzing two prototype structures, with butterfly-shaped links and simple conventional beam. The results of the nonlinear response history analysis are summarized for 44 ground motions under Maximum Considered Event (MCE) and Design Basic Earthquake (DBE) ground motion hazard levels. It is shown that implementation of the butterfly-shaped links will lead to higher dissipated energy compared to conventional Eccentrically Braced Frame (EBF) systems. It is concluded that implementation of the seismic shear links significantly improves the energy dissipation capability of the systems compared to conventional systems, while the stiffness and strength are close in these two systems.
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    Evaluation of Seismic Vulnerability of Hospitals in the Tehran Metropolitan Area
    Ghaychi Afrouz, Setareh; Farzampour, Alireza; Hejazi, Zahra; Mojarab, Masoud (MDPI, 2021-02-05)
    The Tehran metropolitan area is extremely vulnerable to earthquakes due to the location of its active faults and its dense population. Assessing the probable damage of a high magnitude earthquake on buildings and facilities relies on a precise structural survey, which has an empirical basis depending on historic ground motions. The probability of damage and failure in discrete limits based on different ground motions is estimated by fragility curves. Using the most matching fragility curves for buildings in Tehran, the vulnerability of the hospitals in the capital, as one of the most critical structures in crisis management of disasters, was investigated in this study. Subsequently, the existing fragility curves, developed for Tehran and the other seismic prone countries such as Japan and the United States, were compared considering the typology of Tehran’s hospitals. Finally, the possible damages for each hospital were calculated based on the most conservative fragility curve and the most pessimistic scenario, which were used to evaluate the seismic vulnerability of hospitals and health care systems for different damage states. After zoning the damage of therapeutic areas of Tehran, it was observed that at least 2% to 10% damage occurred in all hospitals of Tehran, and none of the healthcare centers would remain structurally undamaged after a strong earthquake with the moment magnitude of 7 or more. In addition, the healthcare buildings could be prone to significant structural damage, especially in southern parts, which necessitates proactive management plans for Tehran metropolitan area.
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    Experimental Investigation of Sound Transmission Loss in Concrete Containing Recycled Rubber Crumbs
    Chalangaran, Navid; Farzampour, Alireza; Paslar, Nima; Fatemi, Hadi (Technopress, 2021-05-15)
    This study represents procedures and material to improve sound transmission loss through concrete without having any significant effects on mechanical properties. To prevent noise pollution damaging effects, and for reducing the transmission of the noises from streets to residential buildings, sound absorbing materials could be effectively produced. For this purpose, a number of several mixture designs have been investigated in this study to reduce the sound transmission through concrete, including control sample and three mixtures with recycled rubber with sizes of from 1mm up to 3 mm to limit the sound transmission. The rubber is used as a replacement of 5, 10, and 15 percent of sand aggregates. First, 7, 14 and 28-day strengths of the concrete have been measured. Subsequently, the sound transmission losses through the samples have been measured at the range of 63 Hz up to 6300 Hz by using impedance tube and the transfer function. The results show specimens containing 15% fine-grained crumbs, the loss of sound transmission were up to 190%, and for samples with 15% coarse-grained rubber, the loss of sound transmission were up to 228%, respectively. It is shown that concrete with recycled rubber crumbs could effectively improve environmental noise absorption.
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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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    Incremental Dynamic Analysis for Estimating Seismic Performance of Multi-Story Buildings with Butterfly-Shaped Structural Dampers
    Farzampour, 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.
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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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    Innovative Structural Fuse Systems for Various Prototype Applications
    Farzampour, Alireza (2022-02-21)
    To resist the imposed lateral forces on the structures, hysteric dampers are developed from steel plates and strategically implemented within various structural applications. The structural shear dampers are recently used to alleviate damages, while remaining members remain intact and undamaged. The practical use of the innovative dampers in structural applications is investigat-ed in this study. For this purpose, the design methodology for as set of innovative shear damp-ers is initially elaborated, for which the dampers are designed considering the governing shear and flexural ductile limit states, while the brittle buckling limit state is prevented. Subsequently, the finite element modeling methodology is verified and compared to laboratory tests for computationally analyzing various shapes of the shear damper in structural applications. Three major general prototype structures are established, and shear dampers are designed to be in-corporated in prototype applications. For each of the proposed applications, at least six different shapes of shear dampers are designed and subsequently compared with conventional systems. The results determined that the use of innovative shear dampers could effectively reduce de-mand forces on the boundary elements more than 40% in average, while the strength and the stiffness alter within less than 5% margin of difference.
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    Investigation of the beams and columns connection with infill plate on the structural behavior of the steel plate shear walls
    Paslar, Nima; Farzampour, Alireza (University of Tokyo, Japan, 2019-10-14)
    Steel plate shear walls are commonly used as structural lateral load resisting load systems in space-constrained areas. Many studies indicated that the implementation of the steel plate shear walls improves the ductility, stiffness and ultimate strength of the structure for which the interconnection of the steel infill plate with boundary members has a significant role. The typical connection of the infill shear plates to the boundary elements has a high-level fixity despite the general convenient construction procedures. In this study, the connection of the infill plates to the boundary elements are precisely investigated by establishing more than 21 computational models after verifying the modeling methodology. The structural performance of the partially connected plates with different commonly used connections types are evaluated and compared to the corresponding conventional fully connected infill plate systems. It is shown that column-only connected infill plate shear wall reduces the structural lateral load resisting capacity tangibly more than beam-only connected infill plates due to limited tension field action development. In addition, results indicated that systems with partial infill plate connection and connectivity ratio of 80% or more generally have similar structural performance compared to conventional systems with full connected infill plates.
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    Investigations on The Structural Behavior of Steel Plate Shear Walls with Partially Interconnected Infill Plates
    Paslar, 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.
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    Multi-Story Buildings Equipped with Innovative Structural Seismic Shear Fuse Systems
    Farzampour, 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.
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    Nano Silica and Metakaolin Effects on the Behavior of Concrete Containing Rubber Crumbs
    Chalangaran, Navid; Farzampour, Alireza; Paslar, Nima (MDPI, 2020-11-08)
    The excessive production of worn tires remaining from the transportation system and the lack of proper procedures to recycle or reuse these materials have caused critical environmental issues. Due to the rubber’s toughness, this material could be implemented to increase concrete toughness, and by crushing the tires concrete aggregates can be replaced proportionally with rubber crumbs and large quantities of scrapped rubber. However, this substitution decreases the concrete strength. In this study, crushed rubber with sizes from 1 to 3 mm and 3 to 6 mm were replaced by 5%, 10%, and 15% sand; the combination of two additives of nano silica and metakaolin additives with optimum values was used to compensate the degradation of the strength and improve the workability of the concrete. Moreover, the compressive strength, tensile behavior, and modulus of elasticity were measured and compared. The results indicate that the optimum use of nano silica and metakaolin additives could compensate the negative effects of the rubber material implementation in the concrete mixture while improving the overall workability and flowability of the concrete mixture.
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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.