Unsupervised identification of arbitrarily-damped structures using time-scale independent component analysis: Part I

Farzampour, Alireza,Kamali-Asl, Arash,Hu, Jong Wan 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2

<P>In this study, a new method is proposed to identify the dynamic parameters of structures with higher accuracy compared to current methods. First, the wavelet-transformed representation of system responses is extracted from measured responses, and then the independent component analysis is used to achieve the modal characteristics. The simulation results of a multi-degree-of-freedom system illustrate that this method is capable of accurately identifying the modal information of lightly- and highly-damped structures. It is represented that continuous wavelet transform, due to its adaptive time-frequency resolution, is more efficient to be incorporated into independent component analysis compared to Short time Fourier transform (STFT). The latter is unable to accurately determine the modal response, especially at higher frequencies, while the proposed method can identify the system with marked accuracy. The efficiency of proposed method is also investigated under additive noise. Results shown that for highly- and lightly- damped system, the proposed method is able to capture the modal parameters especially in higher frequencies of vibration, along with the modal assurance criterion values with satisfactory accuracy, which indicates the robustness of the procedure compared to other available methodologies.</P>

Unsupervised identification of arbitrarily-damped structures using time-scale independent component analysis: Part II

Farzampour, A.,Kamali-Asl, A.,Hu, J. W. 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

<P>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 applied loading condition is shown by applying the white noise, and extracting the simulation results of a multi-degree-of-freedom system to illustrate the applicability of the proposed methodology for both lightly- and highly-damped structures. In this study, it is determined 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 studying the IASCASCE structural health monitoring benchmark. It is shown that in all the cases the modal properties along with the modal assurance criterion (MAC) values are in satisfactory agreement with their exact values and the proposed method is sufficiently robust in accurate extraction of higher modes of vibration.</P>

Temperature and humidity effects on behavior of grouts

Farzampour, Alireza Techno-Press 2017 Advances in concrete construction Vol.5 No.6

Grouts compared to other material sources, could be highly sensitive to cold weather conditions, especially when the compressive strength is the matter of concern. Grout as one the substantial residential building material used in retaining walls, rebar fixation, sidewalks is in need of deeper investigation, especially in extreme weather condition. In this article, compressive strength development of four different commercial grouts at three temperatures and two humidity rates are evaluated. This experiment is aimed to assess the grout strength development over time and overall compressive strength when the material is cast at low temperatures. Results represent that reducing the curing temperature about 15 degrees could result in 20% reduction in ultimate strength; however, decreasing the humidity percentage by 50% could lead to 10% reduction in ultimate strength. The maturity test results represented the effect of various temperatures and humidity rates on maturity of the grouts. Additionally, the freeze-thaw cycle's effect on the grouts is conducted to investigate the durability factor. The results show that the lower temperatures could be significantly influential on the behavior of grouts compared to lower humidity rates. It is indicated that the maturity test could not be valid and precise in harsh temperature conditions.

Force–Displacement Relationship of the Butterfly-Shaped Beams Based on Gene Expression Programming

Alireza Farzampour,Iman Mansouri,Seyed Javad Mortazavi,허종완 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.6

Structural steel plates with engineered cut-outs to exhibit a controlled yielding mechanism is recently proposed for desirable structural performance compared to conventional systems. Butterfl y-shaped beams with hexagonal cut-outs inside of the beam’s web are 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 suffi cient ductility which necessities further investigations and structural behavior prediction studies. In this study, a set of 240 nonlinear fi nite element models are developed for the creation of a database and subsequently calibrated with fi nite element software packages. The capability of the gene expression programming (GEP) is explored for the prediction of the force–displacement relationship of a butterfl y-shaped beam. Two new models are developed based on the reliable generated database. Subsequently, the proposed models are validated with several conducted analyses 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 butterfl y-shaped beam with satisfactory accuracy.

Effect of flexural and shear stresses simultaneously for optimized design of butterfly-shaped dampers: Computational study

Alireza Farzampour,Matthew R. Eatherton,Iman Mansouri,Jong Wan Hu 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.4

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.

Seismic Behavior Investigation of the Corrugated Steel Shear Walls Considering Variations of Corrugation Geometrical Characteristics

Alireza Farzampour,Iman Mansouri,허종완 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.4

The corrugated steel plate shear walls have recently been proposed to address the seismic issues associated with simple steel plate shear walls; however, stiff ness, strength, and ductility of the corrugated shear walls are signifi cantly aff ected by varying the corrugation geometry under seismic loading. The present study investigates steel shear walls’ models with corrugated or simple infi ll plates subjected to monotonic and cyclic loads. The performance of the corrugated steel plate is evaluated and then compared to that of the simple steel plates by evaluating the damping ratios and energy dissipation capability. The eff ect of corrugation profi le angle, the existence of an opening, and the corrugation subpanel length are numerically investigated after validation of the fi nite element modeling methodology. The results demonstrate that incorporating corrugated plates would lead to better seismic damping ratios, specifi cally in the case of opening existence inside of the infi ll plate. Specifi cally, the corrugation angle of 30° decreases the ultimate strength, while increasing the initial stiff ness and ductility. In addition, the subpanel length of 100 mm is found to be able to improve the overall performance of shear wall by providing each subpanel appropriate support for the adjacent subpanel, leading to a suffi cient buckling resistance performance.

Experimental investigation of sound transmission loss in concrete containing recycled rubber crumbs

Chalangaran, Navid,Farzampour, Alireza,Paslar, Nima,Fatemi, Hadi Techno-Press 2021 Advances in concrete construction Vol.11 No.6

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.

Experimental study on the optimized design of butterfly-shaped dampers

Jong Wan Hu,Young Wook Cha,Alireza Farzampour,Nadia M. Mirzai,Iman Mansouri 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.5

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.

Seismic behavior investigation of the steel multi-story moment frames with steel plate shear walls

Iman Mansouri,Ali Arabzadeh,Alireza Farzampour,Jong Wan Hu 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.1

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.

Investigation of steel fiber effects on concrete abrasion resistance

Mansouri, Iman,Shahheidari, Farzaneh Sadat,Hashemi, Seyyed Mohammad Ali,Farzampour, Alireza Techno-Press 2020 Advances in concrete construction Vol.9 No.4

Concrete surfaces, industrial floors, sidewalks, roads and parking lots are typically subjected to abrasions. Many studies indicated that the abrasion resistance is directly related to the ultimate strength of the cured concrete. Chemical reactions, freeze-thaw cycles, and damages under abrasion are among many factors negatively affecting the concrete strength and durability. One of the major solutions to address the abrasive resistance of the concrete is to use fibers. Fibers are used in the concrete mix to improve the mechanical properties, strength and limit the crack propagations. In this study, implementation of the steel fibers in concrete to enhance the abrasive resistance of the concrete is investigated in details. The abrasive resistance of the concrete with and without steel fibers is studied with the sandblasting technique. For this purpose, different concrete samples are made with various hooked steel fiber ratios and investigated with the sandblasting method for two different strike angles. In total, 144 ASTM verified cube samples are investigated and it is shown that those samples with the highest steel fiber ratios have the highest abrasive resistance. In addition, the experiments determine that there is a meaningful correlation between the steel fiber percentage in the mix, strike angle and curing time which could be considered for improving structural behavior of the fiber-reinforced concrete.