• Earthquakes and Structures
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• v.23 no.1
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• pp.59-73
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• 2022

In this study, the seismic behavior of an all-steel buckling-restrained (AB) steel plate shear wall (SPSW) with incline slits under fire and cyclic loading was investigated. ABSPSW was composed of two thin steel infill plates with a narrow distance from each other, which were embedded with incline slits on each plate. These slits were in opposite directions to each other. The finite element (FE) numerical model was validated with three test specimens and after ensuring the modeling strategy, the parametric study was performed by considering variables such as wall plate thickness, slit width, strip width between two slits, and degree of temperature. A total of 256 FE numerical models were subjected to coupled temperature-displacement analysis. The results of the analysis showed that the high temperature reduced the seismic performance of the ABSPSW so that at 917℃, the load-bearing capacity was reduced by 92%. In addition, with the increase in the temperature, the yield point of the infill plate and frame occurred in a small displacement. The average decrease in shear strength at 458℃, 642℃, and 917℃ was 18%, 46%, and 92%, respectively, compared to the shear strength at 20℃. Also, with increasing the temperature to 917℃, ductility increased by an average of 75%

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.507-514
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• 2022

This study proposes an optimal design process for a high-frequency transformer that has a large leakage inductance for dual-active-bridge converters. Notably, conventional design processes have large errors in designing leakage transformers because mathematically modeling the leakage inductance of such transformers is difficult. In this work, the geometric parameters of a shell-type transformer are identified, and finite element analysis(FEA) simulation is performed to determine the magnetization inductance, leakage inductance, and copper loss of various shapes of shell-type transformers. Regression models for magnetization and leakage inductances and copper loss are established using the simulation results and the machine learning technique. In addition, to improve the regression models' performance, the regression models are tuned by adding featured parameters that consider the physical characteristics of the transformer. With the regression models, optimal high-frequency transformer designs and the Pareto front (in terms of volume and loss) are determined using NSGA-II. In the Pareto front, a desirable optimal design is selected and verified by FEA simulation and experimentation. The simulated and measured leakage inductances of the selected design match well, and this result shows the validity of the proposed design process.

• Steel and Composite Structures
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• v.41 no.5
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• pp.747-759
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• 2021

Built-up Double-I (BD-I) columns have been commonly used for mid-rise steel-frame structures in Iran. These columns consist of two hot rolled IPE sections which are connected by two cover plates and fillet welds. Until 2017, BD-I columns were employed in intermediate moment resisting frames (MRF) using welded flange plate (WFP) connections. To evaluate the seismic behavior of the connections, four samples were made and tested based on cyclic loading according to AISC 341-16. It was concluded that typical samples cannot satisfy the seismic provisions related to intermediate MRFs. In contrast, the proposed connections retrofitted with two-part external diaphragms were able to satisfy not only the seismic requirements related to intermediate MRFs but also those related to special MRFs according to AISC. The numerical modeling of these samples was performed using ABAQUS finite element software. This study compared the hysteresis moment-rotation curves, plastic strains, and behavior modes in both experimental samples and numerical models.

• Computers and Concrete
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• v.28 no.5
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• pp.507-519
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• 2021

In this study, a new procedure was proposed in order to predict the crack pattern and failure mode of steel fiber reinforced concrete (SFRC) corbels. Moreover, an experimental study was carried out in order to investigate the effect of several parameters, such as compressive strength, tensile strength, steel fiber ratio, shear span on the mechanical behavior of SFRC corbels in detail. Totally, 24 RC and SFRC corbels were prepared for the experimental study. Experimental results indicate that each investigated parameter has noticeable effect on the load capacity and failure mode of SFRC corbels. Moreover, finite element (FE) model of the tested corbels were prepared and efficiency of FE model was investigated for further studies. Comparison of FE and experimental results show that there is an acceptable fit between them regarding load capacity and crack patterns. Thereafter, parametric study was carried out via FE analyses in order to obtain a methodology for crack pattern and failure mode prediction of SFRC corbels. As a result of parametric studies, a new procedure was proposed as flowcharts in order to predict the failure mode of SFRC corbels for normal and high strength concrete class separately.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.89-104
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• 2023

This work presents a proposal for employing reduced numerical integration in the formulation of the 4-node quadrilateral solid finite element. The use of these low-order integration rules leads to numerical instabilities such as those producing the hourglass effect. The proposed procedure allows evaluating a given constitutive model only in one integration point, achieving an attractive computational cost reduction and, also, successfully controls the hourglass effect. A validation of the proposal is included and discussed throughout the paper. To show the efficiency of the proposal, several application examples of masonry structures are studied and discussed. To represent the non-linear mechanical behaviour of masonry a plastic-damage model is implemented within the application of this sub-integration scheme. Also, in order to have a full and computationally efficient strategy to determine the behaviour of masonry structures, involving its evolution to collapse, a homogenization technique with a macro-modeling approach is used. The methodology discussed throughout this paper demonstrates a substantial computational cost reduction and an improved approximation of the non-linear problem evidenced by a reduction of up to 85% of the computational time for some cases.

• Journal of the Korean Geotechnical Society
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• v.24 no.9
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• pp.5-11
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• 2008

Seepage induced earthern slope failures occurs in concert with meteorological events when large quantities of groundwater are channeled into slopes through infiltration. The presence of flowing groundwater in earthern slopes can induce ground failures that result in significant property damage and potential loss of life. Seepage induced earthen slope failures represent a serious problem in geotechnical engineering. This research applies existing fluid-solid numerical modeling capabilities to the study and prediction of seepage induced earthen slope failures. Study of the targeted application holds potential for much needed advances in geotechnical engineering analysis technology which could be used to design more effective engineering slope stabilization interventions.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.95-106
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• 2023

In the developing country like India, groundwater is the main sources for household, irrigation and industrial use. Its contamination poses hydro-geological and environmental concern. The hazardous waste sites such as landfills can lead to contamination of ground water. The contaminants existing at such sites can eventually find ingress down through the soil and into the groundwater in case of leakage. It is necessary to understand the process of migration of pollutants through sub-surface porous medium for avoiding health risks. On this backdrop, the present paper investigates the behavior of pollutants' migration through porous media. The laboratory experiments were carried out on a soil-column model that represents porous media. Two different types of soils (standard sand and red soil) were considered as the media. Further, two different solutes, i.e., non-reactive and reactive, were used. The experimental results are simulated through numerical modeling. The percentage variation in the experimental and numerical results is found to be in the range of 0.75- 11.23 % and 0.84 - 1.26% in case of standard sand and red soil, respectively. While a close agreement is observed in most of the breakthrough curves obtained experimentally and numerically, good agreement is seen in either result in one case.

• Steel and Composite Structures
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• v.42 no.5
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• pp.685-697
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• 2022

In this paper, a vibration-based method using the change ratios of modal data and the experience-based learning algorithm is presented for quantifying the position, size, and interface layer of delamination in laminated composites. Three types of objective functions are examined and compared, including the ones using frequency changes only, mode shape changes only, and their combination. A fine three-dimensional FE model with constraint equations is utilized to extract modal data. A series of numerical experiments is carried out on an eight-layer quasi-isotropic symmetric (0/-45/45/90)s composited beam for investigating the influence of the objective function, the number of modal data, the noise level, and the optimization algorithms. Numerical results confirm that the frequency-and-mode-shape-changes-based technique yields excellent results in all the three delamination variables of the composites and the addition of mode shape information greatly improves the accuracy of interface layer prediction. Moreover, the EBL outperforms the other three state-of-the-art optimization algorithms for vibration-based delamination detection of composites. A laboratory test on six CFRP beams validates the frequency-and-mode-shape-changes-based technique and confirms again its superiority for delamination detection of composites.

• Structural Engineering and Mechanics
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• v.83 no.4
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• pp.475-493
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• 2022

The results of research focusing on the experimental and numerical performance of ferrocement RC beams with openings reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh, and polyethylene mesh independently are presented in this article. Casting and testing of fourteen reinforced concrete beams with dimensions of 200×100×2000 mm under concentric compression loadings were part of the research program. The type of reinforcing materials, the volume fraction of reinforcement, the number of mesh layers, and the number of stirrups are the major parameters that change. The main goal is to understand the impact of using new appealing materials in reinforcing RC beams with openings. Using ANSYS-16.0 Software, nonlinear finite element analysis (NLFEA) was used to demonstrate the behavior of composite RC beams with openings. A parametric study is also conducted to discuss the variables that can have the greatest impact on the mechanical behavior of the proposed model, such as the number of openings. The obtained experimental and numerical results demonstrated the FE simulations' acceptable accuracy in estimating experimental values. Furthermore, demonstrating that the strength gained of specimens reinforced with fiber glass meshes was reduced by approximately 38% when compared to specimens reinforced with expanded or welded steel meshes is significant. In addition, when compared to welded steel meshes, using expanded steel meshes in reinforcing RC beams with openings results in a 16 percent increase in strength. In general, when ferrocement beams with openings are tested under concentric loadings, they show higher-level ultimate loads and energy-absorbing capacity than traditional RC beams.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.793-815
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• 2023

The current study looks at the experimental and numerical performance of ferrocement RC channel slabs reinforced with welded steel mesh, expanded steel mesh, and fiber glass mesh individually. Ten RC channel slabs with dimensions of 500 mm×40 mm×2500 mm were subjected to flexural loadings as part of the testing program. The type of reinforcing materials, the number of mesh layers, and the reinforcement volume fraction are the key parameters that can be changed. The main goal is to determine the impact of using new inventive materials to reinforce composite RC channel slabs. Using ANSYS -16.0 Software, nonlinear finite element analysis (NLFEA) was used to simulate the behavior of composite channel slabs. Parametric study is also demonstrated to identify variables that can have a significant impact on the model's mechanical behavior, such as changes in slab dimensions. The obtained experimental and numerical results indicated that FE simulations had acceptable accuracy in estimating experimental values. Also, it's significant to demonstrate that specimens reinforced with fiber glass meshes gained approximately 12% less strength than specimens reinforced with expanded or welded steel meshes. In addition, Welded steel meshes provide 24% increase in strength over expanded steel meshes when reinforcing RC channel slabs. In general, ferrocement specimens tested under flexural loadings outperform conventional reinforced concrete specimens in terms of ultimate loads and energy absorbing capacity.