Metals

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26 pages, 34704 KiB

Open AccessArticle

Seismic Experimental Assessment of Remote Terminal Unit System with Friction Pendulum under Triaxial Shake Table Tests

by Sung-Wan Kim, Bub-Gyu Jeon, Da-Woon Yun, Woo-Young Jung and Bu-Seog Ju

Metals 2021, 11(9), 1428; https://doi.org/10.3390/met11091428 - 09 Sep 2021

Cited by 3 | Viewed by 1859

In recent years, earthquakes have caused more damage to nonstructural components, such as mechanical and electrical equipment and piping systems, than to structural components. In particular, among the nonstructural components, the electrical cabinet is an essential piece of equipment used to maintain the [...] Read more.

In recent years, earthquakes have caused more damage to nonstructural components, such as mechanical and electrical equipment and piping systems, than to structural components. In particular, among the nonstructural components, the electrical cabinet is an essential piece of equipment used to maintain the functionality of critical facilities such as nuclear and non-nuclear power plants. Therefore, damage to the electrical cabinet associated with the safety of the facility can lead to severe accidents related to loss-of-life and property damage. Consequently, the electrical cabinet system must be protected against strong ground motion. This paper presents an exploratory study of dynamic characteristics of seismically isolated remote terminal unit (RTU) cabinet system subjected to tri-axial shaking table, and also the shaking table test of the non-seismically isolated cabinet system was conducted to compare the vibration characteristics with the cabinet system installed with friction pendulum isolator device. In addition, for the shaking table test, two recorded earthquakes obtained from Korea and artificial earthquakes based on the common application of building seismic-resistant design standards as an input ground motions were applied. The experimental assessment showed that the various damage modes such as door opening, the fall of the wire mold, and damage to door lock occurred in the RTU panel fixed on the concrete foundation by a set anchor, but the damage occurred only at the seismic isolator in the seismically isolated RTU panel system. Furthermore, it was considered that the application of the seismic isolator can effectively mitigate the impact and amplification of seismic force to the RTU panel system during and after strong ground motions in this study. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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15 pages, 4319 KiB

Open AccessArticle

Structural Behavior of Large-Diameter Cylindrical Shell with Stiffened Opening

by Sung-Yong Kang, Deokhee Won, Jong-Sup Park, Young-Jong Kang and Seungjun Kim

Metals 2021, 11(9), 1413; https://doi.org/10.3390/met11091413 - 07 Sep 2021

Cited by 2 | Viewed by 2023

Abstract

In recent years, there has been a growing demand for renewable energy that is free of power generation by products to address the global climate and resource limitation crises. Wind power generation is maximizing efficiency through constant research and development, and as the [...] Read more.

In recent years, there has been a growing demand for renewable energy that is free of power generation by products to address the global climate and resource limitation crises. Wind power generation is maximizing efficiency through constant research and development, and as the use of large capacity turbines increases, the scale of supporting structure also increases. The structural maintenance of hollow towers, the supporting structure of wind turbines, requires the installation of an opening through which workers can access the tower to check corrosion, cracks, and damage to the tower body. However, these access points can affect the buckling strength of the tower structures due to section loss. In this study, the effects of the opening on the structural stability and ultimate strength of a large diameter cylindrical shell, which could be used as a wind turbine supporting tower structure, were studied through elastic buckling and nonlinear analyses. Based on the analytical results, the effects of the thickness of a collar stiffener around the opening on the structure’s ultimate strength were investigated. The results were compared to the design criteria, and through regression analysis, an effective equation to determine the collar stiffener’s thickness for large diameter cylindrical shells was proposed based on an opening that satisfied the design strength criteria. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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17 pages, 12062 KiB

Open AccessArticle

Experimental and Finite Element Study of Polymer Infilled Tube-in-Tube Buckling Restrained Brace

by Robel Wondimu Alemayehu, Youngsik Kim, Min Jae Park, Manwoo Park and Young K. Ju

Metals 2021, 11(9), 1358; https://doi.org/10.3390/met11091358 - 29 Aug 2021

Cited by 3 | Viewed by 2631

Abstract

This study presents a tube-in-tube buckling-restrained brace (BRB) infilled with lightweight and rapid hardening polymer. The proposed BRB consists of a circular or square tube core encased with a tube of similar shape and polymer infill. The tube-in-tube arrangement minimizes the filler material [...] Read more.

This study presents a tube-in-tube buckling-restrained brace (BRB) infilled with lightweight and rapid hardening polymer. The proposed BRB consists of a circular or square tube core encased with a tube of similar shape and polymer infill. The tube-in-tube arrangement minimizes the filler material volume and enables the use of rolled steel section as opposed to welded profiles commonly utilized when large BRB axial strength is required, although welded profiles suffer from low assembly accuracy resulting from welding deformation. The infilled polymer has a density of approximately half that of mortar and requires a curing time of 24 h, enabling weight and fabrication time reduction. The stability and inelastic deformation capability of the BRB were investigated through brace and subassembly tests of six circular and four-square full-scale specimens, followed by finite element analysis. The test results show that circular BRB designed with a P_cr/P_y ratio of 1.46 exhibited a stable hysteresis up to 1.42% and 1.06% core strain in tension and compression, respectively. Circular and square specimens designed with P_cr/P_y ratios ranging from 0.82 to 1.06 exhibited stable hysteresis before failing by global buckling at compressive core stains ranging from 0.86% to 1.09%. The slot weld detail adopted for welding core projection stiffener displayed a stable performance in circular BRB specimens, while it resulted in large plastic strain demand in square BRB specimens, leading to core fracture at tensile core strains ranging from 0.64% to 0.71%. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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19 pages, 4357 KiB

Open AccessArticle

Effect of Load Combinations on Distortional Behaviors of Simple-Span Steel Box Girder Bridges

by Jeonghwa Lee, Heesoo Kim, Keesei Lee and Young-Jong Kang

Metals 2021, 11(8), 1238; https://doi.org/10.3390/met11081238 - 04 Aug 2021

Cited by 4 | Viewed by 3057

Abstract

When eccentric live loads are applied on the deck overhang of steel-box girder bridges, torsional moments, comprising pure torsional and distortional moments are generated on the box sections. The torsional moment on the bridge girders distorts the box girder cross-sections, inducing additional normal [...] Read more.

When eccentric live loads are applied on the deck overhang of steel-box girder bridges, torsional moments, comprising pure torsional and distortional moments are generated on the box sections. The torsional moment on the bridge girders distorts the box girder cross-sections, inducing additional normal stress components and causing instability of the box girder sections in severe cases. Hence, it is essential to install intermediate diaphragms in the box sections to minimize distortional behaviors. Although the applied live loads are critical parameters that influence intermediate diaphragm spacings, the effects of live load combinations have rarely been addressed in the design of intermediate diaphragm spacings. Thus, load combinations should be evaluated to design the intermediate diaphragm spacing of the box girder bridges more thoroughly. In this study, the load combination effects on the distortional behavior and adequate intermediate diaphragm spacing were evaluated through a finite element analysis (FEA). Composite rectangular box girder bridges with different cross-sectional aspect ratios (

H / B

) and spans (

L

) were analyzed in the parametric study. It was found that the truck load, which represents the concentrated load, significantly influences the distortional warping normal stress, normal stress ratio, and intermediate diaphragm spacing. In addition, the FEA results showed that the controlling load combinations could be varied with the span. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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18 pages, 10375 KiB

Open AccessFeature PaperArticle

Experimental and Analytical Study of Horizontally Curved I-Girders Subjected to Equal End Moments

by Jeonghyeon Lim, Young-Jong Kang, Jeonghwa Lee, Seungjun Kim and Keesei Lee

Metals 2021, 11(7), 1132; https://doi.org/10.3390/met11071132 - 17 Jul 2021

Viewed by 1677

Abstract

If bending and torsional moments are applied to an I-shaped beam member, the coupling of those two forces could reduce the bending moment capacity of that member. Therefore, the interaction between bending and torsional moments is an important issue for horizontally curved members [...] Read more.

If bending and torsional moments are applied to an I-shaped beam member, the coupling of those two forces could reduce the bending moment capacity of that member. Therefore, the interaction between bending and torsional moments is an important issue for horizontally curved members that are always simultaneously subjected to bending and torsion. In this study, the behavior of the horizontally curved steel I-beam was investigated through numerical analysis. The ultimate state of sharply curved members that showed large displacement was defined in accordance with the stiffness reduction ratio to consist of strength curves. Based on the analysis results, interaction curves were established, and a strength equation was derived. The uniform torsional moment capacity, curvature, and slenderness parameters were considered in the equation, which were the main factors that affected the ultimate strength of curved members. The curvature effect was considered individually, so that the strength of the straight or curved girder could be estimated with a unified equation. To verify the accuracy of the suggested equation, experimental studies were also conducted. Consequently, the suggested equation shows very good agreement with the test results, and is expected to provide useful information for the design of curved members. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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36 pages, 16943 KiB

Open AccessFeature PaperArticle

Study of Metallic Housing of the Adder Gearbox to Reduce the Noise and to Improve the Design Solution

by Nicoleta Gillich, Nicolae Sîrbu, Sorin Vlase and Marin Marin

Metals 2021, 11(6), 912; https://doi.org/10.3390/met11060912 - 03 Jun 2021

Cited by 4 | Viewed by 2235

Abstract

In the manufacture of commercial trucks, used in oil installations or the army, two identical engines are used on a single chassis, whose power is summed by a gearbox, a compact metal construction, which must meet multiple operating requirements. The paper studies the [...] Read more.

In the manufacture of commercial trucks, used in oil installations or the army, two identical engines are used on a single chassis, whose power is summed by a gearbox, a compact metal construction, which must meet multiple operating requirements. The paper studies the behavior of such an adding box, currently used in manufacturing, and an improved, welded solution that produces less noise and has a lower weight. The finite element method is used for modeling the gearbox in order to analyze stresses and strains and obtain a modal analysis of the system. The results obtained from the calculation are then verified by experimental measurements. The two versions are analyzed in parallel to highlight the advantages of the second version. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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19 pages, 9433 KiB

Open AccessArticle

Experimental Investigations on Ultimate Behavior of Fabricated Mobile Scaffolds

by Heesoo Kim, Jeonghyeon Lim, Jeonghwa Lee, Young Jong Kang and Seungjun Kim

Metals 2021, 11(6), 851; https://doi.org/10.3390/met11060851 - 21 May 2021

Cited by 5 | Viewed by 2448

Abstract

A fabricated mobile scaffold has various components, including vertical members, horizontal members, braces, work plates, and castor wheels. In Korea, the structural performance of each member must be validated based on member-level structural safety criteria; this means that rigorous evaluation methods are required [...] Read more.

A fabricated mobile scaffold has various components, including vertical members, horizontal members, braces, work plates, and castor wheels. In Korea, the structural performance of each member must be validated based on member-level structural safety criteria; this means that rigorous evaluation methods are required to secure the system-level structural safety of the fabricated mobile scaffold. To suggest rational system-level structural safety criteria and effective evaluation methods, the characteristics of the structural behaviors of the assembled structure must be investigated first. Unlike other temporary equipment, it is a product that requires convenience of use and ease of movement. Therefore, to secure the safety and usability of the structure, it is necessary to evaluate the ultimate behavior of a mobile scaffold fabricated with various material and structural types. In an experimental study, the ultimate mode and load-bearing capacity were investigated, and the appropriateness of the required performance of the mobile scaffold was reviewed. Three types of experimental test models with different materials (steel and aluminum) and stories (single-story and three-story erection) were selected and examined for vertical loads. Based on the experimental results, the ultimate behavior characteristics of the fabricated mobile scaffold were analyzed, and the ultimate load was identified. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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19 pages, 13194 KiB

Open AccessFeature PaperArticle

Inelastic Strength for Fire Resistance of Composite I-Beam Covered by Insulation Material Subjected to Basic Loading Condition

by Xuan Tung Nguyen and Jong Sup Park

Metals 2021, 11(5), 739; https://doi.org/10.3390/met11050739 - 29 Apr 2021

Cited by 5 | Viewed by 2628

Abstract

This paper presents a nonlinear numerical study on the moment resistance of composite steel-concrete beam using fire insulation subjected to various fire scenarios and basic loading conditions. The temperature-dependent material properties of fire insulation, concrete and steel were taken into consideration. The nonlinear [...] Read more.

This paper presents a nonlinear numerical study on the moment resistance of composite steel-concrete beam using fire insulation subjected to various fire scenarios and basic loading conditions. The temperature-dependent material properties of fire insulation, concrete and steel were taken into consideration. The nonlinear finite element analysis was done by utilizing a commercial finite element program, ABAQUS. The obtained moment capacity of the composite I-beam from the current fire code was also performed and compared. The results showed that the fire scenarios and the fire insulation thickness have a great influence on the temperature distribution and strength degradation of the composite beam. The capacity of the beam in hydrocarbon fires, which is the most severe scenario, decreases faster than that in ISO834 standard fire and external fire. The fire resistance of the beam increases as the fire insulation thickness increases due to the temperature degradation in the steel beam. The calculated results from the current fire codes give conservative value at normal temperature and low temperature. The current fire codes can give unconservative values at high temperature when there is a great temperature discrepancy between parts of the beam. A new factor was proposed to determine the fire moment resistance of the composite beam with non-uniform temperature. Full article

(This article belongs to the Special Issue Advances in Structural Application of Metals)

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