• Structural Engineering and Mechanics
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• v.54 no.6
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• pp.1111-1133
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• 2015

Rebar corrosion in concrete is one of the main causes of reduction of service life of reinforced concrete buildings. This paper presents the influence of rebar corrosion on the structural behavior of reinforced concrete (RC) buildings subjected to strong earthquake ground motion. Different levels of rebar corrosion scenarios were applied on a typical four story RC frame. The deteriorated conditions as a result of these scenarios include loss in cross-sectional area and loss of mechanical properties of the reinforcement bars, loss in bond strength, and loss in concrete strength and its modulus of elasticity. Dynamic analyses of the frame with different corrosion scenarios are performed with selected strong earthquake ground motion records. The influences of degradation in both concrete and reinforcement on structural behavior are investigated by comparing the various parameters of the frame under different corrosion scenarios with respect to each other. The results show that the progressive deterioration of the frame due to rebar corrosion causes serious structural behavior changes such as change in failure mode. The intensity, propagation time, and extensity of rebar corrosion have very important effects on the level of degradation of steel and concrete, as well as on the earthquake behavior of the structure.

• Steel and Composite Structures
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• v.20 no.3
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• pp.693-718
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• 2016

This paper presents a finite element procedure based on Bridging multi-scale method (BMM) in order to incorporate the effect of local/cross-sectional deformations (e.g., flange local buckling and web crippling) on the global behaviour of thin-walled members made of fibre-reinforced polymer composite laminates. This method allows the application of local shell elements in critical regions of an existing beam-type model. Therefore, it obviates the need for using computationally expensive shell elements in the whole domain of the structure, which is otherwise necessary to capture the effect of the localized behaviour. Consequently, highly accurate analysis results can be achieved with this method by using significantly smaller finite element model, compared to the existing methods. The proposed method can be used for composite polymer laminates with arbitrary fibre orientation directions in different layers of the material, and under various loading conditions. Comparison with full shell-type finite element analysis results are made in order to illustrate the efficiency and accuracy of the proposed technique.

• Journal of the Korean institute of surface engineering
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• v.18 no.3
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• pp.95-104
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• 1985

A study has been made of preferred orientation, crose sectional microstructure, surface morphology and mechanical properties of copper foils fabricated by electrodeposition on 304 stainless steel plate from copper sulfate baths for high speed plating. The preferred orientation of the copper foils changed from the [110] to the [111] to ture with decreasing bath temperature and increasing cathode current density. The foils with the [110] texture had the field oriented texture type structure and the surface of many asperities grooved approximately perpendicular to the subtrate. A specimen with the [111]+[311] texture had the lower strength than one with the [10] texture, if they were obtained under similar electrolysis conditions.

• Structural Engineering and Mechanics
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• v.77 no.4
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• pp.523-533
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• 2021

The present study investigates the lateral torsional buckling behaviour of pultruded glass fiber reinforced polymer (GFRP) simply supported channel beams subjected to uniform bending about their major axis. A parametric study by varying the sectional geometry and span of channel beams is carried out by using ABAQUS software. The accuracy of the FE models was ensured by verifying them against the available results provided in the literature. The effect of geometric nonlinearity, geometric imperfections, and the dependency of finite element mesh on the lateral torsional buckling were carefully considered in the FE model. Lateral torsional buckling (LTB) strengths obtained from the numerical study were compared with the theoretical LTB strengths obtained based on the Eurocode 3 approach for steel sections. The comparison between the numerical strengths and the design procedure proposed in the literature based on Eurocode 3 approach revealed disagreements. Therefore, a simplified improved design procedure is proposed for the safe design strength prediction of pultruded GFRP channel beams. The proposed equation has been provided that might aid the structural engineers in economically designing the pultruded GFRP channel beams in the future.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.643-650
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• 2012

The limitation of the yield strength in reinforced concrete columns is given for the effective use of high-strength steel bar, because very high-strength steel bar does not yield while concrete fails in compression. In order to overcome this limitation, it is required to increase peak strain of the concrete. The objective of this study is to examine the confinement effect of plate type lateral reinforcement in reinforced concrete columns. From this experimental study, the reinforced concrete columns confined by plate type carbon fiber sheets showed higher compressive strength and peak concrete strain comparing to the unconfined columns. The confinement effect is higher when cross-sectional type is a circular one than a square one. Moreover, the confinement effect was also higher for circular type confinement. Based on this study, high-strength steel bars with strength exceeding 800 MPa can be effectively used for reinforced concrete columns confined by plate type lateral reinforcements.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.1-12
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• 2018

A curved member should resist bending and torsional moments simultaneously even though the primary load is usually supposed to be gravitational load. The torsional moment causes complicate stress state and also can result in early yielding of material to reduce member strength. According to analysis results, the strength of a curved member that has 45 degrees of subtended angle could decrease more than 50% compare to straight girder. Nevertheless, there have been very few of researches related with ultimate strength of curved girders. In this study, various kinds of stiffness about bending, pure torsion and warping were considered with a number of models in order to verify the main factor that affects ultimate behavior of curved girder. Lateral and rotational displacement of curved member were introduced as lateral-torsional-vertical behavior and bending-torsional moment interaction curve was derived. Finally, a strength equation for ultimate moment of horizontally curved steel I-girders subjected to equal end moments based on the interaction curves. The equation could take account of the effect of curvature, unbraced length and sectional properties.

• Journal of the Korean Wood Science and Technology
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• v.45 no.5
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• pp.535-543
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• 2017

For column-beam gussets of wooden structures, slit-processed members inserted with a steel plate are used in general. In this study, a rigid portal frame bonded with a joint was fabricated and a semi-rigid portal frame was fabricated by making a wooden gusset, a replacement for steel plate, of which a half was integrated into the column member and the other half was joined with the beam member by drift-pins. The lateral strength performance of the wooden portal frame was compared with that of the steel plate-inserted joint portal frame. The lateral strength performance was evaluated through a perfect elasto-plasticity model analysis, sectional stiffness change rate, and short-term permissible shear strength. As a result of the experiment, the maximum strength of the rigid portal frame was lower than that of the steel plate-inserted joint portal frame. The yield strength and ultimate strength were calculated as 0.58 and 0.48, respectively, but the measurements of initial stiffness and cumulative ductility improved by 1.35 and 1.1, respectively. As a result of the perfect elasto-plasticity model analysis of the semi-rigid portal frame, the maximum strength was lower than that of the rigid portal frame, but the toughness after failure was excellent. Thus, the ultimate strength was higher by 1.05~1.07. The steel plate-inserted portal frame showed rapid decrease in stiffness with the progress of repeated tests, but the stiffness of the portal frames with a wooden joint decreased slowly.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.267-278
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• 2012

In general, the H-shaped steel ribs or triangular lattice girders have been mostly used in constructing tunnels through the NATM construction method. The H-shaped steel rib has higher flexural and axial strength than the triangular lattice girder, but many unexpected gaps can occur in the concrete lining system after shotcreting if the H-shaped steel rib is used as the support system. To achieve better shotcreting quality, the triangular lattice girder was developed. However, in general, the triangle lattice girder has low flexural and axial strength. Likewise, the triangular lattice girder, which has circular sectional members, has so many fractures from welded points at the joints between the members. Finally, the new type of tetragonal lattice girder was developed to overcome those problems. In this study, the structural performance of the tetragonal lattice girders was evaluated through analytical and experimental studies. In the analytical studies, the four-point bending analysis, the traditional evaluation method to determine the flexural strength of the lattice girder, was performed. Moreover, the linear-elastic analysis and stability analysis of the arch structure made by the lattice girders were performed to measure structural performance. Experiments were likewise performed to compare the structural performances of the tetragonal girder with traditional triangular lattice girders.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.327-336
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• 2012

This study presents the effects of various geometric properties on the ultimate behavior of steel cable-stayed bridges. In general, cable-stayed bridges are well known as a very efficient structural system, because of those geometric characteristics, but at the same time, the structure also shows complex structural behavior including various nonlinearities which significantly affect to the ultimate behavior of the structure. In this study, the effects of various geometric properties of main members on the ultimate behavior under specific live load cases, which had been studied in previous studies, were investigated using a rational analytical method. In this parametric study, sectional dimensions of main members were considered as main geometric parameters. For the rational ultimate analysis under specific live load cases, the 2-step analysis method, which contains initial shape analysis and live load analysis, was used. As the analysis model, 920.0 m long steel cable-stayed bridges were used and two different types of cable arrangement were considered to study the effect of the cable arrangement types. Through this study, the effects of various geometric properties on the characteristics of the ultimate behavior of steel cable-stayed bridges were intensively investigated.

• Safety and Health at Work
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• v.8 no.1
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• pp.99-104
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• 2017

Background: Workers laboring in steel industries in tropical settings with high ambient temperatures are subjected to thermally stressful environments that can create well-known risks of heat-related illnesses and limit workers' productivity. Methods: A cross-sectional study undertaken in a steel industry in a city nicknamed "Steel City" in Southern India assessed thermal stress by wet bulb globe temperature (WBGT) and level of dehydration from urine color and urine specific gravity. A structured questionnaire captured self-reported heat-related health symptoms of workers. Results: Some 90% WBGT measurements were higher than recommended threshold limit values ($27.2-41.7^{\circ}C$) for heavy and moderate workloads and radiational heat from processes were very high in blooming-mill/coke-oven ($67.6^{\circ}C$ globe temperature). Widespread heat-related health concerns were prevalent among workers, including excessive sweating, fatigue, and tiredness reported by 50% workers. Productivity loss was significantly reported high in workers with direct heat exposures compared to those with indirect heat exposures ($x^2=26.1258$, degrees of freedom = 1, p < 0.001). Change in urine color was 7.4 times higher among workers exposed to WBGTs above threshold limit values (TLVs). Conclusion: Preliminary evidence shows that high heat exposures and heavy workload adversely affect the workers' health and reduce their work capacities. Health and productivity risks in developing tropical country work settings can be further aggravated by the predicted temperature rise due to climate change, without appropriate interventions. Apart from industries enhancing welfare facilities and designing control interventions, further physiological studies with a seasonal approach and interventional studies are needed to strengthen evidence for developing comprehensive policies to protect workers employed in high heat industries.