• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.262-268
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• 2003

Organic coatings are widely used to control the corrosion of steel structure. The water in coatings may cause swelling or solvation of coatings, leading to the degradation of coatings. In addition, water affects the permeation of oxygen and other corrosive agents, and consequently the presence of such substances at coating-metal interface promotes corrosion of metal substrate. In this study, the anticorrosive properties of 4 types of coating, such as epoxy-epoxy, epoxy-urethane, urethane-epoxy, urethane-urethane, were evaluated. The evaluation tests were carried out under cyclic water-absorption/desorption conditions, consisting of alternative exposure to diluted 0.001M-LiCl($a_{1120}{\fallingdotseq}1$) and concentrated l0M-LiCl($a_{1120}{\fallingdotseq}0.05$). The anticorrosive performances of coatings were found to decrease in the order of urethane-urethane> urethane-epoxy> epoxy-epoxy coating.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.609-623
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• 2021

Buckling restrained bracing (BRB) was firstly introduced in Japan construction industry in year 1989. With time, BRB performance has been advanced to self-centering BRB (SC-BRB) which has exceptional energy dissipation, addressing the improvement in the structure performance in post-seismic affect. Although the BRB performance specifications are defined in design codes of several countries, specific design provisions are not generally provided since BRBs are usually considered a manufactured device. Furthermore, most of review papers focused on BRB rather than SC-BRB. Thus, this paper explores the background of both BRB and SC-BRB. The importance of self-centering components in BRB and literature related to it have been studied. This review study also highlights the significance of corrosion-resistance materials in the configuring BRB and SC-BRB since most of such members are made of carbon steel that is susceptible to corrosion.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.75-80
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• 2002

Cycle life tests have been carried out to evaluate the influence of safety valve pressure on valve regulated lead/acid batteries under deep cycling applications. Batteries were cycled at 5 hour rates at 100% DOD, and safety valve pressure was set to 1.08 and 2.00 bar, respectively. The batteries lost 248.3 g and 235.3 g of water for each case after about 1,200 cycles, but the cyclic performances of the batteries were comparable. Most of the gas of the battery during discharging was hydrogen, and the oxygen concentration increased to 18% after 3 hours of charging. The micro structure of the positive active materials was completely changed and the corrosion layer of the positive grid was less than $50{\mu}m$, regardless of the pressure of the safety valve after cycle life tests. The cause of discharge capacity decrease was found to be water loss and the shedding of the positive active materials. The pressure of safety valve does not give little effect to the cyclic performances and the failure modes of the gelled electrolyte valve-regulated lead acid batteries.

• Journal of Ocean Engineering and Technology
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• v.1 no.1
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• pp.111-119
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• 1987

The corrosion fatigue crack propagation characteristics of SS41 steel in 3.5% NaCl solution have been evaluated for loading frequencies of 1Hz and 0.2Hz. A sine wave loading profile was used for fatigue testing. Each test was carried out at a constant stress ratio, R(0.1). The main results are summarized as follows; 1. Fatigue crack propagation rate was higher in 3.5% NaCl solution than in air, higher in the base metal than in the weld metal, and higher at f =0.2Hz than at f =1Hz. 2. The crack closure level of the base metal was not influenced by cyclic frequencies, but that of the weld metal was much influenced. 3. When the crack closure effect was eliminated in the evaluation of crack propagation characteristics by using $\Delta K_{eff}$, the envirommental influence was distinctly observed. At the base metal, crack propagation rate was enhanced by the hydrogen embrittlement, and the weld metal was reduced by the crac closure. 4. There was clearly observed hydrogen embrittlement and severely corroded aspect at fracture surface of lower frequency than that of higher frequency, and at that of base metal than that of the weld metal.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.247-259
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• 2017

This paper presents a fatigue assessment model that was developed for corroded reinforced concrete (RC) beams strengthened using prestressed carbon fiber-reinforced polymer (CFRP) sheets. The proposed model considers the fatigue properties of the constituent materials as well as the section equilibrium. The model provides a rational approach that can be used to explicitly assess the failure mode, fatigue life, fatigue strength, stiffness, and post-fatigue ultimate capacity of corroded beams strengthened with prestressed CFRP. A parametric analysis demonstrated that the controlling factor for the fatigue behavior of the beams is the fatigue behavior of the corroded steel bars. Strengthening with one layer of non-prestressed CFRP sheets restored the fatigue behavior of beams with rebar at a low corrosion degree to the level of the uncorroded beams, while strengthening with 20- and 30%-prestressed CFRP sheets restored the fatigue behavior of the beams with medium and high corrosion degrees, respectively, to the values of the uncorroded beams. Under cyclic fatigue loading, the factors for the strengthening design of corroded RC beams fall in the order of stiffness, fatigue life, fatigue strength, and ultimate capacity.

• Advances in concrete construction
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• v.10 no.3
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• pp.185-193
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• 2020

An analytical model is developed in this paper to predict the shear capacity of reinforced concrete (RC) columns with corroded transverse reinforcements. The shear strength model for corroded RC columns is proposed based on modifying the existing strut-and-tie model, which considers the deformational compatibility between truss and arch mechanisms. The contributions to the shear strength from both truss and arch mechanisms are incorporated in the proposed model. The effects of corrosion level of transverse reinforcements are considered in the proposed model through the minimum residual cross-sectional area of transverse reinforcements and the reduction of concrete compressive strength for the cover area. The shear strengths calculated from the developed model are compared with the experimental results from Vu's study (2017), which consisted of RC columns with corroded transverse reinforcements showing shear failure under the cyclic loading. The comparison results indicate satisfactory correlations. Parametric studies are conducted based on the developed shear strength model to explore the effects of column axial loading, aspect ratios, transverse reinforcements and the corrosion levels in transverse reinforcements to the shear strength of RC columns with corroded transverse reinforcements.

• Steel and Composite Structures
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• v.30 no.3
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• pp.231-251
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• 2019

In the present study, a numerical and experimental investigation has been carried out on the seismic behavior of RC columns of a bridge which damaged under corrosive environments and retrofitted by various techniques including combined application of CFRP sheets and steel profiles. A novel hybrid retrofitting procedure, including the application of inner steel profiles and outer peripheral CFRP sheets, has been proposed for strengthening purpose. Seven large-scale RC columns of a Girder Bridge have been tested in the laboratory under the influence of simultaneous application of constant axial load and the lateral cyclic displacements. Having verified the finite element modeling, using ABAQUS software, the effects of important parameters such as the corrosion percentage of steel rebars and the number of CFRP layers have been evaluated. Based on the results, retrofitting of RC columns of the bridge with the proposed technique was effective in improving some measures of structural performance such as lateral strength degradation and higher energy absorption capability. However, the displacement ductility was not considerably improved whereas the elastic stiffness of the specimens has been increased.

• Steel and Composite Structures
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• v.35 no.6
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• pp.739-752
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• 2020

This paper aims to investigate cyclic plasticity of a new type of high-performance austenitic stainless steel with both high strength and high ductility. The new stainless steel termed as QN1803 has high nitrogen and low nickel, which leads to reduction of cost ranging from 15% to 20%. Another virtue of the new material is its high initial yield strength and tensile strength. Its initial yield strength can be 40% to 50% higher than conventional stainless steel S30408. Elongation of QN1803 can also achieve approximately 50%, which is equivalent to the conventional one. QN1803 also has a corrosion resistance as good as that of S30408. In this paper, both experimental and numerical studies on the new material were conducted. Full-range true stress-true strain relationships under both monotonic and cyclic loading were obtained. A cyclic plasticity model based on the Chaboche model was developed, where a memory surface was newly added and the isotropic hardening rule was modified. A user-defined material subroutine was written, and the proposed cyclic plasticity model can well evaluate full-range hysteretic properties of the material under various loading histories.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.4
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• pp.53-60
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• 2003

Large sized marine structures are used under corrosion environment of seawater and applied by severe service loading such as an ocean current, a billow and a tempest. Marine structures are usually constructed by lots of thick wall steel pipes joining welded joints. The thickness of such as steel pipes is usually more than 40mm. The such as steels are called "Thermo-Mechanical Control Process steel (TMCP steel)" strengthened by a heat treatment in process of steel manufactures. The failure, especially crack initiation, of marine structures was starting at weld joints under service condition. Then they should be designed by basis of the fatigue strength under seawater corrosion environment of weld joints. To clarity the fatigue crack initiation behavior is important more than to clarify the crack propagation behavior on the strength design of marine structures, because it is very difficult to find out the crack initiation and propagation phenomena and then even if it will be able to find out, it is considered that the refit of the damaged parts of welded joints have a technical difficulty under the sea. Therefore, it is most important to clarify the corrosion fatigue crack initiation behavior under the seawater condition. But, there is one big difficulty to make a test for thick plate specimen, for example thicker than 40mm. Because, it is need large capacity loading apparatus to test such as thick plate specimen. In this research, the new configuration specimen for fatigue crack initiation tests was proposed. Using this new specimen, it is easy to carry out the fatigue clack initiation tests with relatively low cyclic loading and to observe a fatigue crack initiation behavior.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.97-108
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• 2016

Thermally sprayed metals or organic coatings is often used in corrosion protection of steel structures. Duplex coating systems of thermally sprayed metal in combination with organic coating are selected as a new generic type of coatings on steel structures under the highly corrosive environments. In this study, three types of corrosion tests were carried out on four types of thermal sprayed specimens with sealing: zinc, zinc-15%aluminum alloy, aluminum and aluminum-5%magnesium alloy, four types of duplex coated specimens; thermally sprayed metals in combination with paint of acrylic urethane, and painted specimens. NORSOK M-501, Wet/dry cyclic seawater tests and outdoor exposure tests of nine types of specimens were conducted. From the corrosion test results, weathering performance of them were presented.