• Structural Engineering and Mechanics
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• v.90 no.2
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• pp.127-142
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• 2024

In recent decades, pultruded glass fiber-reinforced polymer (GFRP) members including those of box sections have attracted the attention of researchers. Nevertheless, the lack of uniform and consistent material properties, simplified design methods, and practical design codes have so far been the main barrier for field applications. Consequently, this paper highlights the existing knowledge concerning the flexural behavior of pultruded GFRP profiles and their failure modes. In particulate, it reviews the most commonly accepted design expressions and code provisions addressing the flange local buckling of pultruded GFRP box beams as the most likely failure mode. In addition, the material characterization of GFRP sections is described in detail along with the standard test methods to quantify the material characterization of GFRP laminates. It is shown that the critical flange local buckling stresses of pultruded GFRP box beams can be predicted with reliable accuracy using the expressions promulgated by ASCE (1984) (in which the flange plates are considered simply-supported at web-flange junction) and EUR 27666. The expressions stipulated in ASCE (2010) highly overestimates the critical flange local buckling stresses of GFRP box beams resulting in unconservative predictions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.21-32
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• 1981

Recent trends in design standards development in some European countries and U.S.A. have encouraged the use of probabilistic limit sate design concepts. Reliability based design criteria such as LSD, LRFD, PBLSD, adopted in those advanced countries have the potentials that they afford for symplifying the design process and placing it on a consistent reliability bases for various construction materials. A reliability based design criteria for RC flexural members are proposed in this study. Lind-Hasofer's invariant second-moment reliability theory is used in the derivation of an algorithmic reliability analysis method as well as an iterative determination of load and resistance factors. In addition, Cornell's Mean First-Order Second Moment Method is employed as a practical tool for the approximate reliability analysis and the derivation of design criteria. Uncertainty measures for flexural resistance and load effects are based on the Ellingwood's approach for the evaluation of uncertainties of loads and resistances. The implied relative safety levels of RC flexural members designed by the strength design provisions of the current standard code were evaluated using the second moment reliability analysis method proposed in this study. And then, resistance and load factors corresponding to the target reliability index(${\beta}=4$) which is considered to be appropriate level of reliability considering our practices are calculated by using the proposed methods. These reliability based factors were compared to those specified by our current ultimate strength design provisions. It was found that the reliability levels of flexural members designed by current code are not appropriate, and the code specified resistance and load factors were considerably different from the reliability based resistance and load factors proposed in this study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.193-202
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• 2018

This paper proposed a crack spacing calculation formulation which is an important parameter for calculating the crack width, that is the main factor for verification of serviceability limit states and durability performance evaluation of reinforced concrete members. The basic equation of average crack spacing is derived by considering the bond characteristics which is the governing equation for the analysis of cracking behavior in reinforced concrete members. In order to consider the effect of the cover thickness and concrete compressive strength, the crack spacing measured in 124 direct tensile tests performed by several researchers was analyzed and each coefficient was proposed. And, correlation analysis was performed from 80 specimen data where the maximum and average crack spacing were simultaneously measured, and a correlation coefficient that can easily predict the maximum crack spacing from the average crack spacing was proposed. The results of the proposed average crack spacing equation and maximum crack spacing correlation were compared with those current design code specification. The comparisons of proposed equations and the Korean design codes show that the proposed formulation for the average crack spacing and the maximum crack spacing improves the accuracy and reliability of prediction compared to the corresponding provisions of the Korean Concrete Structural Design Code and Korean Highway Bridge Design Code (Limit States Design).

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.398-407
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• 2018

Standard guidelines for marine accident investigation have been prepared through the enforcement of the Casualty Investigation code as of January 2010. In addition, as the International Maritime Organization (IMO) recommended contracting the state to manage a marine incident system established under this code, Korea also has newly established provisions for a marine incident system in the 'Act on the Investigation of and Inquiry into Marine Accidents' also as of 2010. The Korean Maritime Safety Tribunal (KMST) has made a multilateral effort to prevent marine accidents through the efficient operation of a marine incident system, but this system has not been properly activated. This study examines the operational status and problems of a marine incident system and analyzes the marine incident systems of foreign countries and similar transportation agencies such as railroads and aviation. Options include switching to voluntary reporting of marine incidents, transferring responsibility to a non judicial private organization, expanding incentive systems for a marine incidents, revising regulation and preparing detailed implementation guidelines.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.772-781
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• 2020

A direct shear member resists external forces through the shear transfer of reinforcing bars placed at the concrete interface. The current concrete structural design code uses empirical formulas based on the shear friction analogy, which is applied to the horizontal shear of concrete composite beams. However, in the case of a member with a large amount of reinforcing bars, the shear strength obtained through the empirical formula is lower than the measured value. In this paper, the limit state of newly constructed composite beams on an existing concrete girder is defined using stress field theory, and material constitutive laws are applied to gain horizontal shear strength while considering the tension-stiffening and softening effects of concrete struts. A simplified method of calculating the shear strength is proposed, which was validated by comparing it with the related design code provisions. As a result, it was confirmed that the method generally shows a similar tendency to the experimental results when the shear reinforcing bar yields, unlike the regulations of the design code, where differences in the predicted value of shear strength occur according to the shear reinforcement ratio.

• The Korean Journal of Air & Space Law and Policy
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• v.23 no.2
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• pp.3-29
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• 2008

The volume of air passengers and cargo transportation has increased rapidly in recent years. This trend will be even more noticeable as the high-tech service industry expands and the globalization progresses. In an effort to reflect and to cope with this trend, many conventions concerning international air transportation have been concluded. The Republic of Korea has also acceded to the Montreal Convention of 1999 on September 20th, 2007 which became effective on December 29th 2007. However, Korea currently does not provide any private law on the liability of domestic air carrier, leaving the regulation wholly to the general conditions of carriage of private air lines. These general conditions of carriage, however, are not sufficient to regulate the liabilities of domestic air carriers, because they cannot be fully recognized as a legitimate source of law applicable in the court. This situation is inconvenient for both air carrier and their customers. Thus, the Ministry of Justice of Korea has decided to enact a law that will regulate domestic air transportation, namely, "Domestic Carriage by Air Act", as a part of the Korean Commercial Code. So was composed a special committee for legislation of the Domestic Carriage by Air Act. This writer has led the committee as a chairman. The committee has held in total 10 meetings so far and has completed a draft bill for the part VI of the Korean Commercial Code, "Air Carriage." The essentials of the draft are as follows: First, the establishment of Part VI in the Commercial Code. The Korean Commercial Code already includes a series of provisions on road transportation in part II and carriage by sea in part V. In addition to these rules regulating different types of transportation, the Domestic Carriage by Air Act will newly establish part VI to regulate air carriages. Eventually, the Commercial Code will provide an integrated legal system on the transportation industry. Second, the acceptance of the basic liability system which major international conventions, such as Montreal Convention of 1999 and Guadalajara Convention of 1961, have adopted. This is very important, because the law of air carriage is unified worldwide through various international conventions, making it necessary and significant for the new act to achieve conformity between rules of international air carriage and that of domestic air carriage. Third, the acceptance of Rome Convention system on damage caused by foreign aircraft to third parties on the surface. Fourth, the application of rules on domestic road carriage or carriage by sea mutatis mutandis with necessary modifications. This very point is the merit of inserting domestic air transportation law into the Commercial Code. By doing so, the number of articles can be reduced and the rules on air carriage can conform to that of road transportation and carriage by sea. The bill is expected to be passed by the parliament at the end of this year and is expected to be effective by end of July 2009.

• Journal of Fisheries and Marine Sciences Education
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• v.13 no.1
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• pp.99-116
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• 2001

Testing is a procedure used to measure a sample of behaviour in order to discover how well a seafarer performs, usually in comparison with others, or compared with identified performance criteria. In this context It is important that the test, in whatever form it is being used, yields consistent results by being valid, reliable and practical. Whilst we can only take a sample of a person's knowledge or comprehension about topic in this way, testing methods do provide a more reliable estimate of performance than most other observational techniques; unsystematic or irregular observation being too unreliable. The method of examination has been specified in the provisions of Regulation 12 of the Decree of the ship officers act as followings. Other necessary matters for conducting oral and written examinations have been set out by the Minister. But written examination is too shortage of period and small number of question to cover the qualification of each level and oral test is just simple and namely Traditionally, written examinations have been provided as the only means for determining the acquisition of knowledge by the mariner. Typically, the examination formats have taken the format of either an essay or multiple choice examinations. Essay items, used in the vast majority of subject examination(not in Korea), consisted of three basic types: situational, descriptive and computational. The level of certificate being examined determined the number and mix of the type of essay questions selected. Oral question has again been used by assessors of seafarer in a wide variety of contexts. Also, oral questioning is often used when observation of performance is undertaken to ask why a certain action has been taken, or to be broaden the scope of what has been observed. At end, Each techniques have their own advantage and disadvantage, so we have to choose some or all of the following techniques, depending upon the certificate, qualification or job for which the trainee is aiming. But in high lank, we have to use both of essay type and multiple choice and with enough time of oral test at least 30 minutes. Who would be the assessor? According to the STCW Code Section A-I/6, instructors, supervisor and assessors are appropriately qualified for particular types and levels of training or assessment of competence of seafarers either on board or ashore, as required under the Convention, in accordance with the provisions of this section.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.161-168
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• 2006

An experimental investigation was conducted to examine the hysteretic behaviors of ultra-high strength concrete tied columns. The purpose of this study is to investigate the safety of ultra-high strength concrete columns with 100 MPa compressive strength for the requirement of ACI provisions. Eight 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the cross section $300{\times}300mm$ and the aspect ratio 4. The main variables are axial load ratio, configurations and volumetric ratios of transverse reinforcement. The results show that the deformability of columns are affected by the configurations and volumetric ratios of transverse reinforcement. Especially, it has been found that the behavior of columns are affected by axial load ratio rather than the amounts and the configurations of transverse reinforcement. Consequently, to secure the ductile behavior of 100 MPa ultra-high strength concrete columns, ACI provisions for the requirement of transverse steel may considered axial load level and the details of transverse reinforcement.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.698-707
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• 2002

A review is presented of experimental studies on the strength performance of concrete exposed at short-term and rapid heating as in a fire and after cooling. Emphasis is placed on concretes with high original compressive strengths, that is, high-strength concrete(HSC). The compressive strength-temperature relationships from the reviewed test programs are distinguished by the test methods used in obtaining the data(unstressed, unstressed residual strength, and stressed tests) and by the aggregate types(normal or lightweight), The compressive strength properties of HSC vary differently with temperature than those of NSC. HSC have higher rates of strength loss than lower strength concrete in the temperature range of between 20$^{\circ}C$ to about 400$^{\circ}C$. These difference become less significant at temperatures above 400$^{\circ}C$ compressive strengths of HSC at 800$^{\circ}C$ decrease to about 30 ％ of the original room temperature strength. A comparison of lest results with current code provisions on the effects of elevated temperatures on concrete compressive strength and elastic modulus shows that the CEN Eurocodes and the CEB provisions are unconservative.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.25-35
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• 2012

For a member subjected to direct shear forces, forces are transferred across interface concrete area and resisted by shear transfer capacity. Shear-friction equations in recent concrete structural design provisions are derived from experimental test results where shear-friction capacity is defined as a function of steel reinforcement area contained in the interface. This empirical equation gave too conservative values for concrete members with large amounts of reinforcement. This paper presents a method to evaluate shear transfer strengths and to define ultimate conditions which result in crushing of concrete struts after yielding of longitudinal reinforcement perpendicular to the interface concrete. This method is based on the bi-axial stress field theory where different constitutive laws are applied in various means to gain accurate shear strengths by considering softening effects of concrete struts based on the modified compression-field theory and the softened truss model. The validity of the proposed method is examined by applying to some selected test specimens in literatures and results are compared with recent design code provisions. A general agreement is observed between predicted and measured values at ultimate loading stages in initially uncracked normal-strength concrete test.