• Journal of Navigation and Port Research
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• v.30 no.6 s.112
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• pp.447-455
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• 2006

Together with the trend of enhancement in domestic industrial development and economic progress due to import and export, the demand for construction of the roads, bridges, especially port facilities, and several coastal protection and ocean structures is increasing rapidly. MOMAF of Korean Government is driving construction cf 9 new ports and renovation cf the existing fishery ports. Among these structures most of bridge base, wharves, dolphins, quays, and jetties are being newly built cf steel or concrete pile. As the base, supporting bulkheads, and piles are underwater after construction, it is difficult to figure out the status of structures and not enough to get maintenance and strengthen the structures. Every year, moreover, these works suck the government budget due to higher incomplete maintenance expense for protection from corrosions cf structures and increased underwater construction period. For the purpose cf cutting down the expense cf government budget, it is necessary to extend the life cycle of the existing structures. Therefore, we developed a new method for maintenance of submerged structures near the waterline by allowing dry work environment with the floating caisson. The method shows easy to move around the working area and handle. It also showed not only a significant reduction of maintenance expenses and time for anti-corrosion work but also better protection This will be a milestone to reduce the maintenance and construction expenses for the shore and water structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.87-99
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• 1982

This study proposes a reliability based design criteria for the R.C. superstructures of highway bridges. Uncertainties associated with the resistance of T or rectangular sections are investigated, and a set of appropriate uncertainties associated with the bridge dead and traffic live loads are proposed by reflecting our level of practice. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM(Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Ellingwood's algorithm and an approximate log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the current R.C. bridge design safety provisions. A set of load and resistance factors is derived by the proposed uncertainties and the methods corresponding to the target reliability. Furthermore, a set of nominal safety factors and allowable stresses are proposed for the current W.S.D. design provisions. It may be asserted that the proposed L.R.F.D. reliability based design criteria for the R.C. highway bridges may have to be incorporated into the current R.C. bridge design codes as a design provision corresponding to the U.S.D. provisions of the current R.C. design code.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.149-158
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• 2008

This study was estimated on performance of deicers, corrosion inhibitors and low corrodible deicer used for removal of snow or ice on the road and on influence on structure. The weight loss rate after freezing and thawing of low corrodible deicer is lower than one of deicer, corrosion inhibitors and these combination. Relative dynamic elastic modulus of all except water, low corrodible deicer and NaCl+JF-1004 was radically reduced after freezing and thawing 150 cycles. And concretes after freezing and thawing were showed severe surface damage. It was found that individual use of low corrodible deicer and corrosion inhibitors had a problem of field application because of lack of early ice melting effect and considerably low durability. Products combined with NaCl was showed rapid weight loss by metal corrosion. Therefore, It will need to circumspectly select combination of deicers having low effect on concrete pavement and bridge if possible.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.132-139
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• 2017

A huge amount of de-icing agent is sprayed during winter to promote traffic safety in cold regions, and the quantity of de-icing agent sprayed has increased each year. The main ingredients in commonly used de-icing agents are chlorides, such as calcium chloride($CaCl_2$) and sodium chloride(NaCl). While calcium chloride is mostly used in Korea and sodium chloride is usually used in the U.S. and Japan, all de-icing agents include chloride ions. The chlorides included in sprayed calcium chloride-based de-icing agents have severe adverse effects, including the corrosion of reinforcing steels through salt damage by infiltrating into road structures, reduced structural performance of pavement or damage to bridge structures, and surface scaling, in combination with freezing damage in winter, as well as water pollution. In addition, the deterioration of paved concrete road surface that occurs after the use of calcium chloride-based de-icing agent accelerates the development of visual problems with traffic structures. Therefore, the present study was performed to prepare an environment-friendly liquid de-icing agent through a reaction between waste organic acids and calcium-based by-products, which are industrial by-products, and to analyze the properties of the de-icing agent in order to evaluate its applicability to road facilities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.254-260
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• 2017

The service life of civil infrastructure needs to be maintained or extended through appropriate inspections and maintenance planning, which results from the optimization process. A multi-objective optimization process can lead to more rational and flexible trade-off solutions rather than a single-objective optimization for the service life management of civil infrastructure. Recent investigations on the service life management of civil infrastructure were generally based on minimizing the life-cycle cost analysis and maximizing the structural performance. Various objectives for service life management have been developed using novel probabilistic concepts and methods over the last few decades. On the other hand, an increase in the number of objectives in a multi-objective optimization problem can lead to difficulties in computational efficiency, visualization, and decision making. These difficulties can be overcome using the objective reduction approach to identify the redundant and essential objectives. As a result, the efficiency in computational efforts, visualization, and decision making can be improved. In this paper, the multi-objective optimization using the objective reduction approach was applied to the service life management of concrete bridges. The results showed that four initial objectives can be reduced by two objectives for the optimal service life management.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.163-170
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• 2006

Together with the trend of enhancement in domestic industrial development and economic progress due to import and export, the demand for construction of the roads, bridges, especially port facilities, and several coastal protection and ocean structures is increasing rapidly. MOMAF of Korean Government is driving construction of 9 new ports and renovation of the existing fishery ports. Among these structures most of bridge base, wharves, dolphins, quays, and jetties are being newly built of steel or concrete pile. As the base, supporting bulkheads, and piles are underwater after construction, it is difficult to figure out the status of structures and not enough to get maintenance and strengthen the structures. Every year, moreover, these works suck the government budget due to higher incomplete maintenance expense for protection from corrosions of structures and increased underwater construction period. For the purpose of cutting down the expense of government budget, it is necessary to extend the life cycle of the existing structures. Therefore, we developed a new method for maintenance of submerged structures near the waterline by allowing dry work environment with the floating caisson. The method shows easy to move around the working area and handle. It also showed not only a significant reduction maintenance expenses and time for anti-corrosion work but also better protection. This will be a milestone to reduce the maintenance and construction expenses for the shore and water structures.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.519-528
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• 2008

A simple steel-concrete composite deck is developed for preventing the lateral torsional buckling of girders that are under construction and for reducing the term of works using H-shaped rolled beams as bridge girders. A new type of shear connectors is also developed for the composite behavior between a simple steel-concrete composite deck and the rolled beams by the connecting conditions between the deck and the girders. One is a connector bolt that is lengthened and split or tightened with two nuts and the other is an I-shaped rolled beam welded on a steel plate with a number of holes punched through the web. In this study, to estimate the shear strength of those shear connectors the push-out tests are performed and the test results are compared with that of the previous studies and the codes. The result of the push-out tests of the connector bolts showed that the shear performance is similar to that of the stud connector and revealed that the equation for the shear strength in the Korean Specification of Highway Bridge overestimates the shear capacity of the connector bolt whose diameter is larger than 19mm. From the push-out tests of punched I-shaped rolled beams with varying welding amounts, with the small amount of welding, shear capacity is governed by the shear capacity of welding. On the other hand, shear capacity is governed by the size of the punched I-shaped rolled beams, regardless of the amount of welding.

• Journal of Korean Society of Disaster and Security
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• v.16 no.3
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• pp.17-26
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• 2023

Prestressed Concrete (PSC) girders are divided into pre- and post-tension types as prestressing method, and I- and U-type as cross-sectional shape. There are both advantages and disadvantages depending on each prestressing method and cross-sectional shape, and each method is applied to bridge construction sites. In this study, a new girder design was attempted to develop that overcomes its shortcomings by using the pretension method and U-type cross sectional shape. Its structural performance was verified in this study. Pretension type girders are mainly manufactured in factories because they require a reaction arm and related facilities, and have the disadvantage of being limited in weight and span length for road transportation. In addition, in the case of the U-type cross-section, structural stability is very reliable during construction against overturning, but its own weight is relatively large comparing to I-type, and the post-tension method is mainly applied after on-site production. In this study, a PSC girder manufacturing method using the field pretension was proposed and a span length of 40 m real-scale test specimen was manufactured and verified its structural performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.21-29
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• 2023

In this study, the stress characteristics of temporary fixed steel rods were analyzed in the "temporary fixing system using internal prestressing tension", which is mainly applied to the construction of superstructures by FCM. It was difficult to confirm the changes in initial tensile force in this system because the steel rod was internally connected to the pier and the PSC BOX. Therefore, measurement was performed before and after the completion of each segment using an FBG sensor to measure the change in the micro length of the steel rod. The results of the analysis showed that 75% to 90% of the maximum vertical contraction of the steel rod that occurred until the completion of the cantilever segment occurred in the fixing ~ 1segment, and the maximum loss of initial prestressing force was 39%. Such excessive loss of tension force to 1 segment means that tension is needed to improve the precision of construction during the fixation, and re-tension is needed to secure stability for conduction of cantilever segments after the completion of 1segment. In the 2 ~ last segment, the stress of the steel rod decreased gradually, and in the summer, the decrease in stress tended to partially recover due to the increase in the length of the steel rod corresponding to the increase in the vertical volume of PSC BOX. The dominant factor in the stress change in 2~ last segment in this phenomenon is judged to be the change in the length of the steel rod according to the temperature. Unlike the change in length, the relaxation was 1.2-2.7%, which was mostly offset by the opposite stress corresponding to the temperature stress. Therefore, a plan was proposed to improve the internal stress, such as adjusting the fixation time.

• 주택과사람들
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• no.54 s.71
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• pp.185-206
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• 1996

1.건설제도의 국제화와 경쟁기반 구축 $\bullet$건설산업을 기획$\cdot$설계$\cdot$시공$\cdot$감리$\cdot$사후관리 등 전 분야에 걸쳐 경쟁력 있는 산업으로 육성-기획$\cdot$설계$\cdot$시공$\cdot$감리$\cdot$유지관리 등 건설산업 전반에 관한 기본사항을 법제화-대규모 공사의 경우 발주자를 대신하여 건설공사의 기획$\cdot$설계$\cdot$발주$\cdot$감리$\cdot$시공관리 등 업무의 전부 또는 일부를 종합적으로 조정$\cdot$관리하는 $\lceil$건설사업관리$\rfloor$제도를 도입 $bullet$건설공사 $\lceil$현장실명제$\rfloor$도입을 통한 하도급제도의 정비-전문건설업자로부터 하도급, 위탁, 고용 등의 형태로 공사에 참여하는 현장근로자를 신고 받아 권익을 보호하고 시공책임도 부과하는 $\lceil$현장실명제$\rfloor$도입 $\bullet$공사완성보증제, 손해배상보증제도를 도입하고, 신용상태 $\cdot$시공능력에 따라 보증 요율 등을 차등화 하여 부실업체를 배제 $\bullet$건설공사관련 각종 계약서와 시방서 등 제기준을 정비하여 발주자$\cdot$시공자 등 건설주체간의 역할과 책임을 명확화$\bullet$건설분쟁을 신속하고 객관적으로 조정$\cdot$중재하기 위하여 $\lceil$건설분쟁중재원$\rfloor$으로 확대 개편 2. 건설인력의 육성과 고용안정$\bullet$경쟁력 제고의 관건인 우수인력 확보를 위하여 대학교육 제도의 개선을 포함한 건설 인력 수급대책을 추진 - 대학의 건설관련 학과 정원을 2000년까지 매년 일정규모로 증원하여 고급기술 인력을 배출 현재 50$\%$에 불과한 건설관련 국가기술자격자를 2000년에 70$\%$까지 제고 - 감리 등 전문인력을 양성하고, 선진외국 감리 회사를 활용하여 국내 업계와의 경쟁을 유도 $\bullet$건설현장의 최일선에서 품질을 담당하고 있는 건설기능공의 고용안정과 복지향상을 위한 획기적인 대책을 마련 - 건설기능공의 자긍심과 사회적 책임의식을 고취하기 위해 기능공이 여러 현장을 전전하여 근무하더라도 경력관리, 공제금 등의 합산 관리가 가능하도록 $\lceil$건설 근로자 복지카드$\rfloor$제도를 도입 *$\lceil$건실시연구단$\rfloor$을 구성$\cdot$구체적인 운영방안을 수립 - 건설 업체 실정에 맞는 현장위주의 기능검정제도 도입 $\cdot$자격증이 현장에서 요구되는 기능수준과 숙련도를 제대로 반영할 수 있도록 검정방법을 현장 실기위주로 개선하고 자격검정업무도 건설협회 등의 자격 검정능력을 향상시켜 위탁$\cdot$시행하는 방안을 검토 3. 공사시행기관의 전문성과 책임성 제고 $\bullet$시장이 개방되어 건설공사가 국제적인 관행에 따라 이루어질 것에 대비하여 시행기관에 계약$\cdot$공사관리 등 전문직공무원을 집중 교육하여 양성 $\bullet$ 조달청이 대행하여 공사계약을 하는 경우라도 설계변경은 발주기관이 자체적으로 할 수 있도록 허용 $\bullet$ 기술직 공무원의 기술향상을 위하여 관련 공무원의 확충, 해외연수, 현장교육 강화 등을 지속적으로 추진 $\bullet$ 충분한 사전조사를 거쳐 사업계획을 수립하도록 $\lceil$건설공사 시행절차$\rfloor$를 규정 $\bullet$ 공사기간 3년 이상의 공사에 대하여는 최대한 계속비사업으로 편성토록 계속비제도의 운영을 활성화 4. 건설현장의 품질관리체제 구축 $\bullet$ 현장배쳐플랜트 설치를 확대하여 레미콘의 품질관리를 일원화하고 현장에서 레이콘을 배합하는 건식공법을 채택 - 현장레미콘생산시설(B/P)설치 확대로 콘크리트 하자에 대한 책임한계 일원화 유도 - 레미콘 재료인 골재$\cdot$시멘트$\cdot$물을 공장에서 혼합하여 공급하는 현행 습식배합 대신에 물만을 현장에서 혼합하는 건식 배합방식을 도입 $\bullet$철강재$\cdot$철구조물의 품질을 보증하기 위하여 일정기술을 갖춘 공장에서만 제작토록 하는$\lceil$공장인증제$\rfloor$를 도입 - 제작시설과 품질관리 등을 심사하여 제작공장을 등급화하고 등급에 따라 철강재 등의 제작업무 범위를 차등화 $\bullet$시설물에 대하여도 시공업체가 제작공장을 등급화하고 등급에 따라 철강재 등의 제작업무 범위를 차등화 $\bullet$시설물에 대하여도 시공업체가 사후관리를 일괄 책임질 수 있도록 $\lceil$시공 및 유지관리 일괄계약제도$\rfloor$를 도입 - 대형교량$\cdot$소각로$\cdot$하수처리장 등 유지관리에 전문성이 요구되는 분야부터 시범적으로 도입 $\bullet$건설자재의 표준화$\cdot$정보화사업을 조속히 추진 5. 건설업체에 대한 지원 강화 $\bullet$일부 공공사업자의 경우 관행화되어 있는 대금일부의 어음 또는 채권지급방법을 단계적으로 축소 $\bullet$매월 감독이나 감리원의 기성확인에 의하여 시공자에게 공사대금을 직접 지급토록 하는 등 대금 지급절차를 간소화 6. 민간 건축물에 대한 안전확보 $\bullet$충실한 설계가 이루어지도록 제도를 개선 - 설계도서 작성기준을 제정하고 다중이용시설에 대하여는 건축심의단계에서 구조검토 등 설계심의를 의무화 $\bullet$대형다중이용시설에 대한 감리 강화 - 감리전문회사 수준의 감리체제로 전환하고 감리대가도 공공수준으로 인상하고 적용요율대로 지도$\cdot$감독 강화