• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.611-620
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• 2006

The composite two plate-girder bridges are generally defined as a non-redundant load path structure because the bridge can collapse if one of the two girders is seriously damaged by a fatigue crack. In this paper, a numerical study on the evaluation of the after-fracture redundancy of the composite two-girder bridges was accomplished. The evaluation has been performed on the simple and three-span continuous bridges with I-section cross beams which serve as transverse bracing, and with or without the bottom lateral bracing system. The load carrying capacities of the intact and damaged bridges with or without lateral bracing were evaluated from material and geometric nonlinear analysis, respectively and the redundancy was evaluated for each case. It was acknowledged from the analytical results that both simple and continuous intact two-girder bridges have sufficient redundancy even without lateral bracing, but it takes an important role to improve the redundancy of damaged bridges.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.611-618
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• 2008

CFRP (carbon fiber reinforced polymer) tendons can be used as an alternative to solve the corrosion problem of steel tendons. Since CFRP tendons are vulnerable to transverse pressure and stress concentration, the conventional anchorage system used for steel tendons can create an unreliable load carrying capacity and may result in a premature failure. Therefore, it is necessary to develop the anchorage system that is well suited for CFRP tendons. There are many types of anchorage systems for CFRP tendons, which can be classified into three types: wedge-type anchorage, bond-type anchorage, and compression-type anchorage. This paper deals with the compression-type anchorage system manufactured through swaging technology. Based on the previous test results performed by the authors, the dimension of anchorage sleeve, the use and non-use of the insert, and the compression pressure on the sleeve have been selected as the major parameters affecting the performance of the compression-type anchorage. Some anchorage sleeves have been tapered to reduce the stress concentration. Test results revealed that the performance of the anchorage system depends mainly on the dimension and the compression pressure. It has been verified that the tapered sleeve can effectively reduce the stress concentration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.61-69
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• 2024

An ultra-high strength prestressed prismatic beam of 100 MPa in compressive strength was developed by increasing the water-tightness of concrete by utilizing centrifugal molding processes without adding expensive admixtures. The centrifugal prismatic PSC beam developed as the superstructure of the avalanche tunnel was constructed on a rahmen bridge in a small local river. In this study, the centrifugal prismatic beam was compared and analyzed based on the results of measurements made through static load tests and the results of numerical analysis of the target structure. The common load-carrying capacity and safety of the rahmen bridge were evaluated. The static·dynamic load tests and finite element analysis results of this bridge were similar, and it was confirmed that the behavior of the centrifugal prismatic beam was well simulated. All centrifugally formed square beams that make up the composite rahmen bridge were evaluated to secure sufficient load carrying capacity under the design live load, and structural reliability was proven by ensuring safety.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.635-642
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• 2003

Although the strengthening effect of deteriorated concrete bridge decks has been studied by various authors, most researches are focused on the experimental works on the pulsating loading in laboratory in spite of deterioration of deck caused by moving vehicle loads. In this research, a theoretical live load model that was proposed to reflect an effect of moving vehicle loads is formulated from a statistical approach on the measurement of real traffic loads for various time periodsin Korea. Fatigue life and strengthening effect of strengthened bridge decks strengthened with either Carbon Fiber Sheet or Grid typed Carbon Fiber Polymer Plastic by the probabilistic and the reliability analyses are assessed. As a results, secondary bridge deck (DB18) strengthened with FRP ensures a sufficient fatigue resistance against the increased traffic loads as well as load carrying capacity in life cycle.

• Journal of the Korea Institute of Building Construction
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• v.7 no.1 s.23
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• pp.79-84
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• 2007

Selection of proper root barrier as destination part of greening is very important in Root penetration resistance plan. To select proper root barrier, it need to understand composition of greening part, size, kind of plant, connection with waterproofing layer. In this point of view, we have establish greening on the roof or concrete structure, not been understand the structural mechanism. It means that we misunderstood about purpose of greening and using it. So, chosen materials and construction method was not proper for greening, it caused water leakage and decrease performance of concrete structure. Therefore, we would suggest 5 items of test methods considering environmental condition for green roof. Watertightness by water of greening part, root penetration resistance test by root penetration, bacteria resistance by must or bacteria in soil, chemical resistance by rain and chemical agent of fertilizer, and load resistance by soil depth, size of plant. These suggested test methods could be referred as guideline to test in green roof system because of not exist any performance appraisal guideline or standard. Consequently, it should be analysis as technical and institutional subdividing test methods and it need to study constantly as varied angles.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.5-8
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• 2007

Selection of proper root barrier as destination part of greening is very important in Root penetration resistance plan. To select proper root barrier, it need to understand composition of greening part, size, kind of plant, connection with waterproofing layer. In this point of view, we have establish greening on the roof or concrete structure, not been understand the structural mechanism. It means that we misunderstood about purpose of greening and using it. So, chosen materials and construction method was not proper for greening, it caused water leakage and decrease performance of concrete structure. Therefore, we examine the practical use of copper sheet considering environmental condition for green roof. Watertightness by water of greening part, root penetration resistance test by root penetration, bacteria resistance by must or bacteria in soil, chemical resistance by rain and chemical agent of fertilizer, and load resistance by soil depth, sire of plant. These suggested test methods could be referred as guideline to test in green roof system because of not exist any performance appraisal guideline or standard. Consequently, it should be analysis as technical and institutional subdividing test methods and it need to study constantly as varied angles.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.611-620
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• 2007

The beam-column connection is the critical design section of general steel frame structures owing to the behavioral characteristics of the structural system. As most members of a frame structure are composed of rolled section beams, the cross-section of the beam members is governed by the negative bending moment near beam-column connections. Such a design concept leaves a redundant load-carrying capacity at the positive bending regions of the beam members leading to design inefficiency. Therefore, it is of utmost importance to redistribute the beam end moments and reduce the stresses at the beam-column connections for a more efficient design of steel frame structures. In this study, reaction-moment prestressing method (RMPM) was proposed for the innovative design and construction of steel frame structures. The RMPM is a prestressing method utilizing the elastic bending deformation of a beam member induced by temporary prestressing for the distribution of a relatively large bending moment to other sections for the efficient use of the beam section. By the application of the RMPM, the negative bending moment at the beam-column connections can be significantly reduced, ultimately leading to possible use of smaller beam sections. Through a series of model tests and numerical analyses of steel frame structures, the moment distributing effect and feasibility of the RMPM was verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.301-306
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• 2016

In bridge performance assessments, a new load carrying capacity evaluation model of simple bridges was proposed, which is based on the developed simple support impact factor spectrum. In this paper, a conservative assumption that the inner span with the both ends fixed boundary condition is ideal for applying the impact factor response spectrum for continuous bridges. The impact factor response spectrum has been proposed based on this assumption. The response spectrum by comparing the numerical analysis result and actual measurement data verified the applicability. The analysis was loading the moving load of DB-24 in a six-span continuous bridge, which was the same as the actual measurement data, the dynamic response was measured in the fourth span. The frequency of the bridge was obtained by FFT on the acceleration response and the span-frequency of sample bridge was calculated by the frequency. The impact factor of the sample bridge was determined by applying the span-frequency of the bridge to the proposed response spectrum; it was similar to the result of comparing the actual measured impact factor. Therefore, the method using the impact factor response spectrum based on the frequency response of both ends-fixed beam was found to be applicable to an actual continuous bridge.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2402-2408
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• 2009

This study conducted a static tensile test in order to prevent the lowering of load carrying capacity caused by critical sections made by over bolt holes in the base plate and the cover plate of steel member joints using high-tension bolts. The change of the load carrying capacity of joints was examined by comparison of the maximum load on joint fracture obtained from the tensile test with critical section rate and design strength. According to the results, the rate of decrease in strength was higher when the critical section rate was high, and in particular, decrease in strength was affected much more by critical sections in the base plate than by those in the cover plate. In high-tension bolt joints using over bolt holes for the base plate and the cover plate, load carrying performance was somewhat lower than that in joints using standard bolt holes, but the maximum tensile strength on facture was over 15% higher than design fracture strength. According to the results of this study, the use of over bolt holes in high-tension bolt joints had an insignificant effect on the lowering of load carrying capacity, so the allowance of over bolt holes in the joints of steel members is expected to enhance to the economy and efficiency of the works.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.8-15
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• 2019

In this study, we synthesized a calcium sulfonate complex grease and a lithium complex grease to investigate their physical, rheological and tribological properties. The thermal stability of the calcium sulfonate was higher than $300^{\circ}C$ and the lithium complex grease was $245^{\circ}C$ in the dropping point test. In the grease viscosity measurement, the calcium sulfonate complex grease was measured as $7.0Pa{\cdot}s$ and the lithium complex grease was as $4.5Pa{\cdot}s$. Therefore, it was confirmed that the calcium sulfonate complex grease is superior to the lithium complex grease in terms of thermal stability and cohesiveness. In the 4-ball wear test, the calcium sulfonate complex grease was measured to be 0.43 mm and the lithium complex grease to 0.85 mm. In the 4-ball extreme pressure test, calcium sulfonate complex grease was measured as 620 kgf and the lithium complex grease was as 125 kgf. Therefore, it was confirmed that the calcium sulfonate complex grease is superior to the lithium complex grease in abrasion resistance and load-bearing property. It was found that the calcium sulfonate complex grease is more effective than the lithium complex grease in the lubrication at high temperature and high load.