• Proceedings of the KSR Conference
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• 2002.10a
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• pp.678-683
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• 2002

Field measurements were conducted to analysis dynamic characteristics of existing steel plate girder railway bridges without ballast. Three bridges which have 9m, 12m, 18m span length in Kyoung-Bu and Ho-Nam Line were selected for test. According to the each bridge, dynamic vertical deflections and vertical and horizontal accelerations were measured. Natural frequencies, vertical deflections and accelerations obtained from field tests were compared with the limit value specified in the UC, Japanese and Korean railway bridge specification.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.605-608
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• 1999

The objective of this research is to examine whether the determination of development length for high strength concrete by the ACI Building Code 318-95 could be applied and the upped limit of compressive strength, 700kg/$\textrm{cm}^2$ is suitable. Eight beam specimens were tested. Each beam was designed to include two bars in tension, spliced at the center of the span. The beams were loaded in positive bending with the splice in a constant moment region. The variables used here were compressive strength and the space of stirrup within splice length. The results indicated that for (c$\div$Ktr)/db of the range of 1.5-2.0 compressive strength up to 800kg/$\textrm{cm}^2$ is acceptable with regard to bond strength and ductility, thus the limit of compressive strength in ACI 318-95 may be extended to 800kg/$\textrm{cm}^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.91-99
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• 2006

Fatigue properties of INVAR/AW wires have been investigated under the heat exposure in order to ensure stable operation and to estimate life span of their power line. In the case of heat exposure for 10000 hr, fatigue life and limit increased. For further heat exposure, fatigue limit decreased due to the decrease in yield strength. The variation fatigue of strand wire was strongly dependent on its amplitude. Also, cracks in wires of 7 strands were caused by stress concentration at the outer surface and fretting between each wire during vibration.

• Steel and Composite Structures
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• v.4 no.3
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• pp.227-246
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• 2004

This paper presents a moment-curvature method that accounts for the strength deterioration of steel at elevated temperature in estimating the response of steel beams exposed to fire. A modification to the EC4 method is proposed for a better estimation of the temperature distribution in the steel beam supporting a concrete slab. The accuracy of the proposed method is verified by comparing the results with established test results and the nonlinear finite element analysis results. The beam failure criterion based on a maximum strain of 0.02 is proposed to assess the limiting temperature as compared to the traditional criteria that rely on deflection limit or deflection rate. Extensive studies carried out on steel beams with various span lengths, load ratios, beam sizes and loading types show that the proposed failure criterion gives consistent results when compared to nonlinear finite element results.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.217-220
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• 2008

A modified FRP-concrete composite deck applicable to cable stayed bridge with long girder-to-girder span is proposed, and its design and economical efficiency are presented. The existing FRP-concrete composite deck has low section stiffness due to adoption of GFRP panel with low elastic modulus, which arrives at difficulty in meet of serviceability limit such as deck deflection. So a new-type FRP-concrete composite deck, named precast FRP-concrete deck, is developed by extensioning concrete at the both ends of FRP-concrete composite deck, which brings the effect of reduction of net span length of deck. Compared to the existing FRP-concrete composite deck this modified deck has the advantage of increasing span length but slightly increases self weight. For this type of deck the section optimization is carried out for the cases of simply supported on girder and composite to girder. The optimized deck was applied to cable stayed bridge with a center span length of 540m, and as a result it is verified that PFC deck can be applied efficiently to cable stayed bridge due to reduction of quantity of upper structure.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.127-133
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• 2013

PURPOSES : The impact performance of flexible barrier system such as structural response, vehicular motion and occupant safety vary depending on the impact point. Thus, to properly evaluate the performance of a flexible barrier system, impact should be made to a point which will lead to the worst possible results. This point is called the Critical Impact Point (CIP). This paper presents the way to determine the CIP for a SB2 class flexible barrier system which is consisted of Thrie-Beam rail and circular hollow tube post of 2m span. METHODS: Barrier VII simulations were made for impact points; Case 1 at a post, Case 2 at 1/3 span downstream from a post, Case 3 at middle of the span, Case 4 at 2/3 span downstream from a post. For the structural performance (deflections), impact simulation of 8000kg-65km/h-15degree was used, and for vehicle motion and occupant safety, simulation of 1300kg-80km/h-20degree impact was made and analysed. RESULTS: Case 1 gave the largest dynamic deflection of 75.72cm and also gave the largest snag value of 44.3cm. Occupant safety and exit angle of the vehicle after the impact were not sensitive to the impact point and were all below the allowable limit. CONCLUSIONS : For the SB2 class flexible barrier system's CIP can be regarded as a post which is sufficiently away from the end of Length of Need in order to avoid the end-effect of the barrier system. It can be more economic in the long run because the normal concrete pavement material is likely to cost more due to higher probability of maintenance and repair and higher social cost due to traffic accident, etc.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.193-204
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• 2019

This paper presents results from experimental and numerical studies on the response of steel-concrete composite box bridge girders under certain localized fire exposure conditions. Two composite box bridge girders, a simply supported girder and a continuous girder respectively, were tested under simultaneous loading and fire exposure. The simply supported girder was exposed to fire over 40% of its span length in the middle zone, and the two-span continuous girder was exposed to fire over 38% of its length of the first span and full length of the second span. A measurement method based on comparative rate of deflection was provided to predict the failure time in the hogging moment zone of continuous composite box bridge girders under certain localized fire exposure condition. Parameters including transverse and longitudinal stiffeners and fire scenarios were introduced to investigate fire resistance of the composite box bridge girders. Test results show that failure of the simply supported girder is governed by the deflection limit state, whereas failure of the continuous girder occurs through bending buckling of the web and bottom slab in the hogging moment zone. Deflection based criterion may not be reliable in evaluating failure of continuous composite box bridge girder under certain fire exposure condition. The fire resistance (failure time) of the continuous girder is higher than that of the simply supported girder. Data from fire tests is successfully utilized to validate a finite element based numerical model for further investigating the response of composite box bridge girders exposed to localized fire. Results from numerical analysis show that fire resistance of composite box bridge girders can be highly influenced by the spacing of longitudinal stiffeners and fire severity. The continuous composite box bridge girder with closer longitudinal stiffeners has better fire resistance than the simply composite box bridge girder. It is concluded that the fire resistance of continuous composite box bridge girders can be significantly enhanced by preventing the hogging moment zone from exposure to fire. Longitudinal stiffeners with closer spacing can enhance fire resistance of composite box bridge girders. The increase of transverse stiffeners has no significant effect on fire resistance of composite box bridge girders.

• Journal of the Korean Wood Science and Technology
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• v.51 no.3
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• pp.197-206
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• 2023

A truss is a structure in which the members are connected and arranged such that they are primarily subjected to axial loading. A truss has the advantage that it can be used for a longer span because the structure distributes the applied force to its members well, and the load is transmitted only in the axial direction of the members. Trusses manufactured using timber have more advantages than those made of other materials. In this study, the properties of parallel chord trusses composed of timber chord and steel-web members were evaluated. We constructed truss specimens with various lengths by using upper and lower chords of 2 × 4 inch spruce-pine-fir lumber and steel-web members manufactured by S and P companies. The specimens were tested in accordance with KS F 2150. The test results showed that the load at the deflection limit and the deflection limit itself increased from L/180 to L/360 regardless of the length of the specimens. For specimens of the same length, the load at the deflection limit increased as the height of the parallel timber chord truss specimens increased from 200 to 300 mm. Successive installations of the steel-web members (SST) showed almost 2 times the load at each deflection limit compared to that of SAT specimens (alternate installation of the steel-web members). When comparing the three load-deflection limits in terms of the manufacturer of the steel-web members, the load at each deflection limit for SST specimens was higher than that for PST specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.14-17
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• 2004

A prefabricated composite hollow slab with perforated I-beams was suggested for the replacement of deteriorated concrete decks or the construction of new composite bridges with long-span slabs. Composite slabs with embedded I-beams have considerably higher stiffness and strength. For the application of prefabricated composite slabs to bridges, joints between slabs should satisfy the requirements of the ultimate limit state and the serviceability limit state. In this paper, three types of the detail for loop joints were selected and their structural performance in terms of strength and crack control was investigated through static tests on continuous composite slabs. A main parameter was the detail of the joint, such as an ordinary loop joint and loop joint with additional reinforcements. Even though there was no connection of the steel beams at the joints, the loop joints showed good performance in ultimate strength. In terms of crack control, the loop joint with additional reinforcements showed better performance. In ultimate limit state, the continuous composite slabs showed good moment redistribution and ductility.

• Wind and Structures
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• v.27 no.3
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• pp.149-161
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• 2018

A reliability analysis method is proposed in this paper based on the maximum entropy (MaxEnt) principle in which constraints are specified in terms of the fractional moments instead of integer moments. Then a multiplicative dimensional reduction method (M-DRM) is introduced to compute the fractional moments. The method is applicable for both explicit and implicit limit state functions of complex structures. After two examples illustrate the accuracy and efficiency of this method in comparison to the Monte Carlo simulation (MCS), the method is used to analyze the flutter reliability of suspension bridge. The results show that the empirical formula method in which the limit state function is explicitly represented as a function of variables is only a too conservative estimate for flutter reliability analysis but is not accurate adequately. So it is not suitable for reliability analysis of bridge flutter. The actual flutter reliability analysis should be conducted based on a finite element method in which limit state function is implicitly represented as a function of variables. The proposed M-DRM provide an alternate and efficient way to analyze a much more complicated flutter reliability of long span suspension bridge.