• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.183-194
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• 2005

In the previous construction method of continuous preflex composite girder bridge, we raised the inner support, and cast slab concrete innegative moment section, then lowered it to introduce compressive force in the slab. There were a few problems in the process such as the time required in raising the support and the bending of the camber. Therefore, this paper represents an improved construction method of continuous preflex composite girder by only moving downward the inner and outer supports to figure out problems in previous construction method. This paper proposes a design formula to find a proper cross section of preflex girder.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.3
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• pp.30-37
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• 2023

The PSCB girder bridge is a closed cross-section in which the top and bottom flanges and the web are integrated, and the structural characteristics are generally different from the bridges in which the girder and the floor plate are separated, so a maintenance plan that reflects the characteristics of the PSCB girder bridge is required. As a result of analyzing damage types by collecting detailed safety diagnosis reports of highway PSCB girder bridges, most of the deterioration and damage occurring during use is concentrated on the top flange. In particular, cracks in the bridge direction on the underside of the top flange occurred in about 70 % of the PSCB girder bridges to be analyzed, and these cracks were judged to be caused by indirect loads such as heat of hydration and drying shrinkage rather than structural cracks caused by external loads. In order to improve durability and reduce maintenance costs of PSCB girder bridges in use, it is necessary to control restraint drying shrinkage cracks from the design stage. Therefore, in this paper, the cracks caused by drying shrinkage under restraint, which is the main cause of cracks under the flanges of the top part of the PSCB girder bridge, were directly calculated using the Gilbert Model, and the influencing factors such as the amount of reinforcing bars, diameter and spacing of reinforcing bars were analyzed. As a result of the analysis, it was found that the crack width caused by restraint drying shrinkage exceeded the allowable crack width of 0.2 mm for reinforcing bars with a reinforcing bar ratio of 0.01 or less based on the H16 reinforcing bar and a reinforcing bar with a diameter greater than H19 based on the reinforcing bar ratio of 0.01. Finally, based on the results of the crack width review, a method for controlling the crack width of the top flange of the PSCB girder bridge was proposed.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.93-103
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• 2009

Two-girder bridge is composed of primary members such as deck slab and main girder, and secondary member such as cross beam, vertical and horizontal stiffeners etc,. Two-girder bridge is prescribed as a non-redundant load path structure in the ASSHTO and the Korean Highway Bridge Design Code. Such structure is that if one girder is damaged, problems of function and safety of the bridge are caused. From the reasons, fatigue cracks in two-girder bridge can affect safety of the bridge seriously. Therefore, in this paper, fatigue evaluation was performed at connection parts of vertical stiffener and web with radius of curvature of scallop of vertical stiffener and thickness of web as variables. Such joint is known as a detail which has high possibility of fatigue crack in the bridge. Based upon the analytical results, preferable joint detail in terms of fatigue and simple empirical formula for fatigue evaluation of the detail were suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2219-2228
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• 2015

The proposed RDT(Reversed Double T) girder bridge is suitable to eco corridor, because of its cross section which resembles Korean alphabet vowel "ㅛ". The total height and cost of bridge would be reduced for its inner space containing some of plant soil. In this study, the performance of the RDT girder was assessed by comparing results of static test with those of nonlinear analysis. The cracking load of the RDT girder was evaluated more than two times of design load.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.349-352
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• 2008

IPC girder is more prestressed and has smaller sectional area than the conventional PSC-I type girder due to incremental prestressing along the construction process. The continuous IPC girder bridge may have problems in serviceability and stresses at internal supports because it is very flexible. In this paper, The long-term behavior of the continuous IPC girder bridge is studied through long-term structural analysis and monitoring the deflections. The long-term behavior is monitored right before the introduction of 2nd prestressing that is the construction process different from the conventional PSC-I type girder bridge. The total station of high-precision was used in measuring the deflections. According to the monitoring result so far, the continuous IPC girder bridges does not show remarkable long-term behavior like severe camber or deflection and the measured deflections are very similar to the results of long-term structural analysis.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.449-458
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• 2016

The temperature data were measured for two years in a bridge specimen and the bridge in service nearby in order to calculate the effective temperature for thermal loads in steel box girder bridge. The maximum and minimum effective temperatures were calculated in the bridge specimen and the bridge according to air temperature in 2014, 2015 and 2years. The effective temperatures calculated in this study were compared the Euro code and the Highway Bridge Design Criteria. The coefficients of determination in the maximum effective temperature and the Euro code for 2 year were calculated from R = 0.927, R = 0.894 in a bridge specimen and the bridge respectively. Those of minimum temperature and the Euro code were analyzed from R = 0.992, R = 0.813 in two bridge respectively. Also, the results were evaluated as being very similar, or slightly increased as compared with the maximum temperature of the Korean Highway Bridge Design Code(Limit State Design).

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.271-280
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• 2007

This paper presents the results of an experimental study to evaluate the redundancy in two plate-girder bridges, which are generally classified as non-redundant load path structures. The study was performed at a time when one of the two girders was damaged. The bottom lateral bracing was considered the experimental variable, and two 1/5-scale bridge specimens of simple span with and without a lateral bracing system were fabricated. Loading tests were first performed on the intact specimens without a cracked girder, within an elastic range. Thereafter, the ultimate loading tests were conducted on the damaged specimens with an induced crack at the center of a girder. The test results showed that the cross beams and the concrete deck redistributed some of the load to the uncracked girder, but the lateral bracing system played an important role in improving the redundancy during the damage and was also effective for load redistribution even when the bridge was intact.

• 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 institute for structural maintenance and inspection
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• v.26 no.6
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• pp.23-32
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• 2022

Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1^st type and 2^nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.131-138
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• 2015

In this paper, the modified live-load and designed formula are studied according to the fact the highway bridge design specifications are recently revised. The two examples for composite steel plates and PSC girder bridges are studied. The envelope is analyzed with the finite element models and lateral load distribution method applying the existing highway bridge specification(2010), the newly revised highway bridge specification(2015) and AASHTO LRFD. In case of composite steel plates, length changes between spans are studied, and in case of PSC girder. changes of the number of cross-beams and spans, and span-lengths, are analyzed.