• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.137-147
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• 2012

In the steel-free bridge concrete deck, steel straps are generally used instead of conventional steel rebar while laterally restrained in the perpendicular direction to the traffic in order fir the arching effect of concrete deck. In this paper, the minimum amount of FRP bar is to be suggested based on the structural strength, crack propagation, stress level and others in order to control cracks. As a result of laboratory tests, the structural strength of deck with 0.15 percentage of steel strap showed improved structural strength including ductility. The long-term serviceability of steel strap deck with FRP bar proved to satisfy the requirements and to be structurally stable while showing the amount of crack and residual vertical displacement within the allowable limits after two million cyclic loadings. The structural failure of RC bridge deck is generally caused from the punching shear rather than moment. Therefore, the ultimate load at failure could be estimated using the shear strength formula in the two-way slab based on ACI and AASHTO criteria. However the design criteria tend to underestimate the shear strength since they don't consider the arching effects and nonlinear fracture in bridge deck with lateral confinement. In this paper, an equation to estimate the punching shear strength of steel strap deck is to be developed considering the actual failure geometries and effect of lateral confinement by strap while the results are verified in accordance with laboratory tests.

• Journal of the Society of Disaster Information
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• v.16 no.4
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• pp.638-649
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• 2020

Purpose: The objective of this study is to evaluate the load carrying capacity of a target bridge structure based on the simple slab bridge of concrete over 20 years of public service. Method: By performing static loading test and dynamic loading test, the displacement, strain, impact factor, and natural frequency values were measured and evaluated through analysis method. Result: The main results of this study are as follows. First, the maximum displacement and maximum strain of S1 were assessed at 2.917 mm and 44.720 𝜇ε( tensile) and -13.760 𝜇ε(compression), respectively, with S2 maximum displacement and maximum strain being 2.100 mm and 4.870 𝜇ε(tensile), respectively. Second, the maximum measured impact factor was 0.191 in section S1 A-A, and the maximum measured impact factor was 0.155 in section S2 C-C. Third, the natural frequency was assessed at 6.086 Hz, and the measurement was found to be within the range of 6.152 Hz to 6.738 Hz. Conclusion: The tested bridge may be evaluated to show good behavior and characteristics for the design load.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.61-68
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• 1988

This study is intended to propose an approach to reliability-based safety evaluation as well as LRFR(Load and Resisitance Factor Rating) type capacity classification of military or civilian bridges based on the limit state models which are delived by incorporating all the uncertainties of resistance and load random variables including deterioration, and are used in a practical AFOSM (Advanced First Order Second Moment) method. The proposed methods for the assement of safety and load carrying capacity are applied for the evaluation of rating and classifications of several practical bridges against the crossing of military vehicles. Based on the observation of the numerical results, it can be concluded that the current NATO classification method which is based on the traditionl allowable stress concept can not provide real load carrying capacity but results in nominal classification, and therefore the reliability-based safety evaluation and LRFR-classification method or the corresponding rational allowable stress method proposed in this paper may have to be introduced into the classification practice.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1275-1280
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• 2009

In recent bridge design, studies on application of external prestress have actively been conducted. When prestress is applied to steel structures, the limit value of elastic strain with large load increases with reduction of steels, this method is economic in cost. According to study by Brodka (1969), steel plate bridges with prestress has an effect on cost saving of about 15% compared with structures without prestress. For that reason, our country recently adopted this method in construction of temporary bridges and various engineering technologies have been developed which made stress correction, droop correction and long-span construction possible with relatively small cross sections. This study verifies the method of application of prestress in temporary steel structures, the influence of high-strength tendon arrangement and the effects of composite structures of steel plates and high-strength tendons based on existing method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.139-146
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• 2003

The objective of the presented study is to develop an efficient procedure of proof load testing for existing bridges. By analytical methods, some of these bridges are not adequate to carry normal highway traffic. However, the actual load carrying capacity is often much higher than what can be determined by conventional analysis. Proof load testing can reveal the hidden strength reserve and thus verify the adequacy of the tested bridge. Proof load level required for meaningful tests should be sufficiently higher than legal load. In the state of Michigan, the legal 11-axle truck can weigh up to 685 kN. In this study, a combination of two military tanks and two Michigan 11-axle trucks was used. The proof loads were gradually increased to ensure the safety of the test. After each move, measurements were taken. For the considered bridge, stress levels were rather low compared to pre-test analysis results. This is due to incorrect material strength, structural contribution of nonstructural components such as parapets and railings, and partially fixed supports.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.3
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• pp.123-134
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• 2006

In this study ship collision risk analysis is performed to determine the design vessel for collision impact analysis of the maritime bridge. Method II which is a probability based analysis procedure is used to select the design vessel for collision impact from the risk analysis results. The analysis procedure, an iterative process in which a computed annual frequency of collapse(AF) is compared to the acceptance criterion, includes allocation method of acceptance criterion of annual frequency of bridge component collapse. The AF allocation by weights seems to be more reasonable than the pylon concentration allocation method because this AF allocation takes the design parameter characteristics quantitatively into consideration although the pylon concentration allocation method brings more economical results when the overestimated design collision strength of piers compared to the strength of pylon is moderately modified. From the assessment of ship collision risk for each bridge pier exposed to ship collision, a representative design vessel for all bridge components is selected. The design vessel size varies much from each other in the same bridge structure depending upon the vessel traffic characteristics.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.197-211
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• 2007

The deteriorated PSC Beam bridge is necessary improved reinforcement method. In the study, it is proposed the box reinforcing method which could make the stiffness of the PSC Beam bridges increase more stably through the secondary composition effect of open type PSC Beam bridge's girder which is converted into the consolidation box type and the half panel is formed between the lower flange of the PSC Beam about the deteriorated PSC Beam bridge suffering the capacity decline. In case the proposed reinforcement method combine with the existed external prestressed method, the close analysis depending on the time is conducted by the construction stage because of searching the effect of reinforcement quantitatively. The reinforcement method of the box type which is proposed an efficiency improvement in objective in application case, by a reinforcement method after proposing the whole and bend sectional reinforcement method, against a each reinforcement method evaluated the upward camber which it follows in secondary composite effect and a member stress characteristics. Also, the structural safety of PSC Beam bridge is evaluated quantitatively by examining of rating factor through load carrying capacity evaluation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2A
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• pp.65-73
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• 2012

In this study, we tested structural performance of Half-Decked PSC girder which was developed for applying to long span bridge. We operated 4 point bending test with 60 m span full scale girder designed as simple bridge with hinge-roller boundary condition. Actuators were set on the both sides of girder, 5.5 m away from the center, and 4 stages of cyclic loading was applied at rate of 1 kN/sec. Through stages 1 to 4, loading and unloading 1,000 kN, 1,200 kN, 1,500 kN, and 2,000 kN were repeated and displacement, strain of concrete and steel, crack of girder were checked. From these results, the strength of girder was assessed and resilience and ductility were observed after removing the load. Since initial flexural crack occurred in the vicinity of 1,400 kN, non-linearity of load-displacement curve appeared and definite residual strain was measured at that point. The test result showed that initial cracking load was over twice the DB-24 load which means the developed girder had sufficient strength. To verify the experimental results, we numerically analyze the test and confirmed that the data were similar with results from the test above. Half-Decked PSC type of 60 m-girder developed in this study showed its adequate structural capacity through static loading test, which proved that possibility of applying the girder to actual bridges practically.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.489-500
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• 1997

The number of railway bridges in Korea reaches to about 3,000. Among them, the ratio of steel bridges is about 47%. Most of the long span railway bridges take the truss type, its number is 15 in Korea. These bridges have more than 30 years service life, it is expected that the damages of cracks and corrosion is going. Therefore, the estimation of fatigue life with random stress is considered as significant subject in maintenance. In this paper, the random stress was measured in bridges and counted the stress cycles using the rainflow counting method So, the stress range frequencies and their equivalent stress are obtained and the amplification factor for the span length, bridge types and traveling speed is assessed by the dynamic testing. From the results, the stress range of the stringer and the lower chord is higher than the other members and the characteristics of the stress histogram is varied to the loading system and the amount of the passing through trains. And the impact effects are depended on the traveling speed as well as the span length.