• International Journal of Highway Engineering
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• v.15 no.1
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• pp.1-9
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• 2013

PURPOSES: The purpose of this study is to evaluate physical properties, durability, fatigue resistance, and long-term performance of poly-urethane concrete (PU) which can be possible application of thin layer on long-span orthotropic steel bridge and to check structural stability of bridge structure. METHODS : Various tests of physical properties, such as flexural strength, tensile strength, bond strength and coefficient of thermal expansion tests were conducted for physical property evaluation using two types of poly urethane concrete which have different curing time. Freezing and thawing test, accelerated weathering test and chloride ion penetration test were performed to evaluate the effect of exposed to marine environment. Beam fatigue test and small scale accelerated pavement test were performed to assess the resistance of PU against fatigue damage and long-term performance. Structural analysis were conducted to figure out structural stability of bridge structure and thin bridge deck pavement system. RESULTS: The property tests results showed that similar results were observed overall however the flexural strength of PUa was higher than those of PUb. It was also found that PU materials showed durability at marine environment. Beam fatigue test results showed that the resistances of the PUa against fatigue damage were two times higher than those of the PUb. It was found form small scale accelerated pavement test to evaluate long-term performance that there is no distress observed after 800,000 load applications. Structural analysis to figure out structural stability of bridge structure and thin bridge deck pavement system indicated that bridge structures were needed to increase thickness of steel deck plate or to improve longitudinal rib shape. CONCLUSIONS: It has been known that the use of PU can be positively considered to thin layer on long-span orthotropic steel bridge in terms of properties considered marine environment, resistance of fatigue damage and long-term performance.

• Steel and Composite Structures
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• v.52 no.3
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• pp.357-376
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• 2024

In this paper, weakly bonded ultra-high-strength steel bars (UHSS) were used as longitudinal reinforcement in recycled aggregate concrete shear walls to achieve resilient performance. The study evaluated the repairability and hysteresis performance of shear walls before and after retrofitting. Quasi-static tests were performed on recycled aggregate concrete (RAC) and steel fiber reinforced recycled aggregate concrete (FRAC) shear walls to investigate the reparability of resilient shear walls when loaded to 1% drift ratio. Results showed that shear walls exhibited drift-hardening properties. The maximum residual drift ratio and residual crack width at 1% drift ratio were 0.107% and 0.01mm, respectively, which were within the repairable limits. Subsequently, shear walls were retrofitted with bonded X-shaped CFRP strips and steel plates wrapped at the bottom and retested. Except for a slight reduction in initial stiffness, earthquake-damaged resilient shear walls retrofitted with a composite method still had satisfactory hysteresis performance. A revised damage assessment index D, has been proposed to assess of damage degree. Moreover, finite-element analysis for the shear wall before and after retrofit retrofitting was established in OpenSees and verified with experimental results. The finite element results and test results were in good agreement. Finally, parametric analysis was performed.

• Steel and Composite Structures
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• v.29 no.3
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• pp.309-318
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• 2018

Steel girders are the structural members often used for passing long spans. Mostly being subjected to patch loading, or concentrated loading, steel girders are likely to face sudden deformation or damage e.g., web breathing. Horizontal or vertical stiffeners are employed to overcome this phenomenon. This study aims at assessing the feasibility of a machine learning method, namely the support vector machines (SVM) in predicting the patch loading resistance of longitudinally stiffened webs. A database consisting of 162 test data is utilized to develop SVM models and the model with best performance is selected for further inspection. Existing formulations proposed by other researchers are also investigated for comparison. BS5400 and other existing models (model I, model II and model III) appear to yield underestimated predictions with a large scatter; i.e., mean experimental-to-predicted ratios of 1.517, 1.092, 1.155 and 1.256, respectively; whereas the selected SVM model has high prediction accuracy with significantly less scatter. Robust nature and accurate predictions of SVM confirms its feasibility of potential use in solving complex engineering problems.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.811-816
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• 2002

An experimental work is performed to evaluate the retrofit method of damaged flexural walls. For two flexural walls damaged up to almost failure, reinforcements yielded and concrete below height of 1d are replaced with new reinforcements and steel fiber concrete, respectively. In order to evaluate the effectiveness of Aramid sheet for retrofitting walls, Aramid sheet is also, attached to longitudinal direction and rolled horizontal direction of one wall specimen. Horizontal cyclic loads are applied to the top of the specimen with constant axial load. Test result showed that retrofitting with steel fiber concrete after replacing reinforcements can not afford to recover 100% of the wall capacity before damage. However, the capacity of walls could be sufficiently strengthened by using Aramid sheet.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.923-928
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• 2005

The estimation of fatigue life at the design stage of the compressed air tank on board is very important in order to arrive at feasible and reliable solutions considering the total lifetime of the tank. In this paper the compressed air tank on board was selected as a model and the change of inside pressure of the tank during normal navigation period was measured and the cycle of fluctuation stress was presumed statistically based on this. Also the effect of stress concentration with the FEM analysis on the longitudinal weld and the mean stress effect on the fatigue strength of compressed air tank were discussed.

• Structural Engineering and Mechanics
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• v.53 no.3
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• pp.455-479
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• 2015

This paper presents a numerical analysis of reinforced concrete slabs under missile impact loading. The specimen used for the numerical simulation was tested by the Technical Research Center of Finland. LS-DYNA, commercial available software, is used to analyze the model. The structural components of the reinforced concrete slab, missile, and their contacts are fully modeled. Included in the analysis is material nonlinearity considering damage and failure. The results of analysis are then verified with other research results. Parametric studies with different longitudinal rebar ratios, shear bar ratios, and concrete strengths are conducted to investigate their influences on the punching behavior of slabs under the impact of a missile. Finally, efficient designs are recommended.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.483-488
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• 2003

Calibration and gauge factor readjustment process made for the health monitoring system installed in the railway bridges is reviewed and some findings are explained in this study: specifically, the calibrators made for this purpose are illustrated and the regression processes of the calibration on long-term displacement using water level sensor, longitudinal displacement using LVDT sensor, instantaneous displacement using LVDT sensors and accelerometer are described in details. Based on the regression results, new gauge factors are obtained from regression equation and another verification is made by performing another calibration again with new factors. From the second calibration, it was found that the suggested regression curves and their factors are appropriate and much better results are expected. Future work will be concentrated on the long-term analysis of the measurement data and on the database structures so that the assessment of the structure such as damage detection and remaining life estimation is possible.

• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.1-7
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• 2010

Over the past few decades various experimental and theoretical investigations have been performed on offshore tubular members with regard to damage resistance and residual strength. Analysis of damaged tubular members requires a three-dimensional shell analysis for accurate results. Even though various commercial packages are available for this purpose, a beam-column analysis is preferred for offshore structural designs. In this paper, empirical equations are provided for a more accurate beam-column analysis of damaged tubes including the relationships between the lateral denting load and the depth of the dent, the rate of dent deepening due to increasing curvature and the longitudinal variation in the dent depth of damaged tubes. A design equation to predict the ultimate bending capacities of damaged offshore tubular members is also presented.

• Journal of the Korean Society of Marine Environment & Safety
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• v.4 no.2
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• pp.35-42
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• 1998

Marine casuality causes not only loss of lives and ships, but also severs damages to marine environment and related economic activities such as fishing industry, sea farming, and tourist industry. Basically, the great effort should be made to prevent the occurrence of maritime accidents by any means. However, once accident has occurred, the salvage works should be done rapidly and properly based on theoretical and technical informations, which could minimize the risk during salvage operation and the overall damage from the maritime accidents. Generally, to calculate accurate hydrostatics of a stranded ship, a large amount of input data is needed. But, an availability and a reliability of input data cannot be guaranteed in most situations, and the adequate time required for preparing all input data is not allowed to perform the timely operations of salvage. In this paper, the development process of simple computer program for salvage operation using limited input data is introduced and its application example is presented. This program was developed to provide technical support for planning salvage operations in the grounding accident.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.267-283
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• 2011

Although earthquakes generate random cyclic lateral loading on structures, a quasi-static cyclic loading pattern with gradually increasing amplitude has been commonly used in the laboratory tests because of its relatively low cost and simplicity compared with pseudo-dynamic and shake table tests. The number, amplitudes and sequence of cycles must be chosen appropriately as important parameters of a quasi-static cyclic loading pattern in order to account for cumulative damage matter. This paper aims to reach a new cyclic displacement pattern to be used in quasi-static tests of well-confined, flexure-dominated reinforced concrete (RC) columns. The main parameters of the study are sectional dimensions, percentage of longitudinal reinforcement, axial force intensity and earthquake types, namely, far-fault and near-fault.