• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.385-392
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• 2001

The stiffness of pavement is scarcely considered in structural analysis of the superstructure bridge. It will be reasonable in the case of asphalt concrete pavement over concrete deck plate because stiffness of the pavement compared with concrete deck plate can be ignored. Additionally, it is considered correct to do a design with a safety. However, various pavement materials which have even value reaching to the elastic modulus of concrete are applied to the orthotropic steel deck plate which has a relatively less stiffness comparing with the concrete deck plate. In this paper, the steel plate deck of the bridge of real project was modeled considering the pavement stiffness for the FEM analysis and the linear elastic analysis was performed. It was assumed to be perfectly bonded between the steel plate deck and the pavement and the temperature effect was ignored. It was analyzed on the vertical deflection of steel deck plate influencing to the serviceability of pavement and the bending stress of steel deck plate related to the fatigue life. As a result, It was indicated that the structural behavior of the orthotropic steel deck plate could be affected by the stiffness of pavement in some cases.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.271-295
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• 2016

In this study, an extensive literature review has been conducted on the material characterization of UHPC and its potential for large-scale field applicability. The successful production of ultra-high performance concrete (UHPC) depends on its material ingredients and mixture proportioning, which leads to denser and relatively more homogenous particle packing. A database was compiled from various research and field studies around the world on the mechanical and durability performance of UHPC. It is shown that UHPC provides a viable and long-term solution for improved sustainable construction owing to its ultrahigh strength properties, improved fatigue behavior and very low porosity, leading to excellent resistance against aggressive environments. The literature review revealed that the curing regimes and fiber dosage are the main factors that control the mechanical and durability properties of UHPC. Currently, the applications of UHPC in construction are very limited due to its higher initial cost, lack of contractor experience and the absence of widely accepted design provisions. However, sustained research progress in producing UHPC using locally available materials under normal curing conditions should reduce its material cost. Current challenges regarding the implementation of UHPC in full-scale structures are highlighted. This study strives to assist engineers, consultants, contractors and other construction industry stakeholders to better understand the unique characteristics and capabilities of UHPC, which should demystify this resilient and sustainable construction material.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.315-323
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• 2010

It is suggested that the service life of the continuous welded rail(CWR) is estimated by the relationship between the rail surface irregularity according to the accumulated passing tonnage and bending fatigue of welded part in CWR. In this study, it measured bending stress of rail according to the rail surface irregularity in the concrete track on the Seoul Metro. In addition, the relationship between rail surface irregularity and bending stress in concrete track is analyzed by results of the field test. Finally, this study clarified the relationship among bending stress(Y) of rail, train speed(U), rail surface irregularity(v, w) in concrete track. The result of this study is able to use the basis data to establishing the periodic replacements criterion of CWR.

• Computational Structural Engineering
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• v.10 no.4
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• pp.229-238
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• 1997

Mechanical behavior of asphalt concrete that accounts for viscoelasticity and damage evolution under cyclic loading conditions is modeled and presented in this paper. An elastic-viscoelastic correspondence principle in terms of pseudo variables is applied to separately evaluate viscoelasticity and time-dependent damage growth in asphalt concrete. A microcrack growth law, which is commonly employed in linear viscoelastic fracture mechanics, is successfully used for describing the damage growth in the body. A constitutive equation in terms of stress and pseudo strain is first established for controlled-strain mode, and then transformed to controlled-stress constitutive equation by simply replacing stress and pseudo strain with pseudo stress and strain. The transformed constitutive equation in terms of pseudo stress satisfactorily predicts the mechanical behavior of asphalt concrete all the way up to failure under controlled-stress modes.

• Advances in concrete construction
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• v.4 no.2
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• pp.123-143
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• 2016

Use of heavy fuel fly ash (HFFA) (diesel and cracked fuel) for power generation in Saudi Arabia has generated and accumulated large quantities of HFFA as a byproduct. In this research, HFFA is studied with the emphasis on the utilization of this waste material in concrete blocks and asphalt concrete mixes. Two types of mixes, one with low and other with high cement content, were studied for concrete blocks. Different mixes having varying percentages of HFFA (0% to 25%), as cement/sand replacement or as an additive, were studied. The performance of concrete blocks is evaluated in terms of compressive strength, water absorption, durability and environmental concerns. The results showed that blocks cannot be cast if more than 15% HFFA is used; also there is a marginal reduction in the strength of all the mixes before and after being exposed to the sulfate solution for a period of ten months. HFFA is studied in asphalt concrete mixes in two ways, as an asphalt modifier (3&5%) and as a filler (50%) replacement, the results showed an improvement in stiffness and fatigue life of mixes. However, the stability and indirect tensile strength loss were found to be high as compared to the control mix due to moisture damage, indicating a need of using antistripping agents. On environmental concerns, it was found that most of the concerned elements are within acceptable limits also it is observed that lower concentration of barium is leached out with the higher HFFA concentrations, which indicates that HFFA may work as an adsorbent for this leaching element.

• Steel and Composite Structures
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• v.21 no.6
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• pp.1227-1250
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• 2016

Most of the research work has been conducted on K-joints under static loading. Very limited information is available in consideration of fatigue strength of K-joints with concrete-filled chord. This paper aims to describe experimental and numerical investigations on stress concentration factors (SCFs) of concrete-filled circular chord and square braces K-joints under balanced axial loading. Experiment was conducted to study the hot spot stress distribution along the intersection of chord and braces in the two specimens with compacting concrete filled in the chord. The test results of stress distribution curves of two specimens were reported. SCFs of concrete-filled circular chord and square braces K-joints were lower than those of corresponding hollow circular chord and square brace K-joints. The corresponding finite element analysis was also conducted to simulate stress distribution along the brace and chord intersection region of joints. It was achieved that experimental and finite element analysis results had good agreement. Therefore, an extensive parametric study was carried out by using the calibrated finite element model to evaluate the effects of main geometric parameters and concrete strength on the behavior of concrete-filled circular chord and square braces K-joints under balanced axial loading. The SCFs at the hot spot locations obtained from ABAQUS were compared with those calculated by using design formula given in the CIDECT for hollow SHS-SHS K-joints. CIDECT Design Guide was generally quite conservative for predicting SCFs of braces and was dangerous for predicting SCFs of chord in concrete-filled circular chord and square braces K-joints. Finally SCF formulae were proposed for circular chord and square braces K-joints with concrete-filled in the chord under balanced axial loading. It is shown that the SCFs calculated from the proposed design equation are generally in agreement with the values derived from finite element analysis, which were proved to be reliable and accurate.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.37-45
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• 2004

The asphalt concrete pavement takes various advantages of better riding quality, serviceability and easier maintenance. At the same time, it addresses a weak point of the premature failures due to rapid increasement of traffic volume, heavy vehicles and high temperature in summer. It increases the expenditure of maintenance and repair. In order to improve the performance of asphalt pavement avoiding this premature failure, the use reinforcements with geosynthetics have been considered. Geosynthetics are known as an effective reinforcement to restrain fatigue and reflective cracks in asphalt pavements. In this study, a comprehensive parametric study is conducted to capture the efficiency of geosynthetic-reinforcements using viscoelastic properties of the asphalt concrete(AC) layer. The investigated parameters were reinforcement location, AC layer thickness, temperature distribution across the AC layer and modulus of AC and base layer. As a result of observations, that reinforced asphalt concrete could be used effectively for improving resistance against fatigue cracks and permanent deformation. Especially, when a geogrid was placed at the interface between the asphaltic base and the subbase, tensile stress in the horizontal direction was significantly reduced.

• International Journal of Highway Engineering
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• v.5 no.3 s.17
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• pp.1-9
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• 2003

This study was performed to evaluate the effect of various joint sealant on reducing the reflection cracking of asphalt concrete overlay on cement concrete pavement. The test method used was an accelerated reflection cracking test in shear mode, which was developed for evaluation of reflection cracking resistance of overlaid asphalt concrete in laboratory. The test results showed that use of joint sealants resulted in a significant reduction of reflection cracking. When sealant E was used, the fatigue life was the highest, with relatively larger horizontal deformation. When Sealant B was used, the dynamic stability was the highest with the smallest horizontal deformation. In general, the greater the tensile strength of sealant, the better the crack resistance of the mixture.

• Journal of the Society of Disaster Information
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• v.8 no.4
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• pp.391-400
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• 2012

Recently, the construction industry commonly uses FRP as a reinforcement material because of its material advantages. FRP attached reinforcement has various advantages such as high strength, stiffness, excellent durability and construction practicability comparing to its weight. However, external attachment of FRP is water-tighted with low water permeable material, not draining water, probably causing damages on a permanent structure. The study manufactured it through pultrusion and examined GP(glass fiber panel) of which material-mechanical properties are almost same as the existing FRP but durability and attachment performance are better by stationary experiments, testing load-deflection curve, destruction types and load-deflection relation under repetitive loading test. As a result of 2,000,000 fatigue tests, it did not result in the destruction and showed excellent permanent attachment and durability as it displays significantly low compressive strain of concrete.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.3
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• pp.11-21
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• 2002

The evaluation of displacement ductility is performed by direct method through tracking the inelastic hysteretic behavior of RC bridge columns subject to cyclic loading using a flexibility-based fiber element mode. To reasonably track the inelastic behavior until the RC bridge column reaches its ultimate state, the average stress-average strain relations and joint elements, which agree well with experiments, are modified and applied considering the tension stiffening behavior and discontinuous displacement between the column and its base. In addition the evaluation of displacement ductility is performed by a direct method easily applicable to numerical analysis. Locations for the integration points, values for the post-crushing concrete strength and low-cycle fatigue failure of longitudinal reinforcement that affect the calculation of yielding and ultimate displacements are proposed for the application to flexibility-based fiber element model. Since less than 10% of error occurs during the displacement ductility analysis, the yielding and ultimate displacements evaluated by the applied analysis method and model appear to be valid.