• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.317-326
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• 1997

An investigation was performed to study the matrix cracking and delamination in laminated composite plates due to transverse impact. A model was developed for predicting the initiation of the matrix cracking and the shape and size of impact-induced delamination in laminated composite plates resulting from the ballistic impact. The model consists of a stress analysis and a failure analysis. A transient finite element analysis which was based on the higher-order shear deformation theory was adopted for calculating the stresses inside the laminated composite plates during impact. A failure analysis was used to predict the initial intraply matrix cracking and the shape and size of the interface delamination in the laminates. As a results, a shear matrix cracking which was governed by the transverse interlaminar shear stress occured at the middle layer near the midplane of laminates and a bending matrix cracking which was governed by the transverse inplane stress occured at the bottom layer near the surface of laminates. In a thick laminates, a shear matrix cracking generated first at the middle layer of laminates, but in a thin laminates, a bending matrix cracking generated first at the bottom layer of laminates.

• Structural Engineering and Mechanics
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• v.43 no.4
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• pp.459-473
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• 2012

Post-tensioned concrete voided slab girders are widely used in highway bridge constructions. To obtain greater section hollow rate and reduce the self-weight, the plate thickness of slab girders are designed to be small with the adoption of flat anchorage system. Since large prestress is applied to the anchor end section, it was found that longitudinal shear cracks are easy to occur along the voided slab girder. The reason is the existence of great shearing effect at the junction area between web and bottom (top) plate in the anchor end section. This paper focuses on the longitudinal anti-cracking problem at the anchor end of post-tensioned concrete voided slab girders. Two possible models for longitudinal anticracking analysis are proposed. Differential element analysis method is adopted to derive the solving formula of the critical cracking state, and then the practical analysis method for longitudinal anti-cracking is established. The influence of some factors on the longitudinal anti-cracking ability is studied. Results show that the section dimensions (thickness of bottom, web and top plate) and prestress eccentricity on web plate are the main factors that influence the anti-cracking ability. Moreover, the proposed method is applied into three engineering examples to make longitudinal anti-cracking verification for the girders. According to the verification results, the design improvements for these girders are determined.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.3-9
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• 2007

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.122-130
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• 2008

The cracking behavior of prestressed concrete members is important for the rational evaluation of PCC pipes. However, the test data on the cracking behavior of PCC pipes are very limited. The purpose of the present study is to investigate the cracking behavior of PCC pipes under different settlement conditions. In this paper, experimental test on the full scale model of PCC pipe was conducted and observed in order to study cracking load in PCC pipes. Based test and FEM analysis results, this paper also presents the cracking load prediction in PCC pipe. Based on the numerical analysis results performed in this research, the cracking behaviors of PCC pipe with the variation of the settlement conditions were evaluated.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.33-40
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• 2001

In this research, the cracking of tunnel concrete lining was investigated and analyzed through long-term measurement and nonlinear numerical analysis. For one year after the casting of lining, the stresses and strains were measured by the sensors installed in hard rock tunnel lining. The measurements showed that only small stresses which were less than cracking stress occurred in every survey sections regardless of sensor directions. It could be induced that the external load applied to the lining was small or ignorable. Also, it was carried out short-term numerical analysis based on such site condition as ambient temperature, the- degree of overbreak and mold staying period. Long-term numerical analysis based on creep & shrinkage and nonlinear cracking was carried out. The output showed that construction condition and ambient environments could make the lining concrete crack without external loads. The cracks formed in this process does not indicate the structural instability of the tunnel.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.458-461
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• 2006

Early age cracking of concrete is a widespread and complicated problem, and diverse applications in practical engineering have focused on this issue. Since massive concrete base slab composes the infrastructure of other concrete structures such as pier, concrete dam, and high rise buildings, early age cracking of that is considered as a crucial problem. In this study, finite element analysis (FEA) implemented with the age-dependent microplane model was performed. For a massive concrete base slab, cracking initiation and propagation, and deformation variation were investigated with concrete age. In massive concrete slab, autogenous shrinkage increases the risk of early age cracking and it reduces reinforcement effect on control of early age cracking. Gradual crack occurrence is experienced from exterior surface towards interior of the slab in case of combined hydration heat and autogenous shrinkage. FEA implemented with enhanced microplane model successfully simulates the typical cracking patterns due to edge restraint in concrete base slab.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.898-905
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• 2006

In the present paper, for a quantitative assessment of early-age cracking in an RC wall, an improved analytical model is proposed. First of all, a three-dimensional finite element model for the analysis of stresses due to hydration heat and differential drying shrinkage is introduced. A discrete steel element derived using the equivalent nodal force concept is used to simulate reinforcing steels, embedded in a concrete matrix. In advance, to quantitatively calculate the cracking potential, an analytical model that can estimate the post-cracking behavior in an RC tension member is proposed Subsequent comparisons. of analytical results with test results verify that the combined use of both the finite element model for the stress analysis as well as the analytical model for the estimation of the post-cracking behavior in an RC tension member make it possible to accurately predict the cracking ,behavior of RC walls.

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.47-56
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• 2009

The first diagonal cracking and ultimate shear load of reinforced girder made of ultra high performance fiber reinforced concrete (UHPFRC) were investigated in this paper. Eleven girders were tested in which eight girders failed in shear. A simplified formulation for the first diagonal cracking load was proposed. An analytical model to predict the ultimate shear load was formulated based on the two bounds theory. A fiber reinforcing parameter was constituted based on the random assumption of steel fiber uniform distribution. The predicted values were compared with the conventional predictions and the test results. The proposed equation can be used for the first cracking status analysis, while the proposed equations for computing the ultimate shear strength can be used for the ultimate failure status analysis, which can also be utilized for numerical limit analysis of reinforced UHPFRC girder. The established fiber reinforcing theoretical model can also be a reference for micro-mechanics analysis of UHPFRC.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.153-159
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• 2001

Recently, the underground reinforced concrete(RC) box structures have been increasingly built in Korea. In such structures, the heat of hydration may cause serious cracking problems. The RC box structures are classified in this category that needs much attention to control the hydration heat during construction, which causes the restraining effects on the boundaries. The purpose of the present study is to develop the rational construction method to control the thermal cracking problem of the box structures. In this study, the causes and mechanism of thermal cracking according to construction stages in the RC box structures are thoroughly analyzed. The major influencing variables are studied through the finite element analysis which affect the thermal cracking of RC box structures. The research results of the present study can be efficiently used for the control of cracking of box structures during construction stages.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.2
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• pp.9-16
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• 2015

High loading of base paper is regarded as one of reasons to aggravate fold cracking of coated paper. But the relationship between the ash content of base paper and fold cracking of coated paper has not been shown yet. We investigated the effect of ash content in base paper on the fold cracking of coated paper. Handsheets with three different ash contents (19.5-23.5%) were prepared, and double layered coating were applied on the top side of the handsheets. A gravimetric water retention meter (AA-GWR) was employed to fold the paper with a uniform pressure after solid printing on the coated surface. The fold cracking was digitized by calculating the cracked area by means of an image analysis technique. Results suggested that high ash content in the base paper increased the fold cracking of the outer surface of coated papers. In the case of inner surface greater fold crack areas were obtained, and the number of cracks decreased because long and wide cracks were formed. Reduction in tensile strength and thickness appeared to give greater fold cracking for highly loaded papers.