• KIPS Transactions on Software and Data Engineering
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• v.7 no.1
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• pp.25-32
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• 2018

Due to heavy computational cost, deformable object simulation requires more effective collision detection method than rigid body simulation. However, when the CPU-based collision detection algorithm is purely applied to the GPU environment, the collision detection algorithm and the data structure optimized for the GPU environment are essential because the performance of the GPU can not be used properly. Therefore, we propose a GPU-based parallel collision detection algorithm for mass-spring system which is widely used for deformable object representation in this paper. The proposed method uses a parallel algorithm and data structure to reduce collision detection cost through GPU-based curling algorithm using AABB-Octree structure. In this paper, we prove the effectiveness of the proposed method by comparing the intersection test of all triangle pairs in parallel. The results of experimental tests show that the proposed method improves the performance by about 24% on average. Therefore, it is expected that the proposed method can improve the performance of real-time simulation for deformable objects.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.107-115
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• 2009

This study was conducted to investigate the effect of the slab thickness on the tensioning design and to determine the optimal slab thickness of the post-tensioned concrete pavement (PTCP). The tensile stresses due to the vehicle and environmental loads were obtained using a finite element analysis model and the tensioning stress was calculated employing an allowable flexural strength. The environmental loads of both the constant temperature gradient and the constant temperature difference between top and bottom of the slab were considered. The tensioning designs for various slab thicknesses were performed considering prestressing losses. The comparison results showed that generally as the thickness increased, the number of tendons became larger. Consequently, the design was not economical for a thicker slab thickness. Even though the number of tendons became smaller with an increase in the thickness under the small environmental load, a thicker PTCP slab was not economical because of a higher cost of concrete than that of steel. Therefore, the slab thickness should be kept in minimum within the construction available thicknesses.

• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.119-130
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• 2006

The behavior of continuously reinforced concrete pavement (CRCP) and the effect of the steel ratio on the behavior under moving wheel loads were investigated in this study. The CRCP sections having different steel ratios of 0.6, 0.7, and 0.8% were considered to evaluate the load transfer efficiency (LTE) at transverse cracks and to investigate the strains in CRCP when the system is subjected to moving vehicle loads. The LTEs were obtained by conducting the falling weight deflectometer (FWD) tests and the tests were performed at three different times of a day to find the curling effect due to the daily temperature changes in CRCP. The strains in the concrete slab and the bond braker layer of the CRCP system under moving vehicle loads were obtained using the embedded strain gages. The results of this study show that the LTEs at transverse cracks are very high and not affected by the time of testing and the steel ratio. The strains in CRCP under vehicle loads become smaller as the vehicle speed increases or as the wandering distance increases; however, the strains are not clearly affected by the steel ratio.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.103-115
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• 2011

Concrete slab curls and warps due to the uneven distribution of temperature and moisture and as the result, internal stress develops within the slab. Therefore, environmental loads must be considered in addition to the traffic loads to predict the lifespan of the concrete pavement more accurately. The strength of the concrete slab is gradually decreases to a certain level at which fatigue cracking is generated by the repetitive traffic and environmental loadings. In this study, a new fatigue regression model was developed based on the results from previously performed studies. To verify the model, another laboratory flexural fatigue test program which was not used in the model development, was conducted and compared with the predictions of other existing models. Each fatigue model was applied to analysis logic of cumulative fatigue damage of concrete pavement developed in the study. The sensitivity of cumulative fatigue damage calculated by each model was analyzed for the design factors such as slab thickness, joint spacing, complex modulus of subgrade reaction and the load transfer at joints. As the result, the model developed in this study could reflect environmental loading more reasonably by improving other existing models which consider R, minimum/maximum stress ratio.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.81-91
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• 2011

This study was conducted to evaluate the necessity of the anchor lug system in continuously reinforced concrete pavement(CRCP) by comparing longitudinal displacements of CRCPs with and without anchor lugs, and to investigate the effect of horizontal cracking on CRCP performance by measuring the vertical displacements. The measurements before and after the anchor lug section was separated were conducted for 12 days in June, and for 14 days in August after the abrupt displacements according to cutting disappeared, respectively. This short term measurement results showed that when anchor lugs were installed, a daily displacement variation at any location was less than 0.1mm; therefore, longitudinal movements were negligibly small. When there were no anchor lugs, longitudinal displacements mainly occurred near the free end and the displacement variation was small; therefore, an expansion joint system seems to be employed at a CRCP terminus without installing anchor lugs. However, further studies are needed to verify the terminus behavior due to annual temperature changes. The horizontal crack width variation was ignorable and did not affect the vertical displacement of the slab. Therefore, the horizontal crack did not delaminate the slab and did not seem to reduce the structural capacity and performance of CRCP.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.449-456
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• 2007

This research was conducted to analyze the features of the critical tensile stresses at the top and bottom of the concrete slab in the jointed concrete pavement (JCP) when subjected to both the environmental and vehicle loads. First, the stress distribution in JCP was analyzed when the system was subjected to only the environmental loads or the vehicle loads by using the finite element model of JCP. Then, the stresses were analyzed when the system was subjected to the environmental and vehicle loads at the same time. From this study, it was found that the critical tensile stresses at the slab bottom under the vehicle loads were almost constant regardless of the loading positions once the loads were applied at the positions having some distance from the transverse joint. The critical tensile stresses at the slab bottom could be obtained using the model consisting of normal springs for underlying layers by adding the critical stresses due to the environmental loads and the vehicle loads for the curled-down slab, and by subtracting the critical stress due to the environmental loads from that due to the vehicle loads for the curled-up slab. The critical tensile stresses at the top of the slab could be obtained using the model consisting of tensionless springs for underlying layers by adding the critical stress due to the environmental loads and the stress at the middle of the slab under the vehicle loads applied at the joint for the curled-up slab. An alternative to obtain the critical stresses at the top of the slab for the curled-up slab was to use the critical stresses under only the environmental loads obtained from the model having normal springs for underlying layers.

• Journal of Korea Game Society
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• v.7 no.1
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• pp.31-42
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• 2007

In the natural world, most materials such as skin, marble and cloth are translucent. Their appearance is smooth and soft compared with metals or mirrors. In this paper, we propose a new GPU based hierarchical rendering technique for translucent materials, based on the dipole diffusion approximation, at interactive rates. Information of incident light, position, normal, and irradiance, on the surfaces are stored into 2D textures by rendering from a primary light view. Huge numbers of pixel photons are clustered into quad-tree image pyramids. Each pixel, we select clusters (sets of photons), and then we approximate multiple subsurface scattering term with the clusters. We also introduce a novel hierarchical screen-space interpolation technique by exploiting spatial coherence with early-z culling on the GPU. We also build image pyramids of the screen using mipmap and pixel shader. Each pixel of the pyramids is stores position, normal and spatial similarity of children pixels. If a pixel's the similarity is high, we render the pixel and interpolate the pixel to multiple pixels. Result images show that our method can interactively render deformable translucent objects by approximating hundreds of thousand photons with only hundreds clusters without any preprocessing. We use an image-space approach for entire process on the GPU, thus our method is less dependent to scene complexity.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.59-68
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• 2009

Torsional behavior of concrete pavement slabs due to temperature and moisture effects is constrained by self weight and friction etc, and causes stress as the result. The stress due to humidity variation in the slab is difficult to calculate while that due to temperature variation can easily be calculated by a commercial structural analysis program. Thus, the slab behavior can be predicted more accurately if the humidity effect is converted to equivalent temperature and is used as an input of structural analysis. In this study, a concrete pavement slab was constructed and strains of the slab due to environmental loadings were measured for long-term period. Thermal strains were subtracted from the measured strains by using thermal expansion coefficient of the concrete measured in a laboratory. Shrinkage strains, the remained strains, was supposed as additional thermal strains to calculate imaginary temperature with equivalent effect of the shrinkage by dividing the shrinkage with the thermal expansion coefficient. An existing shrinkage model was modified by considering the self weight and friction to be used in another model which can convert differential shrinkage between top and bottom of the slab to equivalent temperature difference. Addition research efforts on tensile stress reduction according to steady increase in the compressive strains are warranted for more accurate stress calculation.