• Geomechanics and Engineering
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• v.22 no.3
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• pp.227-236
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• 2020

Expansive soils are renowned for their swelling-shrinkage property and these volumetric changes resultantly cause huge damage to civil infrastructures. Likewise, subgrades consisting of expansive soils instigate serviceability failures in pavements across various regions of Pakistan and worldwide. This study presents the use of polypropylene fibers to improve the engineering properties of a local swelling soil. The moisture-density relationship, unconfined compressive strength (UCS) and elastic modulus (E₅₀), California bearing ratio (CBR) and one-dimensional consolidation behavior of the soil treated with 0, 0.2, 0.4, 0.6 and 0.8% fibers have been investigated in this study. It is found that the maximum dry density of reinforced soil slightly decreased by 2.8% due to replacement of heavier soil particles by light-weight fibers and the optimum moisture content remained almost unaffected due to non-absorbent nature of the fibers. A significant improvement has been observed in UCS (an increase of 279%), E₅₀ (an increase of 113.6%) and CBR value (an increase of 94.4% under unsoaked and an increase of 55.6% under soaked conditions) of the soil reinforced with 0.4% fibers, thereby providing a better quality subgrade for the construction of pavements on such soils. Free swell and swell pressure of the soil also significantly reduced (94.4% and 87.9%, respectively) with the addition of 0.8% fibers and eventually converting the medium swelling soil to a low swelling class. Similarly, the compression and rebound indices also reduced by 69.9% and 88%, respectively with fiber inclusion of 0.8%. From the experimental evaluations, it emerges that polypropylene fiber has great potential as a low cost and sustainable stabilizing material for widespread swelling soils.

• Composites Research
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• v.28 no.1
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• pp.15-21
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• 2015

The purpose of this paper is to investigate the current trends of composite applications in the marine and leisure fields and to study the development of 33ft class America's cup training CFRP sailing yacht. In the field of marine and leisure, composite materials have been just used to marine and leisure structures, recently. Especially, since the America's cup of sailing yacht racing has required the light weight and high mechanical performance to make a high speed, CFRP have been recognized as the critical material to construct the racing yacht structures. To establish the process of CFRP racing yacht construction, the design optimizations and production methods of carbon mast and CFRP yacht hull were discussed in this paper. Finally, the constructed CFRP sailing yacht exhibited high performance as the racing yacht through the sailing test.

• Composites Research
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• v.12 no.4
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• pp.42-54
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• 1999

FMLC(Fiber-Metal Laminate Composites) is a new structural material combining thin metal laminate with adhesive fiber prepreg, it nearly include all the advantage of metallic materials, for example: good plasticity, impact resistance, processibility, light weight and excellent fatigue properties. This research studied the optimum design of the FMLC subject to various loading conditions using genetic algorithm. The finite element method based on the shear deformation theory was used for the analysis of FMLC. Tasi-Hill failure criterion and Miser yield criterion were taken as fitness functions of the fiber prepreg and the metal laminate, respectively. The design variables were fiber orientation angles. In genetic algorithm, the tournament selection and the uniform crossover method were used. The elitist model was also used to be effective evolution strategy and the creeping random search method was adopted in order to approach a solution with high accuracy. Optimization results were given for various loading conditions and compared with CFRP(Carbon Fiber Reinforced Plastic). The results show that the FMLC is more excellent than the CFRP in point and uniform loading conditions and it is more stable to unexpected loading because the deviation of failure index is smaller than that of CFRP.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1549-1554
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• 2010

Recently, plastic screws have replaced metal screws because of the former's light weight, thermal and electrical insulating properties, and anticorrosion characteristics. Plastic screws are usually produced by injection molding, which involves material shrinkage during the solidification of the polymer. This shrinkage results in the degeneration of the dimensional accuracy. In the present study, the effect of injection-molding conditions on the dimensional accuracy of plastic screws was investigated through a numerical simulation of injection molding; on the basis of this simulation, we could determine the mold-design parameters. The design of experiment was applied in accordance with the numerical analysis in order to optimize the injection-molding conditions with a view to improving the dimensional accuracy of the precision plastic screw.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.33-40
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• 2011

The resilient modulus which is presented mechanical properties of compacted subbase material is the design parameter on the Mechanistic - Empirical pavement design guide. The compaction control method on the Mechanistic - Empirical pavement design guide will be the way to confirm whether the in-situ elastic modulus measured after the compaction meets the resilient modulus which is applied the design. The resilient modulus in this study is calculated by the neural network suggested by Korea Pavement Research Program, and degree of compaction as the existing compaction control test and plate bearing capacity test(PBT) was performed to confirm whether the in-situ elastic modulus is measured. The Light Falling Weight Deflectometer(LFWD) is additionally tested for correlation analysis between each in-situ elastic modulus and resilient modulus, and is proposed correlation equation and test interval which can reduced overall testing cost. Also, the subbase compaction control procedure based on the in-situ elastic modulus is proposed using the in-situ PBT and LFWD test result.

• International Journal of High-Rise Buildings
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• v.5 no.3
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• pp.233-241
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• 2016

This paper describes the structural solution for the design of a 29-story high-rise tower, which features a large office space above the Kabukiza Theatre. Kabuki is a type of Japanese traditional drama, and Kabukiza is the home building of Kabuki. GINZA KABUKIZA is the fifth generation of the Kabukiza Theatre, the first of which was built in 1889. In order to support 23 stories of office space above the theater - featuring a large void in plan - two 13-meter-deep mega-trusses, spanning 38.4 meters, are installed at the fifth floor of the building. Steelwork is used as a primary material for the structure above-ground, and a hybrid response control system using a buckling-restrained brace and oil damper is adopted in order to achieve a high seismic performance. This paper also describes the erection process of installing hydraulic jacks directly above the mega-truss at column bases, in order to keep the structure above the truss level during construction. The temple architecture of the previous Kabukiza is carefully restored by incorporating contemporary light-weight materials supported by steelwork.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.801-804
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• 2008

Fiber reinforced plastics (FRP) are light in weight, non-corrosive and exhibits high tensile strength. FRPs having superior material properties to corrosive steels have been widely replacing steel bars or tendons used in concrete structures as flexural reinforcements. Although current design guidelines for estimating shear strength of FRP concrete beam follow the format of conventional reinforced concrete design method, there are noticeable differences among the existing formulas in calculating the contributions of concrete to shear resistance. In this paper, the artificial neural network (ANN) technique is employed as an analytical alternative to existing methods for predicting shear capacity of FRP concrete beams. Influential factors on shear strength were identified through literature review and input in ANN and the ANN was trained for the target ultimate shear obtained from database. The results from ANN were compared with existing formulas for its accuracy. It was found that the developed ANN were more closely predicting the test data than those of the currently available predictive equations.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.53-62
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• 2014

In Korea, the pipe type that has been well used as sewage pipe from the past is primarily a rigid pipe which is represented by concrete hume pipe, but the use of it is being decreased sharply because of the problems such as tube erosion and incomplete watertightness securing through the time. On the other hand, the use of flexible pipe has been increased because its construction ability is excellent on account of its light weight as well as it is resistant to corrosion. However, because there are lacks of market's confidence in flexible pipe and occurrence cases of partial damage incomplete caused by compaction control, cause analysis and management for them are needed. Therefore, this study tried to estimate the deformation characteristics of pipe caused by each condition through numerical analysis changing construction sequence, rigidity of pipe, strength of ground concrete under the pipe, relative compaction ratio of sand foundation under the pipe and relative compaction ratio of backfill material above the pipe. Evaluation result is that influence on each factor is confirmed and the quality control of sand around the pipe are turned up to be important.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.43-55
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• 2003

As the development of If industries and their electronic device manufacturing technology have been accelerated recently, the request for electronic devices with small size, light weight, and high performance has been inducing that electronic package and substrate (PCB) companies have to develop substrates with low cost, high dense I/O, excellent thermal properties and electrical properties. Therefore, world-wide chip makers have been setting their own severe reliability standards and requiring their suppliers to keep specification and to develop green, high frequency and high-performing substrates. Because properties of substrates are dependent mainly on their constituent materials, the application of them showing superior properties is expected to satisfy the customer's requirement. Therefore, substrate companies should ensure the superiority of materials and assure their competitive capability of substrates by analyzing the latest trends of technology and properties of the materials.

• Design & Manufacturing
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• v.14 no.1
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• pp.42-48
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• 2020

Titanium alloy has been in the spotlight as a core material in high-tech industries that require high strength and light weight because it has excellent strength and corrosion resistance and strength is higher than that of steel. Therefore, in various industries, existing steel products are intended to be replaced with titanium alloys. Titanium alloys can cause cutting tool breakage during cutting, and heat generated during cutting does not dissipate, accumulates in tools and workpieces, resulting in large wear and tear on thin workpieces. In addition, since titanium alloy is a metal with high chemical activity, the wear of the tool becomes more severe when the cutting speed is high, so machining of titanium bolt through cutting is very disadvantageous in terms of productivity. Therefore, the production of bolts using titanium alloys is being produced through a forging process to improve productivity and product quality. In this paper, hot forging molding analysis was performed on bolts used for fastening automobile parts using Ti-6Al-4V alloy, which is the most commonly used titanium alloy.