• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.770-773
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• 2004

The full-width, full-depth precast panel system is very efficient for the rehabilitation of deteriorated decks as well as for new bridge construction.. The horizontal bond strength at the interface between the two interconnected elements is of primary importance in order to achieve composite action. The strength of the bond between the two precast members should be high enough to prevent any progressive slip from taking place. However, the case when both of the interconnected elements are precast members bonded by means of grout, is not currently addressed by KBDC or AASHTO. This is the main impetus for this study. A total 43 push-off tests were performed to evaluate the horizontal bond strength and to recommend the best practice for the system. Test parameters included different interface surface conditions, different amount and different types of shear connectors. The presence of the shear keys at the top surface of the beam increased the interface bond capacity tremendously compared to the bond capacity with a different surface conditions.

• Steel and Composite Structures
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• 제10권5호
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• pp.373-383
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• 2010

This paper presents the experimental studies of the flexural behavior of steel-concrete composite beams. Herein, steel-concrete composite beams were constructed with a welded steel I section beam and concrete slab with different material strength. Four simply supported composite beams subjected to two-point concentrated loads were tested and compared to investigate the effect of high strength engineering materials on the overall flexural response, including failure modes, load deflection behavior, strain response and interface slip. The experimental results show that the moment capacity of composite beams has been improved effectively when high-strength steel and concrete are used. Comparisons of the ultimate flexural strength of beams tested are then made with the calculated results according to the methods specified in guideline Eurocode 4. The ultimate flexural strength based on current codes may be slightly unconservative for predicating the moment capacity of composite beams with high-strength steel or concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.931-936
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• 2003

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. Lap splicing is also permitted if hoops or spiral reinforcement are provided over the lap length in the current seismic design provision. But sudden brittle failure of lap splices may occur under inelastic cyclic loading. The purpose of this study is the analytical prediction of nonlinear hysteretic behavior and ductility capacity of reinforced concrete bridge piers with lap splices under cyclic loading. For this purpose, a nonlinear analysis program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. Lap spliced bar element is developed to predict behaviors of lap spliced bar. Maximum bar stress and slip of lap spliced bar is considered.

• Structural Engineering and Mechanics
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• 제21권3호
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• pp.295-313
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• 2005

This paper evaluates the effective width of composite steel beams with precast hollowcore slabs numerically using the finite element method. A parametric study, carried out on 27 beams with different steel cross sections, hollowcore unit depths and spans, is presented. The effective width of the slab is predicted for both the elastic and plastic ranges. 8-node three-dimensional solid elements are used to model the composite beam components. The material non-linearity of all the components is taken into consideration. The non-linear load-slip characteristics of the headed shear stud connectors are included in the analysis. The moment-deflection behaviour of the composite beams, the ultimate moment capacity and the modes of failure are also presented. Finally, the ultimate moment capacity of the beams evaluated using the present FE analysis was compared with the results calculated using the rigid - plastic method.

• 콘크리트학회논문집
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• 제21권1호
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• pp.47-53
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• 2009

탄소 섬유와 유리 섬유를 체적 비율 1 : 8.8로 조합하여 강성이 높은 탄소 섬유가 인장에 저항한 후 먼저 파단되고 그 후 유리 섬유가 인장에 저항하여 높은 연성을 발휘하도록 한 하이브리드 시트를 제작하고 시트 길이를 100, 200, 400 mm로 각각 다르게 하여 시트 길이에 따른 콘크리트와 하이브리드 시트 계면에서의 부착 특성에 대해 고찰하였다. 실험 결과, 시트의 유효 부착 길이는 100$\sim$200 mm 사이에서 존재하고, 시트의 콘크리트 계면에서의 효율적인 부착강도를 발휘하기 위해서는 150 mm 이상의 부착 길이가 확보되어야 하며, 콘크리트와 하이브리드 시트 계면에서의 부착강도는 대략 3.0 MPa이고 슬립량은 0.175 mm로 나타나는 것을 알 수 있었다.

• Steel and Composite Structures
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• 제50권3호
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• pp.319-336
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• 2024

Ultra-high-performance concrete (UHPC) has attracted increasing attention in prefabricated steel-concrete composite beams as achieving the onsite construction time savings and structural performance improvement. The inferior replacement and removal efficiency of conventional prefabricated steel-UHPC composite beams (PSUCBs) has thwarted its sustainable applications because of the widely used welded-connectors. Single embedded nut bolted shear connectors (SENBs) have recently introduced as an attempt to enhance demountability of PSUCBs. An in-depth exploration of the mechanical behavior of SENBs in UHPC is necessary to evidence feasibilities of corresponding PSUCBs. However, existing research has been limited to SENB arrangement impacts and lacked considerations on SENB geometric configuration counterparts. To this end, this paper performed twenty push-out tests and theoretical analyses on the shear performance and design recommendation of SENBs. Key test parameters comprised the diameter and grade of SENBs, degree and sequence of pretension, concrete casting method and connector type. Test results indicated that both diameters and grades of bolts exerted remarkable impacts on the SENB shear performance with respect to the shear and frictional responses. Also, there was limited influence of the bolt preload degrees on the shear capacity and ductility of SENBs, but non-negligible contributions to their corresponding frictional resistance and initial shear stiffness. Moreover, inverse pretension sequences or monolithic cast slabs presented slight improvements in the ultimate shear and slip capacity. Finally, design-oriented models with higher accuracy were introduced for predictions of the ultimate shear resistance and load-slip relationship of SENBs in PSUCBs.

• Journal of Biosystems Engineering
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• 제28권1호
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• pp.1-10
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• 2003

A computer simulation was carried out to determinate the optimum capacity of bulk type trailer which is used as a tractor attachment. Soil physical properties. such as soil moisture content. bulk density, soil hardness and soil texture were measured in the 10 major rice production area for computer simulation. Mathematical model which include soil physical properties and vehicle factor was used for computer simulation. Most of the soil texture of the investigated area was silty loam. Soil moisture content ranged between 30 and 40% mostly. Soil bulk density was in the range of 1.500 to 1.700 kg/㎥. Soil hardness ranged between 1 to 18 kg/$\textrm{cm}^2$. Soil hardness incorporate the effects of many soil physical properties such as moisture content texture and bulk density, and so the range of soil hardness was greater than any other physical properties. The capacity of bulk type trailer was above 3000 kg$_{f}$ fer the most of the investigated area. and mostly in the range of 4000 to 6000 kg$_{f}$ depending upon the slip. But for the soft soil area such as Andong and Namyang. tractor itself had mobility problem and showed minus trailer capacity for some places. For this area. the capacity of bulk type trailer ranged between 1000 and 2000 kg$_{f}$ mostly so bulk type trailer should be designed as a small capacity compared to the other area.ared to the other area. area.

• Steel and Composite Structures
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• 제16권2호
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• pp.221-231
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• 2014

The purpose of this study was to evaluate the cyclic behavior of steel column-tree moment connections used in steel moment resisting frames. These connections are composed of shop-welded stub beam-to-column connection and field bolted beam-to-beam splice. In this study, the effects of beam splice length on the seismic performance of column-tree connections were experimentally investigated. The change of the beam splice location alters the bending moment and shear force at the splice, and this may affect the seismic performance of column-tree connections. Three full-scale test specimens of column-tree connections with the splice lengths of 900 mm, 1,100 mm, and 1,300 mm were fabricated and tested. The splice lengths were roughly 1/6, 1/7, 1/8 of the beam span length of 7,500 mm, respectively. The test results showed that all the specimens successfully developed ductile behavior without brittle fracture until 5% radians story drift angle. The maximum moment resisting capacity of the specimens showed little differences. The specimen with the splice length of 1,300 mm showed better bolt slip resistance than the other specimens due to the smallest bending moment at the beam splice.

• Journal of Biosystems Engineering
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• 제28권5호
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• pp.395-402
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• 2003

Standard ginseng seedling, selected after one year's rearing in the seedling bed has been conventionally transplanted in Korea. Recently, the direct seeding areas have been increasing to product high quality ginsengs for red-ginseng processing. Reciprocating push-rod brush, holed-roller and vacuum suction seeders, planting with 30 ${\times}$ 30mm spacings and adjustable to the folds were designed and theirs performances were evaluated. The developed three types of seeders reliably performed at the success rate over 95% with less than 10% in slip rate, and could be used a seeder for the greater spacings by adjusting metering parts. The research concluded that the vacuum suction seeder was the most feasible and practical with the greatest metering success and the least slip among three type seeders of the reciprocating push-rod brush, holed-roller and vacuum suction seeders. The vacuum suction seeder holds a seed with each needle nozzle using the negative pressure created by a vacuum pump. The capacity was 24.5 times greater than a man power at the speed of 5 m/min.

• Structural Engineering and Mechanics
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• 제48권5호
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• pp.643-660
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• 2013

Reinforced concrete structures are vulnerable to high temperature conditions such as those during a fire. At elevated temperatures, the mechanical properties of concrete and reinforcing steel as well as the bond between steel rebar and concrete may significantly deteriorate. The changes in the bonding behavior may influence the flexibility or the moment capacity of the reinforced concrete structures. The bond strength degradation is required for structural design of fire safety and structural repair after fire. However, the investigation of bonding between rebar and concrete at elevated temperatures is quite difficult in practice. In this study, bond constitutive relationships are developed for normal and high-strength concrete (NSC and HSC) subjected to fire, with the intention of providing efficient modeling and to specify the fire-performance criteria for concrete structures exposed to fire. They are developed for the following purposes at high temperatures: normal and high compressive strength with different type of aggregates, bond strength with different types of embedment length and cooling regimes, bond strength versus to compressive strength with different types of embedment length, and bond stress-slip curve. The proposed relationships at elevated temperature are compared with experimental results.