• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.10a
• /
• pp.287-292
• /
• 1998

In particle or short-fiber reinforced composites. cracking of the reinforcements is a significant damage mode because the broken reinforcements lose load carrying capacity. This paper deals with the load carrying capacity of intact and broken ellipsoidal inhomogeneities embedded in an infinite body and a damage theory of particle or short-fiber reinforce composites. The average stress in the inhomogeneity represents its load carrying capacity. and the difference between the average stresses of the intact t and broken inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The composite in damage process contains intact and broken reinforcements in a matrix. An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive cracking damage of the reinforcements have been developed based on the Eshelby's equivalent inclusion method and Mori and Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.5 no.2
• /
• pp.191-197
• /
• 2001

In this study, the admixtures for agents for enduring cold weather used widely are collected and applied to cement mortar to analyze the strength development due to variation of curing temperature at early age. The test results show that anti-freezing admixture have some problems due to high chloride content, which may cause the corrosion of reinforcement embedded in concrete. However, the mortar applied by accelerator and another kind of agent for enduring cold weather produced by S company lead to delay of strength development in low temperature. Also, it is clarified that there are no significant problems for cement mortar in strength development due to low temperature if a suitable kind of agent enduring cold weather is used and cement mortar is cured for more than $7.5^{\circ}D.D$ at early age.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.241-247
• /
• 1997

Reinforced concrete is in general known as high durability construction material under normal enviroments due to strong alkalinity of cement. Marine and harbour concrete as well as concrete mixed with seasand for fine aggregate are exposed to detrimental saltwater wich cause to accel-eate corrosion of reinforcing steel in concrete. If corrosion resistance of concrete gets to weaken due to carbonation and crack in cover concrete, concrete durability rapidly decrease by corrosion of reinforcement steel embedded in concrete. This research is to investigate basic physical properties of various corrosion inhibitors and to evaluate their corrosion resistance in concrete mixed with seasand. The object of this study is develop appropriate corrosion protection systems so as to enhance the durability of concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.319-322
• /
• 2005

Experimental results on splice strength of concrete and hybrid fiber reinforced cementitious composite are reported. Two series of tests, with six specimens each, were carried out. The research parameters were: bar diameter(D16, D22), lap splice length(50, 75, 100$\%$). The current experimental results demonstrated clearly that the use of hybrid fibers in cementitious matrixes increases significantly the splice strength of reinforcing bars in tension. Also, the presence of fibers increased the number of cracks formed around the spliced bars, delayed the growth of the splitting cracks, and consequently, improved the ductility of bond failure.

• Journal of Ocean Engineering and Technology
• /
• v.14 no.1
• /
• pp.52-59
• /
• 2000

Flexural fracture characteristics of newly-developed Grid-type carbon fiber plastics in the deteriorated reinforced concrete structures were investigated by the four-points fracture test to verify the strengthening effects in the beam specimens. Results showed that initial cracks appeared in the boundary layers of fibers embedded in the newly-placed mortar concrete slowly progressed to the direction of supports and showed fracture of fiber plastics and brittle failure of concrete in compression in sequence after the yielding of steel reinforcement. Accordingly the reasonable area of Grid-type carbon-fiber plastics in the strengthening design of deteriorated RC structures should be limited and given based on the ultimate strength design method to avoid the brittle failure of concrete structures.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.366-373
• /
• 2002

This paper describes the load distribution and settlement of rockbolted-drilled shafts subjected to axial and lateral loads with the view to shortening the embedded depth of the pile shaft. The emphasis was on quantifying the reinforcing effects of rockbolts placed from the shafts to surrounding weathered rocks based on small-scale model tests peformed on instrumented piles. The major influencing parameters on reinforcing drilled shaft behavior are the number, the positions on the shaft, the grade, and the inclination angle at which the rockbolts are placed. The model tests was 1/40 scaled simulations of the behavior of the drilled shafts with varying combinations of the major influencing parameters. The incremental effects of reinforcement based on the various parameters have been weighed against load transfer characteristics before and after rockbolt installations.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.10a
• /
• pp.599-606
• /
• 2003

An analytical model which can simulate the post-cracking nonlinear behavior of reinforced concrete (RC) members such as bars and panels subjected to uniaxial and biaxial tensile stresses is presented. The proposed model includes the description of biaxial failure criteria and the average stress-strain relation of reinforcing steel. Based on strain distribution functions of steel and concrete after cracking, average response of an embedded reinforcement, a criterion to consider the tension-stiffening effect is proposed using the concept of average stresses and strains. The validity of the introduced model is established by comparing the analytical predictions for reinforced concrete tension members with results from experimental studies. Finally, correlation studies between analytical results and experimental data from biaxial tension test are conducted with the objective to establish the validity of the proposed models and identify the significance of various effects on the response of biaxially loaded reinforced concrete panels.

• Annual Conference of KIPS
• /
• 2018.10a
• /
• pp.537-540
• /
• 2018

본 논문은 Jetson_TX2(임베디드 보드)의 ROS(Robot Operating System)기반으로 맵 지도를 작성하고, SLAM 및 DQN(Deep Q-Network)을 이용한 목적지까지의 이동명령(목표 선속도, 목표 각속도)을 자이로센서로 측정한 현재 각속도를 이용하여 Cortex-M3의 기반의 MCU(Micro Controllor Unit)에 하달하여 엔코더(encoder) 모터에서 측정한 현재 선속도와 자이로센서에서 측정한 각속도 값을 이용하여 PID제어를 통한 실내 자율주행 서비스 로봇.

• Steel and Composite Structures
• /
• v.19 no.2
• /
• pp.327-348
• /
• 2015

A numerical procedure is presented that provides ultimate curvature and moment domains for composite rectangular and circular cross-sections of reinforced concrete columns with or without an embedded steel section subjected to combined axial loading and biaxial bending. The stress resultants for the concrete and reinforcement bars are calculated using fiber analysis and the stress resultants for the encased structural steel are evaluated using an exact integration of the stress-strain curve over the area of the steel section. A dimensionless formula is proposed that can be used for any section with similar normalized geometric and mechanical parameters. The contribution of each material to the bearing capacity of a section (resistance load and moments) is calculated separately so that the influence of each geometric or mechanical parameter on the bearing capacity can be investigated separately.

• Earthquakes and Structures
• /
• v.16 no.4
• /
• pp.455-468
• /
• 2019

The behavior of pile-deck connections of pile-supported marginal wharfs subjected to earthquake loading is of key importance to ensure a good performance of this type of structures. Two precast-pretensioned pile-deck connections used in the construction of pile-supported marginal wharfs were tested under cyclic loading. The first is a connection with simple reinforcement details and light steel ratio developed for use where moderate pile-deck rotation demands are expected in the wharf. The second is specifically developed to sustain the large rotation, shear force and bending moment demands, as required for the shortest piles in a marginal wharf. Data obtained from the test program is used in the paper to calibrate an equivalent plastic hinge length that can be incorporated into nonlinear analysis models of these structures when prestressed pile-deck connections with duct embedded dowels are used.