• Journal of Korean Society of Steel Construction
• /
• v.22 no.6
• /
• pp.599-608
• /
• 2010

Steel trusses that act compositely with concrete slabs have proven to be an economical system for long-span floors. The composite action is generally achieved by providing shear connections between the steel top chord and the concrete topping. The composite sections have greater stiffness than the sum of the individual stiffnesses of the slab and truss. Therefore, steel trusses that act compositely with concrete slabs can carry larger loads and are stifferand less prone to transient vibration. During the tests that were performed in this study, the crack pattern and deflection of the beam of the composte truss were investigated. The test results were compared with the results for the noncomposite trusses.

• Journal of Digital Convergence
• /
• v.12 no.4
• /
• pp.343-348
• /
• 2014

This paper suggested a theoretical approach and an implementation for the design of an unequal Wilkinson power divider with a high dividing ratio operating at two-frequencies. The T-section transmission lines and the two-section of Monzon's theory are proposed to operate a dual-band application. To achieve the high dividing ratio divider, the high impedance line using a T-shaped structure and low impedance lines with periodic shunt open stubs are implemented. For the validation of this divider, a dual-band power divider with a high dividing ratio of 5 is simulated and measured at 1 GHz and 2 GHz. The measured performances of the divider are in good agreements with simulation results.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.2
• /
• pp.209-222
• /
• 2013

Eccentric axial loading test was performed for concrete-encased columns using 800MPa steel and 100MPa concrete. To maximize the contribution of the high-strength steel, L-shaped steel sections were placed at four corners, and connected to each other by lattices, links, or battens. Compared to a H-section of the same area, the moment-arm and strain of the L-sections are increased. Also, the corner L-sections provide good lateral confinement to concrete core. The test results showed that the peak strength and effective flexural stiffness of the L-section columns were increased by more than 1.4 times those of the H-section column.

• Structural Engineering and Mechanics
• /
• v.64 no.1
• /
• pp.135-143
• /
• 2017

To upgrade shear performance of reinforced concrete (RC) beams, and particularly of the segments under negative moment within continuous T-section beams, a series of original schemes has been proposed using carbon fibre-reinforced polymer (CFRP) U-shaped strips for shear-strengthening. The current work focuses on one of them, in which CFRP U-strips are wound around steel bars against the top of the flange of a T-beam and then spliced on its bottom face in addition to being bonded onto its sides. The test results showed that the proposed scheme successfully provided reliable anchorage for U-strips and prevented premature onset of shear failure due to FRP debonding. The governing shear mode of failure changed from peeling of CFRP to its fracture or crushing of concrete. The strengthened specimens displayed an average increase of about 60% in shear capacity over the unstrengthened control one. The specimen with a relatively high ratio and uniform distribution of CFRP reinforcement had a maximum increase of nearly 75% in strength as well as significantly improved ductility. The formulas by various codes or guidelines exhibited different accuracy in estimating FRP contribution to shear resistance of the segments that are subjected to negative moment and strengthened with well-anchored FRP U-strips within continuous T-beams. Further investigation is necessary to find a suitable approach to predicting load-carrying capacity of continuous beams shear strengthened in this way.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.1033-1039
• /
• 2006

To overcome the drawback of currently available curved beam theories having non-symmetric thin-walled cross sections, a curved beam theory based on centroid-shear center formulation is presented for the spatially coupled free vibration and elastic analyses. For this, the elastic strain and kinetic energies considering the thickness-curvature effect and the rotary inertia of curved beam are derived by degenerating the energies of the elastic continuum to those of curved beam. And then the equilibrium equations and the boundary conditions are consistently derived for curved beams having non-symmetric thin-walled cross section. It is emphasized that for curved beams with L- or T-shaped sections, this thin-walled curved beam theory can be easily reduced to tl1e solid beam theory by simply putting the sectional properties associated with warping to zero. In order to illustrate the validity and the accuracy of this study, FE solutions using the Hermitian curved beam elements are presented and compared with the results by previous research and ABAQUS's shell elements.

• Steel and Composite Structures
• /
• v.18 no.5
• /
• pp.1177-1195
• /
• 2015

Six specimens are tested to investigate the cyclic behavior of beam-to-column abnormal joints in steel moment-resisting frames, which are designed according to the principle of strong-member and weak-panel zone. Key parameters include the axial compression ratio of column and the section depth ratio of beams. Experimental results indicate that four types of failure patterns occurred during the loading process. The $P-{\Delta}$ hysteretic loops are stable and plentiful, but have different changing tendency at the positive and negative direction in the later of loading process due to mechanical behaviors of specimens. The ultimate strength tends to increase with the decrease of the section depth ratio of beams, but it is not apparent relationship to the axial compression ratio of column, which is less than 0.5. The top panel zone has good deformation capacity and the shear rotation can reach to 0.04 rad. The top panel zone and the bottom panel zone don't work as a whole. Based on the experimental results, the equation for shear strength of the abnormal joint panel zone is established by considering the restriction of the bottom panel zone to the top panel zone, which is suitable for the abnormal joint of H-shaped or box column and beams with different depths.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.12
• /
• pp.694-701
• /
• 2018

Larger crack widths can be observed more in FRP-reinforced concrete members than in steel-reinforced concrete members as a result of the lower elastic modulus and bond strength of FRP reinforcement. The ACI 440.1R-15 design guide provides equations derived as the maximum bar spacing to control the crack widths indirectly. On the other hand, it is not concerned with long-term effects on the crack control design provisions. This study provides suggestions for how to incorporate time-dependent effects into the crack width equation. The work presented herein includes the results from 8 beams composed of four rectangular and T-shaped FRP-reinforced concrete beams tested for one year under four-point bending. Over a one year period, the crack widths increased as much as 2.6~3.0 times in GFRP and AFRP-reinforced specimens and 1.1~1.4 times in the CFRP-reinforced specimens compared to steel-reinforced specimens. In addition, the average multiple for crack width at one year relative to the instantaneous crack width upon the application of the sustained load was 2.4 in the specimens with a rectangular section and 3.1 in the specimens with a T-shaped section. As a result, it is recommended conservatively that the time-dependent coefficient be taken as 2.5 for the rectangular beams and 3.5 for T-beams.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1999.06a
• /
• pp.209-225
• /
• 1999

Detailed description of the crystal growth methods permitting one to obtain complicated shape crystals from the melt is given. The variable shaping technique provides the growth of crystals with a discrete altering cross-section configuration during crystallization. The dynamic local shaping technique enables one to grow items with a continuous alteration of the side surface profile by a preset program.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.9 no.4
• /
• pp.417-423
• /
• 1999

Detailed description of the crystal growth methods permitting one to obtain complicated shape crystals from the melt is given. The variable shaping technique provides the growth of crystals with a discrete altering cross-section configuration during crystallization. The dynamic local shaping technique enables one to grow items with a continuous alteration of the side surface profile by a preset program.

• The Plant Pathology Journal
• /
• v.22 no.2
• /
• pp.155-160
• /
• 2006

A strain of Pepper mottle virus (PepMov) was isolated from chili pepper plants in Korea. In host range study, this virus, designated PepMoV-SNU1, shared most characteristics with PepMoV isolates reported previously. Thermal inactivation point ($45^{\circ}C\;to\;75^{\circ}C$) and dilution end point ($10^{-1}\;to\;10^{-4}$) of PepMoV-SNU1 showed differences depending on the propagation hosts. Cylindrical and pinwheel-shaped inclusions were always observed in pepper leaf tissues infected with the virus alone. Unexpectedly, a special structure of pinwheel shaped inclusion surrounded with unknown small spots was also observed in the leaf section when co-infected with a strain of pepper mild mottle virus. The partial sequence of coat protein gene and 3' untranslated region of PepMoV-SNU1 showed 98% identity with those of other PepMoV isolates. A primer pair derived from 3' end of the coat protein gene and poly A tail regions were designed. Optimal detection condition of PepMoV-SNU1 by RT-PCR was tested to determine appropriate annealing temperature and additional volumes of oligo-dT (18-mer), dNTP, and Taq polymerase. Under the optimized condition, an expected 500 Up PCR-product was detected in pepper leaves infected with PepMoV-SNU1 but not in healthy plants.