• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.189-192
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• 2008

Most existing double tee systems have need to improve flexure and shear design at their flanges in the section. In order to solve this problem we have devised MTS(Multi-tee slab) system, which is composed of several T-beams and applied spandrel end beams at each slab unit. The application of spandrel end beams has an beneficial effect on the shear strength and force distribution of slab unit because they support the ribs in the transverse direction. Numerical analysis shows that the spandrel end beams increase the shear strength. This paper represents the analysis of shear strength in MTS system and the effect of the spandrel end beams on the system.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.19-30
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• 2000

The major design parameters of the anchored sheet-pile wall include the determination of required penetration depth, the force acting on the anchor, and the maximum bending moment in the piling. Blum solved the fixed earth supported wall using the equivalent beam method, assuming that the wall can be separated into upper and lower parts of the point of contraflexure. Design charts help designer by simplifying the design procedure. But they have some difficulties under some Geotechnical and geometrical conditions. For example, the conventional design charts can compute design parameters only when the ground water table exists above the dredge line. In this paper, the design charts which can be used for the ground water table existing under the dredge line are presented. And simplified formulae are developed by regression analysis. It is found that simplified formulae are not only very useful for the practice of design but also they can evaluate the result of numerical methods or design charts.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.163-174
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• 2004

A number of experiments were performed to investigate the punching shear strength of flat plate-column connections. According to the experiments, the punching shear strength varies significantly with design parameters such as the column size of the connection, reinforcement ratio, and boundary condition. However, current design methods do not properly address the effects of such design parameters. In the present study, a theoratical approach using Rankine's failure cirterion was attempted to define the failure mechanism of the punching shear According to the study, the failure mechanism can be classified into the compression-controlled and the tension-controlled, depending on the amount of bottom re-bars placed at the connection, and the punching shear strength is also significantly affected by the flexural damage of slab. Based on the finding, a new strength model of punching shear was developed, and verified by the comparisons with existing experiments and nonlinear finite element analyses. The comparisons show that the proposed strength model addressing the effects of various design parameters can predict accurately the punching shear strength, compared to the existing strength models.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.181-187
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• 2011

This paper deals with free vibrations of the Timoshenko beam supported by two elastomeric bearings at two far ends. The ordinary differential equation governing free vibrations of such beam is derived, in which both effects of rotatory inertia and shear deformation are included as the Timoshenko beam theory. Also, boundary conditions of the free end are derived based on the Timoshenko beam theory. The ordinary differential equation is solved by the numerical methods for calculating natural frequencies and mode shapes. Both effects of the rotatory inertia and shear deformation on natural frequencies are extensively discussed. Also, relationships between natural frequencies and slenderness ratio, foundation modulus and bearing length are presented. Typical mode shapes of bending moment and shear force as well as deflection are given in figures which show the positions of maximum amplitudes and nodal points.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.717-726
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• 2006

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for steel composite bridges. However, the method has some disadvantages such as stress concentration at anchorages and inefficient load-carrying capability of live loads. Multi-stepwise prestressing method using thermal expanded coverplate is a newly proposed prestressing method, which was originally developed for prestressing steel structures. A new retrofitting method for steel girder bridges founded on a simple concept of thermal expansion and contraction of cover plate, the method is a hybrid of and combines the advantages of external post-tensioning and thermal prestressing. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect was substantiated and the FEM approach for its analysis was verified. The retrofitting effects ofa single-span bridge were analyzed and the feasibility of the developed method was examined.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.289-298
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• 2015

The steel tube of Concrete-Filled Tube(CFT) confines the concrete and the concrete restrains the buckling of the tube, The objective of this study is to investigate the influences of the opening shape of the through diaphragm in case of the rectangular CFT column-to-beam connection through the structural experiment. The experiment results are compared with analysis results obtained by using the FEM program. These results are shown that strength of the rectangular CFT column-to-beam connection have similar structural performance regardless of the opening shape if opening areas of the through diaphragm are same. Also in case the connection area/shape of the through diaphragm and the flange of H-beam are similar, it was ascertained that the bending stress occurred at the beam can be transferred to the column through the diaphragm.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.261-271
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• 2015

Steel concentrically braced frame is an efficient system that can acquire resistance against the lateral force of buildings with the least amount of quantity. In this study is intended to proceed on the research of schemes for reinforcement by supplementing previously installed H-formed brace with non-welded cold-formed plastic stiffening materials restricting the flexure and buckling and acquire a consistent strength on the tensile and compressive force. As for the measures of supplementing previously-installed inverted V-formed braced frame, stiffening materials in the previous studies were converted to weak-axial supplementing materials to suggest a specific scheme evaluating the structural function through an experiment of members, interpretation of members, and frame-focused experiment. Reinforced brace satisfied the requirement to be prevent AISC brace from being ruptured due to imbalanced strength in the beam.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.121-128
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• 2010

The current trends in steel construction involve the use of tapered sections to minimize the use of excess materials to the extent possible, by choosing cross-sections that are as economical as possible abandoning the classical approach of using prismatic members. In addition, snug-tightened connections, especially the end-plate type, have the advantage of fetching less construction costs and shorter assembly times as opposed to fully tightened joints. Although they have many merits, however, snug-tightened bolted end plates are extremely complex in their structural behavior. In this study, an experimental investigation of the snug-tightened flush end-plate connections of tapered beams were conducted. The primary test parameters were the torque for the clamping bolt, the loading pattern, the bolt type and the connection failure type. Using initial stiffness and load-carrying capacity as proposed by Silva et al. and AISC (2003), the moment-rotation curve of a linearly tapered member with a snug-tightened flush end-plate connection was predicted. Moreover, numerical and experimental data for moment-rotation curves were compared.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.785-796
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• 2008

Longitudinal elongation develops in reinforced concrete beams that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the beams. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams. The results showed that residual tensile plastic strain of the longitudinal reinforcing bar in the plastic hinge is the primary factor causing the member elongation, and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the analysis results, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.59-67
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• 1993

The variations of the natural frequencies and the peak response acceleration at the top of prestressed concrete reactor building due to random variability and/or model uncertainty of structural parameters are studied. The results may be used as essential input parameters in seismic probabilistic risk assessment or seismic margin assessment of the reactor building. The sensitivity test of each structural parameter is first performed to determine the most influential parameter upon the natural frequency of structure model. Then Monte Carlo simulation technique is applied to evaluate the effect of parameter variation on the natural frequencies and the peak response acceleration. The acceleration time history is obtained by direct integration scheme. As the study results, it is found that the fundamental natural frequency and the peak response acceleration at the top of the building are most strongly affected by Young's modulus among the structural parameters, in which the value of mean plus one standard deviation obtained by probabilistic approach deviates up to about (+)12% from the result of deterministic method. Considering the uncertainty of flexural rigidity, the structural responses vary in range of (-)4%~(+)14%.