• Earthquakes and Structures
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• v.7 no.5
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• pp.891-906
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• 2014

The purpose of this study is to propose a modification factor to reflect the lateral stiffness modification when a step is located in flat plates. Reinforced concrete slabs with steps have different structural characteristics that are demonstrated by a series of structural experiment and nonlinear analyses. The corner at the step is weak and flexible, and the associated rotational stiffness degradation at the corner of the step is identified through analyses of 6 types of models using a nonlinear finite element program. Then a systematic analysis of stiffness changes is performed using a linear finite element procedure along with rotational springs. The lateral stiffness of reinforced concrete flat plates with steps is mainly affected by the step length, location, thickness and height. Therefore, a single modification factor for each of these variables is obtained, while other variables are constrained. When multiple variables are considered, each single modification factor is multiplied by the other. Such a method is verified by a comparative analysis. Finally, a complex modification factor can be applied to the existing effective slab width.

• Transactions of Materials Processing
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• v.14 no.9 s.81
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• pp.791-797
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• 2005

Extensive width reduction of slabs is an important technology for achieving continuous production between the steelmaking and hot rolling processes. However, the vertical horizontal rolling process has many disadvantages, e.g., large width deviations and less efficient width reduction. This study was carried out to investigate the deformation of slab by sizing press with two steps die. To do it, dog-bone and camber are discussed in width sizing process considering the deformation behavior according to the deviation of anvil velocity and the deviation of initial slab temperature. In this paper, the various causes of the sizing press phenomena are mentioned for the purpose of understanding of rolling conditions. As a result, the optimal anvil shape having a minimum-forming load is obtained by FE-simulation and ANN.

• Magazine of the Korea Concrete Institute
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• v.20 no.2
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• pp.25-36
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• 2008

Seismic design of reinforced concrete flat plate structures is often complicated as it deals with three dimensionality and continuous spans, and mostly material complexity and reinforcement variation. A great degree of uncertainty in such structural and material properties is thus inherent in the RC flat plate systems, and hinders simplification of the design process in terms of slab flexure, unbalanced moment transfer at a slab-column connection, and punching shear. For these reasons, there have been substantial changes and updates in building codes relating to flat plates and slab-column connections over a handful of decades. Also, for the same reason, some of codes never have been revised. As a consequence of nonsimultaneous development of each provision, it tends to confuse structural engineers when using a mixture of all different US code provisions. In this paper, in the step-by-step logical order, seismic design of the RC flat plate systems is re-organized and clarified to make it easier to apply. Furthermore, recent changes or proposed changes are introduced, and are explained as to how it will apply in practice.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.447-455
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• 2013

In this study, reinforced concrete slabs with steps were experimentally studied to analyze their structural performance and to suggest reinforcing details in the step. Because the stepped slabs may behave very poorly in terms of bending strength, stiffness, deflection, cracking, etc., the study is aimed to suggest proper reinforcing details such that the same bending strength is obtained as that without steps. The bending strengths of 12 test specimens with a variety of different reinforcing detail types or other parameters were compared with each other. The specimen without any additional reinforcement in the step had a very low bending strength and significant damage, and the specimens with diagonal reinforcements in the step showed substantial early cracks, experienced hinging of the step, and had a substantial loss of the bending strength. In contrast, the specimens with a combination of U-bars, reversed U-bars, L-bars, and reversed L-bars performed very well and almost reached to 100% of the slab bending strength. The U-bars and reversed U-bars were effective in controling the diagonal cracks, while the L-bars and reversed L-bars were effective in preventing from yielding of slab reinforcement near the step.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.126-133
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• 1997

For each construction material used, there is certain theoretical limit in sizes. For tall building construction, the reduction in slab weight is the first step to take in order to break such size limits. In this paper, the feasibility of such objective is proven and given by numerical analysis result. For a typical building slab, both concrete and advanced composite sandwich panels are considered. The concrete slab is treated as a special orthotropic plate to obtain more accurate result. For each panel, the deflection under the dead and live loads is compared, since both tensile and compressive strengths of the composites are far more higher than those of concrete. All types of sandwich panels considered, except one case, have weights less than one tenth of that of reinforced concrete slab, with deflections less than that of the concrete slab. The cost analysis result and manufacturing methods will be reported later.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.861-866
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• 2000

This experimental were investigated on the influence of steel fiber reinforcement on flexural behavior characteristics of slabs with various steel fiber contents $V_f$ and aspect ratio($\ell $/$\phi$). Deflection, crack widths, and strains of steel bar were measured with every load step. In the results of this experimental, the addition of steel fibers to conventionally reinforced concrete slab increased the ultimate load, reduced the creak width, the average crack spacing, and deflection.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.3
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• pp.199-206
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• 2006

Extraordinary displacement and vibration by heavy vehicle causes passengers to feel mental uncomfortableness and bridge to be damaged. To increase serviceability, the research on the human influence for vibration to happen at the bridge has been performed for a long time in oversea but it does not draw concern relatively in the domestic. The purpose of this research is to develop an evaluation method for vibration serviceability of continuous slab bridge. This research is focused on establishing theoretical method to assess vibration serviceability of bridge considering natural frequency, displacement, and acceleration since the criteria for the human responses to vibration is generally based on frequency band. By examining the characteristics of vibration serviceability which has been assessed with human response curve through field experiments as well as analytical study, the evaluation method of vibration serviceability for continuous slab bridges is proposed. Based on applications to the example of continuous slab bridge, the simple evaluation of vibration serviceability in the paper may be used in the initial step of design practice.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.88-89
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• 2015

In cold weather, the speed of concrete strength development is slow. As a result, construction speed becomes slow and it is problem for all construction site to solve this. So in this study, to shorten removing frame time after placing concrete, mix proportion using early-strength-binder(ESB) and curing method such as using heat line in concrete was considered. At first, concrete mix proportion was examined at -5℃ temperature between ordinary portland cement(OPC) and ESB. And second step, concrete, using mix proportion with OPC, was examined according to curing method(: 1) heat line used and 2) no heat line) and kinds of form (: 1) Deck slab, 2) Half PC slab and 3) SOG slab). All cases are same condition: slab thickness is 1,500mm, double-bubble sheet is used as a curing sheet after placing concrete. After the test, OPC is enough to get strength compared to ESB in special condition and 48~60 hours is needed according to form condition.

• Composites Research
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• v.27 no.1
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• pp.7-13
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• 2014

For each construction material used, there is certain theoretical limit in sizes. For tall building construction, the reduction in slab weight is the first step to take in order to break such size limits. In this paper, the feasibility of such objective is proven and given by numerical analysis result. For a typical building slab, both concrete and advanced composite sandwich panels are considered. The concrete slab is treated as a special orthotropic plate to obtain more accurate result. For each panel, the deflection under the dead and live loads is compared, since both tensile and compressive strengths of the composites are far more higher than those of concrete. All types of sandwich panels considered, except one case, have self-weights less than one tenth of that of the reinforced concrete slab, with deflections less than that of the reinforced concrete slab.

• Geomechanics and Engineering
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• v.22 no.1
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• pp.49-63
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• 2020

Studying the critical response characteristics of box culverts with diverse geometrical configurations under seismic excitations is a necessary step to develop a reasonable design method. In this work, a numerical parametric study is conducted on various soil-culvert systems, aiming to highlight the critical difference in the seismic performances between three- and four-sided culverts. Two-dimensional numerical models consider a variety of burial depths, flexibility ratios and foundation widths, assuming a visco-elastic soil condition, which permits to compare with the analytical solutions and previous studies. The results show that flexible three-sided culverts at a shallow depth considerably amplify the spectral acceleration and Arias intensity. Larger racking deformation and rocking rotation are also predicted for the three-sided culverts, but the bottom slab influence decreases with increasing burial depth and foundation width. The bottom slab combined with the burial depth and structural stiffness also significantly influences the magnitude and distribution of the dynamic earth pressure. The findings of this work shed light on the critical role of the bottom slab in the seismic responses of box culverts and may have a certain reference value for the preliminary seismic design using R-F relation.