• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.381-390
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• 2012

The KCI Building Code (2003 and 2007) provisions to control flexural cracking in beams and one-way slabs are discussed for related researches and the development of the provisions. Based on the basic ideas over the development of current provisions, possible problems with cracking control are identified and discussed for the remedies to fix the problems. Simple and clear equations to control flexural cracking in beams and one-way slabs are presented. The presented equations would avoid any conflicts with other provisions for the spacing of reinforcement.

• Smart Structures and Systems
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• v.17 no.1
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• pp.59-72
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• 2016

The Impact Echo method can be used to measure the thickness of concrete plate like structures. Measurements are based on the identification of a clear thickness resonance frequency which can be difficult in very thick or highly attenuative plates. In this study the detectability of the measured resonant frequency is enhanced by time domain summation of signals with different source receiver spacing. The proposed method is based on the spatial and temporal properties of the first higher symmetric zero group velocity Lamb mode (S1-ZGV) which are described in detail. No application dependent tuning or filtering is needed which makes the method robust and suitable for implementation in automatic IE thickness measurements. The proposed technique is exemplified with numerical data and field data from a thick concrete wall and a highly attenuative asphalt concrete layer.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.291-302
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• 2009

A compression lap splice can be calculated longer than a tension lap splice in high strength concrete according to current design codes. New criteria for the compression lap splice including the effects of concrete strength are required for practical purpose of ultra-high strength concrete. Characteristics of compression lap splice have been extensively investigated and main parameters are derived. In addition, an experimental study has been conducted with column specimens in concrete strength of 40 and 60 MPa. The strength of the compression lap splice consists of bond and end bearing and two contributors are combined. Therefore, combined action of bond and end bearing should be assessed. Compared with tension splices, concrete strength significantly affects the strength of compression splices due to short splice length and existence of end bearing. Test results show that the splice strength can be evaluated to be proportional to square root of compressive strength of concrete. The stress states of concrete surrounding spliced bars govern the strengths of bond and end bearing. Because the axial stress of the concrete is relatively high, the splice strength is not dependent on clear spacing. End bearing strength is not affected by splice length and clear spacing and is expressed with a function of the square root of concrete strength. The failure mode of specimens is similar to side-face blowout of pullout test of anchors and the strength of end bearing can be evaluated using the equation of side-face blowout strength. Because the stresses developed by bond in compression splices are nearly identical to those in tension splices, strength increment of compression splices is attributed to end bearing only.

• International Journal of Safety
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• v.11 no.2
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• pp.26-28
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• 2012

In this thesis, fracture tests were carried out in order to investigate the flexural strength behavior of FRC(fiber reinforced concrete) structures. FRC beams were used in the tests, the initial crack load and the ultimate load of the beams were observed under the static loading. According to the results, the ultimate loads increase with the fiber content, and these tendency is clear in the specimens with large fiber aspect ratio. From the results of the regression analysis, practical formulae for predicting the flexural strength of FRC were suggested.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.573-582
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• 2014

Since there is no clear installation criteria on minimum spacing between signalized intersection and minor road, many problems have occurred in terms of traffic operation and safety. Even though many studies about entrance/exit intersection have been done in operational aspects, there is no specific and detailed research between the signalized intersection and minor road by now. Thus, this research suggests the optimal spacing between signalized intersection and minor road considering traffic operation and safety. Also, survey on vehicle behavior was conducted in this research. In conclusion, by suggesting the required minimum spacing between signalized intersection and minor road, it can be contribute in establishing and operating the installation criteria between signalized intersection and minor road.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.471-478
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• 2011

For a practical simplicity in designing of reinforced concrete structures, the indirect crack controlling method of limiting bar spacing is adopted in KCI structural design provisions. In addition, a direct method for evaluating crack width is also provided in the appendix of the code. But there may be some mismatched results between these two crack controlling methods. In this study, limit values of maximum bar spacing calculated from KCI provisions, KCI appendix, and Frosch's equation are examined as concrete strength, cross-section height, and concrete cover are varied, and the differences are analyzed. From the results, it becomes clear that the differences between maximum bar spacing calculated from KCI code text provisions and those from KCI code appendix provisions are too significant to be neglected. Therefore, rational crack models are suggested in order to get rid of the discrepancy between the direct and indirect control methods.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.507-534
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• 2015

The present work investigates the behavior of the embankment models resting on soft soil reinforced with ordinary and stone columns encased with geogrid. Model tests were performed with different spacing distances between stone columns and two lengths to diameter ratios (L/d) of the stone columns, in addition to different embankment heights. A total number of 42 model tests were carried out on a soil with undrianed shear strength $${\sim_\sim}10kPa$$. The models consist of stone columns embankment at s/d equal to 2.5, 3 and 4 with L/d ratio equal 5 and 8. Three embankment heights; 200 mm, 250 mm and 300 mm were tested for both tests of ordinary (OSC) and geogrid encased stone columns (ESC). Three earth pressure cells were used to measure directly the vertical effective stress on column at the top of the middle stone column under the center line of embankment and on the edge stone column for all models while the third cell was placed at the base of embankment between two columns to measure the vertical effective stress in soft soil directly. The performance of stone columns embankments relies upon the ability of the granular embankment material to arch over the 'gaps' between the stone columns spacing. The results showed that the ratio of the embankment height to the clear spacing between columns (h/s-d) is a key parameter. It is found that (h/s-d)<1.2 and 1.4 for OSC and ESC, respectively; (h is the embankment height, s is the spacing between columns and d is the diameter of stone columns), no effect of arching is pronounced, the settlement at the surface of the embankment is very large, and the stress acting on the subsoil is virtually unmodified from the nominal overburden stress. When $(h/s-d){\geq}2.2$ for OSC and ESC respectively, full arching will occur and minimum stress on subsoil between stone columns will act, so the range of critical embankment height will be 1.2 (h/sd) to 2.2 (h/s-d) for both OSC and ESC models.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1094-1099
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• 2010

Three dimensional laminar flows are numerically simulated around the submerged spheres. The finite volume based Navier-Stokes equations with unstructured grids are solved to make clear the hydrodynamic phenomena near and far away from the body. Reviews are made on with the vorticity, velocity, dynamic pressure, residuals, drags, etc. The Reynolds numbers under consideration are 425, 300, 250 and 100. In case of small spacing between spheres, the flow is more stable than that past a single sphere. According to the analysis, the flow past two spheres is found to be unstable as the spacing becomes larger. The rear sphere shows the deduction of stagnation pressure, which results in the decrease of the resistance. The predicted drag coefficients verify that the present numerical calculation is reasonable.

• Fire Science and Engineering
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• v.33 no.1
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• pp.105-112
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• 2019

In this study, an architectural acoustics simulation was conducted to examine the clear and uniform transmission of emergency broadcasting sound in a T junction corridor space. The sound absorption performance of the corridor space and the location and spacing of the loudspeaker for emergency broadcasting were varied. The distribution of the sound pressure level and the distribution of sound transmission indices (STI, RASTI) were compared. The simulation showed that the loudspeaker for emergency broadcasting should be installed approximately 10 m from the center of the T junction corridor connection for clear voice transmission. Narrowing the 25 m installation interval of the NFSC shows that an even clearer and sufficient volume of emergency broadcast sound can be delivered evenly.

• The Journal of the Petrological Society of Korea
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• v.26 no.3
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• pp.297-309
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• 2017

Jurassic granite from Geochang was analysed with respect to the characteristics of the rock cleavage. The comprehensive evaluation for rock cleavages was performed through the combination of the 16 parameters derived from the enlarged photomicrographs of the thin section and the spacing-cumulative frequency diagrams. The results of analysis for the representative values of these spacing parameters with respect to the rock cleavage are summarized as follows. First, the above parameters can be classified into group I (spacing frequency (N), total spacing ($1m{\geq}$), constant (a), exponent (${\lambda}$), slope of exponential straight line (${\theta}$), length of line (oa') and trigonometric ratios ($sin{\theta}$, $tan{\theta}$) and group II (mean spacing (Sm), difference value between mean spacing and median spacing (Sm-Sme), density (${\rho}$), lengths of lines (oa and aa'), area of a right-angled triangle (${\Delta}oaa^{\prime}$) and trigonometric ratio($cos{\theta}$). The values of the 8 parameters belonging to group I show an order of H(hardway, H1+H2)