• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.55-64
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• 2012

Experimental investigation on the structural behavior of steel fiber-reinforced ultra high performance concrete (UHPC) beams subjected to shear are presented. Six tests carried out on simply supported I-beams under concentrated loads are presented. The parameters varied were the volume fraction of the fibers (1.0, 1.5 and 2.0%) and shear span-effective depth ratio (2.5, 3.4). The test results indicated that ultimate shear strength increased with increasing fiber volume, and that ultimate shear strength decreased with increasing shear span-effective depth ratio. In addition, applicability of predictive equations for evaluating the ultimate shear strength of steel fiber-reinforced UHPC beams are estimated based on the test results. The comparison between computed values and the experimentally observed values are shown to validate the proposed theoretical equations. It is found that predictions by using AFGC and JSCE recommendations provide the most accurate estimates of shear strength of steel fiber-reinforced UHPC beams.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.330-338
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• 2012

Though the uniaxial compressive strength (UCS) of rock material is one of the key properties for rockmass characterization purposes, core samples for the test cannot always be obtained from the field. Indirect tests such as the point load test (PLT) can be a useful alternative. In this study, correlation between the UCS and the point load strength index of limestone of Imgye area was analyzed, and the linear regression equation obtained from regression analysis of two variables was suggested. The results of this study were also compared with previous studies on limestone. It was suggested that conversion factors for the same rock type from diverse areas in Korea may have different values, and more data should be obtained to increase the accuracy of regression analysis.

• Journal of the Society of Disaster Information
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• v.14 no.4
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• pp.466-473
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• 2018

Purpose: Nowadays, it is the trend that seismic isolation method and combined method are used for seismic retrofitting, if concrete sphere foundation(CSF) system is applied to mid and low rise RC structure for the seismic isolation, the characteristics of concrete sphere, etc split tensile strength will be need. Method: The various experiments are carried out to know the split strength of high strength concrete sphere(60Mpa) and the ratio of split strength of concrete sphere to standard cylinder specimen, the size effect of concrete sphere with diameter. Results: It was purposed that the split strength of concrete sphere with diameter 150mm will be lower than that of cylinder specimen but, the average value is 4.39 Mpa and the ratio is higher than that of cylinder specimens, each 3.8% and 13.7%, the reason of this result is thought that the internal stress action of spot load and line load are different. Conclusion: There is a standard method for split tensile strength of cylinder type specimen, but there are few studies for the tensile split of concrete sphere. And therefore, in this study, theoretical and experimental details of concrete sphere will be served for the concrete sphere foundation or other sequent studies.