• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.381-386
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• 1993

This paper describes the dynamic fracture behavior of brittle materials under impact loading by using INSAMCR program with instrumented charpy test machine. To calculate the Dynamic Stress Intensity Factor The finite element analysis methods program, INSAMCR, was used. Dynamic fracture characteristic was researched to verify a relationship between Dynamic Stress Intensity Factor and crack tip propagation velocity in WC-6%Co. The relationship between Dynamic Stress Intensity Factor and crack tip velocity revealed typical .GAMMA. shape. INSAMCR was run to verify experimental results in WC-6%Co and shows a good coincidence.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2007-2014
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• 2000

It has been reported that the dynamic stress intensity factor for a propagating crack is increasing or decreasing according to the increasement of the crack propagating velocity. It is confirmed in this study that the increasement or decreasement of stress intensity factor with crack growing velocity is accused by loading condition. When the crack propagates under a constant displacement along upper and lower boundary in finite plate, the dynamic stress intensity factor decreases according to the increasement of the propagating crack velocity. When the crack propagates under a constant stress along upper and lower boundary in finite plate, the dynamic stress intensity factor increases according to the increasement of the propagating crack velocity. The increasement or decreasement of stress intensity factor with crack growing velocity is greater in a fast crack propagation velocity than in a slow one.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.304-309
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• 2000

Strain gage method is used to evaluate the mode I dynamic stress intensity factor of marging steel(18Ni) and titanium alloy(Ti-6A1-4V). To decide the best strain gage position on specimen, static fracture toughness test was performed. Then instrumented charpy impact test and dynamic tensile test was performed by using strain gage method for evlauating dynamic stress intensity factor. Strain gage signals on the crack tip region are used to calculate the stress intensity factors. It is found that strain gage method is more useful than method by using load which is obtained from impact tup to assess dynamic characteristics such as dynamic stress intensity factor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2220-2227
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• 2000

In this paper, dynamic photoelastic hybrid method is developed and its validity is certified. The dynamic photoelastic hybrid method can be used on the obtaining of dynamic stress intensity factors and dynamic stress components. The effect of crack length on the dynamic stress intensity factors is less than those on the static stress intensity factors. When structures are under the dynamic mixed mode load, dynamic stress intensity factor of mode I is almost produced. Dynamic loading device manufactured in this research can be used on the research of dynamic behavior when mechanical resonance is produced and when crack is propagated with the constant velocity.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.331-341
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• 1993

The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.279-282
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• 2005

The aim of this study is to suggest the method of measuring the dynamic stiffness and loss factor of materials used under floating floors in the dwelling by korea standard (KS F 2868). According to the results, the amplitude change of an impact source have no effect on the variation of the dynamic stiffness and loss factor. Comparing with the heating before, heating makes lower the dynamic stiffness except the EPS. In EVA material, the loss factor is increased by heating.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1631-1635
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• 2011

To consider dynamic magnification effect at the static design stage, impact load factor is applied to design load. Current impact load factor adopted EUROCODE without verification while Japan suggested impact load factor including velocity of high-speed train throughout theoretical and experimental studies. On the purpose of evaluate current impact load factor, this study investigated the calculation of impact load factor from dynamic response of running train.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.43-49
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• 2012

In the design of high speed railway bridges is important a impact factor as a tool of assessing the dynamic capacitys of bridges. However, the impact factor(or dynamic amplification factor, DAF) of high speed railway bridges may essentially be changeable because the dynamic response is affected by the long train length(380 m), number of axles and high speed velocity(300 km/h)(Korea Train eXpress: KTX). Therefore, on this study will be examined the dynamic capacity and stability of the typical PSC Box Girder of high speed railway bridge. At first, the static/dynamic analysis is performed considering the axle load line of KTX based upon existing references. Additionally, the KTX moving load is transformed into the dynamic time series load for conducting various parameter studies like axle length, analytical time increment, velocity of KTX. The time history analysis is repeatedly performed to get maximum dynamic responce by varying axle load length, analytical time increment, velocity of KTX. The study shows that dynamic analysis has resonable results with optimal axle load length(0.6 m) and time increment(0.01 sec.) and maximum DAF and dynamic resonance happens at 270 km/h velocity of KTX.

• Steel and Composite Structures
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• v.30 no.3
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• pp.253-269
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• 2019

This paper investigates the effects of the tensile catenary action on dynamic increase factor (DIF) in the nonlinear static analysis for progressive collapse of steel-frame buildings. Numerical analyses were performed to verify the accuracy of the empirical and analytical expressions proposed in the literature in cases where the catenary action is activated. For this purpose, nonlinear static and dynamic analyses of a series of steel moment frame buildings with a different number of spans and stories were carried out following the alternate path method. Different column removal scenarios were considered as separate load cases. The dynamic increase factor that approximately compensates for the dynamic effects in the nonlinear static analysis was selected so to match results from the nonlinear dynamic analysis. The study results showed that the many expressions in literature may not work in cases where the catenary stage is fully developed.

• Structural Engineering and Mechanics
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• v.12 no.3
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• pp.249-266
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• 2001

Current seismic design provisions allow structures to deform into inelastic range during design level earthquakes since the chance to meet such event is quite rare. For this purpose, design base shear is defined in current seismic design provisions as the value of elastic seismic shear force divided by strength reduction factor, R (${\geq}1$). Strength reduction factor generally consists of four different factors, which can account for ductility capacity, overstrength, damping, and redundancy inherent in structures respectively. In this study, R factor is assumed to account for only the ductility rather than overstrength, damping, and redundancy. The R factor considering ductility is called "ductility factor" ($R_{\mu}$). This study proposes ductility factor with correction factor, C, which can account for dynamic P-${\Delta}$ effect. Correction factor, C is established as the functional form since it requires computational efforts and time for calculating this factor. From the statistical study using the results of nonlinear dynamic analysis for 40 earthquake ground motions (EQGM) it is shown that the dependence of C factor on structural period is weak, whereas C factor is strongly dependant on the change of ductility ratio and stability coefficient. To propose the functional form of C factor statistical study is carried out using 79,920 nonlinear dynamic analysis results for different combination of parameters and 40 EQGM.