• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.567-571
• /
• 1997

Recently, automobile industry has led to increasing use of aluminum alloy for weight reduction. Automobile made of aluminum alloy can be given lighter, stronger and a harder surface by anodizing than one made of steel-alloy. In this paper, we investigate the influence of lap length, adherend thickness and adhesive thickness on adhesive strength of single-lap adhesive joints by conducting tensile-shear tests. Single-lap adhesive joints of aluminum was calculated using joint factor by using adhesive length, adherend thickness of specimen.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.12
• /
• pp.83-92
• /
• 2018

The lapse of time may cause in the slope structure various deterioration phenomenon progresses in the ground of slope, and collapse due to deterioration of strength, resulting in a decrease in the service life. The approach to slope stability due to the ground deterioration is a different concept from the existing limit equilibrium analysis, which is limited to the physical characteristics and geometrical structure of ground. In this study, we conducted a comparative analysis of various literature studies related to the slope failure characteristics and behaviors to presented the optimal formulas for shear strength reduction, such as the exponential function, the logarithmic function and the inverse hyperbolic function. And then a case study was performed on cut slope of Gyeongbu High Speed Rail construction site along the Yangsan fault zone, where the slope failure of shale layer vulnerable to deterioration occurred. As a result, it was confirmed that landslide occurred due to reduction of shear strength by deterioration, as safety factor is approx. 1.0 at the time when the slope failure occurred. Based on the comprehensive case study, as a quantitative approach to the evaluation of slope stability due to deterioration of ground, finally we propose a method for evaluating slope stability with optimal strength reduction curves.

• Journal of the Korean Society of Safety
• /
• v.16 no.1
• /
• pp.59-64
• /
• 2001

Even though there is a guideline for the required strength of pipe support in inspection, it does not mean the nominal strength which can be used for the form work design. And, Concrete Specification defines that the pipe support should be designed according to the steel design guidelines but the design details are not provided, such as buckling length and the sectional modulus, etc. For the better prediction of strength of pipe support, the slenderness ratio of support which reflects the boundary condition should be considered. In this paper, the elastic buckling formula based on the slenderness is derived. The formula contains the strength reduction factor that consider the strength deduction caused by initial lateral deformation and is 0.65 consistently regardless of boundary conditions. And the coefficient of effective buckling length is calculated from the experiment.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04a
• /
• pp.37-44
• /
• 1998

The objective of this study is development of high strength lightweight concrete and application or structural use. For this, mix proportions for each strength level were selected from lab tests, and adapted to producing ready-mixed concrete in batcher plant. It was very important to prewet the lightweight aggregates sufficiently for producibility and also workability. Splitting tensile strength of high-strength lightweight concrete produced has lower values than that of normal weight concrete, but modulus of rupture and modulus of elasticity are not less than normal weight concrete. The strength reduction factor ($\lambda$) for sand-lightweight concrete make higher than 0.85 present in structures using high-strength lightweight concrete. And it was showed that not parabola distribution but triangular distribution of stress in compression zone.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.5 s.51
• /
• pp.1-9
• /
• 2006

In this study, axial and lateral loading experiments for both circular and square plain concrete columns confined with carbon fiber tube manufactured by carbon filament winding technique were performed. Based on the test results, reliability analyses to estimate strength reduction factors were carried out by utilizing Monte Carlo technique. CASE I was for plain concrete columns confined with the carbon tubes, CASE II was for reinforced concrete columns confined with the carbon tubes. As results, the strength reduction factors, ${\phi}$, were estimated as 0.7 for CASE I and 0.85 for CASE II respectively.

• Journal of Advanced Research in Ocean Engineering
• /
• v.2 no.2
• /
• pp.86-98
• /
• 2016

In this study, after the installation of a subsea pipeline, backfilling was performed in the trenched area. During these operations, a stability problem in the subsea pipeline occurred. The pipeline was directly impacted by environmental loading such as waves and currents that were caused by backfill material when scouring or sediment transport and siltation was carried out. Therefore, this study reviewed whether trenching was necessary, and conducted research into an indigenous seabed property that contains granular soil. A study of cohesive soil was also conducted in order to cross-correlate after calculating the values of the critical Shields parameter relevant to elements of the external environment such as waves and current, and the shear Shields parameter that depends on the actual shearing stress. In case of 1), sedimentation or erosion does not occur. In the case of 2), partial sedimentation or erosion occurs. If the case is 3), full sedimentation or erosion occurs. Therefore, in the cases of 1) or 2), problems in structural subsea pipeline stability will not occur even if partial sedimentation or erosion occurs. This should be reflected particularly in cases with granular and cohesive soil when a reduction in shear strength occurs by cyclic currents and waves. In addition, since backfilling material does not affect the original seabed shear strength, a set-up factor should be considered to use a reduced of the shear strength in the original seabed.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.6
• /
• pp.33-44
• /
• 2011

The shape of an inelastic demand spectrum may have a major impact on the seismic evaluation results of a structure. The inelastic demand spectrum could be obtained by scaling down from the elastic response spectrum by applying the strength reduction factor (SRF). This study has investigated formulas for SRFs that were suggested by numerous previous studies. This paper compares their characteristics, including the shapes of the curves of the SRFs and the inelastic demand spectra that were produced by applying the various formulas for SRFs. The mean curve was computed from the SRF curves generated by the various formulas. This study derives a new formula for the SRF curve through regression analysis. From the comparative study, it is shown that the proposed formula for the SRF can generate the mean curve of the inelastic demand spectra which have been previously suggested by others.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.2
• /
• pp.45-54
• /
• 2019

This paper describes the results of finite element analysis (FEA), in order to investigate a characteristics of pile pullout behavior according to the conditions of the relative density and fines content in original ground. In the FEA, a boundary elements and strength reduction factors ($R_{inter}$) on pile-soil interface were applied to simulate appropriately the shear behavior at the pile-soil interface, and then the reliability of numerical analysis method was verified by comparison of FEA results and previous experimental research(You et al., 2018). In addition, a the deformation characteristics at the pile-soil interface and determination method of $R_{inter}$ value was laid out. The results showed that the FEA, based on the analytical model applied in this study simulates appropriately the characteristics of the pile-soil interface by pullout model test of pile. In order to apply the suggested $R_{inter}$ value, it is necessary to consider the condition of the relative density and the fines content in ground.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.4
• /
• pp.13-22
• /
• 2023

In this paper, through experimental research, the period when rock bolts exert support effects is presented as grout strength and through numerical analysis, the rock bolt pull-out behavior according to ground conditions and strength reduction factors is analyzed. As a result, it is determined that rock bolts exhibit their reinforcing effect at a grout strength of 5 MPa (cured for 18 hours). The influence of the boundary interface strength reduction factor was found to be significant for rock bolt displacement in weak ground conditions, for shear stress between grout and ground in highly elastic ground conditions, and for grout stress in all ground conditions. These findings are expected to contribute to the establishment of specific standards for rock bolt testing and numerical analysis, and to facilitate improved design and implementation of rock bolt reinforcement.

• Journal of the Korea Concrete Institute
• /
• v.21 no.3
• /
• pp.311-318
• /
• 2009

An experimental investigation was conducted to examine the hysteretic behaviors of ultra-high strength concrete tied columns. The purpose of this study is to propose the volumetric ratio of transverse reinforcement for ultra-high strength concrete tied columns with 100 MPa compressive strength. Nineteen 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the main variables of axial load ratio, configurations and volumetric ratios of transverse reinforcement. The results show that the deformability of columns are affected by the configurations and volumetric ratios of transverse reinforcement. Especially, it has been found that the behavior of columns are affected by axial load ratio rather than the amounts and the configurations of transverse reinforcement. To improve the ductility behavior of RC column using ultra high strength concrete in a seismic region, We suggested the amount of transverse reinforcement for all data that satisfy the required displacement ductility ratio over 4. It is means that the lateral confining reduction factor (${\lambda}^c$) considering the effective legs, configuration and spacing of transverse reinforcement and axial load ratio was reflected for the volumetric ratio of transverse reinforcement.