• Journal of Korean Tunnelling and Underground Space Association
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• 제9권4호
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• pp.351-359
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• 2007

Multi-axial compression tests have been frequently conducted to evaluate the in situ properties of rock masses and the mechanical behaviors of rock strata through the model tests. Without the proper boundary condition for the model tests, the mechanical behavior of rock mass would deviate, as can be expected, from the in situ conditions. The boundary condition will affect the internal stress distribution of the specimens and cause some distortion on the measurement. In this study, a design process regarding the steel brush, which has been employed for multi-axial compression test to reduce the frictional restraint along the specimen/loading platen interface, is introduced. The individual brushes are regarded as a simple column and beam to calculate the cross-sectional size and length of the brushes in consideration of the buckling capacity and the allowable deflection.

• Journal of the Earthquake Engineering Society of Korea
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• 제3권3호
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• pp.21-32
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• 1999

A ground motion resulting from the destructive earthquakes can subject reinforced concrete members to very large forces. The reinforced concrete shear walls are designed as earthquake-resistant members of building structure in order to prevent severe damage due to the ground motions. The current research activities on seismic behavior of reinforced concrete member under ground motions have been limited to the shaking table test or equivalent static cyclic test and the obtained results have been summarized and proposed for the seismic design retrofit of structural columns or shear walls. The present study predicted the seismic response and failure behavior of reinforced concrete shear wall subjected to base acceleration using the finite element method. A decrease in strength and stiffness, yielding of reinforcing bar, and repetition of crack closing and opening due to seismic load with cyclic nature are accompanied by the crack which is necessarily expected to take place in concrete member. In this study the nonlinear material models for concrete and reinforcing bar based on biaxial stress field and algorithm of dynamic analysis were combined to construct the analytical program using the finite element method. The analytical seismic response and failure behaviors of reinforced concrete shear wall subjected to several base accelerations were compared with reliable experimental result.

• Journal of Ocean Engineering and Technology
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• 제28권2호
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• pp.133-139
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• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• Journal of Korean Association for Spatial Structures
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• 제8권6호
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• pp.49-57
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• 2008

The seismic isolation systems could be used to reduce the seismic response of a structure. The natural period of a structure with seismic isolation system got be long to avoid the prominent seismic period. The purpose of this study is to analyzed the seismic behavior of the truss arch that is supported to column with LRB. Truss arch structures subjected to horizontal seismic have large horizontal and vertical response unlike seismic behavior of normal rahmen structures. When seismic load is applied to the truss arch with isolation systems, the horizontal acceleration response of the truss arch is reduced and the vertical seismic response is remarkably reduced. Also, the seismic behaviors of the truss arch with strengthen column as like lattice column are very similar to that of the truss arch supported to directly foundation. The Seismic Isolation system can be applied to reduce efficiently the seismic response of the spacial structure with not strong column.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제13권4호
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• pp.199-208
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• 1993

Using several soil parameters which are obtained from the PI-experimental formulas and the back analysis method, the elastic analysis, the elasto-plastic analysis and the elasto-viscoplastic analysis for soil deformation are executed. Comparing the results with those of consolidation test, the indirect estimation method for soil parameters and the suitability of constitutive models are studied. The elastic analysis using back analysis result and the elasto-plastic analysis using the perconsolidation test. The elasto-viscoplastic analysis disagrees with the results of meability coefficient obtained from back analysis are the nearest to the results of the consolidation test. It is inferred that elasto-viscoplastic model is not adequate to the soil of which plasticity index is low.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제13권5호
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• pp.109-122
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• 1993

ln this paper, a finite element analysis procedure is proposed for the incremental multi-step excavations in a fluid-saturated porous medium such as saturated soil ground. As the basis of derivation, Biot's equation was used. The proposed procedure was applied to some one- and two-dimensional problems under incremental excavations. Unsaturated cases as well as saturated cases were considered for comparison. Through numerical tests, the effects of permeability and excavation speed on the deformation history was investigated. Results showed that pore pressure built up during incremental excavation has a significant effect on the deformation and stresses of solid skeleton and validated the use of the present procedure for the analysis of multi-step excavations in fluid-saturated media such as in saturated shallow ground.

• Journal of Korean Society of Steel Construction
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• 제18권5호
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• pp.585-596
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• 2006

This study focuses on the seismic behavior of 3-, 9-, and 20-story steel moment resisting frame (MRF) structures designed in accordance with the 2000 International Building Code using different Response Modification factors (R factors), i.e., 8, 9, 10, 11, and 12. For a detailed case study, 30 different structures were evaluated for 20 ground motions representing the hazard level, which is equal to a 2% probability in 50 years (2% in 50 years). The results showed that the current R factors provide conservative designs for the 3- and 9-story buildings for the Collapse Prevention performance objective. the 20-story buildings, which were designed without using the minimum requirement of spectral acceleration CS prescribed in IBC 2000, did not satisfy the seismic performance for Collapse Prevention performance.

• Journal of the Korea Concrete Institute
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• 제24권5호
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• pp.517-524
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• 2012

In this study, the effects of the inelastic shear behavior of beam-column joint and the vertical distribution of lateral load are evaluated considering higher modes on the response of RC OMRF using the pushover analysis. A structure used for the analysis was a 5-story structure located at site class SB and seismic design category C, which was designed in accordance with KBC2009. Bending moment-curvature relationship for beam and column was identified using fiber model. Also, bending moment-rotation relationship for beam-column joint was calculated using simple and unified joint shear behavior model and moment equilibrium relationship for the joint. The results of pushover analysis showed that, although the rigid beam-column joint overestimated the stiffness and strength of the structure, the inelastic shear behavior of beam-column joint could be neglected in the process of structural design since the average response modification factor satisfied the criteria of KBC2009 for RC OMRF independent to inelastic behavior of joint.

• Journal of Korean Tunnelling and Underground Space Association
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• 제5권3호
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• pp.227-239
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• 2003

For environment-friendly construction, cut-and-cover tunnels have been constructed, thereby leading to embankment slopes with a number of steps. The slopes cause eccentric load on concrete lining of the tunnel. Nevertheless, uniform vertical and horizontal earth pressures, which are determined by considering a self-weight of embankment and $K_0$, are routinely used in structural calculation. Distribution of the earth pressures applied to the lining will lead to a biased calculation far from the actual behavior of the lining. In this study, basic study, therefore, was performed to consider the eccentric load properly in design and analysis of a cut-and-cover tunnel. A method capable of considering the eccentric load in design was proposed and its applicability was numerically examined through a number of examples.

• Journal of the Korea institute for structural maintenance and inspection
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• 제8권4호
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• pp.223-230
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• 2004

It is growing the application of the removal ground anchor with tension force for earth retaining constructions in the downtown. Nowadays, we can find the compression dispersion anchor on many site. But, it is occur some probelems in behabior of anchors because of impossible to tense p.c strand uniformly with existing equipment due to different length of p.c strand. So we tried to tense each p.c strand uniformly with auto back equipment in-situ test. This study compared and analyzed apply to elastic theory in-situ test results of an existing equipment with those of auto back equipment. As a result of the test, It has been proved that differences of tension force in the existing equipment increases with increasing the number of p.c strand. This can cause an ultimate failure of the concentrated p.c strand and a shear failure of ground. So it has been proved that auto back equipment is necessary.