• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.87-87
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• 1990

Fatigue crack closure levels based on the behavior of residual displacements on crack surfaces, are determined analytically according to the microscopic crack closure mechanisms, i.e., whether the first contact of crack surfaces takes place at the very crack tip or on the surfaces near the tip. The comparative analysis on the two models is carried out empirically by the constant amplitude fatigue tests on 2024-T3 aluminum alloy plate, and it shows that under negative stress ratio, the case of the first contact at crack tip gives better agreement with the experimental results than the other.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1091-1096
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• 1994

Since horizontal movements due to shrinkage and thermal gradients in concrete pavements involve no actual load, the stresses induced will be those due to closing of the pavement joints and subbase friction. Consequently, complete derivations of stiffness matrix and equivalent nodal loads due to planar effects on the concrete pavements was throughly undertaken using the finite rectangular elements with two degrees of freedom at each node. The numerical example shows that the tensile stress induced in a pavement due to concrete shrinkage might be negligible except at very long slab and very high coefficient of frictions. However the stresses in conjunction with principal traffic loads might cause cracking problems.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.197-213
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• 2019

We simulated the fault reactivation experiment conducted at 'Main Fault' intersecting the low permeability clay formations of Mont Terri Underground Research Laboratory in Switzerland using TOUGH-FLAC simulator. The fluid flow along a fault was modelled with solid elements and governed by Darcy's law with the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by creating interface elements between two separating rock blocks in FLAC3D. We formulate the hydro-mechanical coupling relation of hydraulic aperture to consider the elastic fracture opening and failure-induced dilation for reproducing the abrupt changes in injection flow rate and monitoring pressure at fracture opening pressure. A parametric study was conducted to examine the effects of in-situ stress condition and fault deformation and strength parameters and to find the optimal parameter set to reproduce the field observations. In the best matching simulation, the fracture opening pressure and variations of injection flow rate and monitoring pressure showed good agreement with field experiment results, which suggests the capability of the numerical model to reasonably capture the fracture opening and propagation process. The model overestimated the fault displacement in shear direction and the range of reactivated zone, which was attributed to the progressive shear failures along the fault at high injection pressure. In the field experiment results, however, fracture tensile opening seems the dominant mechanism affecting the hydraulic aperture increase.