• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.148-155
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• 2009

A remarkable discrepancy of lateral deformation of shear wall structures for seismic loads due to a rigid diaphragm assumption without floor slab modelling asks a study how much effective the slab stiffness ratio is to the lateral behaviour. Typical shear wall type 15 stories structure is selected to analysis using MIDAS-ADS2008 commercial softwares modelling three types; 1) rigid diaphragm (RD model) 2) considered out-of plane slab flexural stiffness (DB model), and 3) considered in and out of plane slab flexural stiffness (SRC model). Based on National Code of KBC2005, the Equivalent Static and Response Spectrum seismic analysis are undertaken to compare each responses of the three models. The differences of lateral responses due to the three slab stiffness ratios applied on the models are compared and discussed.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.141-149
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• 2018

In this paper, the creep behavior of bolted rock was analyzed by using the unconfined creep tests and the numerical results. Based on the test results, the Bolted Burgers creep model (B-B model) was proposed to clarify the creep mechanism of rock mass due to rock bolts. As to the simulation of the creep behaviour of bolted rock, a new user-defined incremental iterative format of the B-B model was established and the open-source $FLAC^{3D}$ code was written by using the object-oriented language (C++). To check the reliability of the present B-B creep constitutive model program, a numerical model of a tunnel with buried depth of 1000 m was established to analyze the creep response of the tunnel with the B-B model support, the non-support and the bolt element support. The simulation results show that the present B-B model is consistent with the calculated results of the inherent bolt element in $FLAC^{3D}$, and the convergence deformation can be more effectively controlled when the proposed B-B model is used in the $FLAC^{3D}$ software. The big advantage of the present B-B creep model secondarily developed in the $FLAC^{3D}$ software is the high computational efficiency.

• Corrosion Science and Technology
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• v.18 no.1
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• pp.1-7
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• 2019

To find proper lathe machining parameters for SA182 Grade 304 stainless steel (SS), six kinds of samples with different machining surface states were prepared using a lathe. Surface morphologies and microstructures of near surface deformed layers on different samples were analysed. Surface morphologies and chemical composition of oxide films formed on different samples in simulated primary water with $100{\mu}g/L\;O_2$ at $310^{\circ}C$ were characterized. Results showed that surface roughness was mainly affected by lathe feed. Surface machining caused grain refinement at the top layer. A severely deformed layer with different thicknesses formed on all samples. In addition to high defect density caused by surface deformation, phase transformation, residual stress, and strain also affected the oxidation behaviour of SA182 Grade 304 SS in the test solution. Machining parameters used for # 4 (feed, 0.15 mm/r; back engagement, 2 mm; cutting speed, 114.86 m/min) and # 6 (feed,0.20 mm/r; back engagement, 1 mm; cutting speed, 73.01 m/min) samples were found to be proper for lathe machining of SA182 Grade 304 SS.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.493-510
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• 2021

Mineral wool is an insulation material commonly used in passive fire protection (PFP) systems on offshore installations. Insulation materials have only been considered functional materials for thermal analysis in the conventional offshore PFP system design method. Hence, the structural performance of insulation has yet to be considered in the design of PFP systems. However, the structural elements of offshore PFP systems are often designed with excessive dimensions to satisfy structural requirements under external loads such as wind, fire and explosive pressure. To verify the structural contribution of insulation material, it was considered a structural material in this study. A series of material tensile tests was undertaken with two types of mineral wool at room temperature and at elevated temperatures for fire conditions. The mechanical properties were then verified with modified methods, and a database was constructed for application in a series of nonlinear structural and thermal finite-element analyses of an offshore bulkhead-type PFP system. Numerical analyses were performed with a conventional model without insulation and with a new suggested model with insulation. These analyses showed the structural contribution of the insulation in the structural behaviour of the PFP panel. The results suggest the need to consider the structural strength of the insulation material in PFP systems during the structural design step for offshore installations.

• Steel and Composite Structures
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• v.42 no.4
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• pp.427-446
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• 2022

Cutouts in the beams or plates are often unavoidable due to inspection, maintenance, ventilation, structural aesthetics purpose, and sometimes to lighten the structures. Therefore, there will be a substantial reduction in the strength of the structure due to the introduction of the cutouts. However, these cutouts can be reinforced with the different patterns of ribs (stiffener) to enhance the strength of the structure. The present study highlights the influence of the elliptical cutout reinforced with a different pattern of ribs on the stability performance of such stiffened composite panels subjected to non-uniform edge loads by employing the Finite element (FE) technique. In the present formulation, a 9-noded heterosis element is used to model the skin, and a 3-noded isoparametric beam element is used to simulate the rib that is attached around a cutout in different patterns. The displacement compatibility condition is employed between the plate and stiffener, and arbitrary orientations are taken care by introducing respective transformation matrices. The effect of shear deformation and rotary inertia are incorporated in the formulation. A new mesh configuration is developed to house the attached ribs around an elliptical cutout with different patterns. Initially, a study is performed on the panels with different stiffener schemes for various ply orientations and for different stiffener depth to width ratios (d_s/b_s) to determine an optimal stiffener configuration. Further, various parametric studies are conducted on an obtained optimal stiffened panel to understand the effect of cutout size, cutout orientation, panel aspect ratio, and boundary conditions. Finally, from the analysis, it can be observed that the arrangement of the stiffener attached to a panel has a major impact on the buckling capacity of the stiffened panel. The stiffener's depth to width ratio also significantly influences the buckling characteristic.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.25-40
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• 2022

In this study, 3D coupled-consolidation numerical parametric study was conducted to predict the deformation mechanism of a 20 storey building sitting on (4×4) piled raft (with length of piles, L_p=30 m) to adjacent 6 m diameter (D) tunnelling in stiff clay. The influences of different tunnel locations relative to piles (i.e., z_t/L_p) were investigated in this parametric study. In first case, the tunnel was excavated near the pile shafts with depth of tunnel axis (z_t) of 9 m (i.e., z_t/L_p). In second and third cases, tunnels were driven at z_t of 30 m and 42 m (i.e., z_t/L_p = 1.0 and 1.4), respectively. An advanced hypoplastic clay model (which is capable of taking small-strain stiffness in account) was adopted to capture soil behaviour. The computed results revealed that tunnelling activity adjacent to a building resting on piled raft caused significant settlement, differential settlement, lateral deflection, angular distortion in the building. In addition, substantial bending moment, shear forces and changes in axial load distribution along pile length were induced. The findings from the parametric study revealed that the building and pile responses significantly influenced by tunnel location relative to pile.

• Geomechanics and Engineering
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• v.31 no.6
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• pp.557-571
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• 2022

Landslides are often triggered by weak interlayers initiated in tailings dam foundations, and hazards gradually occur. This is serious for landslides in high tailings dams due to their high potential energy. Tailing samples with a fine-grained interlayer at a set dip angle were prepared. Consolidated undrained (CU) triaxial shear tests were carried out by using a high-pressure triaxial apparatus. The results were compared with the results under a low confining pressure. Four reasons were summarized for high tailings dams more prone to instability than low dams. The shear strength of the samples with dipping interlayers decreases with increasing dip angle. An obvious straight drop in the stress path after the peak occurs in samples with dipping interlayers at an angle of 60°. The effect of the interlayer on the mechanical behaviour of tailings is very sensitive, especially for the sample with a dipping interlayer at an angle of 60°. Shear slipping along the interlayer should be given more attention in tailings dams. Compared with the results under low confining pressure, the stress decreases continuously for the samples with dipping interlayers at large angles under high confining pressure. The positive pore pressure, which reduces the effective stress, occurred in tailings samples under high confining pressure. The residual strength of tailings under high confining pressure is smaller than that under low confining pressure. These factors increase the dam break risk and the disaster impact for high tailings dams.

• Journal of the Korean Geotechnical Society
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• v.22 no.5
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• pp.39-45
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• 2006

A field instrumentation for a recycled waste concrete geobag wall was performed to investigate the performance of the geobag wall, and uniaxial compression tests for a recycled waste concrete geobag were executed in laboratory. The strength of a recycled waste concrete geobag, the lateral earth pressure of a geobag wall, the horizontal deflection of a geobag wall, and the deformation of a backfill in geobag wall are mainly evaluated in this study. Based on the results of analysis on the measurements, it was found that the geobag wall displacement was within the recommendation for mechanically stabilized earth walls. It was also found that the use of a recycled waste concrete in geobag wall provides economical benefit, construction easiness, and good performance.

• Computers and Concrete
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• v.31 no.6
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• pp.537-543
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• 2023

To study the seismic behavior of recycled aggregate concrete filled circular steel tube (RACFCST) frames, the seismic behavior experiment of RACFCST frame was carried out to measure the hysteresis curve, skeleton curve and other seismic behavior indexes. Moreover, based on the experimental study, a feasible numerical analysis model was established to analyze the finite element parameters of 8 RACFCST frame specimens, and the influence of different variation parameters on the seismic behavior index for RACFCST frame was revealed. The results showed that the skeleton curve of specimens under different axial compression ratios were divided into three stages: elastic stage, elastic-plastic stage and descending stage, and the descending stage was relatively stable, indicating that the specimen had stronger deformation capacity in the descending stage. With the increase of axial compression ratio, the peak bearing capacity of all specimens reduced gradually, and the reduction was less than 5%. With the decrease of beam-column linear stiffness ratio, the peak bearing capacity decreased gradually. With the decrease of yield bending moment ratio of beam-column, the peak bearing capacity decreased gradually, and the decreasing rate of peak bearing capacity gradually accelerated. In addition, compared with the axial compression ratio, the beam-column linear stiffness ratio and the yield bending moment ratio of beam-column had a more significant influence on the peak bearing capacity of RACFCST frame.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.447-455
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• 2006

A general purpose of 4-node co-rotational resultant shell element is developed for the solution of nonlinear problems of reinforced concrete, steel and fiber-reinforced composite structures. The formulation of the geometrical stiffness presented here is defined on the mid-surface by using the second order kinematic relations and is efficient for analyzing thick plates and shells by incorporating bending moment and transverse shear resultant forces. The present element is free of shear locking behavior by using the ANS (Assumed Natural Strain) method such that the element performs very well as thin shells. Inelastic behaviour of concrete material is based on the plasticity with strain hardening and elasto-plastic fracture model. The plasticity of steel is based on Von-Mises Yield and Ivanov Yield criteria with strain hardening. The transverse shear stiffness of laminate composite is defined by an equilibrium approach instead of using the shear correction factor. The proposed formulation is computationally efficient and versitile for most civil engineering application and the test results showed good agreement.