• Tunnel and Underground Space
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• v.31 no.1
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• pp.66-81
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• 2021

The effects of directional fracture tensor components and first invariant of fracture tensor on deformation moduli and shear moduli of fractured rock masses is analyzed based on regression analysis performed between 3-D fracture tensor parameters and deformability of DFN blocks. Using one or two deterministic joint sets, a total of 224 3-D discrete fracture network (DFN) cube blocks were generated with various configurations of deterministic density and probabilistic size distribution. The fracture tensor parameters were calculated for each generated DFN systems. Also, deformability moduli with respect to three perpendicular direction of the DFN cube blocks were estimated based on distinct element method. The larger the first invariant of fracture tensor, the smaller the values for the deformability moduli of the DFN blocks. These deformability properties present an asymptotic pattern above the certain threshold. It is found that power-law function describes the relationship between the directional deformability moduli and the corresponding fracture tensor components estimated in same direction.

• Computers and Concrete
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• v.27 no.5
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• pp.457-472
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• 2021

Reinforced concrete (RC) buildings in Taiwan have suffered failure from strong earthquakes, which was magnified by the non-ductile detailing frames. Inadequate reinforcement as a consequence of the design philosophy prior to the introduction of current standards resulted in severe damage in the column and beam-column joint (BCJ). This study establishes a finite element analysis (FEA) of the non-ductile detailing RC column, BCJ, and three-story building that was previously tested through a tri-axial shaking table test. The results were then validated to laboratory specimens having the exact same dimensions and properties. FEA simulation integrates the concrete damage plasticity model and the elastic-perfectly plastic model for steel. The load-displacement responses of the column and BCJ specimens obtained from FEA were in a reasonable agreement with the experimental curves. The resulting initial stiffness and maximum base shear were found to be a close approximation to the experimental results. Also, the findings of a dynamic analysis of the three-story building showed that the time-history data of acceleration and displacement correlated well with the shaking table test results. This indicates the FEA implementation can be effectively used to predict the RC frame performance and failure mode under seismic loads.

• Geomechanics and Engineering
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• v.27 no.5
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• pp.497-509
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• 2021

A large deformation FEM (Finite Element Method) based numerical analysis has been performed to study the behaviour of the bell-shaped anchor embedded in undrained saturated (cohesive) soil with the help of finite element based software ABAQUS. A typical model anchor with bell-diameter of 0.125 m, embedded in undrained saturated soil with varying cohesive strength (from 5 kN/m² to 200 kN/m²) has been chosen for studying the characteristic behaviour of the bell-shaped anchor installed in cohesive soil. Breakout factors have been evaluated for each case and verified with the results of experimental model tests for three different types of soil samples. The maximum value of breakout factor was found as about 8.5 within a range of critical embedment ratio of 2.5 to 3. An explicit model has been developed to estimate the breakout factor (F_c) for uplift capacity of bell-shaped anchor within clay mass in terms of H/D ratio (embedment ratio). It was also found that, the ultimate uplift capacity of the anchor increases with the increase of the value of cohesive strength of the soil and H/D ratio. The empirical equation developed in the present investigation is usable within the range of cohesion value and H/D ratio from 5 kN/m² to 200 kN /m² and 0.5 to 3.0 respectively. The proposed model has been validated against data obtained from a series of model tests carried out in the present investigation. From the stress-profile analysis of the soil mass surrounding the anchor, occurrence of stress concentration is found to be generated at the joint of anchor shaft and bell. It was also found that the vertical and horizontal stresses surrounding the anchor diminish at about a distance of 0.3 m and 0.15 m respectively.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.12-16
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• 2022

Currently, Induction welding is attracting attention as a non-contact, clean and fast welding process. However, since thermoplastic resins are not affected by electromagnetic fields, induction welding requires a heating element called a susceptor. Researches are being conducted with the aim of achieving high-quality bonding, however, the factor of a heating element is an issue, hence the need to set a standard. Specimen fabrication and testing are conducted according to ASTM D5868. In this study, we propose that the evaluation criteria be judged on the basis of three factors; the condition of the welded joint surface, void content, and lap shear strength. Since the adhesive surface to be welded melts and solidifies as it cools, rapid temperature changes can generate pores. In addition, if the heating is not uniform, it is difficult to expect the desire performance. Using PA6 (CF 30%) thermoplastic, susceptor fabrication, induction welding and performance verification were conducted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.517-528
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• 2008

This paper presents a hysteretic damage model for reinforced concrete (RC) joints that explicitly accounts for the bond-slip between the reinforcing bars and the surrounding concrete. A frame element whose displacement fields for the concrete and the reinforcing bars are different to permit slip is developed. From the fiber section concept, compatibility equations for concrete, rebar, and bond are defined. Modification of the hysteretic stress-strain curve of steel is conducted for partial unloading and reloading conditions. Local bond stress-slip relations for monotonic loads are updated at each slip reversal according to the damage factor. The numerical applications of the reinforcing bar embedded in the confined concrete block, the RC column anchored in the foundation, and the RC beam-column subassemblage validate the model accuracy and show how including the effects of bond-slip leads to a good assessment of the amount of energy dissipation during loading histories.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.581-591
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• 2005

This paper proposes a design formulae that evaluates the design strength of T-joints made of cold-formed square hollow steel sections with longitudinal branch plate. The T-joints had a configuration that a branch member used to longitudinal plate to the main chord in the plane. This study focused on the branch plate T-joints governed by the main chord flange failure mode among the experimental results. Based on the test results of the longitudinal branch plate T-joint in the square hollow sections, the ultimate strength on the T-joints was defined as 1.5 times the load at 1% B the strength of joints that governed the serviceability in control for $16.7{\leq}2\gamma(B/T){\leq}31.3$ and $0.20{\leq}{\beta}(b1/B){\leq}0.75$. Existing yield line models for normal T-joints were investigated to be the main chord flange failure for the branch plate T-joint, and this proposal design formula was based on the theory of the yield line model. Finally, the value of the finite element method compared with the value of the test and theory for the T-joints verified the validity of the design formulae.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.545-553
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• 2014

This study suggested an integrated classification method for generalized characteristics of PC beam-column connection according to connection details. Quantifying the failure mode of PC-beam column connection and characteristics of corresponding details, this study suggested to use deformation contribution of each element of beam-column assemblage. According to the expected failure mode of beam-column connection assemblage, PC beam-column connection can be classified into 'equivalent monolithic system' and 'jointed system'. In this study, four test specimens were tested for verification of detailed classification method of PC beam-column connections. Test was carried out with typical beam-column connection test method. Load was applied at the top of test specimen and end of beams were restrained by hinge. In order to verify the deformation contribution of each test specimen, 34-LVDTs were mounted on test specimen. According to test results, deformation contribution of each test specimen have different characteristics. Deformation characteristics of joint and other components which are quantified by test results, equivalent monolithic system can be classified into two categories. Strong connection have extremely small deformation contribution of joint and much larger deformation contribution was shown in flexural behavior of beam. The other type of beam-column connection is ductile connection which allows the larger deformation in joint area compared with strong connection.

• Economic and Environmental Geology
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• v.40 no.1 s.182
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• pp.47-66
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• 2007

The Sitting Buddha Carved on Rockcliff (National treasure No. 201) in Bukjiri consists of porphyritic biotite granite, which was fractured by three joint sets of NE-SW, EW and NS directions. They produced a physical weathering that broke many parts of the Buddha and background. The chemical index of alteration is 59 to 61 from the major elements in the granite that was weathered into producing kaolin minerals from alteration of feldspars and biotite. With weathering degree, major element compositions increase in $SiO_2$ and MnO, whereas decrease in $TiO_2,\;{Fe_2O_3}^t,\;MgO,\;CaO\;and\;K_2O$. Change proporations of trace elements to $Al_2O_3$ increase in all transition elements, Rb and Y, whereas decrease in Li, Sr and Ba. REE pattern increases only in HREE. Particularly, a decrease in CaO, $K_2O$, Sr and Ba results in what they are effluxed to dissolve from feldspars by groundwater. The Buddha image has been deteriorated into joints, color changes, brown rusts, granular decay, microorganic smears by the such weathering causes as deformation, moisture, temperature variation and microorganic living. The moisture, which leaks along the joints in the granite, not only dissolve to decompose minerals but also grows many microorganism and is frozen over during winter. NE-SW and NS joint sets affect to seep in water during rainy days to deteriorate the image because they extend outward.

• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.61-69
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• 2008

The purpose of this study is to examine the success or failure on the balance beam in element group requirements posture which is bending salto side-ward tucked through kinetic analysis. The national team players were participated. The goal was to present training methods to coaches and athletes so as to provide scientifically useful information. The results from this study were summarized as below. When the performance was successful, the features of the body's center of gravity during the side somersault motion showed to spread from the center of the balance beam and the center of the gravity moved to the direction of the body's rotation. In the spring sections - event2 and 3, when the performance was successful, up/down fluctuation became more wider and increased air time. It supported the result that the projecting variable was higher than in failure trial. In addition, the right side hip joint angles and speed, and angular velocity as jumping up for a leap were larger than in failure trial. Those variables showed the optimal conditions for a leap. By increasing the speed of the upper limb from the shoulder and the speed of the shoulder joint angular velocity, the momentum was increased. Especially the right side shoulder joint angular velocity increased dramatically because the right leg was held. As to the side somersault motion, the angular momentum of successful trial with respect to x-axis was bigger than failed trial. It indicated that the increasing angular momentum with respect to x-axis was an important factor in flying motion. Besides, as to side somersault, the appropriate proportion of angular momentum with respect to y-axis and z-axis was a key to successful trails.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.97-102
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• 2007

Though the stability analysis of soil slopes widely employs the limit equilibrium method, the study on the jointed rock slopes must consider the direction of joint and the characteristics of Joint at the same time. This study analyzes the result of the change in the factors which show the characteristics of discontinuity and the shape factor of rock slopes, and so on, in an attempt to validate the propriety as to the interpretation of jointed rock slope stability which uses the general finite element program. First, the difference depending on the flow rules was compared, and the factor effect study was conducted. The selected independent variables included the direction of joint which displays the mechanical characteristics of discontinuity, adhesive cohesion, friction angle, the inclination and height of rock slope which reveal the shape of slope and surcharge load. And the horizontal displacement was numerically interpreted at the 1/3 point below the slope, a dependent variable, to compare the relative degree of factor effects. The findings of study on factor effects led to the validation that the result of horizontal displacement for each factor satisfied various engineering characteristics, making it possible to be applied to stability interpretation of jointed rock slope. A modelling is possible, which considers the application of the result of real geotechnical surveys & laboratory studies and the non-linear characteristics when designing the rock slope. In addition, the stress change which may result from the natural disaster, such as precipitation, and the construction, can be expressed. Furthermore, as the complicated rock condition and the ground supporting effect can be considered through FEM, it is considered to be very useful in making an engineering decision on the cut-slope, reinforcement and so on.