• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.763-768
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• 2000

The purpose of this paper is to predict the flexural strengthening of reinforced concrete beams by the external bonding of carbon fiber reinforced plate(CFRP) to the tension face of the beam. Used computational equation is derived by relation of stress an strain. This equation is applied to four-nondamage beam and tow-preloading beam. Six scale beams were tested to evaluate the strength enhancement provided by the CFRP. And describes the strength enhancement provided to the flexural capacity of reinforced concrete beam by the external bonding of CFRP. An inelastic section analysis procedure was developed that accurately predicts the load displacement response of the retrofitted beams.

• Smart Structures and Systems
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• v.1 no.3
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• pp.309-324
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• 2005

This paper presents an efficient and accurate coupled beam model for piezoelectric bimorphs based on improved first-order shear deformation theory (FSDT). The model combines the equivalent single layer approach for the mechanical displacements and a layerwise modeling for the electric potential. General electric field function is proposed to reasonably approximate the through-the-thickness distribution of the applied and induced electric potentials. Layerwise defined shear correction factor (k) accounting for nonlinear shear strain distribution is introduced into both the shear stress resultant and the electric displacement integration. Analytical solutions for free vibrations and forced response under electromechanical loads are obtained for the simply supported piezoelectric bimorphs with series or parallel arrangement, and the numerical results for various length-to-thickness ratios are compared with the exact two-dimensional piezoelasticity solution. Excellent predictions with low error estimates of local and global responses as well as the modal frequencies are observed.

• Advances in Computational Design
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• v.1 no.2
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• pp.195-206
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• 2016

Dams play a vital role in the development and sustainment in a country. Failure of dams leads to the catastrophic event with sudden release of water and is of great concern. Hence earthquake-resistant design of dams is of prime importance. The present study involves static, modal and transient analyses of dam-reservoir-foundation system using finite element software ANSYS 15. The dam and the foundation are modeled with 2D plane strain element "PLANE 42" and the reservoir by fluid acoustic element "FLUID 29" with proper consideration of fluid-structure interaction. An expression for the fundamental period of concrete dams is developed based on modal analysis. Seismic response of gravity dams subjected to earthquake acceleration is evaluated in terms of peak displacement and stress.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.321-330
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• 2011

Long-term properties of concrete affect structures in many respects, not excepting dynamic behaviors. This paper investigates the influence of concrete creep on the dynamic behaviors of concrete filled steel tube (CFT) arch bridges, by means of combining the analytical method for the creep of axially compressed CFT members, which is based on Model B3 for concrete creep, with the finite element model of CFT arch bridges. By this approach, the changes of the stress and strain of each element in the bridge with time can be obtained and then transformed into damping and stiffness matrices in the dynamic equation involved in the finite element model at different times. A numerical example of a long-span half-through CFT arch bridge shows that creep influences the natural vibration characteristics and seismic responses of the bridge considerably, especially in the early age. In addition, parameter analysis demonstrates that concrete composition, compressive strength and steel ratio have an obvious effect on the seismic response of the CFT arch bridge.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.467-468
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• 2005

Low cycle fatigue test results of Type 316 stainless steel in $310^{\circ}C$ water environment can be summarized as follows. 1. Cyclic stress response of Type 316 stainless steel shows negative strain rate sensitivity, primary hardening and secondary hardening. 2. Fatigue life in $310^{\circ}C$ water environment was shorter than fatigue life in room temperature air environment. This was because of water environment and temperature effects.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.4
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• pp.189-196
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• 2020

In this study, two full-scale gravity load-designed reinforced concrete corner beam-column joints were tested by being subjected to uniand bi-directional cyclic lateral loading. The test variable was loading type: uni- or bi-directional loading. To investigate the effect of the loading type on the cyclic behavior of joint specimens, damage progression, force-deformation relation, contribution of joint deformation to total drift, joint stress-strain response, and cumulative energy dissipation were investigated. The test data suggest that bidirectional loading can amplify damage accumulation in the joint region.

• Advanced Composite Materials
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• v.18 no.3
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• pp.251-264
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• 2009

Nonlinear mechanical behaviors of unidirectional carbon fiber-reinforced plastic (CFRP) laminates using cup-stacked carbon nanotubes (CSCNTs) dispersed epoxy are evaluated and compared with those of CFRP laminates without CSCNTs. Off-axis compression tests are performed to obtain the stress-strain relations. One-parameter plasticity model is applied to characterize the nonlinear response of unidirectional laminates, and nonlinear behaviors of laminates with and without CSCNTs are compared. Clear improvement in stiffness of off-axis specimens by using CSCNTs is demonstrated, which is considered to contribute the enhancement of the longitudinal compressive strength of unidirectional laminates and compressive strength of multidirectional laminates. Finally, longitudinal compressive strengths are predicted based on a kink band model including the nonlinear responses in order to demonstrate the improvement in longitudinal strength of CFRP by dispersing CSCNTs.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.333-336
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• 2006

The response of a reinforced concrete element under cyclic shear is characterized by the hysteretic loops of the shear stress-strain curves. Recent tests have shown that the orientation of steel grids in RC shear elements has a strong effect on the "pinching effect" and ductility in the post-yield hysteretic loops. In this paper, four RC elements are considered to study the effect of the steel grid orientation on "pinching effect" and ductility. The presence and absence of the pinching mechanism in the post-yield shear hysteretic loops are studied using the Rotating Angle Softened Truss Model (RA-STM) theory.

• Transactions of Materials Processing
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• v.29 no.6
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• pp.347-355
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• 2020

The mechanical responses of multilayered aluminum sheet fabricated by roll bonding, i.e., A1050/A3004 (65% A1050, 35% A3004 by thickness), were investigated via combined experiment and finite element (FE) analysis. The mechanical properties were measured using uniaxial tensile tests in various loading directions for the multilayered sheet. The corresponding tests for individual layers were also conducted. The testing samples were prepared by wire electro discharge machining (EDM). Stress-strain curves and Lankford coefficients of the multilayered sheet were then predicted by FE simulations. The measured mechanical properties of the individual layers were utilized as inputs for the simulation. Two yield functions, i.e., isotropic von-Mises and anisotropic non-quadratic Hill1948, were employed. Predicted results were compared with the experimental data and further discussed.

• Smart Structures and Systems
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• v.5 no.6
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• pp.633-644
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• 2009

A simple method has been developed to detect the bonding condition of active fiber composites (AFC) adhered to the surface of a host structure. Large deformation actuating capability is one of important features of AFC. Edge delamination in adhesive layer due to large interfacial shear stress at the free edge is typically resulted from axial strain mismatch between bonded materials. AFC patch possesses very good flexibility and toughness. When an AFC patch is partially delaminated from host structure, there remains sensing capability in the debonded part. The debonding size can be determined through axial resonance measured by the interdigitated electrodes symmetrically aligned on opposite surfaces of the patch. The electrical impedance and modal response of the AFC patch in part adhered to an aluminum plate were investigated in a broad frequency range. Debonding ratio of the AFC patch is in inverse proportion to the resonant frequency of the fundamental mode. Feasibility of in-situ detecting the progressive delamination between AFC patch and host plate is demonstrated.