• Smart Structures and Systems
• /
• v.1 no.2
• /
• pp.141-158
• /
• 2005

A new design of distributed crack sensors based on the topological change of transmission line cables is presented for the condition assessment of reinforced concrete (RC) structures during and immediately after an earthquake event. This study is primarily focused on the performance of cable sensors under dynamic loading, particularly a feature that allows for some "memory" of the crack history of an RC member. This feature enables the post-earthquake condition assessment of structural members such as RC columns, in which the earthquake-induced cracks are closed immediately after an earthquake event due to gravity loads, and are visually undetectable. Factors affecting the onset of the feature were investigated experimentally with small-scale RC beams under cyclic loading. Test results indicated that both crack width and the number of loading cycles were instrumental in the onset of the memory feature of cable sensors. Practical issues related to dynamic acquisition with the sensors are discussed. The sensors were proven to be fatigue resistant from shake table tests of RC columns. The sensors continued to show useful performance after the columns can no longer support additional loads.

• Computers and Concrete
• /
• v.23 no.1
• /
• pp.11-23
• /
• 2019

Nowadays, the characterization of Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) tensile behavior still remains a challenge for researchers. For this purpose, a simplified closed-form non-linear hinge model based on the Third Point Bending Test (ThirdPBT) was developed by the authors. This model has been used as the basis of a simplified inverse analysis methodology to derive the tensile material properties from load-deflection response obtained from ThirdPBT experimental tests. In this paper, a non-linear finite element model (FEM) is presented with the objective of validate the closed-form non-linear hinge model. The state determination of the closed-form model is straightforward, which facilitates further inverse analysis methodologies to derive the tensile properties of UHPFRC. The accuracy of the closed-form non-linear hinge model is validated by a robust non-linear FEM analysis and a set of 15 Third-Point Bending tests with variable depths and a constant slenderness ratio of 4.5. The numerical validation shows excellent results in terms of load-deflection response, bending curvatures and average longitudinal strains when resorting to the discrete crack approach.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.32 no.1
• /
• pp.43-53
• /
• 2008

Surface edge crack in transversely isotropic piezoelectric material is analyzed. The concentrated antiplane mechanical and inplane electrical loadings are applied to an arbitrary point of the surface, where the impermeable crack boundary condition is imposed. Using Mellin transform the problem is formulated, from which Wiener-Hopf equations are derived. By solving the equations the solution is obtained in a closed form. Mechanical and electric intensity factors and energy release rate are obtained and discussed. This problem could be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Structural Engineering and Mechanics
• /
• v.42 no.3
• /
• pp.313-334
• /
• 2012

This paper examines the problem of a penny-shaped crack in a thermoporoelastic body. On the basis of the recently developed general solutions for thermoporoelasticity, appropriate potentials are suggested and the governing equations are solved in view of the similarity to those for pure elasticity. Exact and closed form fundamental solutions are expressed in terms of elementary functions. The singularity behavior is then discussed. The present solutions are compared with those in literature and an excellent agreement is achieved. Numerical calculations are performed to show the influence of the material parameters upon the distribution of the thermoporoelastic field. Due to its ideal property, the present solution is a natural benchmark to various numerical codes and simplified analyses.

• Structural Engineering and Mechanics
• /
• v.82 no.3
• /
• pp.313-323
• /
• 2022

Steel laminated elastomeric bearings are commonly used in bridge structures to control displacements and rotations and transfer forces from the superstructure to the substructure. Proper knowledge of design, fabrication and erection procedures is important to ensure stability and adequate structural performance during the lifetime of the bridge. Difference in elevations sometimes leads to large size gaps between the bearing and the girder which makes the grout thickness that is commonly used for leveling deviate beyond standards. This paper investigates the structural response of High Strength Fiber Reinforced Cementitious (HSFRC) thin plinths that are used to close gaps between bearing pads and precast girders. An experimental program was developed for this purpose where HSFRC plinths of different size were cast and tested under vertical loads that simulate bridge loading in service. The structural performance of the plinths was closely monitored during testing, mainly crack propagation, vertical reaction and displacement. Analytically, the HSFRC plinth was analyzed using the beam on elastic foundation theory as the supporting elastomeric bearing pads are highly compressible. Closed form solutions were derived for induced displacement and forces and comparisons were made between analytical and experimental results. Finally, recommendations were made to facilitate the practical use of HSFRC plinths in bridge construction based on its enhanced load carrying capacity in shear and flexure.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.5
• /
• pp.562-569
• /
• 2007

This paper presents plastic limit loads and approximate J estimates for axial through-wall cracked pipe bends under internal pressure and in-plane bending. Geometric variables associated with a crack and pipe bend are systematically varied, and three possible crack locations (intrados, extrados and crown) in pipe bends are considered. Based on small strain finite element limit analyses using elastic-perfectly plastic materials, effect of bend and crack geometries on plastic limit loads for axial through-wall cracked pipe bends under internal pressure and in-plane bending are quantified, and closed-form limit solutions are given. Based on proposed limit load solutions, a J estimation scheme for axial through-wall cracked pipe bends under internal pressure and in-plane bending is proposed based on reference stress approach.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.24 no.2
• /
• pp.94-100
• /
• 1988

Recently with the rapid development in marine and shipbuilding industries such as marine structures, ship, and chemical plants, there occurs much interest in the study of corrosion fatigue characteristics was closed up an important role in mechanical design. In this study, the 5086 Al-Alloy was tested by used of a rotary bending fatigue tester and was investigated under the environments of various specific resistance and air. The specific resistance, as a corrosion environment, was changed 15, 20, 25 and 5000$\Omega$.cm. The corrosion fatigue crack initiation sensitivity was quantitatively inspected for 5086 Al-Alloy in the various specific resistance. The experimental constants of Paris rule were examined in the various specific resistances, and the influences of load and corrosion with affect the crack growth rate were compared with. Main results obtained are as follows: (1) Number of stress cycles to corrosion fatigue crack initiation delaies and corrosion fatigue crack initiation sensitivity decreases with the increasing for the specific resistance. (2) The experimental constant m of Paris rule decreases with the decreasing for specific resistance. Hence the effect of corrosion is more susceptible than that of stress intensity factor. (3) The corrosion fatigue crack of 5086 Aluminium Alloy appears intergranular fracture. (4) Corrosion sensitivity is decreased with the increasing stress intensity factor and is nearly uniform when stress intensity factor is over 40kg.mm super(-3/2)

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.9
• /
• pp.967-974
• /
• 2007

A general form solution is considered for a piezoelectric material containing impermeable cracks subjected to a combined mechanical and in-plane electrical loading. The analysis is based upon the Hilbert problem formulation. Using this solution, typically for a central crack in transverse isotropic piezoelectric material, a closed form solution is obtained, where one concentrated mechanical and electrical load is subjected to the crack surface. This problem could be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.5
• /
• pp.1530-1537
• /
• 1991

본 연구에서는 반무한 직선 계면균열의 상하면에 임의로 분포하는 어떠한 하 중에 대해서도 그 해석이 가능한 그린함수(Green's function)를 구하고자 한다. 이 를 위하여 반무한 직선 계면균열상의 임의의 한 점에 평면 집중하중이 작용하는 문제 와 비평면 집중전단하중이 작용하는 문제를 각각 택하였고, 이때 계면균열의 선단은 열려있다고 가정하였다. 이 문제를 풀므로써 균열선단부근의 응력성분을 결정하고 이로부터 그린함수의 의미를 지니는 응력강도계수에 대한 폐형해를 얻었다.

• Journal of ILASS-Korea
• /
• v.20 no.2
• /
• pp.101-106
• /
• 2015

Gas leakage and dispersion in the underground LNG power plant can lead to serious fire and explosion accident. In this study, computational fluid dynamics simulation was applied to model the dynamic process of gas leakage and dispersion phenomena in a closed space. To analyze the risk assessment factor, such as the flammable volume ratio, transient simulations were carried out for different scenarios. The simulation results visualized the gas distribution with time in the closed space. The flammable volume ratio was introduced for quantitative analysis the fire/explosion probability.