• Structural Engineering and Mechanics
• /
• v.81 no.5
• /
• pp.575-589
• /
• 2022

In order to enhance the greenness in the strain-hardening composites and to reduce the high cost of typical polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC), an affordable strain-hardening composite with green binder content has been proposed. For optimizing the strain-hardening behavior of cementitious composites, this paper investigates the effects of polypropylene fibers on the first cracking strength, fracture properties, and micromechanical parameters of cementitious composites. For this purpose, digital image correlation (DIC) technique was utilized to monitor crack propagation. In addition, to have an in-depth understanding of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. To understand the effect of fibers on the strain hardening behavior of cementitious composites, ten mixes were designed with the variables of fiber length and volume. To investigate the micromechanical parameters from fracture tests on notched beam specimens, a novel technique has been suggested. In this regard, mechanical and fracture tests were carried out, and the results have been discussed utilizing both fracture and micromechanical concepts. This study shows that the fiber length and volume have optimal values; therefore, using fibers without considering the optimal values has negative effects on the strain-hardening behavior of cementitious composites.

• Proceedings of the Korean Society for Rock Mechanics Conference
• /
• 1999.03a
• /
• pp.25-31
• /
• 1999

암석 내에 포함된 불연속면으로 인하여 암석은 압축하중 하에서 복잡한 거동을 한다. 이러한 복잡한 거동은 변형률강화(strain hardening), 변형률연화(strain softening), 부피팽창(dilatancy)등의 비선형 거동을 포함하는데, 이들은 균열의 성장, 상호작용(interaction), 연합(coalescence) 등을 통하여 발생한다(Brace et al., 1972; Kranz, 1983). 이와 같은 암석의 비선형적 거동을 설명하기 위하여 여러 형태의 균열모형이 개발된 바 있다(Costin, 1985; Nemat-Nasser ＆ Horii, 1982; Wang & Kemeny, 1993; Jeon, 1998). (중략)

• Smart Structures and Systems
• /
• v.4 no.4
• /
• pp.439-448
• /
• 2008

Optical fiber sensors are by now broadly accepted as an innovative and reliable device for structural health monitoring, to be used either embedded into or bonded on structures. The accuracy of the strain measurement achievable by optical fiber sensors is critically dependent on the characteristics of the bonding of the various interface layers involved in the sensor bonding/embedding (structure material and gluing agent, fiber coating and gluing agent, fiber coating and fiber core). In fact, the signal of the bonded/embedded optical fiber sensor must correspond to the strain experienced by the monitored structure, but the quality of each involved interface can affect the strain transfer. This paper faces the characterization, carried on by both mechanical tests and morphological analysis, of the strain transfer function resulting with epoxidic and vinylester gluing agent on polyimide and acrylate coated optical fibers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.573-576
• /
• 2003

HTS superconducting tapes are now commercially available for practical applications such as magnets and cables. Since superconductors in such applications are subjected to high mechanical loads that can significantly degrade the superconducting properties, mechanical properties and the strain tolerance known as the strain effect on superconducting properties are needed to be estimated for developing superconducting devices. Influences of loading mode on the Ic degradation and the interaction on strain effect were discussed in this study.

• Interaction and multiscale mechanics
• /
• v.6 no.2
• /
• pp.107-125
• /
• 2013

A strain smoothing meshfree formulation with stabilized conforming nodal integration is presented for modeling the consolidation process in saturated porous media. In the present method, nodal strain smoothing is consistently introduced into the meshfree approximation of strain and pore pressure gradient variables associated with the saturated porous media. Meanwhile, in order to achieve a consistent numerical implementation, a smoothing approximation of the meshfree shape function within a nodal representative domain is also proposed in the stiffness construction. The resulting discrete system of equations is all expressed in smoothed nodal measures that are very efficient for numerical evaluation. Subsequently the space-time fully discrete equations are further established by the generalized trapezoidal rule for time integration. The effectiveness of the proposed meshfree consolidation analysis method is systematically illustrated by several benchmark problems.

• Structural Engineering and Mechanics
• /
• v.38 no.2
• /
• pp.231-247
• /
• 2011

This study introduces a new load increment method for the ductile reinforced concrete (RC) frame structures by including strain-hardening effects. The proposed method is a nonlinear static analysis technique employed for RC frame structures subjected to constant gravity loads and monotonically increasing lateral loads. The material nonlinearity in RC structural elements is considered by adopting plastic hinge concept which is extended by including the strain hardening as well as interaction between bending moment and axial force. Geometric non-linearity, known as second order effect, is implemented to the method as well.

• Coupled systems mechanics
• /
• v.3 no.3
• /
• pp.319-327
• /
• 2014

This study investigated the collision of ships withfloating pier structures. The nature of the collision phenomenon is complex, and the understanding of it has developed through the modelling of offshore structures. ABAQUS software was used to investigate the collision phenomenon. The interaction between the ship and structural system was modelled, and the stress distribution both at thetime of collision and afterwardswasobserved and modelled. The strain energy absorption by different structural partswas calculated and comparisonswere made.

• Korean Journal of Social Welfare
• /
• v.57 no.3
• /
• pp.133-164
• /
• 2005

This study examined the effects of children's perceived stress of economic strain, resulting family conflict, and stress coping strategies on their adjustment. Dimensions of children's adjustment studied in this research were problem behaviors (aggression, delinquency, withdrawal and anxiety depression) and school adjustment. Interaction effects between children's stress variables and coping strategies on the adjustment were also explored. 1,115 fifth to eighth graders from Chungbuk regions participated in self-administered structured questionnaires. Data were processed with SPSS PC 10.0 statistical package. Results were: First, the level of children's problem behaviors and school adjustment indicated differences according to their academic achievement, gender, and their age. Middle schoolers with rather low grade average reported higher level of aggression, delinquency, withdrawal and that of depression/anxiety. Boys tended to be more prone to external problems while girls to internal problems. Second, stresses originated from children's perceived economic strain and family conflicts showed consistent meaningful explanatory power on adjustment. Boys' adjustment was influenced by stress from economic strain and family conflict while girls by family conflict and academic achievements. The support seeking coping strategy among others was the most popularly employed coping strategy of children followed by aggressive coping strategy. In boys' cases, interaction effects of stress and coping strategies were significant in all of the adjustment variables, the more frequent the use of support seeking coping strategies, the lower the problem behavior, while interaction effect of family conflict stress and support seeking coping strategies played the opposite significant role in girls' cases. Further research efforts are required. Research results suggest; when developing a program facilitating children's adjustment, training on stress coping strategies should be considered as a potent new arena of interest.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.04a
• /
• pp.443-450
• /
• 2000

In this study a numerical method for soil-pile interaction analysis buried in multi-layered half planes is presented in frequency domain using FE-BE coupling. The total soil-pile interaction system is divided into two parts so called far field and near field beam elements are used for modeling a pile and coupled with plain strain elements for soil modeling. Boundary element formulation using the multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered half-planes are performed and compared with experiment results. Through this developed method the dynamic response analysis of a pile buried in multi-layered half planes can be calculated effectively in frequency domain.

• Structural Engineering and Mechanics
• /
• v.22 no.3
• /
• pp.351-370
• /
• 2006

In this study, the earthquake damage response of the concrete arch dams was investigated including dam-reservoir interaction. A continuum damage model which is a second-order tensor and includes the strain softening behavior was selected for the concrete material. Fluid-structure interaction problem was modeled by Lagrangian approach. Sommerfeld radiation condition was applied to the truncated boundary of reservoir. The improved form of the HHT-${\alpha}$ time integration algorithm was used in the solution of the equations of motion. The arch dam Type 5 was selected for numerical application. For the dynamic input, acceleration records of the 10 December 1967 Koyna earthquake were chosen. These records were scaled with earthquake acceleration scale factor (EASF) and then used in the analyses. Solutions were obtained for empty and full reservoir cases. The effects of EASF and damping ratio on the response of the dam were studied.