• Computers and Concrete
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• v.22 no.6
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• pp.527-538
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• 2018

Buckling of longitudinal bars is a brittle failure mechanism, often recorded in reinforced concrete (RC) structures after an earthquake. Studies in the literature highlights that it often occurs when steel is in the post elastic range, by inducing a modification of the engineered stress-strain law of steel in compression. A proper evaluation of this effect is of fundamental importance for correctly evaluating capacity and ductility of structures. Significant errors can be obtained in terms of ultimate bending moment and curvature ductility of an RC section if these effects are not accounted, as well as incorrect evaluations are achieved by non-linear static analyses. This paper presents a numerical investigation aiming to evaluate the engineered stress-strain law of reinforcing steel in compression, including second order effects. Non-linear FE analyses are performed under the assumption of local buckling. A role of key parameters is evaluated, making difference between steel with strain hardening or with perfectly plastic behaviour. Comparisons with experimental data available in the literature confirm the accuracy of the achieved results and make it possible to formulate recommendations for design purposes. Finally, comparisons are made with analytical formulations available in the literature and based on obtained results, a modification of the stress-strain law model of Dhakal and Maekawa (2002) is proposed for fitting the numerical predictions.

• PNF and Movement
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• v.17 no.2
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• pp.253-261
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• 2019

Purpose: The purpose of this study was to identify the causal relationship between workplace stress and working posture and the development of work-related neck pain in office workers. Methods: The study participants included 62 office workers who had not experienced neck pain in the previous 12 months. A battery of measures to evaluate potential workplace risk factors in an office setting were conducted at baseline, and the 12-month incidence of work-related neck pain was reported via monthly questionnaires. Survival analysis was used to evaluate the longitudinal relationship between the workplace risk factors and the development of work-related neck pain. Results: The incidence of work-related neck pain was 1.91 (95% CI: 1.06-3.45) per 100 person months. The incidence of neck pain was predicted to be less likely to happen when workers had a more upright thorax posture during computer work (hazard ratio, 0.94; 95% CI: 0.89-0.99). However, stress may deteriorate the preventative effects of other risk factors on neck pain and showed a positive relationship with episodes of neck pain (hazard ratio, 1.37; 95% CI: 1.03-1.84). Conclusion: Understanding the psychophysiological effects of neck pain may explain the development of neck pain in office workers. Our interest in prevention plans and treatments should therefore involve a multifactorial pathology of neck pain in the workplace.

• Composites Research
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• v.36 no.1
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• pp.42-47
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• 2023

In this paper, we present a fatigue life prediction methodology using multiple S-N curves according to the different stress states of laminated composites. The stress states of the plies of the laminated composites are classified into five modes: longitudinal tension or compression and transverse tension or compression, and shear according to the maximum stress criterion and Puck's criterion with a scaling factor K. This methodology has advantages in computational cost, and it can also consider microstructural characteristics of the composites by applying different S-N curves. The S-N curves for the fatigue analysis are obtained by experimental fatigue test. The proposed methodol is implemented into commercial software, ABAQUS user material subroutine and therefore, the fatigue analysis is conducted using the structural analysis results. The finite element (FE) simulation results are presented for unidirectional composites with and without open-hole. The FE simulation results show that the stress condition is different depending on the fiber orientation of the unidirectional composite, so the fatigue life is calculated with different S-N curves.

• Physical Therapy Rehabilitation Science
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• v.12 no.1
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• pp.72-79
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• 2023

Objective: Despite known associations between negative body image and health declines in chronic pain patients, few studies have examined longitudinal associations between psychological stress and perceived hand deformities. This study examined whether psychological distress was associated with hand deformities 4 years later and if rural and urban adults differed in the association. Design: A community-based cohort study. Methods: Community dwelling adults (mean age=51.97, 52.3% women) in a rural (n=2968) and urban area (n=2784) provided demographic data at baseline and, in the 4-year follow-up, responded to questionnaires about psychological distress. Perceived hand deformities were assessed at the 8-year follow-up. Linear regression was conducted to examine the effects of psychological distress on hand deformities and moderation by residential areas. Results: The perceived hand deformities were more likely among those with severe psychological stress, hand osteoarthritis, or any chronic disease condition (p<0.01) but less likely among those with younger age, higher education, or income (p<0.01). The regression results showed that psychological distress predicted more perceived hand deformities 4 years later even after adjusting for demographic and health covariates (p<0.01). The residential areas did not significantly moderate the association between distress and hand deformities. Conclusions: This study suggected that psychological distress may trigger later perception of hand deformities in both urband and rural adults. The findings indicate that stress management interventions that are customizable to regional contexts may be effective at preventing negative body image related health problems of community-dewelling adults.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.119-123
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• 1993

Axial load-strain relationships of confined concrete with spiral reinforcement were investigated. The main variables were compressive strength of concrete, spacing of hoop reinforcement, and specimen height of plain concrete. The program included tests of eleven confined specimens, and twelve plain specimens, but for all specimens no longitudinal reinforcement was provided. Load-strain curves of confined and plain concrete specimens are reporeted.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1161-1166
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• 2001

Fatigue behavior of reinforced concrete(RC) elements has been experimentally and analytical investigated. Fatigue behavior influenced by longitudinal reinforcement ratio, strength of concrete and load ratio $P_{u}$/ $P_{o}$. The purpose of these studies is to propose an empirical formula for fatigue behavior on basis of experimental results. Also an analytical method to predict the crack propagation of RC beams has been developed based on the relationships between bond stress and slip.

• Steel and Composite Structures
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• v.17 no.4
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• pp.535-548
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• 2014

In this paper, the exact closed-form solutions for torsional analysis of heterogeneous magnetostrictive circular cylinder are derived. The cylinder is subjected to the action of a magnetic field produced by a constant longitudinal current density. It is also acted upon by a particular kind of shearing stress at its upper base. The rigidity of the cylinder is graded through its axial direction from one material at the lower base to another material at the upper base. The distributions of circumferential displacement and shear stresses are presented through the radial and axial directions of the cylinder. The influence of the magnetostrictive parameter is discussed. The effects of additional parameters are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.499-503
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• 2001

Fatigue behavior of reinforced concrete (RC) elements has been experimentally and analytical investigated. Fatigue behavior influenced by longitudinal reinforcement ratio, strength of concrete and load ratio P／sub u／／P／sub o／. The purpose of these studies is to propose an empirical formula for fatigue behavior on basis of experimental results. Also an analytical method to predict the crack propagation of RC beams has been developed based on the relationships between bond stress and slip.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.379-384
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• 2003

In this paper, dynamic behavior of steel fiber reinforced concrete(SFRC) by experimental method is discussed. Because of its improved ability to dissipate energy, impact resistance and fatigue behavior, SFRC has a better dynamic behavior than that of plain concrete. Dynamic behavior is influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and the stress level. Impact resistance and damping in the SFRC has been evaluated from dynamic experimental test data at various levels of cracked states in the elements

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.862-867
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• 2004

In this paper, the crack properties of steel fiber reinforced concrete (SFHC) beams by experimental method are discussed. The major role played by the steel fiber occurs in the post-cracking zone, in which the fibers bridge across the cracked matrix. Because of its improved ability to break crack, SFRC has better crack properties than that of reinforced concrete (RC). Crack properties are influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete and the stress level. Crack width and crack number in the SFRC beams havebeen evaluated from experimental test data at various levels in the beams.