• International Journal of Highway Engineering
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• v.13 no.2
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• pp.167-174
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• 2011

This research was conducted to propose the design methodologies of post-tensioned concrete pavements (PTCPs) for specialized section pavements. The specialized sections considered in this study included bus stop sections in urban bus-only lanes and culvert existing highway sections that often showed severe failures. The PTCP designs of those specialized sections were performed based on both the stresses and the fatigue failures, and more conservative design results were selected. In the stress based design, the maximum tensile stress under extreme load conditions was obtained using finite element analyses first. Then, the number of tendons and the tendon spacing were determined so that the tensile stress was less than the allowable flexural strength. The AASHTO fatigue failure equations were used in the fatigue failure based design. From this study, the design methodologies of PTCP for bus stop sections in bus-only lanes and culvert existing highway sections were successfully suggested.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.127-137
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• 1999

In the previous study in relation to the current study, a test program for the verification of the proposed design equation was carried with fourteen prestressed concrete beams with unbonded tendons. Experimental results were compared with the computed results by the proposed design equations. The previous design equations are ACI code, AASHTO LRFD code, the analysis equation with the strain compatibility, Harajli/Kanj' design equation, Chakrabarti' design equation. As a result of comparative studies, it turned out that the proposed design equation could predict the ultimate tendon stress with comparatively high accuracy.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.441-455
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• 1997

The need for rehabilitation of the existing bridges is a growing concern in many countries and has been emphasized in various research reports and publications. Many bridges constructed between 1960s and 1970s in Korea were designed for relatively light traffic volumes, speeds and the weight, thus they are inadequate for the present traffic conditions. This together with some design deficiencies, has resulted in deficiencies of various degrees of many bridges. One strengthening method which has significant advantages is the application of external post-tensioning tendons. This paper presents an example of three span continuous composite bridge strenghtened by application of external post-tensioning.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.169-178
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• 2010

In this study, the optimal strengthening by micro genetic algorithm(${\mu}$-GA) method is proposed for improvement of load-carrying capacity of RC hollow slab bridges using external prestressing. The Qeen-post type and King-post type are considered for the optimal strengthening. The type for optimal strengthening, deviator, areas of tendons and the number of anchor are calculated by ${\mu}$-GA. The objective function is constituted with dimensionless cost of tendon and steel for optimal strengthening. The constraints are formulated by design specification for bridges and anchors. The validity of this study is presented by analysis of the results after the optimal strengthening of the RC hollow slab bridge.

• Journal of Oral Medicine and Pain
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• v.30 no.1
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• pp.79-85
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• 2005

This study was designed to confirm the association between the pain of Tension-Type Headache(TTH) patients and their Oral Parafunction(OPF). Patients with TTH(n=58) visited the Department of Oral Medicine, Kyung Hee University Dental Hospital during two months were recruited to this study. 20 patients with OPF(bruxism, clenching, bruxism & clenching) are the experimental group and 38 patients without OPF are the control group. Both groups were asked to answer the questionnaire based on the diagnostic criteria of TTH(IHS). Then it was analyzed statistically. This study was designed to confirm the association between the pain of Tension-Type Headache(TTH) patients and their Oral Parafunction(OPF). Patients with TTH(n=58) visited the Department of Oral Medicine, Kyung Hee University Dental Hospital during two months were recruited to this study. 20 patients with OPF(bruxism, clenching, bruxism & clenching) are the experimental group and 38 patients without OPF are the control group. Both groups were asked to answer the questionnaire based on the diagnostic criteria of TTH(IHS). Then it was analyzed statistically. 1. There was no difference in sex(p=0.91) and age(p=0.73) between two groups. 2. In the experimental group, dull pain was presented more frequently than in the control group. But, there was no difference between two groups(p=0.69). 3. In the experimental group, severe pain was presented more frequently than in the control group. But, there was no difference between two groups(p=0.40). 4. In the experimental group, pain shown bilaterally was presented more frequently than in the control group. But, there was no difference between two groups(p=0.52). 5. In the experimental group, pain was more increased by physical activities than in the control group. But, there was no difference between both groups(p=0.74). The pain of TTH patients with OPF was presented to be non-dull pain frequently and more bilaterally and severely, also increased more by physical activities than the pain of TTH patients without OPF. But, there was no significant difference between two groups. Therefore, it is considered that the pain of TTH is not influenced by OPF.

• Korean Journal of Ichthyology
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• v.12 no.1
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• pp.38-45
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• 2000

Depending on the fish species the vascular tone is distinctively regulated by numerous vasoactive substances. In most fish species the regulatory role of autonomic neurotransmitters and other vasoactive substances are not well defined. This research was designed to delineate the regulatory role of various endogenous autonomic neurotransmitters known to be important in mammalian vascular systems on isolated Israeli carp ventral aorta. Acetylcholine(ACh) contracted the aorta regardless of the pre-existing level of vascular tone, and the contraction was almost completely abolished by a cholinergic-muscarinic antagonist atropine. Endogenous, multiple receptor ($\alpha$ and $\beta$)-acting adrenergic agonist epinephrine (Epi) relaxed the vessel in the presence and absence of the pre-existing tones. Another endogenous multiple receptoracting agonist norepinephrine (NE) weakly contracted the aorta in non-preconstrcted state, but the response was reversed to relaxation when preconstricted. Isoproterenol, ${\alpha}\;{\beta}$ adrenergic receptor agonist, was a potent vasodilator whereas an ${\alpha}_1$ agonist phenyephrine was a contractor. The ${\alpha}_2$ adrenergic receptor agonist clonidine has not any significant effect in altering the vascular tone. The vasorelaxing action of Epi, NE and isoproterenol was significantly attenuated by $\beta$ receptor antagonist propranolol. These results imply that ACh may primarily play a contractor role via muscarinic receptor activation while adrenergic agonists, Epi and NE, are relaxants through activation of $\beta$ adrenergic receptors in vivo.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.513-521
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• 2009

Recently, the externally prestressed unbonded concrete structures are increasingly being built. The mechanical behavior of prestressed concrete beams with external unbonded tendon is different from that of normal bonded PSC beams in that the slip of tendons at deviators and the change of tendon eccentricity occurs as external loads are applied in external unbonded PSC beams. The purpose of the present paper is therefore to evaluate the flexural behavior by performing static flexural test according to tendon area and tendon force. From experimental results, before flexural cracking, there was no difference between external members and bonded members. However, after cracking, yielding load of reinforcement, ultimate load, and the tendon stress of external members was lower than that of bonded members. For the relationship of load-tendon stress, the increasing of tendon strain was inversely proportional to the initial tendon force. However, even if the initial tendon force was large, the tendon strain with small effective stress was smaller than that with large effective stress. The concrete compressive strain was proportional to the effective stress of external tendon. From the comparison between test results and codes, the ACI-318 could not consider the effect of tendon force or effective stress, and especially the results of ACI-318 were very small, so it was very conservative. And the AASHTO 1994 could be influenced on the tendon area, initial force and effective stress, but as it was made on the basis of internal unbonded tendon, its results were much larger than the test results. For this reason, the new correct predict equation of external tendon stress will be needed.

• Korean Journal of Social Welfare
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• v.64 no.1
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• pp.273-297
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• 2012

Using grounded theory method, this study analyzed the in-depth interviews with 11 parents of institutionalized children in order to find out how the experience of the parents on the process of the children's family reunification. According to the results, it was 'leaving one's child' that composed causal conditions, and also it was 'sentenced life' and 'adapting to a life without child' that composed existing conditions. Thus, the contextual condition was found out as 'a belief of family' and 'a belief of child caring' and the mediation conditions were 'power to recover' and 'not being as one's intentions'. Also, reaction/interaction strategies turned out as 'preparing a basis of child-care', 'playing a parent', 'standing against being adapted' and 'adjusting as their children back to family'. Finally, the analysis showed 'burdens on caring', 'wanting to leave one' child again', 'having stronger family membership' and 'being hopeful in a future' as results. The specific levels of the process were found out as following 4 steps, as time goes by. 1)Fostering children at institutions: become harsh parents(or a harsh parent), 2)After fostering: rebuild collapsed family in order to take the children back, 3)Family reunification: become aboveboard to oneself, family and the world, 4)After family reunification: try to keep the family taking precautions against resending. While taking their children back, the parents turned out to experience long, unremitting tension. Reflecting results of the analysis above, and in order to promote sending institutionalized children back to their families this article suggests practical alternatives for parents who left their children in institutions.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.99-110
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• 2017

This paper presents the study of the bending behavior of mooring chain links for keeping the position of the offshore floating structures. In general, chain links have been thought as the axial members due to the fundamental boundary condition. But, the flexural stiffness can be induced to the contact surface between chain links when friction occurs at the surface of the chain links due to high tensile force. Especially, the mooring chains for offshore floating platforms are highly tensioned. If the floater suffers rotational motion and the mooring chain links are highly tensioned, the rotation between contact links, induced by the floater rotation, generates the bending moment and relevant stresses due to the unexpected bending stiffness. In 2005, the mooring chain links for the Girassol Buoy Platform were failed after just 5 months after facility installation, and the accident investigation research concluded the chain failure was mainly caused by the fatigue due to the unexpected bending stress fluctuation. This study investigates the pattern of the induced bending stiffness and stresses of the highly tensioned chain links by nonlinear finite element analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.427-435
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• 2020

Modular structures are relatively lightweight compared to reinforced-concrete or steel structures. However, it is difficult to achieve structural integrity between the columns of unit modules in a modular structure, which causes undesirable effects on the lateral force resistance capacity against wind and earthquake loads. This is more prominent in modular structures whose overall heights are greater. Hence, a post-tensioned modular structural system is proposed herein to improve the lateral force resistance capacity of a typical modular structure. A post-tensioned column-base connection, which is the main component of the proposed modular structural system, is configured with shapes and characteristics that allow inducing self-centering behaviors. Finite element analysis was then performed to investigate the hysteretic behaviors of the post-tensioned column-base connection. The analysis results show that the hysteretic behaviors are significantly affected by the initial tension forces and beam-column connection details at the base.