• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.235-244
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• 2016

This study was conducted to verify seismic performance of special moment frame's joints at roof-level with high-strength concrete and SD600 bars. K-RC-H was designed according to the seismic code and K-HPFRC-H had 150% of the original hoop spacing and 1.0% steel fiber volume fraction compared with K-RC-H. Both specimens had remarkable seismic performance without noticeable decrease in moment, but with very good energy dissipation before rebar failure. The U-bars in the joint sufficiently constrained rebar's action that pushed the cover upward. SD600 bars with $1.25l_{dt}$ had minimum slip in the joint. It was considered that the steel fiber contributed to improvement of the bending moment and joint shear distortion, and the result showed that it would be possible to increase the hoop spacing to 150% of the regular spacing.

• Journal of Oral Medicine and Pain
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• v.44 no.2
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• pp.59-64
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• 2019

Purpose: The aim of this study was to analyse and evaluate the morphology of the articular eminence of temporomandibular joint in young Korean adults using cone-beam computed tomography (CBCT). Methods: One hundred seventy-one subjects (59 males, 112 females) in the 20s were examined using CBCT. Width and height of articular eminence, top-roof line angle, best-fit line angle, joint space were measured. For the group comparisons, independent t-test was used with the level of significance established at $p{\leq}0.05$. Results: In asymptomatic young Korean adults, average eminence width was $9.49{\pm}1.62mm$ in males and $9.33{\pm}1.36mm$ in females. Average eminence height was $7.23{\pm}1.81mm$ in males and $6.82{\pm}1.31mm$ in females. Average eminence inclination of measured by top-roof line angle was $37.09^{\circ}{\pm}7.74^{\circ}$ in males and $36.12^{\circ}{\pm}5.65^{\circ}$ in females. Average eminence inclination measured by best-fit line angle was $50.79^{\circ}{\pm}11.49^{\circ}$ in males and $48.43^{\circ}{\pm}9.05^{\circ}$ in females. Average joint space was $3.03{\pm}0.67mm$ in males and $2.63{\pm}0.68mm$ in females. Conclusions: Increasing age did not affect the morphology of the articular eminence in asymptomatic young Korean adults. Males had slightly larger eminence width, height, top-roof line angle, best-fit line angle and joint space, but no statistical significance (p>0.05) was observed only in the joint space (p=0.001). There was no side-to-side difference in morphology (p>0.05).

• Earthquakes and Structures
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• v.11 no.5
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• pp.905-924
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• 2016

Several two-dimensional analytical beam column joint models with varying complexities have been proposed in quantifying joint flexibility during seismic vulnerability assessment of non-ductile reinforced concrete (RC) frames. Notable models are the single component rotational spring element and the super element joint model that can effectively capture the governing inelastic mechanisms under severe ground motions. Even though both models have been extensively calibrated and verified using quasi-static test of joint sub-assemblages, a comparative study of the inelastic seismic responses under nonlinear time history analysis (NTHA) of RC frames has not been thoroughly evaluated. This study employs three hypothetical case study RC frames subjected to increasing ground motion intensities to study their inherent variations. Results indicate that the super element joint model overestimates the transient drift ratio at the first story and becomes highly un-conservative by under-predicting the drift ratios at the roof level when compared to the single-component model and the conventional rigid joint assumption. In addition, between these story levels, a decline in the drift ratios is observed as the story level increased. However, from this limited study, there is no consistent evidence to suggest that care should be taken in selecting either a single or multi component joint model for seismic risk assessment of buildings when a global demand measure such as maximum inter-storey drift is employed in the seismic assessment framework.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1391-1404
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• 2015

A radially retractable roof structure based on the concept of the hybrid grid shell is proposed in this paper. The single-layer steel trusses of the radially foldable bar structure are diagonally stiffened by cables, which leads to a single-layer lattice shell with triangular mesh. Then comparison between the static behavior between the retractable hybrid grid shell and the corresponding foldable bar shell with quadrangular mesh is discussed. Moreover, the effects of different structural parameters, such as the rise-to-span ratio, the bar cross section area and the pre-stress of the cables, on the structural behaviors are investigated. The results show that prestressed cables can strengthen the foldable bar shell with quadrangular mesh. Higher structural stiffness is anticipated by introducing cables into the hybrid system. When the rise-span ratio is equal to 0.2, where the joint displacement reaches the minimal value, the structure shape of the hyrbid grid shell approaches the reasonable arch axis. The increase of the section of steel bars contributes a lot to the integrity stiffness of the structure. Increasing cable sections would enhance the structure stiffness, but it contributes little to axial forces in structural members. And the level of cable prestress has slight influence on the joint displacements and member forces.

• Steel and Composite Structures
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• v.4 no.2
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• pp.77-94
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• 2004

Steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current specifications for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 10% of the beam's plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present paper is to describe some experimental and numerical work carried out at the University of Coimbra to try to extend the philosophy of the component method to deal with the combined action bending moment and axial force.

• Journal of the Korea Institute of Building Construction
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• v.11 no.1
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• pp.51-59
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• 2011

With the increased demand for membrane structures in recent years, there have been many studies of their mechanical properties, to the extent that such structures have become recognized as independent structures with a level of safety and durability comparable to those of other general structures. But in reality, the study for the maintenance of membrane structures has not been as active. In particularly, the study of watertightness from the perspective of maintenance has been very limited. Accordingly, a study on securing watertightness performance and the guidelines for maintenance is necessary. In this study, through a case study of water leakage accidents in membrane structures overseas, causes of leakage were selected from the membrane material itself, joint parts and open door of roof part in membrane structure. The water leakage and deterioration elements were analyzed from those leakage causes. The degree of importance of the water leakage and deterioration index was also designated using the AHP (Analytic Hierarchy Process) method. As a result, the basic technical index was suggested for the maintenance of the roofs of large-span membrane structures to prevent water leakage. This index will be used to make a guideline for the long-term maintenance of the roofs of large-span membrane structures.