• Steel and Composite Structures
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• v.29 no.5
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• pp.603-622
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• 2018

Precast concrete structures are erected from individual prefabricated components, which are assembled on-site using different types of connections. In the present design of these structures, beam-to-column connections are assumed pin jointed. Bolted billet beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is currently limited information concerning their detailed structural behaviour under vertical loadings. The experimental work has involved the determination of moment-relative rotation relationships for semi-rigid precast concrete connections in full-scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and bolt arrangements conformed to successful commercial practice. Proprietary hollow core floor slabs were tied to the beams by 2T25 tensile reinforcing bars, which also provide the in-plane continuity across the connections. The contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. The flexural strength of the connections in the double-sided tests was at least 0.93 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.94 to 1.94 times the flexural stiffness of the attached beam. In general, the double-sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided bolted billet connection test results are presented in this paper. The behaviour of single sided bolted billet connection test results is the subject of another paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.2
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• pp.71-82
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• 2022

This paper presents the effect on the inelastic behavior and structural performance of concrete and filled steel pipe through a numerical method for reliable judgment under various load conditions of the CJS composite structural system. Variable values optimized for the CJS synthetic structural system and the effects of multiple variables used for finite element analysis to present analytical modeling were compared and analyzed with experimental results. The Winfrith concrete model was used as a concrete material model that describes the confinement effect well, and the concrete structure was modeled with solid elements. Through geometric analysis of shell and solid elements, rectangular steel pipe columns and steel elements were modeled as shell elements. In addition, the slip behavior of the joint between the concrete column and the rectangular steel pipe was described using the Surface-to-Surface function. After finite element analysis modeling, simulation was performed for cyclic loading after assuming that the lower part of the foundation was a pin in the same way as in the experiment. The analysis model was verified by comparing the calculated analysis results with the experimental results, focusing on initial stiffness, maximum strength, and energy dissipation capability.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.30-39
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• 2016

The evaluation of the lateral load performance for larch glulam portal frames was carried out using glass fiber reinforced plastic (GFRP) as connector in two different systems: the GFRP-reinforced laminated plates combined with veneer, and GFRP rod joints glued with epoxy resins to replace usual metal connectors for the structural glulam rahmen joints. As a result the yield strength, ultimate strength, initial stiffness of glulams of GFRP rod joints glued with epoxy resin decreased to 49%, 52% and 61% compared to those of the conventional metal connector. This connector will be a stress device where the bonding strength between the GFRP rod and glued laminated timber is important. Thus, there will be a high possibility that a problem may occur when it is applied to the field. On the other hand, the GFRP-reinforced laminated plates and wood (Eucalyptus marginata) pin were measured all within 3% for all measurements of the yield strength, ultimate strength, initial strength and ductility factor, regardless of high cross sectional loss on the glued laminated timber slit joint. In addition, the variation of stiffness on the cycle was 35%, which was the lowest, confirming that it was almost the same performance as the specimen prepared with the metal connector.

• Journal of Korean Foot and Ankle Society
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• v.10 no.2
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• pp.213-217
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• 2006

Purpose: To evaluate the clinical and radiological results of tibio-talo-calcaneal arthrodesis using ipsilateral distal fibula buttress which had advantages of extended operative field and release of contracted soft tissue. Materials and Methods: We retrospectively reviewed 4 postraumatic compartment syndrome, 2 residual poliomyelitis, 1 posttraumatic osteoarthritis with subtalar joint infection and 1 posttarumatic sciatic nerve palsy patients who underwent a tibio-talo-calcaneal arthrodesis from April, 1996 to March, 2002. Each of the cases was notable for a severe rigid equinovarus, persistent pus drainage of calcaneal area and paralytic foot. The mean duration of follow up was 18 months (range, $13{\sim}42$ months). The pain, function and alignment were evaluated by the modified ankle hindfoot scale of the American Orthopaedic Foot and Ankle Society (AOFAS) and patients satisfaction clinically. The radiological union were evaluated by plain AP and lateral radiographs. Results: The AOFAS score improved from 58 points (range, $47{\sim}78$) preoperatively to 82 (range, $60{\sim}89$) postoperatively. Patents satisfaction checked at 12 months after operation had favorable results (excellent and good 80%). Union rate was 100% radiographically and the mean duration of union was 12.5 weeks (range $8{\sim}22$ weeks). There was 2 cases of superficial pin tract infection and one protrusion of screw. Conclusion: Tibio-talo-calcaneal arthrodesis using ipsilateral distal fibula buttress was good modality of arthrodesis which provides wide operative field and release of contracted soft tissue in some cases of contracted foot.

• Journal of the Korean Wood Science and Technology
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• v.43 no.1
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• pp.60-67
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• 2015

In order to evaluate the bond performance of domestic larch glulam and the glass fiber reinforced plastic (GFRP) rod, the specimen with the GFRP rod bonded-in domestic larch glulam for pull-out test was produced. The test was carried out using various specimens with different gluing depth, width of glue-line and type of adhesive. The cantilever type rahmen structure specimen with bonded-in GFRP rods was produced based on the result of pull-out test, and its moment resistance performance was compared and examined with the moment resistance performance of slotted-in steel plate specimen. As a result of the pull-out test, the most excellent bond performance was found when the insertion depth of GFRP rods was 5 times larger than the diameter of GFRP rods. When the glue-line thickness was 1 mm, the bond performance improved by 17%~29% in comparison to the bond performance in the case of the glue-line thickness of 2 mm. Also, the bonded strength of the specimen used with poly-urethane adhesive was 2.9~4.0 times greater than the bonded strength of specimen used with resorcinol adhesive. The cantilever type rahmen structure specimen with bonded-in GFRP rods showed the moment resistance performance 0.82 times lower in comparison to the slotted-in steel plate specimen used with the drift pin, but the initial stiffness was similar as 0.93 times.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.4
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• pp.382-388
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• 2019

Increased anterior teeth mastication following posterior teeth loss leads to greater anterior occlusal force. It may cause greater attrition of anterior teeth, traumatic force occlusion (TFO), also often followed by antagonist extrusion and occlusal disharmony. This clinical report describes the treatment for a 67-year-old female patient diagnosed with loss of both maxillary and left mandibular posterior teeth, severe attrition of maxillary and mandibular anterior teeth and extrusion of multiple teeth. A diagnostic cast was mounted on articular in centric relation (CR) position to evaluate vertical dimension (VD) and interspace. To provide adequate space for the prosthetic reconstructions, VD was increased by 3 mm on the anterior pin. And then diagnostic wax-up was completed upon that VD. Wax-up was converted to provisional restorations and verified in the patient's mouth and the final restorations were delivered. Clinical follow up examination held 3 months after temporary restoration owing to changes in vertical dimension revealed proper function in mastication without evidence of temporo-mandibular joint (TMJ) disorders. This clinical report presents successfully restoring severe attrition case with increasing vertical dimension resulting in satisfaction in esthetics and function.

• Composites Research
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• v.22 no.5
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• pp.15-23
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• 2009

The lubricant tribological characteristics of $Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) fabricated by squeeze casting method was investigated using a pin-on-disk wear tester. The wear tests of the MMCs were performed according to fiber/particle hybrid ratio in the planar-random (PR) and normal (N) orientations sliding against a counter steel disk at a fixed speed and $25\;kg_f$ loading under different sliding distances and temperatures. The test results showed that the wear behavior of MMCs varied with fiber orientation and hybrid ratio. At room temperature, the lubricant wear behavior of F20P0 unhybrid PR-MMCs was superior to that of N-MMCs while the hybrid composites exhibited the reverse lubricant wear behavior. It was also revealed that the wear resistance of PR-MMCs was superior to that of the N-MMCs due to the joint action of reinforcements and lubricant film between the friction surfaces at an elevated temperature of $100^{\circ}C$ for both fiber only and hybrid cases. In case of $150^{\circ}C$, although the trend of weight loss was similar to that of others, the wear resistance of PR-MMCs was better than that of N-MMCs for hybrid MMCs.

• Journal of Korean Foot and Ankle Society
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• v.1 no.2
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• pp.102-111
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• 1997

The tibial Pilon fracture, which is defined as a comminuted intraarticular fracture of the distal tibia, is difficult to manage because high axial compression and rotational forces to the ankle joint result in impaction, severe comminution, metaphyseal disruption and soft tissue damage. There are variable methods of treatment such as manipulation and cast, calcaneal traction and cast, external fixation, pin and plaster, limited open reduction and external fixation, and open reduction and rigid internal fixation. Though most of authors reported better result after a surgical treatment. than that of conservative treatment, many complications such as posttraumatic arthritis and soft tissue problem still remain troublesome. We have reviewed 19 cases of the tibial Pilon fractures in 18 patients which were treated with limited open reduction and internal fixation from September 1993 to May 1996. The results were as follows: 1. The fractures were classified into five types according to the system of Ovadia and Beals, and the most frequent type was type 3 (53%). The most common cause of injury was traffic accident (47%). 2. All of the cases of type 1 and 2, in which the injury of the ankle joint was less severe, revealed good or excellent clinical results. But in type 4 and 5, because the injury is much severe and accurate reduction is difficult, the clinical results were unsatisfaetory. 3. The most frequent complication was posttraumatic osteoarthritis, and which developed in second frequent complication, was developed m the three cases of type 3 in which the radiographic results were less than fair, but there were no correlation with the clinical results. 4. We could markedly reduce the complications related to the soft tissue problem of Pilon fracture by treatment with limited open reduction and internal fixation, and consider that this is a good method of treatment of Pilon fracture when the injury is less severe and accurate reduction is possible.

• The Journal of the Korean bone and joint tumor society
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• v.11 no.2
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• pp.134-140
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• 2005

Purpose: We evaluated the effectiveness of temporary using the extendible external fixator (EF) for lengthening of soft tissue that contracture caused by tumor prosthesis removal in the treatment of complications after limb salvage surgery like deep infection and loosening. Materials and Methods: Five patients six cases were included who underwent extendible EF (Dyna-extor(r)). EF was applied after insertion of half pin to the proximal and distal bone of defect area. EF lengthening started at third day of post-operation, above 2-3 mm per day in the range of no neurological sign. Results: The treatment area was three in femur and two in tibia. Mean age when the time of EF apply was 22.2 years old (range 15-29), but its primary limb salvage operation had done in 13.4 years old (range 9-19), therefore mean times of interval between initial tumor prosthesis reconstruction and temporary EF apply was 8.8 years (range 3-14). One patient had EF for 150 days with 7.2 cm lengthening. Others 5 cases of 4 patients had EF for mean 37 days (range 25-50) and mean soft tissue lengthening was 5.8 cm. Three patients underwent re-insertion of tumor prosthesis and two patients underwent knee fusion as final operation and showed no evidence of infection through mean 22 months follow up period. Conclusion: Temporary using of extendible EF is an effective method for correction of leg shortening which occurred by soft tissue contracture in the complications of limb salvage operation or their treatment process, and it could be provide easily application of tumor prosthesis and knee fusion as final operation.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.441-448
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• 2014

From several researches, recently, it was found that using hollowed precast concrete (HPC) column made more compact concrete casting in joint region possible than using normal solid PC (Precast concrete) column. Therefore, the rigidity of joints can be improved like those of monolithic reinforced concrete (RC). After filling the hollow with grout concrete, however, it is expected that the HPC column behaviors like composite structure since PC element and grout concrete have different materials as well as there is a contact surface between two elements. These may affect the structural behavior and strength of the composite column. A compressive strength test was performed for the HPC column with parameter of hollow ratio for the case with and without grout in the hollow and the result is presented in this paper. The hollow ratios in the test are 35, 50 and 59% of whole section of column. Concentrated axial force was applied to top of the specimens supported as pin connection for both ends. In addition, finite element (FE) analysis was performed to simulate the failure behavior of HPC column for axial compression. As a result, it was found that the hollow ratio did not affect the initial stiffness of HPC filled with grout regardless of the strength difference of HPC and grout. However the strength was increased inversely corresponding to the hollow ratio. The structural capacity of HPC without grout closely related to the hollow size. Especially, the local collapse governs the overall failure when the thickness of HPC is too thin. Based on these effect, a suitable equation was suggested for calculation of the compressive strength of HPC column with or without grout. FE analysis considering the contact surface between HPC and grout produced a good result matched to the test result.