• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.161-175
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• 1998

The objective of this study is to investigate the structural behavior of Concrete-Filled Steel Tubular Column-H Beam connections with plate stiffeners. The first, we made experiment on the Column to H-beam flange connections stiffened with simple tensile loading. The paramaters of tensile experiment are the area of each plates. The simple tensile experiment is conducted to 5 kinds of specimens. Eestimating the load, displacement, and strain from each kind, we compared them with results of second experiment. The second, we made experiment on the Column to H-beam connections stiffened with the sames under monotonic and cyclic load. we made specimens of 5 for the second experiment. In analysis, comparing each strengthes and stiffnesses we estimated deformation capacity. Comparing and estimating each yielding strength ratios and maxium-strength ratios on the basis of Yield line theory, we suggested new Strength Formula of Beam-to-Column Connections.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.9-16
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• 2006

The moment resisting frame has been well-known as it had very excellent seismic performance, and it has been widely used and constructed in the design of a lot of buildings. However, the moment resisting frame system did not exert the seismic performance during the earthquake in Northridge and Kobe sufficiently, and it produced the crack or brittle fracture on the joint. this study was to ]m tests with the full-scale test subject as parameters of existence of H-beam web high tensile bolt shearing joint and reinforcement of H-flange rib. This researcher was to anticipate the decrease of number of high tensile bolts and the improvement of workability through the double shear joint by the experiment, and improve the seismic performance through the reinforcement of rib plate. In addition, this study was to prevent the brittle fracture by the stress concentration through the non scallop.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.37-49
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• 1997

The buckling behavior of the web of steel girders are largely dependent on the size and the location of stiffeners and the restraining effect of top and bottom flanges. Elastic and inelastic buckling analyses based or the Spline Finite Strip Method were executed to study the stiffening effect of the longitudinal stiffener on the web of box girders and to find how the top and bottom flanges had effects on the web, where geometric boundary conditions were limited by both hinged, both fixed and the flange sections. The basic assumption for the longitudinal end boundary conditions was that the vertical stiffeners had the rigidity enough to force nil deflection line on the web panel so that the junction line between web and vertical stiffener was assumed to be hinged boundary conditions. The provisions on the longitudinal stiffener of the plate and box girders of the Korean Standard Highway Bridge Specifications(1995) and AASHTO Specifications(1994 LRFD) were compared with the results obtained numerically for the various longitudinal stiffener size of box girders. Simple equations and design curves for the longitudinal stiffener of the web were proposed for the practical use.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.19 no.4
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• pp.383-394
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• 1997

This study was done to examine adherence of oral bacteria to titanium dental implant and to know the effective prophylactic antibiotics using an in vivo model. Three samples each of the implant material were set in an acrylic resin flange and placed in the maxillary buccal sulcus of twenty volunteers. At 6- and 54-hour intervals, each sample was placed on blood agar plate (BAP) and chocolate agar, and then they were incubated and identified. Also antibiotic susceptibility test was performed. The results obtained mere as follows ; 1. The microorganisms were chain-like Gram positive cocci and staphyline Gram positive cocci, Gram positive bacilli in order of frequency were found at 6-hour and 54-hour samples by Gram staining. 2. Streptococci was found predominantly at both 6-hour and 54-hour samples, but number of streptococci was decreased as compared to 6-hour samples. 3. There was no difference in the bacterial species adherent to implant between 6-hour and 54-hour samples. 4. All the microbes were sensitive to AMC (amoxacillin clavulanic acid), chloramphenicol, quinolone and vancomycin in the antibiotic susceptibility test. Above results suggest that streptococcus are mainly adhered to titanium implant after implant was placed in the oral cavity and AMC is the most recommendable antibiotics to prevent the peri-implant inflammation.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.562-567
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• 2006

Micro-alloyed steel or heat-treatment-free used in clean technology have been replacing for conventional quenched-and-tempered structural steels since the micro-alloyed forging steel was developed in early 1970s in Germany for saving money of heat treatment, simplified process, short delivery and good productivity. In this paper, ball stud assembled in steering system for automobile was selected to compare conventional process making heat treatment with new process using high strength micro-alloyed steel without heat treatment. The conventional process for ball stud was composed of a total of 6 steps including upsetting, forward extrusion, machining, burnishing and tread rolling with heat treatment and shot blasting. As opposed to conventional process, newly proposed process for ball stud using the clean technology without heat treatment is simplified such as forward extrusion, heading, upsetting, forming having a flange shape and tread rolling. Also net shape forming process to achieve specified process not to include machined step fur manufacturing the ball stud was applied to newly simplified process since micro-alloyed steel is difficult to be formed.

• Steel and Composite Structures
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• v.26 no.3
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• pp.315-328
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• 2018

Built-up Double-I (BD-I) columns consist of two hot rolled IPE sections and two cover plates which are welded by fillet welds. In Iran, this type of column is commonly used in braced frames with simple connections and sometimes in low-rise Moment Resisting Frames (MRF) with Welded Flange Plate (WFP) beam-column detailing. To evaluate the seismic performance of WFP connection of I-beam to BD-I column, traditional and modified exterior MRF connections were tested subjected to cyclic prescribed loading of AISC. Test results indicate that the traditional connection does not achieve the intended behavior while the modified connection can moderately meet the requirements of MRF connection. The numerical models of the connections were developed in ABAQUS finite element software and validated with the test results. For this purpose, moment-rotation curves and failure modes of the tested connections were compared with the simulation results. Moreover to avoid improper failure modes, some improvements of the connections were evaluated through a numerical study.

• Steel and Composite Structures
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• v.1 no.2
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• pp.187-200
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• 2001

Most of the portal frames are designed these days by the application of plastic analysis, with the normal assumption being made that the column bases are pinned. However, the couple produced by the compression action of the inner column flange and the tension in the holding down bolts will inevitably generate some moment resistance and rotational stiffness. Full-scale portal frame tests conducted during a previous research program had suggested that this moment can be as much as 20% of the moment of resistance of the column. The size of this moment of resistance is particularly important for the design of the tensile capacity of the holding down bolts and also the bearing resistance of the foundation. The present research program is aiming at defining this moment of resistance in simple design terms so that it could be included in the design of the frame. The investigation also included the study of the semi-rigid behaviour of the column base/foundation, which, to a certain extent, affects the overall loading capacity and stiffness of the portal frames. A series of column bases with various details were tested and were used to calibrate a finite element model which is able to simulate the action of the holding down bolts, the effect of the concrete foundation and the deformation of the base plate.

• Steel and Composite Structures
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• v.20 no.2
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• pp.267-293
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• 2016

It is well known that, in order to accurately predict the behaviour of steel structures a requirement the definition of the mechanical behaviour of beam-to column joints is of primary importance. This goal can be achieved by means of the so-called component method, which, in order to obtain the whole behaviour of connections, provides to break up joints in basic components of deformability and resistance. One of the main joint components used to model bolted connections is the so-called equivalent T-stub in tension, which is normally used to predict the behaviour of bolted plates in bending starting from the behaviour of the single bolt rows. In past decades, significant research efforts have been devoted to the prediction of the behaviour of bolted T-stubs but, to date, no particular attention has been devoted to the characterization of their plastic deformation capacity. To this scope, the work presented in this paper, taking into account the existing technical literature, proposes a new theoretical model for predicting the whole behaviour up to failure of bolted T-stubs under monotonic loading conditions, including some complexities, such as the bolt/plate compatibility requirement and the bolt fracture, which are necessary to accurately evaluate the ultimate displacement. After presenting the advances of the proposed approach, a comparison between theoretical and experimental results is provided in order to verify its accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1537-1542
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• 2007

In this study, based on a I-roll embedded steel composite deck, it is suggested a new type of simplified composite deck and analyzed under construction loading. Using ABAQUS, it's estimated effects of welding amount of steel plate and I-section, existence of a hole of I-section's flange, and a location of hole. For a reasonable verification of modeling, compare Euler-Beam theory with F.E.M models. In result, it is verified that change of welding amount increase more maximum bending tension stresses at the central part's section of span when elements are partial-welded. Also, verify that deflection is slightly increased when a hole existed compared with no hole.

• Journal of Korean Association for Spatial Structures
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• v.18 no.4
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• pp.123-130
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• 2018

U-flanged truss beam is composed of u-shaped upper steel flange, lower steel plate of 8mm or more thickness, and connecting lattice bars welded on the upper and lower sides. The hybrid beam with U-flanged steel truss is made in the construction site through pouring the concrete, and designated as U-flanged truss hybrid beam. In this study the structural experiments on the 4 hybrid beams with the proposed basic shapes were performed, and the flexural capacities from the tests were compared with those from the theoretical approach. The failure modes of each specimen were quite similar. The peak load was reached with the ductile behavior after yielding, and the failure occurred through the concrete crushing. The considerable increasement of deformation was observed up to the concrete crushing. The composite action of concrete and steel member was considered to be reliable from the behavior of specimens. The flexural strength of hybrid beam has been evaluated exactly using the calculation method applied in the boubly reinforced concrete beam. The placement of additional rebars in the bottom instead of upper side is proposed for the efficient design of U-flanged truss hybrid beam.