• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.55-60
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• 2010

The honeycomb composite joint structure designed for application to a tilting KTX railroad car body is subjected to bending loads of a cantilever type. Honeycomb sandwich composite panel-joint attached in the real tilting car body was fabricated and sectioned as several beam-joint specimens for the bending test. The fracture behaviors of these specimens under static loads were different from those under cyclic loads. Static bending loads caused shear deformation and fracture in the honeycomb core region, while fatigue cyclic bend loading caused delamination along the interface between the composite skin and the honeycomb core, and/or caused a fracture in the welded part jointed with the steel under-frame. These fracture behaviors could occur in other industrial honeycomb composite joints with similar sub-structures, and be used for improving design parameters of a honeycomb composite joint structure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.1
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• pp.49-55
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• 2017

Welding deformation is a permanent deformation that is caused in structures by welding heat. Welding distortion is the primary cause of reduced productivity, due to welded structural strength degradation, low dimensional accuracy, and appearance. As a result, research and numerous experiments are being carried out to control welding deformation. The aim of this study is to analyze the mechanism of longitudinal bending deformation due to welding. Welding experiments and numerical analyses were performed for this study. The welding experiments were performed on 4 mm and 8.5 mm thickness steel plates, and the numerical analysis was conducted on the welding deformation using the FE software MSC.marc.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.149-154
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• 2012

The size and distribution of welding residual stress and welding deformation in welding structures have an effect on various sorts of damage like brittle failure, fatigue failure and stress corrosion cracking. So, research for this problem is necessary continuously. In this study, non-destructive technique using laser electronic speckle pattern interferometry, plate of welding specimen according to the external load on the entire behavior of residual stress are presented measurement techniques. Once, welding specimen force tensile loading, using electronic speckle pattern interferometry is measured. welding specimen of base metal and weld zone measure strain from measured result, this using measure elastic modulus. In this study, electronic speckle pattern interferometry use weld zone and base metal parts of the strain differences using were presented in residual stress calculated value, This residual stress value were calculated by numerical calculation. Consequently, weld zone of modulus high approximately 3.7 fold beside base metal and this measured approximately 8.46 MPa.

• International Journal of Concrete Structures and Materials
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• v.8 no.1
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• pp.83-97
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• 2014

This paper presents the results of an investigation aimed at developing reinforced concrete beams consisting of precast permanent U-shaped reinforced mortar forms filled with different types of core materials to be used as a viable alternative to the conventional reinforced concrete beam. To accomplish this objective, an experimental program was conducted and theoretical model was adopted. The experimental program comprised casting and testing of thirty beams of total dimensions $300{\times}150{\times}2,000mm$ consisting of permanent precast U-shaped reinforced mortar forms of thickness 25 mm filled with the core material. Three additional typical reinforced concrete beams of the same total dimensions were also cast to serve as control specimens. Two types of single-layer and double-layers steel meshes were used to reinforce the permanent U-shaped forms; namely welded wire mesh and X8 expanded steel mesh. Three types of core materials were investigated: conventional concrete, autoclaved aerated lightweight concrete brick, and recycled concrete. Two types of shear connections between the precast permanent reinforced mortar form and the core material were investigated namely; adhesive bonding layer between the two surfaces, and mechanical shear connectors. The test specimens were tested as simple beams under three-point loadings on a span of 1,800 mm. The behavior of the beams incorporating the permanent forms was compared to that of the control beams. The experimental results showed that better crack resistance, high serviceability and ultimate loads, and good energy absorption could be achieved by using the proposed beams which verifies the validity of using the proposed system. The theoretical results compared well with the experimental ones.

• Steel and Composite Structures
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• v.15 no.6
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• pp.585-603
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• 2013

Generally the required strength and stiffness of an I-shaped beam to the box-shaped column connection is achieved if continuity plates are welded to the column flanges from all sides. However, welding the forth edge of a continuity plate to the column flange may not be easily done and is normally accompanied by remarkable difficulties. This study was aimed to propose an alternative for box columns with continuity plates to diminish such problems. For this purpose a double-web I-shaped column was proposed. In this case the strength and rotational stiffness of the connection was provided by nearing the column webs to each other. Finite element studies on about 120 beam-column connections showed that the optimum proportion of the distance between two column webs and the width of the column flange (parameter ${\beta}$) was a function of the ratio of the beam flange width to the column flange width (parameter ${\alpha}$). Hence, based on the finite element results, an equation was proposed to estimate the optimum value of parameter ${\beta}$ in terms of parameter ${\alpha}$ to achieve the highest connection performance. Results also showed that the strength and ductility of post-Northridge connections of such columns are in average 12.5 % and 54% respectively higher than those of box-shaped columns with ordinary continuity plates. Therefore, a double-web I-shaped column of optimum arrangement might be a proper replacement for a box column with continuity plates when beams are rigidly attached to it.

• Steel and Composite Structures
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• v.26 no.4
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• pp.485-499
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• 2018

In this paper, a hollow steel tube (HST) shear connector is proposed for use in a slim-floor system. The HST welded to a perforated steel beam web and embedded in concrete slab. A total of 10 push-out tests were conducted under static loading to investigate the mechanical behavior of the proposed HST connector. The variables were the shapes (circular, square and rectangular) and sizes of hollow steel tubes, and the compressive strength of the concrete. The failure mode was recorded as: concrete slab compressive failure under the steel tube and concrete tensile splitting failure, where no failure occurred in the HST. Test results show that the square shape HST in filled via concrete strength 40 MPa carried the highest shear load value, showing three times more than the reference specimens. It also recorded less slip behavior, and less compressive failure mode in concrete underneath the square hollow connector in comparison with the circular and rectangular HST connectors in both concrete strengths. The rectangular HST shows a 20% higher shear resistance with a longer width in the load direction in comparison with that in the smaller dimension. The energy absorption capacity values showed 23% and 18% improvements with the square HST rather than a headed shear stud when embedded in concrete strengths of 25 MPa and 40 MPa, respectively. Moreover, an analytical method was proposed and predicts the shear resistance of the HST shear connectors with a standard deviation of 0.14 considering the shape and size of the connectors.

• Computers and Concrete
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• v.17 no.1
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• pp.1-27
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• 2016

Final construction project cost is significantly determined by construction rate. The Industrialized Building System (IBS) was promoted to enhance the importance of prefabrication technology rather than conventional methods in construction. Ensuring the stability of a building constructed by using IBS is a challenging issue. Accordingly, the connections in a prefabricated building have a basic, natural, and essential role in providing the best continuity among the members of the building. Deficiencies of conventional precast connections were observed when precast buildings experience a large induced load, such as earthquakes and other disasters. Thus, researchers aim to determine the behavior of precast concrete structure with a specific type of connection. To clarify this problem, this study investigates the capacity behavior of precast concrete panel connections for industrial buildings with a new type of precast wall-to-wall connection (i.e., U-shaped steel channel connection). This capacity behavior is compared with the capacity behavior of precast concrete panel connections for industrial buildings that used a common approach (i.e., loop connection), which is subjected to monotonic loading as in-plane and out-of-plane loading by developing a finite element model. The principal stress distribution, deformation of concrete panels and welded wire mesh (BRC) reinforcements, plastic strain trend in the concrete panels and connections, and crack propagations are investigated for the aforementioned connection. Pushover analysis revealed that loop connections have significant defects in terms of strength for in-plane and out-of-plane loads at three translational degrees of freedom compared with the U-shaped steel channel connection.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.661-667
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• 2002

Welding-induced buckling distortion is one of the most problematic concerns in both design and fabrication of welded thin-plate structures. This paper deals with experimental and numerical results of the welding-induced longitudinal and/or buckling distortion occurring in welding of 6mm-thick AH36 high strength steel plates. Effects of the heat input and the plate size on the distortion were experimentally evaluated for square plates. Bead-on-plate welding was performed with the submerged arc welding process along the middle line of plate specimens. Experimental results showed that the longitudinal distortion made a single curvature in the plate, and the distortion magnitude along the weld centerline was proportional to the heat input and the plate size. The experimental results were used to examine the validity of the numerical simulation procedure for welding-induced distortion where the longitudinal distortion mode and magnitude were numerically quantified. Three-dimensional, large deformation, welding simulations were performed for selected weld models. Numerical results of the distortion mode and magnitude were in a good agreement with experimental ones. Depending on the presence of halting the distortion growth during the cooling cycle of welding, the condition discriminating buckling distortion from longitudinal distortion was established. Eigenvalue analyses were performed to check the buckling instability of tested plates with different sizes subjected to different heat inputs. The perturbation load pattern for the analysis was extracted from longitudinal inherent strain distributions. Critical buckling curve from the eigenvalue analyses revealed that the buckling instability is manifested when plate size or heat input increases.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.305-316
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• 2011

As the building structures are higher and bigger, the high-performance steels of high strength, toughness, and low yield ratio had been required and developed. In this paper the behavior of the moment connection with bolted web and high strength steel was studied by using the finite-element analysis computer program of ABAQUS. The analysis model is based on the test results and the same cyclic load history was applied at the FE(Finite Element) model until it failed in the test. Through the FEA, several indicators hardly measured from the test were acquired. These indicators related to stress and strain were selected from three plastic rotation stages: 0.003 rad, 0.03 rad, and final failure rotation. Specifically, at the final failure stage, the strain indicators producing the full plastic behavior were suggested as a mechanical property for steel.

• Steel and Composite Structures
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• v.6 no.1
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• pp.71-85
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• 2006

This paper presents the results of a series of tests carried out on cold-formed steel rectangular hollow and concrete infilled beam to column connections and frames. A stub column was chosen such that overall buckling does not influence the connection behaviour. The beam chosen was a short-span cantilever with a concentrated load applied at the free end. The beam was connected to the columns along the strong and weak axes of columns and these connections were tested to failure. Twelve experiments were conducted on cold-formed steel direct welded tubular beam to column connections and twelve experiments on connections with concrete infilled column subjected to monotonic loading. In all the experiments conducted, the stiffness of the connection, the ductility characteristics and the moment rotation behaviour were studied. The dominant mode of failure in hollow section connections was chord face yielding and not weld failure. Provision of concrete infill increases the stiffness and the ultimate moment carrying capacity substantially, irrespective of the axis of loading of the column. Weld failure and bearing failure due to transverse compression occurred in connections with concrete infilled columns. Six single-bay two storied frames both with and without concrete infill, and columns loaded along the major and minor axes were tested to failure. Concentrated load was applied at the midspan of first floor beam. The change in behaviour of the frame due to provision of infill in the column and in the entire frame was compared with hollow frames. Failure of the weld at the junction of the beam occurred for frames with infilled columns. Design expressions are suggested for the yielding of the column face in hollow sections and bearing failure in infilled columns which closely predicted the experimental failure loads.