• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.73-83
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• 2006

The failure mechanism of a hollow bridge deck which is made of fiber reinforced polymer (FRP) to improve its durability and life time significantly is investigated using both experiments and analyses. While the Load-displacement behavior of the deck in the longitudinal direction is almost linear just before the failure, the behavior in the transverse direction shows a strong nonlinearity even in its initial response with relatively small magnitude of loads. We found that the nonlinearity is due to the imperfection of the connection between the flange and the web; a plastic deformation can t라e place in the connection. The argument is demonstrated using a simple structural model in which a rigid plastic hinge is introduced to the connection. We also checked the contribution of the delamination mechanism to the failure. But the delamination is not the main mechanism which initiates and causes the failure of the bridge deck. In order to improved the structural behavior of the deck in the transverse direction, we suggested that the empty space of the bridge deck is filled with a foam and confirmed the improved behavior by a numerical analysis.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.493-504
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• 2008

This paper deals with the experimental analysis of the flexural behaviour of encased composite beams with hollow core slabs and channels. The shear force between steel beams and hollow core slabs are transferred by channels. Three full-scale specimens were constructed and tested with different steel beam heights, which were compared with those of previous studies. Based on observation of the experiments, the encased composite beams exhibited full shear connection behaviour without any other shear connectors due to their inherent mechanical and chemical bond stress. Experimental results show a behaviour similar to steel-concrete composite beams with classical connectors: elastic and yield domains, great ductility, flexural failure mode (plastic hinge), low relative movement at steel-concrete interface and all specimens failed in a very ductile manner. Consequently, this study enables the validation of the proposed connection device under static loading and shows that it meets modern structural requirements.

• Structural Engineering and Mechanics
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• v.32 no.3
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• pp.383-398
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• 2009

Applying nonlinear statistical analysis methods in estimating the performance of structures in earthquakes is strongly considered these days. This is due to the methods' simplicity, timely lower cost and reliable estimation in seismic responses in comparison with time-history nonlinear dynamic analysis. Among nonlinear methods, simplified to be incorporated in the future guidelines, Modal Pushover Analysis, known by the abbreviated name of MPA, simply models nonlinear behavior of structures; and presents a very proper estimation of nonlinear dynamic analysis using lateral load pattern appropriate to the mass. Mostly, two kinds of connecting joints, 'hinge' and 'rigid', are carried out in different type of steel structures. However, it should be highly considered that nominal hinge joints usually experience some percentages of fixity and nominal rigid connections do not employ totally rigid. Therefore, concerning the importance of these structures and the significant flexibility effect of connections on force distribution and elements deformation, these connections can be considered as semi-rigid with various percentages of fixity. Since it seems, the application and implementation of MPA method has not been studied on moment-resistant steel frames with semi rigid connections, this research focuses on this topic and issue. In this regard several rigid and semi-rigid steel bending frames with different percentages of fixity are selected. The structural design is performed based on weak beam and strong column. Followed by that, the MPA method is used as an approximated method and Nonlinear Response History Analysis (NL-RHA) as the exact one. Studying the performance of semi-rigid frames in height shows that MPA technique offers reasonably reliable results in these frames. The methods accuracy seems to decrease, when the number of stories increases and does decrease in correlation with the semi-rigidity percentages. This generally implies that the method can be used as a proper device in seismic estimation of different types of low and mid-rise buildings with semi-rigid connections.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.60-65
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• 2017

This study examined the effect of rotational stiffness of joints between vertical and horizontal members in system supports. In order to prevent repeated disasters of system supports, it is important to examine the accurate behavior of system supports. Among various factors affecting the complex behavior of system supports, this study focused on the stiffness of joints between vertical and horizontal members. The considered joint was modelled by a rotational spring, but the translational displacements were fixed. The stiffness of rotational spring was calculated by utilizing the usable experimental data. In addition, the hinge connection condition, which is generally considered in design and only restrict the translational displacements, was modelled to compare the results. The case with the rotational stiffness in joints showed 3.5 times buckling loads compared to the case without the rotational stiffness. Thus, the structural behavior of the vertical member in system supports was similar to the vertical member with the fixed condition. For the combined stresses of vertical members, the combined stress ratios were reduced 5~6% by considering the rotational stiffness of connecting parts. However, for the horizontal member where showed relatively small stress range, the stresses were increased 2.3~7.6 times by considering the rotational stiffness in connecting parts.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.535-545
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• 2001

A refined method of analysis which is called the Advanced Analysis has been introduced This method is to consider the intial member imperfection residual stress and second-order effects so as to estimate the overall behavior of steel frame accurately Based on the refined plastic hinge method that is more suitable and practical in design practice. the program RPH-2DF is coded using the log model which represents the moment-rotation relationship of connection. The validity of this program is examined by frame test data. Finally to investigate the difference between behaviors of rigid and semi-rigid frame. the 10-story frame analysis results designed by MIDAS-GEN v4.2.2 are compared with the results by RPH-2DF.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1A
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• pp.9-18
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• 2011

Generally the connection of structural members is assumed as hinge, rigid and semi-rigid connections. The exact tangent stiffness matrix of a semi-rigid frame element is newly derived using the stability functions considering shear deformations. Also, linearized elastic- and geometric-stiffness matrices of shear deformable semi-rigid frame are newly proposed. For the exact stiffness matrix, an accurate displacement field is introduced by equilibrium equation for beam-column under the bending and the axial forces. Also, stability functions considering sway deformation and force-displacement relations with elastic rotational spring on ends are defined. In order to illustrate the accuracy of this study, various numerical examples are presented and compared with other researcher's results. Lastly, shear deformation and semi-rigid effects on buckling behaviors of structure are parametrically investigated.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.221-232
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• 1998

This study presents a fatigue line with a plastic rotational angle to a great extent of plastic strain of Low-Cycle-Fatigue period, such as earthquake, etc. This fatigue line with a plastic rotational angle is measured and analysed more simply in practice rather than Woehler's fatigue line which is developed in stress variation of the structure. It shows that the slope of fatigue line with a plastic rotational angle is equal to that with plastic strain through the experiments by proving the correlation that the plastic strain ratio is directly proportional to the plastic rotational angle in plastic hinge. The theory is induced by Manson and Coffin strain fatigue line, and the experiments are tested by ECCS. The location of the plastic hinge is achieved and accurate plastic strain ratio is calculated through FEM.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Journal of the Korean Geosynthetics Society
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• v.14 no.3
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• pp.31-42
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• 2015

The Reinforced subgrade for railroad (RSR) was constructed for one way railway line with the dimension of 5 m high, 6 m wide and 20 m long to evaluate its performance under train design load. The RSR has characteristics of short length (0.3-0.4 H) of reinforcement and rigid wall, 30 and 40 cm vertical spacing of reinforcement installation. To enhance economics and constructability, three kinds of connections (welding, hinge & bolt, bold wire) were also designed to realize the integration between rigid wall and reinforced subgrade. Two times of static loading tests were done on the full size railroad subgrade. The maximum applied pressure was 0.98 MPa (the maximum test load 5.88 MN), which corresponds to 19.6 times of the design load for railroad subgrade, 50 kPa. The performance on the RSR was evaluated with the safety on the failure, subgrade bearing capacity and settlement, horizontal displacement of wall, and reinforcement strain. Based on the full scale test, we confirmed that the RSR with the conditions of 0.35 H (35% of height) short reinforcement length, hinge & bolt type connection for integration between rigid wall and reinforced subgrade, and 40cm vertical spacing of reinforcement installment shows good performance under train design load.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.195-205
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• 2015

The rahmen bridge is well known common type of bridge in which all members are connected rigidly. The rahmen bridge is built for several situations because it has many advantages such as no need of bridge bearing system, easy of maintenance, reduction of the cross-sectional area of superstructure, and relatively low construction cost compared with other bridge types. Recently, to lengthen the span of rahmen bridge system, steel-concrete composite beam is used for superstructure of rahmen bridge instead of normal concrete girder with slab. However, member forces are increased because of extension of span length of superstructure and substructure is designed and constructed inefficiently when steel-concrete composite rahmen bridge is designed. In this study, new-type steel-concrete composite bridge is suggested. New-type steel-concrete composite rahmen bridge is adopted hinge connection between abutment and foundation for the reduction of the bending momemt at the foundation. In this study, we present the results of experiment conducted to estimate the load carrying capacity of new-type steel-concrete composite rahmen bridge and the structural characteristics of hinge connection.