• Journal of Korean Association for Spatial Structures
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• v.10 no.3
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• pp.81-90
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• 2010

Large spatial structures have the different dynamic characteristics from general rahmen structures and many studies on dynamic behavior of it is conducted. But most studies was conducted about the particular shape of large spatial structures and, directly, the usable results of studies are very limited for seismic design of large spatial structures with the lower structure. So, this study is conducted about the truss arch structure that the basic dynamic characteristics of large spatial structure is inherent in, and the change of its seismic response is analyzed when columns have different length on both ends of it. According to the difference of column's length on both ends, the vertical acceleration response of truss arch structure is affected more than the horizontal acceleration response of it. Therefore, when the stiffness of lower structures that support the upper structure is different, the consideration of the vertical response is significantly required for the seismic design of large spatial structures.

• Computational Structural Engineering
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• v.10 no.4
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• pp.165-175
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• 1997

In this paper, the stress, buckling and vibration analyses have been performed for several case with the spot weld stiffened rear side frame, the unstiffened rear side frame and the dual thickness laser weld rear side frame. For stress and vibration analyses, the clamped boundary condition with spring supports are used. But for the buckling analyses, the both ends simply supported boundary conditions are used. For the nummerical analyses, ANSYS 5.0 code is adopted. Maximum stress of the spot weld stiffened rear side frame occurs in the main frame and is 80.9 MPa. Maximum strain is 501 .mu.. The maximum stress of the dual thickness laser weld rear side frame of 1.8mm thickness structure is equal with the stress of spot weld stiffened frame. The weight of dual thickness laser weld frame can be reduced about 17.2%. For the stiffened spot weld rear side frame with both ends simply supported boundary conditon, the bucking load is 52.54 kN. When the thickness of the dual thickness laser weld rear side frame become 1.9mm thickness structure, the buckling load of the stiffenerd rear side frame is equal to that of dual thickness laser weld frame. The reduction of the structure weight is about 5%. The fundamental natural frequency of the stiffened spot weld rear side frame for bending mode is 163.6 Hz and that of the dual thickness laser weld rear side frame is 179.8 Hz.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.27-33
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• 2004

Dynamic response analysis is conducted for a floating bridge subjected to multiple support earthquake excitation. The floating bridge used in this study is supported by discrete floating pontoons and horizontal pretension cables supported at both ends of the bridge. The bridge is modeled with finite elements and the hydrodynamic added mass and added damping due to the surrounding fluid around pontoons are obtained using boundary elements. During the analysis the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients. Multiple support excitation is introduced at both ends of the bridge and the time history response is compared to that of a simultaneous excitation. The results show that the multiple support excitation yields larger values in some responses. for example in cable tensions. than the sumultaneous excitation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.123-134
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• 2019

This paper proposed a new design equation for the inelastic lateral torsional buckling (LTB) of singly symmetric stepped I-beams with non-compact flange sections. The proposed equation was generated using a finite element program, ABAQUS, and a statistical program, MINITAB. The parameters used were the stepped beams parameters; ${\alpha}$, ${\beta}$, and ${\gamma}$ and the length-to-height ratio ($L_b/h$) of the beam. The proposed equation was further validated by means of experimental test, where beams were subjected to four-point bending and supported by roller and lateral braces near the end supports. In addition, finite element models were simulated using the same parameters used in the experimental test to verify the results of the test conducted. It was proved that LTB capacity calculated from the proposed equation is accurate and conservative in comparison with the yielded values from the FEM and actual test, making it a reliable and safe approach in calculating the buckling capacities of singly symmetric stepped beams with non-compact flange sections.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.327-334
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• 1998

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and toll.or structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates with free edges supported on elastic foundation and with a pair of opposite edges under axial forces is presented. Such plates represent the concrete highway slab and hybrid composite pavement of bridges. The reinforced concrete slab can be assumed as a special orthotropic plate, as a close approximation. The highway slab is supported on elastic foundation, with free boundaries. Sometimes, the pair of edges perpendicular to the traffic direction may be subject to the axial forces. The plate is subject to the concentrated load/loads, in the form of traffic loads, or the test equipments. Any method nay be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation, the aspect ratio of the plate, and the magnitudes of the axial forces and the concentrated attached mass on the plate, on the natural frequency is thoroughly studied.

• Computational Structural Engineering
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• v.10 no.1
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• pp.149-158
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• 1997

This paper presents the illustration of application under attached point mass to the special orthotropic plates with a pair of opposite edges simply supported and the other pair of opposite edges free. Design engineers need to calculate the natural frequencies of such elements but obtaining exact solution to such problems is very much difficult. Pretlove reported a method of analysis of beams with attached masses using the concept of effective mass. This method, however, is useful only for certain simple types of beam. Therefore, considering the method has been developed by D. H. Kim(1974) is simple, accurate, and very effective for the plates with arbitrary boundary conditions and irregular sections, this paper calculates the natural frequencies of composite laminated plate under attached point mass/masses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5984-5989
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• 2011

The buckling strength of a pin-ended column may be increased significantly by reinforcing it with an assemblage of cross-arm members rigidly connected to the modpoint of the column and stayed members connecting the ends of the columns and cross-arm members. The purpose of the stays and cross-arm members is to introduce restraint against translation and rotation and thereby decrease the effective buckling length of the column. In this study, buckling strengths of the reinforced columns were quantitatively evaluated from analytical solutions and elastic/inelastic finite elements analysis and the results were compared each other. It was found that the reinforcing system may increase the buckling strength up to 8 times compared to ones without reinforcing system.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.261-274
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• 1998

The brief results of laboratory and field tests of yieldable steel arches are represented. The test supports were fabricated with three U-sectional beams which are 25.8 kg/m of Glocken profile. The structural analyses of semi-circular and arch supports were conducted to find out shape factor of U beam to be 1.35 and the location of 2nd plastic hinges. Load capacity of arch supports under crown loading were examined as a function of leg length. Yieldable characheristics of test supports were investigated with various bolting torque of connection part. Determination method of bolting torque were also studied. Finally, test supports were installed in-situ with torque of 21 kg .m, which showed a typical yielding procedure.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.237-246
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• 2008

The cross-sections of continuous multi-span beams sometimes suddenly increase, or become stepped, at the interior supports of continuous beams to resist high negative moments. The three-dimensional finite-element program ABAQUS (2006) was used to analytically investigate the inelastic lateral-torsional buckling behavior of stepped beams subjected to pure bending moment and resulted in the development of design equations. The flanges of the smaller cross-section were fixed at 30.48 by 2.54 cm, whereas the width and/or thickness of the flanges of the larger cross-section varied. The web thickness and height of beam was kept at 1.65 cm and 88.9 cm, respectively. The ratios of the flange thickness, flange width, and stepped length of beams are considered analytical parameters. Two groups of 27 cases and 35 cases, respectively, were analyzed for double and single stepped beams. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. First, the distributions of residual stress of the cross-section is same as shown in Pi, etc (1995), and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The new proposed equations definitely improve current design methods for the inelastic LTB problem and increase efficiency in building and bridge design. The proposed solutions can be easily used to develop new design equation for inelastic LTB resistance of stepped beams subjected to general loading condition such as a concentrated load, a series of concentrated loads or uniformly distributed load.

• Journal of the Korean Wood Science and Technology
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• v.27 no.2
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• pp.15-22
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• 1999

Polymeric meterials that are used for noise and vibration damper in wood/polymer/wood sandwich composites, must have a high loss factor(tan ${\delta}$), and at the same time the storage modulus(E) of $5{\times}10^7$ to $10^9$ dyne/$cm^2$ must withstand over a wide temperature and frequency ranges. In this study, the series of epoxy resinlpolyacrylate interpenetrating polymer networks(IPNs) were synthesized by simultaneous polymerization. Their dynamic tensile properties were measured at 110Hz using Rheovibron instrument. Composite damping factor(tan ${\delta}_c$) and dynamic bending modulus($E_c,\;E_^{\prime\prime}c$) of wood/polymer/wood sandwich composites were measured at 110Hz using a Rheovibron in bending mode of vibration. These dynamic tensile studies indicated that cured epoxy resin/polyacrylates IPNs were semicompatible in the sense that both the shifting of T($E^{\prime\prime}_{max}$) or T(tan ${\delta}_{max}$) and the broadening of glass transition temperature range were observed. Especially, the cured Epikote871/P(n-BMA) IPNs of composition 70/30 to 50/50 showed a relatively high tan a and appropriate E' value over a wide temperature range; consequently the tan a e curves of wood/IPNs/wood sandwich composites was broadened over a wide temperature range.