• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.4
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• pp.157-167
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• 2020

In this study, a field bridge test was conducted to find the dynamic properties of cable supported bridges with resilient-friction base isolation systems (R-FBI). Various ambient vibration tests were performed to estimate dynamic properties of a test bridge using trucks in a non-transportation state before opening of the bridge and by ordinary traffic loadings about one year later after opening of the bridge. The dynamic properties found from the results of the tests were compared with an analysis model. From the result of the ambient vibration tests of the cable supported bridge with R-FBI, it was confirmed that the dynamic properties were sensitive to the stiffness of the R-FBI in the bridge, and the seismic analysis model of the test bridge using the effective stiffness of the R-FBI was insufficient for reflecting the dynamic behavior of the bridge. In the case of cable supported bridges, the seismic design must follow the "Korean Highway Bridge Design Code (Limit State Design) for Cable supported bridges." Therefore, in order to reflect the actual behavior characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure should be proposed.

• Korean Journal of Construction Engineering and Management
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• v.18 no.5
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• pp.3-10
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• 2017

The HBS slab is a method in which a lightweight sieve is installed on top of the psc slab and two ribs of the neighboring psc slab are combined with ribs formed by the site concrete to act as a single member on the same axis. The purpose of this study is to implement the performance comparison with the existing method through the experimental study on the PSC slab method. In this study, the HBS slab was developed as a method to improve the limit of the existing method and the performance comparison with the existing method is tried to verify its superiority. The comparison of the structural performance with the existing method is carried out through the experimental study of the HBS slab, and the structural performance against the bending performance and shear and the bonding performance between the pc beam and the hbs slab are examined and compared with the existing method through the theoretical method.

• Computers and Concrete
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• v.26 no.6
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• pp.547-563
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• 2020

In this paper, the influence of axial compression ratio on the mechanical properties of new type joints of side span of rectangular concrete-filled steel tubular column-H-type steel beam is studied. Two new types of side-span joints of rectangular concrete-filled steel tubular column-H-type steel beam are designed and quasi-static tests of five new type joints with 1:2 scale reduction ratios are performed. The axial compression ratio of joint JD1 is 0.3, 0.4 and 0.5, and the axial compression ratio of joint JD2 is 0.3 and 0.5. In the joint test, different axial forces were applied to the top of the column according to different axial compression ratios, and low-cyclic reciprocating load was applied on the beam. The stress and strain distribution, beam and column deformation, limit state, failure process, failure mechanism, stiffness degradation, ductile deformation and energy dissipation capacity of the joint were measured and analyzed. The results show that: with the increase of axial compression ratio, the ultimate bearing capacity of the joint decreases slightly, the plastic deformation decreases, and the stiffness and ductility decrease. According to the energy dissipation curve of the specimen, the equivalent damping coefficient also increases with the increase of axial compression ratio in a certain range, indicating that the increase of axial compression ratio can improve the seismic performance of the joint to a certain extent. The finite element method is used to simulate the joint test, and the test results are in good agreement with the simulation results.

• Journal of Veterinary Science
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• v.24 no.4
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• pp.34.1-34.12
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• 2023

Background: There has not been a thoroughly reported study of the comparison between spectral domain-optical coherence tomography (SD-OCT) with both ultrasound biomicroscopy (UBM) and gonioscopy on the evaluation of the iridocorneal angle (ICA) in dogs. Objectives: To investigate the diagnostic value of SD-OCT for the early detection of narrowing ICA by comparing and assessing inter-device agreement in anterior chamber angle (ACA) measurements obtained by SD-OCT and UBM, and ICA evaluations by gonioscopy. Methods: A total of 28 eyes from 28 client-owned dogs with normal intraocular pressure were included for examination. The ACA and angle opening distance (AOD) were measured from the SD-OCT and UBM images, and gonioscopy images were analyzed using the ICA grade and ZibWest angle index. Results: The mean ACA and AOD for SD-OCT were 28.31° ± 5.37° and 658.42 ± 219.90 ㎛, and for UBM, 28.34° ± 5.82° and 859.29 ± 221.80 ㎛, respectively. The mean difference in ACA between the average values of SD-OCT and UBM measurements was 0.03° with a 95% limit of agreement (LoA) span of 16.2°, indicating positive agreement; that in AOD was 200.85 ㎛ with a 95% LoA span of 1,110.95 ㎛, indicating poor agreement. The Pearson correlation coefficient of the ACA of SD-OCT and ZibWest indices of gonioscopy was 0.624, indicating strong agreement; that of UBM and gonioscopy was 0.43, indicating moderate agreement. Conclusions: SD-OCT is well tolerated by canine patients due to its non-contact method and might be an alternative option for early screening of ICA narrowing in clinical settings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.125-135
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• 2015

The tendency of more longer span length being required economical in railway bridges is studying about PSC I shaped girder. In this case, it is important to analyze and choose the effective girder section for stiffness of bridge. This study investigates the dynamic properties and safety of PSC I shaped girder being used wide upper flange whose selection based on radii and efficiency factor of flexure for railway bridge in different span type. In addition, 40m PSC Box girder bridge adopted in Honam high speed railway is further analyzed to compare dynamic performance of PSC I shaped girder railway bridge with same span length. Time history response is acquired based on the mode superposition method. Static analysis is also analyzed using standard train load combined with the impact factor. Consequently, the result met limit values in every case including vertical displacement, acceleration and distort.

• KCI Concrete Journal
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• v.14 no.1
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• pp.36-42
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• 2002

Flexural behaviors of the two typical precast beam sections (inverted tee and rectangular) for buildings were investigated and compared. The height of web in the inverted tee beam was generally less than half of beam depth to be adapted to that of the nib in the ends of double-tee where the total building height limited considerably. The inverted-tee beams were designed for a parking live load - 500kgf/$m^2$ and a market - 1,200kgf/$m^2$ from the currently used typical shape of a domestic building site in Korea. The area and bottom dimension of rectangular beams were the same as those of inverted tee beams. These woo beams were also reinforced with a similar strength. following results were obtained from the studies above; 1) the rectangular beam is simpler in production, transportation, and erection, and more economic than the inverted tee beam in the construction test for these two beams with a same dimension and a similar strength, 2) all of the beams considered in the tests were generally failed in values close to those of the strength requirements in ACI Provisions. The ratios of test result to calculated value are averaged to 1.04. One rectangular and one inverted tee beams failed in a value only 2-3％ larger than the estimated volue of the Strength Design Methool the results of the Strain Compatibility Method wire slightly more accurate than those of the Strength Design Method, 4) the maximum deflections of all of the beams under the full service loads were less than those of the allowable limit in ACI Code Provisions. The rectangular beams experienced more deflection then inverted tee in the same loading condition and failed with more deflection, and 5) the rectangular and inverted tee beams showed good performances under the condition of service and ultimate loads. However, one inverted tee beams with fm span developed an initial flexural crackings under 88％ of the full service load even though they designed to satisfy the ACI tensile stress limit provisions.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.3
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• pp.92-100
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• 2002

The advent or high-strength steel has enabled the arch structures to be relatively light, durable and long-spanned by reducing the cross sectional area. On the other hand, the possibility of collapse may be increased due to the slender members which may cause the stability problems. The limit analysis to estimate the ultimate load is based on the concept of collapse mechanism that forms the plastic zone through the full transverse sections. So, it is not appropriate to apply it directly to the instability analysis of arch structures that are composed with compressive members. The objective of this study is to evaluate the ultimate load carrying capacity of the parabolic arch by using the elasto-plastic finite element model. As the rise to span ratio (h/L) varies from 0.0 to 0.5 with the increment of 0.05, the ultimate load has been calculated fur arch structures subjected to uniformly distributed vertical loads. Also, the disco-elasto-plastic analysis has been carried out to find the duration time until the behavior of arch begins to show the stable state when the estimated ultimate load is applied. It may be noted that the maximum ultimate lead of the parabolic arch occurs at h/L=0.2, and the appropriate ratio can be recommended between 0.2 and 0.3. Moreover, it is shown that the circular arch may be more suitable when the h/L ratio is less than 0.2, however, the parabolic arch can be suggested when the h/L ratio is greater than 0.3. The ultimate load carrying capacity of parabolic arch can be estimated by the well-known formula of kEI/L$^3$where the values of k have been reported in this study. In addition, there is no general tendency to obtain the duration time of arch structures subjected to the ultimate load in order to reach the steady state. Merely, it is observed that the duration time is the shortest when the h/L ratio is 0.1, and the longest when the h/L ratio is 0.2.

• Advances in aircraft and spacecraft science
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• v.2 no.2
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• pp.125-168
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• 2015

Dynamic aeroelastic behavior of structurally nonlinear Joined Wings is presented. Three configurations, two characterized by a different location of the joint and one presenting a direct connection between the two wings (SensorCraft-like layout) are investigated. The snap-divergence is studied from a dynamic perspective in order to assess the real response of the configuration. The investigations also focus on the flutter occurrence (critical state) and postcritical phenomena. Limit Cycle Oscillations (LCOs) are observed, possibly followed by a loss of periodicity of the solution as speed is further increased. In some cases, it is also possible to ascertain the presence of period doubling (flip-) bifurcations. Differences between flutter (Hopf's bifurcation) speed evaluated with linear and nonlinear analyses are discussed in depth in order to understand if a linear (and thus computationally less intense) representation provides an acceptable estimate of the instability properties. Both frequency- and time-domain approaches are compared. Moreover, aerodynamic solvers based on the potential flow are critically examined. In particular, it is assessed in what measure more sophisticated aerodynamic and interface models impact the aeroelastic predictions. When the use of the tools gives different results, a physical interpretation of the leading mechanism generating the mismatch is provided. In particular, for PrandtlPlane-like configurations the aeroelastic response is very sensitive to the wake's shape. As a consequence, it is suggested that a more sophisticate modeling of the wake positively impacts the reliability of aerodynamic and aeroelastic analysis. For SensorCraft-like configurations some LCOs are characterized by a non-synchronous motion of the inner and outer portion of the lower wing: the wing's tip exhibits a small oscillation during the descending or ascending phase, whereas the mid-span station describes a sinusoidal-like trajectory in the time-domain.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.75-82
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• 2000

Flexural behaviors of two typical architectural precast beam sections ; inverted tee and rectangular - were compared and investigated. The heights of web in inverted tee beams are generally less than half of beam depth in building structures to accomodate the nib of double-tee where the total building height limited considerably. The inverted-tee beams are designed for parking live load - 500kgf/$\m^2$ and market - 1,200kgf/$\m^2$ according to the currently used typical shape in the domestic market building site in Korea. The bottom dimension and area of rectangular beams are same to those of inverted tee beams to compare the flexural behaviors of two beams. These two beams are also reinforced for similar strength. Four flexural tests are performed on two beams. Following results are obtained from the tests; 1) The rectangular beam is simpler in production, transportation, and election, and more economic than the inverted tee beam for these two beams with same dimension and similar strength. 1) The estimations of flexural strength of two beams by Strength Design Method and Strain Compatibility Method is fully complied with the result of tests. However, Strain Compatibility Method is slightly ore accurate than Strength Design Method. 2) Overall deflections of two type beam under the service loads are less than those of the allowable limit in ACI Code provision. 3) The rectangular beam is failed in large deflection (average 12.56mm large) than those of inverted tee beams. 4) The rectangular and inverted tee beams with 6m span develop initial flexural crackings under the 88% of full service loading even though they designed to satisfy the ACI tensile stress limit provisions.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.543-552
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• 2006

The current design for crack width control in concrete bridges is incomplete in analytical models. As one of the important serviceability limit states, the crack width be considered with the quantitative prediction of the initiation and propagation of corrosion and corrosion-induced cracking. A serviceability limit state of cracking can be affected by the combined effects of bond, slip, cracking, and corrosion of the reinforcing elements. Considering life span of concrete bridges, an improved prediction of crack width affected by time-dependent general corrosion has been proposed for the crack control design. The developed corrosion models and crack width prediction equation can be used for the design and the maintenance of prestressed and non-prestressed reinforcements by varying time, w/c, cover depth, and geometries of the sections. It can also be used as the rational criteria for the maintenance of existing concrete bridges and the prediction of remaining life of concrete structures.