• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.19-29
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• 2023

An ultra-high strength prestressed prismatic beam of 100 MPa in compressive strength was developed by increasing the watertightness of concrete by utilizing centrifugal molding processes without adding expensive admixtures such as silica fume. The ultra-high strength centrifugal shaped square beam installed on the wall is composited with the upper slab concrete and then subjected to a service load. Horizontal shear stress is generated by bending between the centrifugal molding beam and the floor plate, which causes the beam and floor plate to perform composite behavior through shear connections such as studs and rebars. In this study, a flexural load test was performed on a mock-up specimen that was synthesized by fabricating an RC slab on top of a 100 MPa-class centrifugal shaped beam produced at the factory. proven reliability.

• Ocean Systems Engineering
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• v.1 no.4
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• pp.285-296
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• 2011

Spar platforms have several advantages for deploying wind turbines in offshore for depth beyond 120 m. The merit of spar platform is large range of topside payloads, favourable motions compared to other floating structures and minimum hull/deck interface. The main objective of this paper is to present the response analysis of the slack moored spar platform supporting 5MW wind turbine with bottom keel plates in regular and random waves, studied experimentally and numerically. A 1:100 scale model of the spar with sparD, sparCD and sparSD configuration was studied in the wave basin ($30{\times}30{\times}3m$) in Ocean engineering department in IIT Madras. In present study the effect of wind loading, blade dynamics and control, and tower elasticity are not considered. This paper presents the details of the studies carried out on a 16 m diameter and 100 m long spar buoy supporting a 90 m tall 5 MW wind turbine with 3600 kN weight of Nacelle and Rotor and 3500 kN weight of tower. The weight of the ballast and the draft of the spar are adjusted in such a way to keep the centre of gravity below the centre of buoyancy. The mooring lines are divided into four groups, each of which has four lines. The studies were carried out in regular and random waves. The operational significant wave height of 2.5 m and 10 s wave period and survival significant wave height of 6 m and 18 s wave period in 300 m water depth are considered. The wind speed corresponding to the operational wave height is about 22 knots and this wind speed is considered to be operating wind speed for turbines. The heave and surge accelerations at the top of spar platform were measured and are used for calculating the response. The geometric modeling of spar was carried out using Multisurf and this was directly exported to WAMIT for subsequent hydrodynamic and mooring system analysis. The numerical results were compared with experimental results and the comparison was found to be good. Parametric study was carried out to find out the effect of shape, size and spacing of keel plate and from the results obtained from present work ,it is recommended to use circular keel plate instead of square plate.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.327-337
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• 2018

Since the track of the ballastless steel plate girder bridge is connected to a main girder without a deck and a ballast, the impact generated by train passage is transferred directly to bridge main members, and it can cause frequent damage of the bridge as well as higher noise and vibration level. Applying the CWR (Continuously Welded Rail) technology can reduce this structural problems, and, to this end, it is necessary to understand the characteristics of factors influencing vehicle-track or track-bridge interaction. In this paper, experimental study results are presented for examining the longitudinal resistance characteristics of the track, including a rail fastener, a sleeper fastener, and a track skeleton, installed on a ballastless steel plate girder bridge. The experiment is conducted using a disposed bridge from service, which is transported to a laboratory. The experimental results show that the rail fastener satisfies the performance criteria of the longitudinal resistance presented in KRS TR 0014-15, and the longitudinal resistance of old and new type sleeper fasteners is higher than the values provided in the existing research. Also, the unloaded longitudinal resistance of the ballastless track is between the ballast and the concrete tracks.

• Journal of the Korea Institute of Building Construction
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• v.22 no.1
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• pp.11-21
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• 2022

Currently, in the domestic construction industry, the free web method has been emerging as a potential solution to the shortage of skilled workers due to the prolonged COVID-19 crisis, as it helps in securing economic feasibility through shortening the construction period and reducing labor costs. To consider one part of the construction method, in this study, the bending behavior according to the load was evaluated for the SY slope-type beam formwork, which was manufactured at a factory, assembled with rebar, brought into the site, and then poured into the site. For the SY Beam standard cross-sectional shape, a cross-sectional dimensional width of 400mm and depth 600mm determined through structural modeling using the MIDAS GEN program were applied. A total of 6 specimens were made with a member length of 5,000mm, 5 specimens and one RC specimen in the comparison group were manufactured in real-size format using the thickness of the steel plate(0.8, 1.0, 1.2mm) as a variable, and bending experiments were performed. In the bending test, the steel plate deck showed high initial stiffness and maximum strength as it yielded, which showed that it sufficiently contributed to the flexural strength. It is judged that additional analysis and experimental studies for 1.05, 1.1, and 1.15mm are needed to derive the appropriate steel plate thickness and the method for calculating the tensile force contribution of the steel plate to secure the manufacturing, construction and economic feasibility of SY Beam in the future.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.707-716
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• 2011

It has been applied using cranes or insertion methods to install heavy structures to strengthen existing railway bridges. These methods are uneconomical because of two reasons. The first one is it is required to construct approach roads for heavy equipment and/or working yard. The second one is the electric lines shall be cutoff during construction. Both require additional construction cost and duration. In this study, new transport equipment was developed which can be applied to heavy structures up to 100 ton. Using this method, the heavy structure can be loaded into the new transport equipment at working yard and transported to the working site. This method can be applied, but not limited to railway bridge or roadbed rehabilitation. It was found that the precious construction can be achieved to install heavy structure using this method. The experimental construction to make non-ballast girder bridge composite with new pc deck slab using this method was carried out for Jewon bridge. The example bridge is in extreme condition because it locates above national road #38 within extreme transition curve and has 10 ‰ slope and skew. The experimental construction results were satisfactory both for safety and construction precision.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.356-361
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• 1994

From the previous experimental test results, it has shown that shear that shear strength in lightweight concrete beams was about 85% on that in normal concrete beams. It is speculated that shear connectors in composite beams of steel and lightweight concrete associated with the longitudinal shear strength decrease more in strength than those in normal concrete. So this paper, as a study on strength of shear connectors in composite beams of steel and lightweight concrete slabs, has a purpose to compare the strength formula resulted from the push-out test of thirteen solid slab and four deck Plate slab with the established ones, and then to suggest a proper strength formula of the shear connectors. The established strength formula of the shear connectors is prescribed for $P_ps = 0.50A_s . \sqrt{f_C . E_C}$by AISC coed, but from the experimental test results the strength values of the shear connectors in lightweignt concrete slabs shows about 70% on those of the shear connectors in normal concrete slabs by AISC code. Therefore, as a strength formula this paper suggests to multiply the established strength formula by reduction factor$(\varphi=0.7)$.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.105-109
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• 2011

As is well appreciated, welding is the most important fundamental process in manufacturing marine structures. However, weld-induced deformation is inevitable because of the non-uniform distribution of temperature during welding. The deformation caused by welding is one of the principal obstacles in enhancing the productivity in the manufacturing procedure for marine structures. This should be much more seriously considered in the case of the thin blocks found in a ship with multi-deck structures. This paper is concerned with the deformation control of thin panel blocks by applying intermittent welding to fillet welding. In order to investigate the quantitative effect of the intermittent welding, a thermo elasto-plastic analysis was carried out with various welding pitches and plate thicknesses. Welding tests were also carried out to show the validity of the present thermo-elasto-plastic analysis. Numerical analysis results showed good agreement with those of the welding tests. As far as the present numerical results are concerned, it has been seen that a more than 50% reduction in angular distortion can be achieved by applying the intermittent welding because of the low heat input.

• Structural Engineering and Mechanics
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• v.27 no.6
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• pp.651-670
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• 2007

An experimental study to evaluate a redundancy capacity in simple span two plate-girder bridges, which are generally classified as a non-redundant load path structure, has been performed under the condition that one of the two girders is seriously damaged. The bottom lateral bracing was selected as an experimental parameter and two 1/5-scale bridge specimens with and without bottom lateral bracing have been prepared. The loading tests were first performed on the intact specimens without cracked girder within elastic range. Thereafter, the ultimate loading tests were conducted on the damaged specimens with an induced crack at the center of a girder. The test results showed that the cross beams and concrete deck redistributed partly the applied load to the uncracked girder, but the lateral bracing system played a significant role of the load redistribution when a girder was damaged. The redundancy was evaluated based on the test results and an appropriate redundancy level was evaluated when the lateral bracing was provided in a seriously damaged simple span two-girder steel bridge.

• Wind and Structures
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• v.11 no.3
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• pp.209-220
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• 2008

Flutter derivatives provide the basis of predicting the critical wind speed in flutter and buffeting analysis of long-span cable-supported bridges. Many studies have been performed on the methods and applications of identification of flutter derivatives of bridge decks under wind action. In fact, strong wind, especially typhoon, is always accompanied by heavy rain. Then, what is the effect of rain on flutter derivatives and flutter critical wind speed of bridges? Unfortunately, there have been no studies on this subject. This paper makes an initial study on this problem. Covariance-driven Stochastic Subspace Identification (SSI in short) which is capable of estimating the flutter derivatives of bridge decks from their steady random responses is presented first. An experimental set-up is specially designed and manufactured to produce the conditions of rain and wind. Wind tunnel tests of a quasi-streamlined thin plate model are conducted under conditions of only wind action and simultaneous wind-rain action, respectively. The flutter derivatives are then extracted by the SSI method, and comparisons are made between the flutter derivatives under the two different conditions. The comparison results tentatively indicate that rain has non-trivial effects on flutter derivatives, especially on and $H_2$ and $A_2$thus the flutter critical wind speeds of bridges.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.2
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• pp.20-25
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• 2011

In this paper, two dimensional concrete slabs for a railroad bridge were analyzed by the specially orthotropic laminates theory. Both the geometrical and material property of the cross section of the slab was considered symmetrically with respect to the neutral surface so that the bending extension coupling stiffness, $B_{ij}$ = 0, and $D_{16}=D_{26}=0$ Bridge deck behaves as specially orthotropic plates. In general, the analytical solution for such complex systems is very difficult to obtain. Thus, finite difference method was used for analysis of the problem. In this paper, the finite difference method and the beam theory were used for analysis.