• The Research Journal of the Costume Culture
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• v.30 no.3
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• pp.403-413
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• 2022

The purpose of this study was to develop a 3D mesh-type impact protection pad with excellent motion adaptability and functionality by applying 3D printing technology. The hexagonal 3D mesh, which constitutes the basic structure of the pad, comprises two types: small and large. The bridge connecting the basic units was designed as the I-type, V-type, IV-type, and VV-type. After evaluating the characteristics of the bridge, it was found that the V-type bridge had the highest flexibility and tensile elongation. The hip joint pad and knee pad were completed by combining the hexagonal 3D mesh structure with the optimal bridge design. The impact protection pad was printed using a fused deposition modeling-type 3D printer with a filament made of thermoplastic polyurethane material, and the protection pad's performance was evaluated. When an impact force of approximately 6,500N was applied to the pad, the force attenuation percentage was 78%, and when an impact force of approximately 8,000N was applied, the force attenuation percentage was 75%. Through these results, it was confirmed that the 3D-printed impact protection pad with a hexagonal 3D mesh structure connected by a V-shaped bridge developed in this study can adapt to changes in the body surface according to movement and provides excellent impact protection performance.

• Interaction and multiscale mechanics
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• v.2 no.3
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• pp.263-276
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• 2009

This paper is intended to investigate interaction response of a train running over a suspension bridge undergoing support settlements. The suspension bridge is modeled as a single-span suspended beam with hinged ends and the train as successive moving oscillators with identical properties. To conduct this dynamic problem with non-homogeneous boundary conditions, this study first divides the total response of the suspended beam into two parts: the static and dynamic responses. Then, the coupled equations of motion for the suspended beam carrying multiple moving oscillators are transformed into a set of nonlinearly coupled generalized equations by Galerkin's method, and solved using the Newmark method with an incremental-iterative procedure including the three phases: predictor, corrector, and equilibrium-checking. Numerical investigations demonstrate that the present iterative technique is available in dealing with the dynamic interaction problem of vehicle/bridge coupling system and that the differential movements of bridge supports will significantly affect the dynamic response of the running vehicles but insignificant influence on the bridge response.

• Structural Engineering and Mechanics
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• v.15 no.1
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• pp.1-19
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• 2003

This paper presents the formulation of a new bridge-vehicle system with validation using the field data. Both pitching and twisting modes of the vehicle are considered in the contribution of the dynamic effects in the bridge responses. A heavy vehicle was hired as a control vehicle with known axle weight, axle spacing and spring coefficients. The measured responses were generated from the control vehicle running at a particular speed at a test span at Ma Tau Wai Flyover. The measured responses were acquired using strain gauges installed beneath the girder beams of the test bridge. The simulated responses were generated using BRVEAN that is a self-developed program based on the proposed bridge-vehicle system. The validation shows that the bridge model is valid for representing the test bridge and the governing equations are valid for representing the motion of moving vehicles.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.17-23
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• 1998

The objective of this study is to investigate the dynamic behaviors of KHSR(Korea High-Speed Railway) bridge supported by elastomeric bearings subjected to high-speed vehicles. The effects of damping on the dynamic behaviors are also studied. The train composed of two power cars, two motor cars and eighteen passenger cars are simulated using constant moving forces for simplicity and effectiveness in the analysis. Direct integration method are used to solve the dynamic equation of motion. The bridge analyzed is real bridge with 2@40m span and concrete continuos box girder. The bridge is model led using frame element in three dimensional space. From the results of this study, the effects of elastomeric bearing on the dynamic responses of bridge(especially vertical accelerations) may cause undesirable behaviors. Damping are very important in the dynamic behaviors of the bridge subjected to high-speed railways. And so, dynamic analysis of steel bridge for high-speed railway supported by elastomeric bearings should be performed carefully.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.329-336
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• 2001

This study examines the fragility curves of a bridge by Capacity Spectrum Method. A sample of 10 nominally identical but statistically different bridge and 80 ground-motion time histories are considered to account for the uncertainties related to the structural capacity and ground motion, respectively. The comparison of fragility curves by Capacity Spectrum Method with those by time-history analysis indicates that the agreement is excellent for the state of at least minor damage, but not as good for the state of major damage where nonlinear effects clearly play a crucial role. Overall, however, the agreement is adequate even in the state of major damage considering the large number of typical assumptions under which the analyses of fragility characteristics are performed.

• Coupled systems mechanics
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• v.3 no.2
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• pp.213-232
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• 2014

Pounding is a major cause of bridge damage during earthquakes. In an extreme situation, it can even contribute to the unseating of bridge girders. Long-span bridges will inevitably experience spatially varying ground motions. Soil-structure interaction (SSI) may play a significant role in the structural response of these structures. The objective of this research is to experimentally investigate the effect of spatially varying ground motions on the response of a three-segment bridge considering SSI and pounding. To incorporate SSI, the model was placed on sand contained in sandboxes. The sandboxes were fabricated using soft rubber in order to minimise the rigid wall effect. The spatially varying ground motion inputs were simulated based on the New Zealand design spectra for soft soil, shallow soil and strong rock conditions, using an empirical coherency loss function. The results show that with pounding, SSI can amplify the pier bending moments and the relative opening displacements.

• Journal of the Korean Geosynthetics Society
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• v.20 no.2
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• pp.35-43
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• 2021

In this paper, the sub-structuring technique-applied train-bridge interaction analysis model, which is formulated based on the simplified three-dimensional train-bridge interaction analysis model for high-speed bridge-train interaction analysis, is presented. In the sub-structuring technique, the super-structure and the supporting structure of railway bridges can be modeled as sub-structures, and train-bridge interaction analysis can be efficiently performed. As a train analysis model, two-dimensional train model is used, and the Lagrange equation of motion is applied to derive the equation of motion of two-dimensional train. In the sub-structuring technique, the number of degrees of freedom can be reduced by using the condensation method, thus reducing the time and cost for calculating the eigenvalues and eigenvectors, and the time and cost for the subsequent calculation. In this paper, Guyan reduction method is used as sub-structuring technique. By combining simplified three-dimensional bridge-train interaction analysis and Guyan reduction method, the efficient and accurate bridge-train interaction analysis can be performed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.111-123
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• 2006

In the design of bridges, exact evaluation of traffic loading is very important for the safety and maintenance of bridges. In general, traffic loading is represented by live load (including impact load) and fatigue load. For exact evaluation of traffic loading, it is important to get reliable and comprehensive truck data including the traffic and weight information. It requires the development of Bridge Weigh-In-Motion (BWIM), which measures the truck weights without stopping the traffic. Objectives of the study is (1) to develop the BWIM system, (2) to verified the system in bridges in Highways.

• Wind and Structures
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• v.19 no.2
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• pp.145-167
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• 2014

Wind-vehicle-bridge (WVB) interaction can be regarded as a coupled vibration system. Aerodynamic forces and moment on vehicles and bridge decks play an important role in the vibration analysis of the coupled WVB system. High-speed vehicle motion has certain effects on the aerodynamic characteristics of a vehicle-bridge system under crosswinds, but it is not taken into account in most previous studies. In this study, a new testing system with a moving vehicle model was developed to directly measure the aerodynamic forces and moment on the vehicle and bridge deck when the vehicle model moved on the bridge deck under crosswinds in a large wind tunnel. The testing system, with a total length of 18.0 m, consisted of three main parts: vehicle-bridge model system, motion system and signal measuring system. The wind speed, vehicle speed, test objects and relative position of the vehicle to the bridge deck could be easily altered for different test cases. The aerodynamic forces and moment on the moving vehicle and bridge deck were measured utilizing the new testing system. The effects of the vehicle speed, wind yaw angle, rail track position and vehicle type on the aerodynamic characteristics of the vehicle and bridge deck were investigated. In addition, a data processing method was proposed according to the characteristics of the dynamic testing signals to determine the variations of aerodynamic forces and moment on the moving vehicle and bridge deck. Three-car and single-car models were employed as the moving rail vehicle model and road vehicle model, respectively. The results indicate that the drag and lift coefficients of the vehicle tend to increase with the increase of the vehicle speed and the decrease of the resultant wind yaw angle and that the vehicle speed has more significant effect on the aerodynamic coefficients of the single-car model than on those of the three-car model. This study also reveals that the aerodynamic coefficients of the vehicle and bridge deck are strongly influenced by the rail track positions, while the aerodynamic coefficients of the bridge deck are insensitive to the vehicle speed or resultant wind yaw angle.

• Wind and Structures
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• v.14 no.2
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• pp.133-151
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• 2011

For a detailed investigation of the dynamic behaviour of slender bridges under wind action especially the motion-induced fluid forces should be available not only for harmonic motions but also for more general ones. If linear transfer behaviour is assumed, the force-displacement relation for almost arbitrary motions can be handled in the frequency domain using aerodynamic transfer functions. In aerospace engineering as well as in bridge engineering, these functions are usually approximated by special kinds of complex-valued rational functions which depend on complex frequencies. The quality of this approximation is evaluated for several bridge cross sections in this article. It is shown that rational functions are for some sections scarcely suitable to realistically represent the transfer behaviour of motion-induced aerodynamic forces for arbitrarily complex frequencies.