• Structural Engineering and Mechanics
• /
• v.82 no.3
• /
• pp.385-400
• /
• 2022

Sky-bridges between adjacent buildings can enhance lateral stiffness and limit the impact of lateral forces. This study analysed the structural capabilities and dynamic performances of sky-bridge-coupled buildings under various sets of ground motions. Finite Element (FE) analyses were carried out with the link being iteratively repositioned along the full height of the structures. Incremental dynamic analysis (IDA) and probabilistic damage distribution were also applied. The results indicated that the establishment of sky-bridges caused a slight change in the natural frequency and mode shapes. The sky-bridge system was shown to be efficient in controlling displacement and Inter-Storey Drift Ratio (%ISDR) and reducing the probability of damage in the higher floors. The most efficient location of the sky-bridge, for improving its rigidity, was found to be at 88% of the building height. Finally, the effects of two types of materials (steel and concrete) and end conditions (hinged and fixed) were studied. The outcomes showed that coupled buildings with a sky-bridge made of steel with hinged connection could withstand ground motions longer than those made of concrete with fixed connection.

• Journal of Environmental Impact Assessment
• /
• v.3 no.2
• /
• pp.25-32
• /
• 1994

This study was carried out as the Anyang creek water quality management using Geographic Information System (GIS) is the purpose of this pilot project to apply a GIS to environmental management field. Analysis of water quality data has been investigated using GIS with modeling of water quality management for the Anyang creek. The results of this study are summarized as follows: 1. The concentration of Mercury in sediment was increased rapidly nearby A26(Nightsoil Treatment Plant) and maximum was showed at A18 (Imgok bridge). Cadmium was increased rapidly at A35(Chulsan bridge). 2. River water quality management using visible computer system as GIS is effective to make decision for water quality management plan and database of environmental factors should be completed before applying GIS. 3. When water pollution accident is occurred in the river water system, pollutant source can be traced and analysed systematically using GIS to manage pollutants discharged into the river water system.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.193-200
• /
• 2004

In this study, the impact load on bridge by vessel collision in consideration of fender system is evaluated by numerical method. The bow of object vessel(DWT5000) is standardized, and modeled by shell elements. The main body of objective vessel is modeled by beam elements that present mass distribution and stiffness of vessel. The buoyancy effect of vessel is considered as linear spring. The two types of fender systems, such as steel and rubber are analyzed in this study. In steel fender system, the steel plates that absorb collision energy by its collapse are modeled by shell element with stiffener. The steel is material modeled elastic-plastic material. In the rubber fender system, the rubber material is modeled hyper-elastic material and the main body of fender is modeled by solid elements. The global impact responses of vessel and fender system are evaluated by explicit dynamic scheme. The results show that the magnitude of vessel collision force are depended on the material behavior of fender system. Also the values of collision load are conservative compare to the those of design codes.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2005.04a
• /
• pp.607-615
• /
• 2005

In this study ship collision risk analysis is performed to determine the design vessel for collision impact analysis of the bridge. Method I in AASHTO LRFD bridge design specifications is a semi-deterministic analysis procedure for determining the design vessel. Method ll which is a more complicated probability based analysis procedure is used to select the design vessel for collision impact. The AF allocation by weights seems to be more reasonable than the pylon concentration allocation method because AF allocation by weights takes the design parameter characteristics quantitatively into consideration although the pylon concentration allocation method brings more economical results when the overestimated design collision strength of piers compared to the strength of pylon is moderately modified. Therefore more researches on the allocation model of AF and the selection of design vessel are required.

• Journal of Environmental Impact Assessment
• /
• v.16 no.4
• /
• pp.285-300
• /
• 2007

The purpose of this study was to ascertain the ecological state and problems of eco-bridges on Korean roads. The study was conducted from March to April 2007 by checking ecological factors and wildlife around the eco-bridges and habitats. 8 representative eco-bridges were selected by their bridge shape and condition of location. After field survey, we analyzed ideal trails for wildlife using field data, digital topology maps, satellite images, and land use map. In addition to trail analysis, we identified the propriety of the eco-bridges through Population Viability Analysis. Because of unsuitable location and management, we found that most of the bridges are not proper for wildlife dispersal. Moreover, in some habitats, we could expect that some local populations might be extinct without appropriate treatments.

• KCI Concrete Journal
• /
• v.13 no.1
• /
• pp.27-34
• /
• 2001

This paper presents the results of a study on the effects of pounding at expansion joints of concrete bridges under earthquake ground motions. An engineering approach, rather than continuum mechanics, is emphasized. First, the sensitivity analysis of the gap element stiffness is performed. Second, usefulness of the analysis method for simulation of pounding phenomena is demonstrated. Third, the effects of pounding on the ductility demands measured in terms of the rotation of column ends are investigated. Two-dimensional FE analysis using a bilinear hysterestic model for bridge substructure joints and a nonlinear gap element for the expansion joint is performed on a realistic bridge with an expansion joint. Effects of the primary factors on the ductility demand such as gap sizes and characteristics of earthquake ground motion are investigated through a parametric study. The major conclusions are that pounding effect is generally negligible on the ductility demand for wide practical ranges of gap size and peak ground acceleration, but is potentially significant at the locations of impact.

• Proceedings of the KSR Conference
• /
• 2001.05a
• /
• pp.281-288
• /
• 2001

In order to evaluate the effect of impact load at support stiffness transition area, the field estimations are performed at the transition zone between earthwork and bridge on test operation of KTX. Due to differential settlement caused by the variations of track support stiffness, large impact forces are investigated. However, the measured values such as wheel load, rail stress, displacement and acceleration in the transition area shows that the stiffness changes in the transition area are not abrupt, and the stiffness in the infra track structure varies continuously. In this experimental study, the parameters influencing safety of transition area are not governed by partial or local stiffness because cumulative passing loads are not sufficient on test operation of KTX.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.335-338
• /
• 2005

This study was performed to verify that the impact vibration test on the damaged concrete pier can be adopted for assessment of the bridge substructure integrity. Using the experimental modal analysis, the dynamic property changes of the concrete pier are investigated according to the damage levels which are modeled by the loss of cross section area of the pier body. As a result of the impact vibration test, it is found that the natural frequency of the bridge substructure is reduced due to the damage on the pier such as loss of cross section area, and the natural frequency can be used for assessment of the integrity index.

• Computers and Concrete
• /
• v.12 no.6
• /
• pp.803-818
• /
• 2013

In this study, analytical and experimental modal analyses of a scaled bridge model are carried out to extract the dynamic characteristics such as natural frequency, mode shapes and damping ratios. For this purpose, a scaled bridge model is constructed in laboratory conditions. Three dimensional finite element model of the bridge is constituted and dynamic characteristics are determined, analytically. To identify the dynamic characteristics experimentally; Experimental Modal Analyses (ambient and forced vibration tests) are conducted to the bridge model. In the ambient vibration tests, natural excitations are provided and the response of the bridge model is measured. Sensitivity accelerometers are placed to collect signals from the measurements. The signals collected from the tests are processed by Operational Modal Analysis; and the dynamic characteristics of the bridge model are estimated using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods. In the forced vibration tests, excitation of the bridge model is induced by an impact hammer and the frequency response functions are obtained. From the finite element analyses, a total of 8 natural frequencies are attained between 28.33 and 313.5 Hz. Considering the first eight mode shapes, these modes can be classified into longitudinal, transverse and vertical modes. It is seen that the dynamic characteristics obtained from the ambient and forced vibration tests are close to each other. It can be stated that the both of Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are very useful to identify the dynamic characteristics of the bridge model. The first eight natural frequencies are obtained from experimental measurements between 25.00-299.5 Hz. In addition, the dynamic characteristics obtained from the finite element analyses have a good correlation with experimental frequencies and mode shapes. The MAC values obtained between 90-100% and 80-100% using experimental results and experimental-analytical results, respectively.

• Wind and Structures
• /
• v.22 no.2
• /
• pp.211-234
• /
• 2016

Super long-span bridges provide people with great convenience, but they also bring traffic safety problems caused by strong wind owing to their high decks. In this paper, the large eddy simulation together with dynamic mesh technology in computational fluid dynamics (CFD) is used to explore the mechanism of a moving vehicle's transient aerodynamic force in crosswind, the regularity and mechanism of the vehicle's aerodynamic forces when it passes through a bridge tower's wake zone in crosswind. By comparing the calculated results and those from wind tunnel tests, the reliability of the methods used in the paper is verified on a moving vehicle's aerodynamic forces in a bridge tower's wake region. A vehicle's aerodynamic force coefficient decreases sharply when it enters into the wake region, and reaches its minimum on the leeward of the bridge tower where exists a backflow region. When a vehicle moves on the outermost lane on the windward direction and just passes through the backflow region, it will suffer from negative lateral aerodynamic force and yaw moment in the bridge tower's wake zone. And the vehicle's passing ruins the original vortex structure there, resulting in that the lateral wind on the right side of the bridge tower does not change its direction but directly impact on the vehicle's windward. So when the vehicle leaves from the backflow region, it will suffer stronger aerodynamic than that borne by the vehicle when it just enters into the region. Other cases of vehicle moving on different lane and different directions were also discussed thoroughly. The results show that the vehicle's pneumatic safety performance is evidently better than that of a vehicle on the outermost lane on the windward.