• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.655-662
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• 2011

For analyzing seismic performance of long-span bridge for multi-support excitation and preparing technically and efficiently for a variety of design demands, the new module on multiple excitation was built in a reliable non-linear analysis program(RCAHEST) by using Influence Line Method, and the study on structures was performed previously. Also, the result of the analysis through RCAHEST was compared and verified with commercial finite element analysis program SAP2000 by using the feature of Multi-Support Excitation. From these results, nonlinear time history analysis considering multi-support excitation was studied after designing FE model of Incheon cable-stayed bridge. It was proved that the maximum response of horizontal displacement decreased as the time delay was increasing at all nodes of bridge. And then the serviceability of analysis model was evaluated by performing ultimate analysis under changes in maximum acceleration of seismic load data.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.36-42
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• 2020

The objectives of this study were to investigate the standard and roof vent type of multi-span greenhouse and to analyze the characteristics of natural ventilation of multi-span greenhouse with different roof vent using computational fluid dynamics (CFD) code. The vent area proportion of surveyed farms averaged 10%, it was analyzed that the vent design for natural ventilation is insufficient. The results of natural ventilation efficiency of multi-span greenhouse according to roof vent type showed that the temperature of the position in which the crops grew was the lowest in the conical roof vent type and the highest in the half conical roof vent type. For the natural ventilation effect, the conical roof vent type was the best one, but the structural stability should be evaluated in light of wind load.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.111-117
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• 2008

This study aims to develop a system which is able to monitor and analyze behavior of long span bridge in real time using multiple GPS. Through setting up many GPS at the important points of long span bridge and measuring displacement in real time, over all behavior of bridge could be analyzed. Behavior analyzing system developed in this study is able to digitize and visualize the overall and points displacement of bridge and deal with events actively. Also it is able to calculate statistical data related to analyze behavior through the constructing a database of measuring data.

• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.713-723
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• 2017

As a new type of ballastless track, longitudinal continuous slab track (CST) has been widely used in China. It can partly isolate the interaction between the ballastless track and the bridge and thus the rail expansion device would be unnecessary. Compared with the traditional track, CST is composed of multi layers of continuous structures and various connecting components. In order to investigate the performance of CST on a long-span bridge, the spatial finite element model considering each layer of the CST structure, connecting components, bridge, and subgrade is established and verified according to the theory of beam-rail interaction. The nonlinear resistance of materials between multilayer track structures is measured by experiments, while the temperature gradients of the bridge and CST are based on the long-term measured data. This study compares the force distribution rules of ballasted track and CST as respectively applied to a long span bridge. The effects of different damage conditions on CST structures are also discussed. The results show that the additional rail stress is small and the CST structure has a high safety factor under the measured temperature load. The rail expansion device can be cancelled when CST is adopted on the long span bridge. Beam end rotation caused by temperature gradient and vertical load will have a significant effect on the rail stress of CST. The additional flexure stress should be considered with the additional expansion stress simultaneously when the rail stress of CST requires to be checked. Both the maximum sliding friction coefficient of sliding layer and cracking condition of concrete plate should be considered to decide the arrangement of connecting components and the ultimate expansion span of the bridge when adopting CST.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.277-284
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• 2018

For the main variables to be selected by the designer for the heating and cooling load calculation in greenhouses, in order to evaluate the effect of these design values on the heating and cooling load, the simulations were carried out by varying the respective design values. Based on these results, we proposed the design values which should pay special attention to selection. The design values which have the greatest effect on the heating load were the overall heat transfer coefficient of the covering material and the design outdoor temperature was next. The effect of the design values according to the number of spans showed little difference. In the case of the single-span greenhouse, the effect of the design values related to the underground heat transfer can not be ignored. However, in the case of the multi-span greenhouse, the effect of the design values related to the underground heat transfer and the infiltration rate were insignificant. The design values which have the greatest effect on the cooling load were the solar radiation into the greenhouse and the evapotranspiration coefficient, followed by the indoor and outdoor temperature difference and the ventilation rate. The effect of the design values showed a great difference between the single-span greenhouse and the multi-span greenhouse, but there was almost no difference according to the number of spans. The effect of the overall heat transfer coefficient of the covering material was negligible in both the single-span greenhouse and the multi-span greenhouse. However, the effect of the indoor and outdoor temperature difference and the ventilation rate on the cooling load was not negligible. Especially, it is considered that the effect is larger in multi-span greenhouse.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.208.1-208.1
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• 2005

• Journal of Bio-Environment Control
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• v.8 no.1
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• pp.9-18
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• 1999

Natural ventilation in a four and one-half span, double polyethylene commercial greenhouse was investigated with actual data collected at Quailcrest Farm near Wooster, Ohio. Moreover, a computational fluid dynamics (CFD) numerical technique, FLUENT V4.3, was used to predict natural ventilation rates, thermal conditions, and airflow distributions in the greenhouse. The collected climate data showed that the multi-span greenhouse was well ventilated by the natural ventilation system during the typical summer weather conditions. The maximum recorded air temperature difference between inside and outside the greenhouse was 3.5$^{\circ}C$ during the hottest (34.7$^{\circ}C$) recorded sunny day; the air temperatures in the greenhouse were very uniform with the maximum temperature difference between six widely dispersed locations being only 1.7$^{\circ}C$. The CFD models predicted that air exchange rates were as high as 0.9 volume per minute (A.C. .min$^{-1}$ ) with 2.5m.s$^{-1}$ winds from the west as designed.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.527-537
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• 2007

The main girders and cross-beams of an H-beam bridge consisted of factory-made H-beams, providing better conditions for quality control. Also, on-site fabrication works can be minimized and most of the stiffeners can be omitted, enabling simple and economic construction. In this study, the effect of the Multi-Stepwise TPSM (M-TPSM) on improving the maximum span length and section efficiency is analyzed. Compared to a 30-m-long, five-girder conventional plate girder bridge, structural analysis results showed that 50.7~55.1% of the girder height and 24.1~26.2% of the self-weight may be reduced by the application of M-TPSM to a five-girder H-beam bridge constructed with H-$900{\times}300$beams. In case of conventional H-beam bridges without M-TPSM, it was found that seven girders are required for a similar level of load-carrying capacity. Therefore, it is concluded that by the application of the M-TPSM, the H-beam bridge would become one of most cost-competitive options for short- and medium-span bridges.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.145-154
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• 1998

The motion-limiting devices can be used for reducing the maximum and residual displacements of the multi-span continuous bridges with inelastic elements such as isolation bearings and plastic hinges formed in piers. For the design of motion-limiting device, the nonlinear time history analysis is required. But the time history analysis is time consuming and very complex. This study suggests the simple design procedure of the motion-limiting devices using the equivalent elastic analysis method and the acceleration-displacement spectrum concept. The suggested design procedure can be used very effectively for determining the location and gap size of the motion-limiting devices.

• Structural Engineering and Mechanics
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• v.66 no.6
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• pp.737-748
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• 2018

The current study presents a new technique in the framework of the nonlocal elasticity theory for a comprehensive buckling analysis of Euler-Bernoulli nano-beams made up of bidirectional functionally graded material (BDFGM). The mechanical properties are considered by exponential and arbitrary variations for axial and transverse directions, respectively. The various circumstances including tapering, resting on two-parameter elastic foundation, step-wise or continuous variations of axial loading, various shapes of sections with various distribution laws of mechanical properties and various boundary conditions like the multi-span beams are taken into account. As far as we know, for the first time in the current work, the buckling analyses of BDFGM nano-beams are carried out under mentioned circumstances. The critical buckling loads and mode shapes are calculated by using energy method and a new technique based on calculus of variations and collocation method. Fast convergence and excellent agreement with the known data in literature, wherever possible, presents the efficiency of proposed technique. The effects of boundary conditions, material and taper constants, foundation moduli, variable axial compression and small-scale of nano-beam on the buckling loads and mode shapes are investigated. Moreover the analytical solutions, for the simpler cases are provided in appendices.