• Korean Journal of Agricultural Science
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• v.40 no.4
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• pp.317-323
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• 2013

This research was conducted to obtain the basic information for establishment of standard guidelines in the design and installation of roof ventilation system in single-span plastic greenhouse. To achieve this, the greenhouse structure & characteristics, cultivation status, and ventilation system were investigated for single-span greenhouse with roof ventilation system cultivating the Cucurbitaceae vegetables, watermelon, cucumber, and oriental melon. Most of single-span watermelon greenhouse in Haman and Buyeo area were a hoop-style and the ventilation system in those greenhouses mostly consisted of two different types of 'roof vent (circular or chimney type) + side vent (hole) + fan' and 'roof vent (circular type) + side vent (hole or roll-up type)'. The diameter of circular and chimney-type vent was mostly 60cm and the average number of vents was 10.5 per a bay with vent spacing of average 6.75m. The ratio of roof vent area to floor area and side vent area in the single-span watermelon greenhouse with ventilation fan were 0.46% and 7.6%, respectively. The single-span cucumber greenhouse in Haman and Changnyeong area were a gable roof type, such as even span, half span, three quarter and the 70.6% of total investigated single-span greenhouses was equipped with a roof ventilation fan while 58.8% had a circulation fan inside the greenhouse. The ratios of roof vent area to floor area in the single-span cucumber greenhouse ranged from 0.61 to 0.96% and in the case of the square roof vent, were higher than that of the circular type vent. On average, the roof ventilation fan in single-span cucumber greenhouse was equipped with the power input of 210W and maximum air volume of $85.0m^3/min$, and the number of fans was 9.75 per a bay. The number of roof vent of single-span oriental melon greenhouse with only roll-up type side vent ranged from 8 to 21 (average 14.8), which was higher than that of other Cucurbitaceae vegetables while the vent number of the greenhouse with a roof ventilation fan was average 7 per a bay.

• Wind and Structures
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• v.19 no.6
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• pp.649-663
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• 2014

The present paper discusses the characteristics of unsteady aerodynamic forces on long-span curved roofs. A forced vibration test is carried out in a wind tunnel to investigate the effects of wind speed, vibration amplitude, reduced frequency of vibration and rise/span ratio of the roof on the unsteady aerodynamic forces. Because the range of parameters tested in the wind tunnel experiment is limited, a CFD simulation is also made for evaluating the characteristics of unsteady aerodynamic forces on the vibrating roof over a wider range of parameters. Special attention is paid to the effect of reduced frequency of vibration. Based on the results of the wind tunnel experiment and CFD simulation, the influence of the unsteady aerodynamic forces on the dynamic response of a full-scale long-span curved roof is investigated on the basis of the spectral analysis.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.13-16
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• 2010

This study is an Investigation on the Watertightness Properties of Rain-Block System on the Sliding-Roof Joint of Large-Span Membrane Structures. In this experimental, we test the watertightness performance of joint part of sliding door in roof of large span membrane structure(for pilot project) under environment of rain and wind. A shape of rain water blocking systems of joint part in sliding door verifies the defects and effects of water leakage prevention in precipitation with the wind conditions. For obtaining watertightness of large span membrane structures, it is necessary quality of joints and performance, and quality of membrane material of a retractable roof as well as a closed roof. Also, for obtaining quality in joints, it is essential to make a watertightness guideline for design of large-span membrane.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.267-270
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• 2001

It is difficult to install a ventilation window on the roof of single span greenhouse of arch shape. Investigation on the roof ventilation structure for those greenhouses was conducted. The effect of roof ventilation was evaluated by comparative experiments between greenhouse installing roof vent and having controlled side vent only. And ventilation efficiency was analyzed by experiments on the opening and closing operation of the roof and side vent.

• Wind and Structures
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• v.13 no.1
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• pp.57-82
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• 2010

The 486m-long roof of Shenzhen Citizens Centre is one of the world's longest spatial lattice roof structures. A comprehensive numerical study of wind effects on the long-span structure is presented in this paper. The discretizing and synthesizing of random flow generation technique (DSRFG) recently proposed by two of the authors (Huang and Li 2008) was adopted to produce a spatially correlated turbulent inflow field for the simulation study. The distributions and characteristics of wind loads on the roof were numerically evaluated by Computational Fluid Dynamics (CFD) methods, in which Large Eddy Simulation (LES) and Reynolds Averaged Navier-Stokes Equations (RANS) Model were employed. The main objective of this study is to explore a useful approach for estimations of wind effects on complex curved roof by CFD techniques. In parallel with the numerical investigation, simultaneous pressure measurements on the entire roof were made in a boundary layer wind tunnel to determine mean, fluctuating and peak pressure coefficient distributions, and spectra, spatial correlation coefficients and probability characteristics of pressure fluctuations. Numerical results were then compared with these experimentally determined data for validating the numerical methods. The comparative study demonstrated that the LES integrated with the DSRFG technique could provide satisfactory prediction of wind effects on the long-span roof with complex shape, especially on separation zones along leading eaves where the worst negative wind-induced pressures commonly occur. The recommended LES and inflow turbulence generation technique as well as associated numerical treatments are useful for structural engineers to assess wind effects on a long-span roof at its design stage.

• Journal of Korean Association for Spatial Structures
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• v.17 no.1
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• pp.31-40
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• 2017

The objective of this study is to analysis the mechanical characteristics and nonlinear behaviors on the geometric nonlinear behavior of a cable spoke wheel roof system for long span lightweight roof structures. The weight of a cable spoke wheel roof dramatically can reduce and the cable roof system can easily make the required rigidity and shape by the sag ratio and pretension forces. Determining the pretension and initial sag of cable roof system is essential in a design process and the shape of roof is changed by pretension. The nonlinear behavior of flexible cable system has greatly an affect on the sag and pretension. This paper will be carried out analyzing and comparing the tensile forces and deflection of a cable spoke wheel system for the large span retractable roof, and analyzed to deflections and tensile forces by the post height of center hub. The double arrangement of a spoke wheel system with reverse curvature works more effectively as a load bearing system, the pretension can easily increase the structural stiffness. The cable truss system can carry vertical load in up and downward direction, and act effectively as load bearing elements.

• Wind and Structures
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• v.25 no.5
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• pp.493-506
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• 2017

Wind-induced response behavior of long-span roof structures is very complicated, showing significant contributions of multiple vibration modes. The largest load effects in a huge number of members should be considered for the sake of the equivalent static wind loads (ESWLs). Studies on essential matters and necessary conditions of the universal ESWLs are discussed. An efficient method for universal ESWLs on long-span roof structures is proposed. The generalized resuming forces including both the external wind loads and inertial forces are defined. Then, the universal ESWLs are given by a combination of eigenmodes calculated by proper orthogonal decomposition (POD) analysis. Firstly, the least squares method is applied to a matrix of eigenmodes by using the influence function. Then, the universal ESWLs distribution is obtained which reproduces the largest load effects simultaneously. Secondly, by choosing the eigenmodes of generalized resuming forces as the basic loading distribution vectors, this method becomes efficient. Meanwhile, by using the constraint equations, the universal ESWLs becomes reasonable. Finally, reproduced largest load effects by load-response-correlation (LRC) ESWLs and universal ESWLs are compared with the actual largest load effects obtained by the time domain response analysis for a long-span roof structure. The results demonstrate the feasibility and usefulness of the proposed universal ESWLs method.

• Journal of Korean Association for Spatial Structures
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• v.17 no.2
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• pp.21-32
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• 2017

The objective of this study is to analysis the mechanical characteristics on the geometric nonlinear behavior of radial cable roof systems for long span retractable cable roof structures. The retractable roof is designed as a full control system to overcome extreme outdoor environments such as extreme hot or cold weather, strong wind or sunlight, and the cable roof greatly can reduce roof weight compared to other rigid structural system. A retractable cable roof system is a type of structures in which the part of entire roof can be opened and closed. The radial cable roof is an effective structural system for large span retractable roofs, the outer perimeter of the roof is a fixed membrane roof and the middle part is a roof that can be opened and closed. The double arrangement cables of a radial cable truss roof system with reverse curvature works more effectively as a load bearing cables, the cable system can carry vertical load in up and downward direction. In this paper, to analyze the mechanical characteristics of a radial cable roof system with central posts, the authors will investigate the tensile forces of bearing cables, stabilized cables, ring cables, and the deflection of roof according to the height of the post or hub that affects the sag ratio of cable truss. The tensile forces of the cables and the deflection of the roof are compared for the cases when the retractable roof is closed and opened.

• Structural Engineering and Mechanics
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• v.11 no.6
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• pp.605-616
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• 2001

The purpose of this study is to investigate the effect of the shear wall location in rigid frames on the dynamic behavior of a roof structure due to vertical and horizontal earthquake motions. The study deals with a gabled long span beam supported by two story rigid frames with shear walls. The earthquake response analysis is carried out to study the responses of the roof: vibration mode, natural period, bending moment and horizontal shear force of the bearings. The study results in the following conclusions: First, a large horizontal stiffness difference between the side frames is caused by the shear wall location, which results in a large vertical vibration of the roof and a large shear force at the side bearings. Second, in this case, the seismic design method for ordinary buildings is not useful in determining the distribution of the static equivalent loads for the seismic design of this kind of long span structures.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.3
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• pp.84-89
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• 1994

Section forces of greenhouse structures were studied to suggest basic information for the structural design of greenhouses with respect to roof types and support conditions. Structural analyses were performed for pitched and arched roof, and fixed and hinged support under snow loads and wind loads. Followings are the results obtained and are expected to be useful in determining the span length and roof type in greenhouse design. 1. Special considerations might he required for roof design at the heavy snow region, and for the support design at the strong wind region, respectively. 2. Single-span structure was found to be stronger than multi-span structure under the snow load, but the former was found to be weaker than the latter under the wind load. 3. Arched roof structure was expected to be safer than pitched roof structure if the dimensions and loads were equal. 4. Greenhouse orientation and roof slope should be considered in optimum structural design of grrenhouses, because these two factors are closely related with the influence of wind load and snow load.