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Keywords: aerodynamics, fluid, statical, wind, textile, roof, architecture, tensile, structure, iterative, method, optimal.

Summary

Textile roofs are flexible, but their behaviour against wind is usually considered as a "still photo" which inexorably leads to results far from reality, as this does not consider the change in the geometry of the roof (and its corresponding load changes) in every state of deformation.

International and local regulations estimate wind loads based in this "stiff" behaviour, and in simplified geometries far from the real textile roof geometry. Reference [1] states that "wind representation in this section is valid for surfaces stiff enough to ignore resonance vibration due to the wind". Textile roofs components (membrane, structure, cables, foundations, fittings) are thus usually over sized, minimizing their desirable lightness and increasing their cost.

The aerodynamic analysis of a textile roof model (a hyperbolic paraboloid) using both computational fluid dynamics (CFD) and textile architecture software is described as the way to obtain more accurate and real results.

Recurrent use of CFD and textile software provides consecutive deformation states (and new loads) that can be studied aerodynamically again, obtaining in turn new deformation states. The end of the process is assumed to be achieved in two possible situations: membrane failure (geometry is deformed until membrane tensions exceed their tensile strength) or aerodynamic equilibrium is not satisfied (several deformations until roof oscillation appears).

During the test, consecutive sequences are performed until the aerodynamic equilibrium is reached (geometrical changes are insignificant). In this state, the membrane remains under its tensile strength limit.

As a first conclusion, it is possible and feasible to evaluate wind loads through the combined use of CFD and textile architecture software. By these means, and the observation of consecutive deformations, it is possible to understand the roof's behaviour due to wind action in a better way.

A comparison with results obtained from strict application of the regulations and the test results shows values around 50% lower in test CFD analysis: the Spanish "CTE" applied in the studied roof yields 1.30KN/m² of wind suction whereas the Fluent and Easy calculation shows a final result of 0.55KN/m².

So, the proposed method (which takes into account the roof geometry and its deformations) shows a wind load result which is much more accurate and lower than the regulations' application, making possible an optimal sizing of all the parts involved in the roof engineering.

The fashionable concept of "sustainable architecture" should not be understood only as it commonly is: adding "devices" to normal buildings to make them "bioclimatic" or "sustainable". The author considers that the most reasonable way to make sustainable buildings is to build with the minimum amount of resources and energy consumption.

References

1: Eurocode UNE-ENV 1991-2-4: cap 5.1, 1998.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 91 PROCEEDINGS OF THE TWELFTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping, L.F. Costa Neves and R.C. Barros Paper 210 Aerodynamic Analysis of Textile Roofs Combining the use of Computational Fluid Dynamics and Textile Architecture Software J. Tejera Parra Architect, BAT - Buro Arquitectura Textil, Madrid, Spain doi:10.4203/ccp.91.210 purchase the full-text of this paper Full Bibliographic Reference for this paper J. Tejera Parra, "Aerodynamic Analysis of Textile Roofs Combining the use of Computational Fluid Dynamics and Textile Architecture Software", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 210, 2009. doi:10.4203/ccp.91.210 Keywords: aerodynamics, fluid, statical, wind, textile, roof, architecture, tensile, structure, iterative, method, optimal. Summary Textile roofs are flexible, but their behaviour against wind is usually considered as a "still photo" which inexorably leads to results far from reality, as this does not consider the change in the geometry of the roof (and its corresponding load changes) in every state of deformation. International and local regulations estimate wind loads based in this "stiff" behaviour, and in simplified geometries far from the real textile roof geometry. Reference [1] states that "wind representation in this section is valid for surfaces stiff enough to ignore resonance vibration due to the wind". Textile roofs components (membrane, structure, cables, foundations, fittings) are thus usually over sized, minimizing their desirable lightness and increasing their cost. The aerodynamic analysis of a textile roof model (a hyperbolic paraboloid) using both computational fluid dynamics (CFD) and textile architecture software is described as the way to obtain more accurate and real results. Recurrent use of CFD and textile software provides consecutive deformation states (and new loads) that can be studied aerodynamically again, obtaining in turn new deformation states. The end of the process is assumed to be achieved in two possible situations: membrane failure (geometry is deformed until membrane tensions exceed their tensile strength) or aerodynamic equilibrium is not satisfied (several deformations until roof oscillation appears). During the test, consecutive sequences are performed until the aerodynamic equilibrium is reached (geometrical changes are insignificant). In this state, the membrane remains under its tensile strength limit. As a first conclusion, it is possible and feasible to evaluate wind loads through the combined use of CFD and textile architecture software. By these means, and the observation of consecutive deformations, it is possible to understand the roof's behaviour due to wind action in a better way. A comparison with results obtained from strict application of the regulations and the test results shows values around 50% lower in test CFD analysis: the Spanish "CTE" applied in the studied roof yields 1.30KN/m² of wind suction whereas the Fluent and Easy calculation shows a final result of 0.55KN/m². So, the proposed method (which takes into account the roof geometry and its deformations) shows a wind load result which is much more accurate and lower than the regulations' application, making possible an optimal sizing of all the parts involved in the roof engineering. The fashionable concept of "sustainable architecture" should not be understood only as it commonly is: adding "devices" to normal buildings to make them "bioclimatic" or "sustainable". The author considers that the most reasonable way to make sustainable buildings is to build with the minimum amount of resources and energy consumption. References 1 Eurocode UNE-ENV 1991-2-4: cap 5.1, 1998. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £140 +P&P)
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