| The in-depth contents | |
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| Publication year | 2021 |
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| Title | Evaluation on structural properties and proposal on setting method of internal air pressure for sealed type air cushion structures |
| Author | Hitoshi YONAMINE,Akira OKADA,Naoya MIYASATO,Shuzo HIROISHI,Ryuta SHINDO |
| Summary |
The Pneumatic structure is classified into an ""Air-supported Structure"" represented by Tokyo Dome, and an ""Air-inflated Structure"" such as beam and arch types. The ""Air Cushion Structure"" that is the subject of this paper is positioned as a structural system that has both characteristics of Air-supported and Air-inflated structures. The Air cushion structure consists of two layers of film, an enclosing framework and pressurized air between t he layers, which makes a highly rigid structural panel system. Here, t he pressure difference between outside and inside of the cushion structure is referred to as ""Internal Air Pressure"". In designing an air-supported structure, it is common to assume that the internal air-pressure is always maintained at a constant value even when an external load applies (this is called a ""Constant Pressure Type""). It is based on the assumption that the time delay of internal air-pressure control by an air supply equipment is so brief that it can be ignored. Following this assumption, it is general that the Air cushion structure is also designed using the constant pressure type assumption. However, the Air cushion structure which is a relatively small scale has a smaller amount of internal air than typical Air-supported structure, and therefore, it would be difficult to achieve the assumption of constant internal pressure, depending on the loading conditions. Furthermore, a sudden change of film stress under a sealed condition (this is called a “ Sealed Type” ) is likely to be predicted due to a change of internal air pressure with the influence of internal air volume change, but its behavior is unclear. In recent years, the Air cushion structure using ETFE (Ethylene tetraf luoroethylene) film has already been used worldwide in not only large-scale buildings such as stadiums but also small canopies as cladding elements. However, the design method is basically based on the constant pressure type, and as far as the author k nows, the design and analysis method considering the sealed type has not been established yet properly. Based on the background mentioned above, it is necessary to understand the ""Sealed Type"" structural characteristics of the Air cushion structure and establish an appropriate structural analysis method under snow and wind loads that may occur normally. Besides, it is vital to establish a structural design f low and setting method of an appropriate internal air pressure for the Air cushion structure multidirectionally considering specific attentions of the Sealed type. Therefore, this paper deals with the following two themes regarding the Sealed type air cushion structures. ・An evaluation method to check behavior of Sealed type air cushion structure is established. ・A structural design f low and a setting method of an appropriate internal air pressure for the Air cushion structure are proposed. In this paper, numerical analysis and experiments were conducted on the Sealed type air cushion structure using the ETFE film that is utilizable in Japan after the revision of the Building Standards in Japan in June 2017. The study concludes that we proposed ""Evaluation method on structural properties for the Sealed type air cushion structure"" and ""Structural design f low and Setting method of internal air pressure"" based on the evaluation method and demonstrated its effectiveness, in order to establish a numerical analysis method that can evaluate fluctuations of internal air pressure and a design method that takes into consideration the Sealed type attentions. In addition, the author confirmed that the Sealed type is a rational and passive structural system, in which an appropriate initial internal pressure is applied at the beginning, and thereafter it is not necessary to mechanically control the pressure under snow and wind loads. |