张拉薄膜结构中膜的常用合理预张力范围是多少？工程实践中取值常为多少？
　　此外，在计算其风荷载作用下的动力响应中，对于伞形，双伞形，拱支形和鞍形的风压系数取值在那些资料上可以查到参考资料？尤其是双伞形和拱支形。谢谢大家能给予帮助！！！

风荷载请参考http://okok.org/forum/viewthread ... amp;bpg=5&age=0

通常对于ptfe膜取2KN/m，pvc膜1KN/m

有什么根据呢，有的文章讲膜的预应力为4~6kn/m

不能笼统的取值。
各种膜材（不同类型、不同规格等）厚度、极限抗拉强度、容许应力等都不同，应根据材性确定。
在满足足够刚度的基础上，尽量减小预应力值，以减小对支撑结构的荷载。

It is a judgment call by the engineer to determine the level of pre-stress (预张力).
  
Usually his judgment is based on 2 criteria, deformation & constructability.
  
If the deformation of the membrane/cable will result in ponding of water or snow, damage of fabric because of abrasion, distortion of clamping plates because of large geometry change or fluttering of fabric under the wind and may be other issues. The pre-stress level should be increased to mitigate these problems.
  
In fabrication the fabric is compensated according to the pre-stress level which can be between 1% and 6% depends on the material. This compensated membrane panel will require you to pull the edge a distance to its clamping position, this may increase the difficulty of installation. It is an issue with cost, time and safety. You may want to lower the pre-stress level if the jacking distance is too long.
  
I recommend 3.5 KN/m pre-stress as a starting point for your project.

请参见专栏中已有的相关讨论：找形后膜的预应力水平
  
http://okok.org/forum/viewthread.php?tid=8281&h=1#36868

由于本人是个新手所以问个简单的问题“膜与风的耦合作用”是怎样作用的请哪位高手指点一下好吗？