现在一般的索膜结构，竣工以后都不把内力测定作为验收标准。
我想问业内知情人士，索膜结构在竣工后如何测其内力，有没有什么通用的测索内力的仪器，膜的内力就更难了吧
在安装时，索的给定内力如何精确的给定。
谢谢指教？

不敢说指教，互相交流
我个人认为是通过形变来控制的，也就是说在膜找形的时候将形变就定好了，那么在安装的时候，只要达到这个量，那么其内力也就接近了。
（一派胡言，还望高人指点）

我当然知道接近了，所以要测定一下，检验一下。how呢？
谢谢！

沈工，很早就听说过您的大名，我对这个问题也很感兴趣，但始终不得其解，我很高兴能和你一起探讨！^_^

沈先生，久仰大名
能不能用土建中测定的预应力钢绞线、钢丝的方发来测定呢？
但好像无法固定两边或圆周
:-)

能不能结合zyqzzz的方法进行分段测试？

未知两位高姓大名，adocom，zyqzzz？
能不能详述一下土建中测定的预应力钢绞线、钢丝的方法？
谢谢！

关于膜内力的测定，是一项很重要的验收参数！现在国外有一种叫做膜表面应力测试仪的设备！

I remember, during the meeting that Birdair held in Shanghai three years ago, Mr. Martin Brown has mentioned, but I never get a chance to read more material about that. A few company control the stress of the membrane by control the strain of cables.

索的应力应该是比较容易测定的吧！

在两端都已固定得前提下，如何测定？贴应变片吗？

你要搞清楚“应变片”是干吗用的？
顾名思义，首先要有应变才能反算其他物理量。
然而你想测的无非就是索的预应力，但当索的张拉到位后，你那来的应变去测？所以，别老盯着贴应变片好不好！

for the tendons stress control ,we may try to use two methods,
  
1, from jacking pump, you can get the value of tension, so you should caculate the tensile stress in the tendons. of couse, you must scale your pump and tendon sample before you do.
  
2,using strain instrument before you jack tendon, that is so simple way.

老兄啊，我做加载试验的时候，索的力是要变的，当然要测定

我能测预应力当然也能测加载后得应力了！

我的测试方法现在还停留在理论阶段，须待试验检验。望各位见谅。

国外有一种索张力计（依索的尺寸大小有不同的量测计）但只能使用于外露的悬索。

A method to accurately determine strain distribution of membrane surface -- digital photogrammetry

日本鹿岛建设自行开发的膜张力计，有以下特点：
(1)非破坏性测量膜张力，使用简便(图为测膜张力情形)。
(2)分别测定横向、纵向膜张力；
(3)实用上，测量精度高。

请问成刚，国内能否买到该仪器？联系方法？谢谢。

tailorbird,你好！
   
我已向鹿岛建设公司发邮件询问有关信息，收到回复后我会及时转告你的。询问邮件内容如下：
==================
* Detail Information
* Requests for Leaflets, Technical Papers or Materials
* Technical Questions
   
Dear Sir:
We are interested in the instrument to measure tension stresses in membrane (膜

收到鹿岛建设公司的回复如下：
====================
Dear Professor CG,
  
My name is Susumu Yoshinaka. I work for kajima technical research institute
and study on shell and spatial structures.
I received the question about a measuring intstument for tensile stresses in
membrane.
  
We submitted the report about detailed information of the intstument for
international association for shell and spatial structures about 10 years
ago.
I will send the report later.
  
Now we don't make it or sell it in Japan, and our company already obtained a
patent on it.
We are examining whether we can sell it and so on.
I will give you more information later by e-mail.
  
Sincerely yours,
  
Susumu Yoshinaka
Research Engineer
Kajima Technical Research Institute
2-19-1, Tobitakyu Chofu City, Tokyo 182-0036, Japan

不要报太大的希望，好好想想，能准吗？

TKS

搜索到几篇有关参考文献：
  
[1] 佐佐木，坪田，膜

hhux2002，能否请你较详细地说明一下哪个公司或网页上有相关内容，说明数字摄影测量学能够精确地确定膜表面应变分布？
  
我搜索了一下网页，找到了美国Geodetic Services, Inc.公司的网页，有介绍Photogrammetry的有关内容，但是没有提到能应用于确定膜表面应变分布。
  
Engineering Applications
--------------------------------------------------------------------------------
Application: Steel plate measurement
Description: Individual plate measurement;
             Assembled plates  
Equipments:  V-STARS/S; PRO-SPOT
--------------------------------------------------------------------------------
Application: Surface Measurement
Description: Component verification;  
             Lay up tools and die measurements;  
             Real time inspection  
Equipments:  V-STARS/S; PRO-SPOT; V-STARS/M
--------------------------------------------------------------------------------
Application: Deformation measurement
Description: Deformation due to changes in position or attitude of components;  
             Deformation due to load;  
             Dynamic measurement  
Equipments:  V-STARS/S; PRO-SPOT; V-STARS/M
--------------------------------------------------------------------------------
Application: Pipe measurement  
Description: Tracing pipe locations;  
             Verification of dimensions;
             Pipe replacement measurements  
Equipments:  V-STARS/S  
--------------------------------------------------------------------------------
Application: Temperature Deformation  
Description: Deformation due to extremes of temperature  
Equipments:  V-STARS/S; V-STARS/M
--------------------------------------------------------------------------------
Application: Repeatability check  
Description: Repeatability of individual components  
Equipments:  V-STARS/S; V-STARS/M
--------------------------------------------------------------------------------
Application: Component Alignment  
Description: Alignment of key features for refurbishment or building  
Equipments:  V-STARS/S; V-STARS/M
--------------------------------------------------------------------------------
Application: Shape analysis  
Description: Measurement of components to verify dimensions;  
             Verification of shape under load  
Equipments:  V-STARS/S; PRO-SPOT
--------------------------------------------------------------------------------
Application: Transportation check  
Description: Check of built components after transportation to customer or from suppliers  
Equipments:  V-STARS/S  
--------------------------------------------------------------------------------
Application: Block measurement  
Description: Measurement of manufactured blocks to verify dimension  
Equipments:  V-STARS/S  
--------------------------------------------------------------------------------
Application: Vibration studies  
Description: Dimensional checks of components and structures undergoing deformation due to vibration
Equipments:  V-STARS/S; V-STARS/M
  
Antenna Applications
--------------------------------------------------------------------------------
Application: Panel measurement  
Description: Individual panel measurement  
             Assembled panels  
Equipments:  V-STARS/S; PRO-SPOT
--------------------------------------------------------------------------------
Application: Surface Measurement  
Description: Antenna component verification  
             Lay up tools and die measurements  
             Real time inspection  
Equipments:  V-STARS/S; PRO-SPOT; V-STARS/M
--------------------------------------------------------------------------------
Application: Deformation measurement  
Description: Deformation due to changes in position or attitude of dish  
             Deformation due to load  
             Dynamic measurement  
Equipments:  V-STARS/S; PRO-SPOT; V-STARS/M
--------------------------------------------------------------------------------
Application: Temperature Deformation  
Description: Deformation due to extremes of temperature  
Equipments:  V-STARS/S; V-STARS/M; I-CAN
--------------------------------------------------------------------------------
Application: Jig Verification  
Description: Periodic inspection of manufacturing jigs  
Equipments:  V-STARS/S  
--------------------------------------------------------------------------------
Application: Feed alignment  
Description: Alignment of feed relative to antenna surface  
Equipments:  V-STARS/S; V-STARS/M
--------------------------------------------------------------------------------
Application: Shape analysis  
Description: Measurement of antenna to verify shape fit to parabola.  
             Verification of shape under load  
Equipments:  V-STARS/S; PRO-SPOT
--------------------------------------------------------------------------------
Application: Transportation check  
Description: Check of built components after transportation to customer or from suppliers  
Equipments:  V-STARS/S

Digital photogrammetry and other optical strain measurement systems are non-contact testing mothed. I checked my material and do not have company or product information about use photogrammetry to determine the strain distribution of membrane structures, but the applications of  photogrammetry include surface measurement  and deformation measurement.  Prof. Grundig, L. from TU Berlin has a research paper "on the feasibility of using large scale photogrammetry to accuratery determine in-service strain distribution across three-dimensional textile roofs"  that published in 1995.
  
My interest is whether can use photogrammetry into fabric surface flatting, i.e. to convert 3D nondevelopable surface into planar strips(2D)? I think can. This may be taken as a MEng or PhD project.
  
BTW, the letters "APCS"  that you mentioned in previous  post stand for Asia-Pacific Conference on Shell and Spatial Structures, Prof. Lan T is the editor of the proceedings. Next  IASS-APCS, Oct. 22-26, 2003, Taipei,Taiwan     http://www.caece.net/iass2003

hhux2002，谢谢你提供数字摄影测量学的有关信息。Prof. Grundig, L.的论文我还没有查到，也没有读过，我会继续查找的。下面我谈谈自己的几点看法。
  
类似的技术我多少知道一点。同济大学在广州新体育馆次桁架足尺试验和FAST射电望远镜反射面模型试验中应用了类似的技术。在适当的部位粘帖标有十字线的专用反射片作为测量标定点，

瞄准标定点发射激光束接收反射激光，就能测定标定点的空间位置。比较标定点的实际位置与理论位置，就能知道偏差有多大。比较标定点受力前后的位置就能计算出位移。
  
要用这种技术精确地确定膜表面应变分布，还有不少困难。
  
首先，需要在张拉膜材之前，预先布置系列标定点，张拉膜材后测量标定点的位移。可能用于新建膜结构膜张力控制，不能用于现存膜结构膜张力检测。我们知道，织物材料的预应力会随时间发生松弛，导致飘动与下垂。当发生这种情况时，必须重新施加预应力。第一个现代膜结构建成至今已有好几十年了，因此，有大量的现存膜结构预应力松弛需要测量。
  
其次，由膜表面位移计算膜应变，可能会产生较大误差。
  
再次，对于复杂的大型膜结构，测量仪器本身定位有困难。测量仪器要能够在合适的角度发射激光，就需要安放在高空平台，对平台位置和刚度有很高的要求。有时需要专门建设多个平台，才能瞄准所有标定点。
  
最后，仪器价格较贵，使用成本也很高。

Here you are.  http://www.survey.tu-berlin.de/~download/lyon95.pdf

谢谢您。我下载了这篇论文，大概读了一遍，内容很丰富的。感觉主要还是讨论如何测膜表面位移、可以达到多少精度等等，实际工程应用恐怕还很难。
  
我先前是找到了Gründig教授的这个网站，怎么就没发现哪里有链接指向这篇论文呢？hhux2002编辑不愧是高人啊。另外，这个网站不支持续传，因proxy太慢，害得我花了一个晚上下载多次不成功。http://www.survey.tu-berlin.de/~download 其它目录下有什麽宝贝呀，还需要密码的，啊啊，随便问问。