The method NT Build 306 is a small-scale test method for determination of pull out strength of mechanical fasteners. On behalf of Nordtest a project has been carried out to create the basis to revise the method.
The original documentation for developing the method was examined. The test series carried out at NBI and the method first used were also examined. Additionally, a literature study has been carried out.
Based on this knowledge a test programme to investigate the importance of several factors for NT Build 306 was planned and executed. 203 small-scale tests, two full-scale tests carried out according to NT Build 307 and two full-scale tests carried out according to NBI 162/90, are reported in this document.
The examination of these tests and documents has given a basis to recommend several improvements and more detailed specifications of the method. These are listed in Chapter 14 in this document.
The summary of this project indicates that NT Build 306 can be further developed, and be used to investigate if crews mounted in profiled steel plates are safe against unwinding. To develop this method further, some more tests have to be carried out.
In the ongoing revision of NT Build 307 “Roof Covering. Wind Load Resistance” the necessity to change the current load procedure will be evaluated. The revision of NT Build 306 has to be seen in conjunction with the revision of NT Build 307.
It is recommended to use the results concerning the load diagram from the ongoing revision of method NT Build 307, and also to develop the method NT Build 306 further concerning investigation of unwinding, before publishing the revised method NT Build 306.