GB/T 39422-2020 in English

Analysis of key terms

This standard clearly defines two core parameters: pin groove bearing capacity and nail connection pull-out bearing capacity:

• Pin groove bearing capacity: reflects the ability of wood materials to resist the pressure deformation of pin-type connectors, directly affects the node stiffness
• Pull-out bearing capacity: characterizes the maximum force required to vertically pull out the nail connector, which is related to the pull-out performance of the structure

Probability and statistical model

The standard requires the use of 5% quantile as the eigenvalue, and recommends the following distribution model:

1. Lognormal distribution (preferred)
2. Weibull distribution (three parameters)
3. Truncation normal distribution

The statistical sample size must satisfy n≥90, and the confidence level is set to 75%

Engineering application example

In a glued timber structure project, Φ6mm wood screws are used for connection:

• The average value of the tested pull-out strength sample is: 8.76N/mm²
• Logarithmic standard deviation: 0.23
• The eigenvalue calculated according to formula (6): 6.54N/mm²

Main breakthroughs of this standard compared with the historical version:

• Introducing the Energy Equivalence Method for the first time to determine the pin groove yield strength (Appendix A)
• Specifying the special requirements for testing wood composite materials
• Establishing a complete probability statistical verification process

1. Strict screening of wood defects is required before testing to ensure that the sampling represents the actual engineering conditions
2. It is recommended to use electronic displacement sensors to synchronously record the load-displacement curve
3. For new composite materials, the sample size should be increased to more than 120 groups