Wood-based Panels – Determination of duration of load and creep factors
The following significant technical modifications have been made to the original draft, voluntary DD ENV 1156:1999,
a) A change in status to a full European standard (EN).
b) The accuracy of the deflection measurement has been changed from 0,001 mm to 0,01 mm – see clauses 4.2.2, 6.2, 6.4.3 and A.3.3.
It specifies a method of determining, in a constant climate, both a duration of load factor and a creep factor for wood-based panels stressed in flatwise bending, with and without a shear component.
The duration of load factor is necessary to modify the characteristic strength values obtained in short-term tests in order to derive long-term values. The creep factor obtained in the test is used to predict a long-term deflection from the initial elastic deflection.
Determination of the load duration factor (loss in strength with time under load) and the creep factor (ratio of increase in deflection with time to the initial elastic deflection) in bending by applying and sustaining a constant moment over the central region of a test piece, both the time to failure and the increase in deflection with time are measured. This occurs in a constant climate.