DUCTILITY FASTENERS SEISMIC PERFORMANCE EXPERIMENTAL TESTS FprEN 14592 (2018) introduces three performance classes for cylindrical shank fasteners used in seismic areas; these take the form of three classes of ductility ("low cycle ductility classes for fasteners used in seismic areas"). The three classes are indicated as S1 (low ductility), S2 (medium ductility) and S3 (high ductility). A fastener is classified in one of the above classes according to the results of specific monotonic and cyclic bending tests conducted on the threaded portion of the fastener. This seismic classification is essential as it helps designers prevent brittle fractures caused by a sudden failure of the metal fastener. The objective of the standard is to verify that, based on the seismic class and choice of fastener, at the end of the third cycle, the residual moment Mres is at least equal to 80% of the average yield moment My determined with monotonic testing.
TEST PROTOCOL USED IN CYCLIC TESTS
αu
Tubular guide
αc
Loading device
Mandrel
Support
Rotation
Fastener
Time
0
2d 16d
Test set-up diagram (static diagram: three-point bending).
-αc 1st cycle
2nd cycle
3rd cycle
determination of the residual bending moment capacity
MOMENT-ROTATION CURVE RESULTING FROM A CYCLIC TEST
Mres
Bending moment
Kel
Mmax M(1st) M(2nd) M(3rd)
-αc
0 Rotation [°]
14 | DUCTILITY | CARPENTRY
αc α + 20°
αu
Test configuration.