Debonding
of CFRP sheets has been a serious limitation in the use of CFRP on reinforced
concrete structures.
Debonding is further magnified in cases where the CFRP
must go through a height transition between surfaces of elements that are not
in the same plane. Forty specimens were tested to investigate the use of carbon
fiber anchors (anchors inserted into predrilled holes and fanned out over the
CFRP sheet) and U-wraps (CFRP sheet wrapped around sides of beam) to develop the
full rupture strength of a CFRP sheet with and without a height transition.
Without any additional
anchorage the CFRP sheet debonded at 40% of its
capacity. Although the number and size of anchors is important, two rows of
anchors, with the cross-sectional area of CFRP in each row equal to or greater
than the area of the CFRP sheet, fully
anchored the CFRP sheet. An equivalent
anchorage using U-wraps required 5 times more CFRP. A height transition with a
1 to 2 transition slope reached only 40% of the CFRP capacity, while a 1 to 4
slope reached full capacity. Finally, surface preparation was unimportant when
the CFRP was well anchored.