Seismic flexural behavior of CFRP strengthened reinforced concrete beams secured with fiber anchors.

An experimental program was conducted to examine the seismic performance of flexural beam members strengthened with carbon fiber-reinforced polymer (CFRP) sheet and anchored using carbon fiber splay anchors. This research study extends the use of carbon fiber anchors to secure the top and bottom CFRP flexural sheets under cyclic loading. In this study, low strength concrete is examined, with lightly reinforced steel ratio (0.0034) to test full-scale rectangular beams. Five reinforced concrete beams were cast, strengthened, and tested under reversed cycles of four-point bending to failure. The beams were categorized into a control specimen, strengthened specimens with thin sheets with and without fiber anchors, and strengthened specimens with thick sheets with and without fiber anchors. They were tested cyclically under displacement control according to the AC 125 loading protocol. The failure modes ranged from classical ultimate failure for the control beam to rupture and intermediate crack (IC) debonding for the beam with unanchored thin CFRP sheets. On the other hand, debonding took place for the thicker sheets with no anchors, while the thicker sheets with fiber anchors underwent cover delamination failure mode despite the fact that the sheets were extended very close to the simple supports. The hysteresis response loops were compared for the different specimens and the analytical envelop curves were predicted resulting in a close agreement to the experimental finding. • Seismic performance of flexural beams CFRP strengthened with and without carbon fiber anchors is successfully examined. • Thicker CFRP sheets yield lower energy dissipation, ductility, but higher strength and seismic pinching. • Failure modes varied from sheet debonding to CFRP rupture and cover delamination. • The use of anchors at sheet ends was not very effective in extending the hysteretic cycles beyond those without anchors. • The need to apply fiber anchors along the entire shear span to harness improved behavior is clearly evident. [ABSTRACT FROM AUTHOR]