PURPOSE: To improve resistance to breakage of chuck in a clamping stage of prestressed concrete using FRP bars by specifying a thickness of resin layer from outermost reinforcing fibers to the surface of the FRP bar material, and the surface hardness of the bar material.
CONSTITUTION: In a fiber reinforced plastic bar material to be used as stretching material for prestressed concrete, the thickness of a resin layer from the reinforced fiber at the outermost layer to the surface of the bar material in a sectional face of the bar material, is regulated to 20-1000μ, and the surface hardness of the bar material is regulated to 20-90 Barcol hardness. If the thickness of the resin layer is <20μ, insufficient effect for preventing clamping is obtd. If it exceeds 1000μ, a breakage of the resin layer may be generated when a lateral compressive stress exerts during clamping. If the surface hardness is <20, a slip of chuck may cause due to insufficiency of rigidity against a lateral compressive stress in the stage of clamping. If it exceeds 90, a breakage of chuck may be caused.
NISHIMURA TSUGIO
NISHIOKA SUMIO
KAKIHARA RYUICHI
MUKAI KUNIHIRO
HONMA HIDEYO
SUMITOMO CONST