Original Paper(Vol.54 No.8 pp.787-794)

Effect of Bending Work of Main Bar to Correct Displacement of Bar Position on Mechanical Behavior of Reinforced Concrete Member

Masanori TSUJI, Yuji ISHIKAWA, Tsuyoshi HATANAKA, Takehiro SAWAMOTO, Ryota IIDA, Masaru OKAMOTO

Abstract:It is important to place reinforcing bars accurately as specified on the drawing and secure bars against movement. Actually, bar positions move under the construction work even though the displacements are large or small. Therefore, the bar arrangements have to be modified to the accurate position by bending work of bars where the displacements are over the allowable tolerances. In this study, the effects of mending work of main bars on mechanical behavior of reinforced concrete members are investigated, and inadequate bending works that adversely affect the strength of concrete members are discussed. Where the main bars displaced from specified position are sharply bent to joint new bars at accurate position, main bars are cut by repetition of bending and rebending under alternative low cyclic fatigue load as a seismic load. When the main bars are bent in member which can sustain sufficient load by a wide margin as a foundation, the inclination of main bars for modification is recommended to be less than 1:5 (desirably 1:7) to ensure specified load capacity. Because larger inclinations make the rigidity of member low by pull out of main bars from base member. Modification of main bars from outside to inside to secure effective depth can be allowed even in column member by confirming the inclination for modification under 1:5 , the sufficient tie bars at all plastic hinge zones extending to cross section where effective depth is modified to be specified value, the enough tie bars to prevent bent main bars which are going to be straight under force from pushing out concrete cover, and durability changed by thinner cover.

Key Words:Reinforced concrete, Bar arrangement, Modification of bar, Bending work of reinforcing bar, Cover, Effective depth