Behavior of bond Under Dynamic Loading

Abstract

PREVIOUS WORK Bond is the phenomenon la reinforced concrete which is respon-Bible for the transfer of loads betwen concrete and reinforement. The word bond 4s probably most commonly mssociated with adhesion of aosort, although even for plain steel bar*, whichthe -at common reinforcement La the earlier days. bond was ahoto be more a friction than adhesion c2) phase-now. la a deformed bar, which is a cuhi reinforcing todany. the bearing of defer-it le-the surrounding concrete takes most the respossibility for load transfer. -d friction and adhesion have lost their significancefactors in boad strength. Theis is extensive literature on bond tests between concrete and st-1. Bond tests base been performed on pull-t specimens and bo-e and it has base found that pullout specimens represent bond conditions in boawith reasonable accuracy. For this reason pull -t tests for bond are comparable to cylinder compression tents for concrete strength. Tests C1*" ha-shown thst bond strength 1) is greater for deformed bars than plala bars; 2) lucres-s with average height and bearing area of deformations: 3) decreases with the inereas ing ratio of shearlap to bearlap a-a of deformations: and 4) is unaffected by the pattern of the do for-t i oss. Bond of plala bars Inereases with co--to strengths below 3000 pel. Abo-3000 pal the i--ala bond strength with increasing co--to ro--sal-strength is very snail.that for most practical cases, bond (3) for plain bars in Independert of co--to coop-salat-ngth. A. P. Clarkhas shovn that for defer-l ba-at the sane amount of slip, bond stress 1---on with 1--ing co-to compress1-strength. The orientation of ba-at the tlof the east lap of co--to la C3 3) inportant f-tor. ' Be-oriented borts-tally will draw up water beneath then and a stiff co--to nix. as it settles. will draw a-y from the bar. resulting in poor bond. The oho-f-to-aelminated if the baat the time of casting a-oriented vertically. Vibration of co--to. and ba-especially, 1---as the quality of bond in both horizontal and * Superseript numbers la parenthesis are references presented La the B abl LoE raph y.