Research On The Effecte Of Aftershocks On Bond Behavior Of Early Age Reinforced Concrete

At present, earthquakes occur frequently, after the wake ofearthquake aftershocks continue. Since reinforced concrete structureunder construction suffered aftershock, supporting frame of templates areloosed and deformed, reinforcing steel switched, crack appeared oncomponents in the construction site. It was common concerned whetherthe overall structures in process are influenced, for the bond strengthbetween steel and concrete of the first pouring of the reinforced concretestructure which’s strength has not fully developed are effected byaftershock. Therefore, for exploring the variation of bond strength of theearly age concrete suffered aftershock, the paper given0.06g,0.15g,0.25g,0.45g peak acceleration of the vibration force on reinforcedconcrete during3days by seismic shaking table test, systematic study ofthe effect on bond properties of different ages and different vibration.Through the analysis of experimental data obtained the variation of bondstrength prediction equation of the early age concrete by vibrated.The main conclusions of this study are:(1) In the early stage ofstrength development of reinforced concrete, if reinforced concrete subjected to different intensity vibration of aftershock, the bondstrength of immediate or after28days will folded, and the bondstrength impairment increased with the earthquake intensity increased.(2)If the reinforced concretes are suffered for aftershock before the initialsetting, the late bond strength between steel and concrete have a littleimprovement.(3) In the final setting of concrete subjected to aftershock,the impairment of bond strength between steel and concrete amount to13.86%, the maintenance function can not restore it; when reinforcedconcrete is vibrated on third day, the bond strength little effected.(4)Under the same load, the greater of the earthquake intensity, the greaterof the steel strain at the same bond length，the smaller the peak bondstress between steel and concrete.(5) Under the same load, the greater ofthe earthquake intensity, the greater of the relative slip between the steeland concrete，the more degradation of bond stiffness.(6) According to thebond strength impairment value at the different ages subjected to differentintensities of seismic forces, the prediction formula of the bond strengthimpairment between steel and concrete can describe the variation of thebond strength when reinforced concretes are vibrated during3days basedon damage theory analysis.