Research On Bond Performance Between Corroded Pre-stressing Steel Strand And Concrete Under Chloride Environment

Durability of pre-stressed concrete structure gradually be in the limelight with the widely application of the pre-stressed concrete structures.The bond performance between corroded steel strand and concrete is the basis of the structure durability evaluation.The serious degradation of bond behavior between pre-stressed steel and concrete will seriously affect the structure durability.There are many researches about the bonding performance for ordinary reinforced concrete structure at present,but the study of bond performance between corroded pre-stressed steel wire and concrete is very less.This thesis carried out theoretical analysis and experimental research about bond performance between corroded pre-stressed strand steel and concrete based on the previous studies.The following research work has been done:(1)Summarizing the influence factors of bond behavior between pre-stressed steel strand and concrete,and mainly discusses the corrosion effect on the properties of bonding mechanism between pre-stressed steel strand and concrete.(2)A batch of pre-tensioning pre-stressed concrete beams were produced,and corrosion specimens with different corrosion degrees were obtained from electric accelerated corrosion.Bond performance test had been done with these specimens.Studies founded that the maximum strain of the surface of concrete at pre-stressed steel strand location point.(3)A simple rust section area calculation model was established and fitted the relation between the mass corrosion rate and the section corrosion rate of the corroded steel strand.Analyzed the distribution rule of the corrosive crack width at different location of the beam.The relation formula between the average quality corrosion rate of steel strand and the maximum corrosive crack width was derived.(4)The strain of the steel strand was calculated from the strain of the concrete surface at the same position.Matrix equation method was used to calculate the bond stress.The bond stress along anchorage length obeyed the multi-peak distribution rule,and the peak value was bigger nearer the loading end.The biggest bond stress of the test beam decreased with the increase of corrosion rate.And finally the relation between the corrosion rate of the stand and the maximum bond force was fitted.(5)Combined with the special stress state of pre-tensioning pre-stressed concrete structure,considering the hoop stress caused by pre-stressed into rust expansion analysis,the ultimate bond strength calculation formula was derived between pre-stressed steel strand and concrete.