Developing Laws Of Corrosion Fatigue Damage Of Steel Strand In PC Structure Under Chloride Environment

As we know, a lot of structures are affected by common effect of corrosion andmechanical fatigue during its service life. Unfortunately, it is a complex coupledprocess rather than the simple math their individual effect together. They areinfluencing and reinforcing each other.Prestressed concrete structures are widely usedin national and urban lifeline engineer, which means if stuctures get injurious ordamaged, a extremely serious consequence will occure. Thus,developing laws ofcorrosion fatigue damage of steel strand in PC structure under chloride environmentare studied in this paper in order to provide initial results to solve the problem.Based on AE monitoring needs, At first, A experiments were conducted to studythe attenuation law of the basic influence from propagation length and the influenceof wrapped concrete status under the AE monitor of PC structures, it shows that AEsignal would be rapidly decrease with the increase of propagation length,(i.e.energe,amplitude,duration and ringing increases quickly with increasing ofpropagation distance). Secondly, The larger the depth of cover layer is, as well as theWater cement ratio. the more sound attenuates.The larger the Saturation degree ofpore water is, the less sound attenuates. At the same time,on the basis of theexperimental results, it establish a sound influence of above factors of the attenuationprediction model by combining with theoretical analysis.On the basic of chloride erosion mechanism on PC structures, a model ofcorrosion rate has been established under coupling effect. Corrosion potential ofstrand under fatigue which is measured shows that the corrosion rate is increasingexponentially with the increasing of fatigue stress.Pits characteistics under the fatigue effect is studied to show that the fatigueeffect have influnce on pits, including its length, width and depth are all increasingwith increasing of fatigue amplitude; the volume damage of pits and mechanicaldamage of pits was raised under fatigue effects, it found that both are increased withfatigue stress amplitude.AE monitoring instruments was used to study fatigue damage characteristicsunder corrosion. It shows that AE parameters can be applied to characterizing thestrand damage; and through the analysis of parameters, corrosion degree and fatiguestress amplitude had Significant impact on steel strand; When fatigue stress amplitudeis a certain amplitude, the greater mix salts, the more accumulated energy is. When mix salts is a constant, the greater the fatigue stress amplitude, the more cumulativeenergy is.Static tensile test of strand under the fatigue effect is studied to indicate that bothmaximum carrying capacity and ultimate average strain decrease with with theincrease of mix salts and stress amplitude.strand can be split in three basic forms andtheir combinations style. Which are milling,cup vertebral and knife fracture.