Influence Of Different Cure Degree On Friction Resistance Of Retard-bonded Pre-stressed Tendons And The Bending Capacity Of Beam

As a new pre-srtessed system,the bond-retarded pre-srtessed concrete has the advantages of unbonded pre-srtessed structure whose construction is easy and available and bonded pre-srtessed structure whose force transfer mechanism is good,so it has been widely used in the civil engineering home and abroad.The basic theory research on bond-retarded pre-stressed technique is relatively less.Especially in the process of retard-bonded adhesive’s cure,the relationship between friction coeffient,cure time and tensile force and the influence of retard-bonded adhesive’ s cure degree on the mechanical performance is still obscure,so the development and application of it has been set back to some extent in our country.In this paper,ten pre-stressed concrete beams with three straight pre-stressed retard-bonded tendons were made on the research basis at home and abroad.The experiments on tensile friction and bending capacity were conducted,and this provided basis for the development and popularization of bond-retarded pre-stressed technique.In this paper,the study on the friction coefficient of different cure degrees and bending capacity of same tensile period in different degree periods has been deeply conducted.Ten retard-bonded pre-stressed concrete beams were made whose length was 3300mm and cross section was 300mm*400mm,and each beam had three straight pre-stressed reinforcement.No.1 to 5 beams were tensile and anchored at the same time in the tensile fit-period,and No.6 to 10 beams were divided into 5 batches to measure the friction coeffient.And after the tensile experiment,the bending resistance experiment were conducted on No.1 to 4 beams,and the load-deflection curves,stress change of pre-stressed tendons in the loading period,cracking distributions were measured.So the force transfer mechanisms,working condition and bearing capacity of pre-stressed beams were clear.The retard-bonded adhesive’s cure degree has great impact on the friction coeffient,the adhesive effect of retard-bonded pre-stressed tendon and friction coeffient is greater with the increase of retard-bonded adhesive’s cure degree.In the condition of same cure degree,the friction coeffient is smaller with the increace of tensile force.In the bending experiment,the cure degree of binder has little impact on the cracking load of PC beams and great impact on the ultimate load;With curing degree developed,the ultimate bearing capacity of the PC beam is also increase;When shore scleroscope hardness of slow binder reaches to 80D,the work condition between slow pre-stressed rebar and concrete is well,crack distribution is almost in pure bending pure bending of PC beam and the bearing capacity and ductility is largest.