Experimental Investigation Of Measuring Method On Effective Prestress

At present, large number of pre-stressed concrete bridges has already constructed in main highway of our country. According to insufficiency of pre-stressed force, among of many pre-stressed concrete bridges which after putting into service, appeared all kinds of diseases like that main span deflections in the middle of span quantity oversized, the crack on the box girder and so on. Therefore, method studied of measuring pre-stressed force effective value has the important practical significance and the project practical value.This article took west the Ministry of Communications the topic "Long, Middle Span Concrete Bridge Pre-stressed Examination Engineering research" the special five-pre-stressed muscles effective pre-stressed examination engineering research main content, first proposed three direct examinations pre-stressed method to the pre-stressed muscle effective pre-stressed examination technology. These three examinations method respectively is:Releases the ordinary reinforcement stress method, the power method, the static method.Releases the ordinary reinforcement stress method, selected has been the long, middle span pre-stressed concrete bridge commonly used ordinary steel bar diameter 12,16mm is the experimental model, how mainly has studied the quantity of heat which cut produces and eliminates to the steel bar strain influence below, drew the conclusion after the analysis:When the strain gauge with cuts the position is bigger than20cm, cuts the quantity of heat which produces to the strain the influence to be allowed to ignore.The power method, through the simulation the overdrawing steel stranded wire after the vibration signal and analysis its vibration signal, after analyzes software to analyze its free frequency, based on the beginnings and ends hinge cable power formula, and carries on the revision according to the tentative data to it, enables the beginnings and ends hinge cable power formula to use in the pre-stressed steel stranded wire survey.The static method, based on the structure mechanics principle, established theory expression between the pre-stressed tensile force F the thrust force T and the crosswise dislodgementδ.through exerts horizontal force surveys its corresponding lateral shear to the pre-stressed steel stranded wire,the analysis horizontal force, the lateral shear and longitudinal force the between relations. Carries on the revision to the theoretical formula, proposed the correction coefficient formula, causes it to satisfy the actual project survey the precision.Through the laboratory cast experiment and the theoretical analysis, indicated that, in service pre-stressed concrete bridge effective pre-stressed force examination methods are simple feasible, the precision credibility, easily grasp to use for engineers and technicians. They may be promoted the application.