Abstract
In the design of prestressing concrete structures, the friction characteristics between strands and channels have an important influence on the distribution of prestressing force, which can be considered comprehensively by curvature and swing friction coefficients. However, the proposed friction coefficient varies widely and may lead to an inaccurate prestress estimation. In this study, four full‐scale field specimens were established to measure the friction loss of prestressing tendons with electromagnetic sensors and anchor cable dynamometers to evaluate the friction coefficient. The least square method and Bayesian quantile regression method were adopted to calculate the friction coefficient, and the results were compared with that in the specifications. Field test results showed that Bayesian quantile regression method was more effective and significant in the estimation of the friction coefficient.
Highlights
Prestressed concrete is used to reduce or offset the tensile stress of concrete under the action of loads, so as to improve the crack resistance and stiffness of components
The friction characteristics between the steel strand and the pipe are directly related to the elongation required by the tensioning operation and the prestress force distribution. e value of friction coefficient is usually obtained from the design specifications or the instructions provided by manufacturers. e recommended friction coefficient [1,2,3,4] ranges widely, which may result in the confusion and inaccuracy. e inaccurate calculation of friction loss can cause unreasonable camber and prestress reduction or even deflection of beams
Four prefabricated prestressed box girder bridges with spans of 20, 25, and 30 meters were adopted for full-scale field tests, and the friction coefficient was investigated, which was very rare in previous relevant studies. e least square method and Bayesian quantile regression method were used to analyze the actual friction coefficient data sets of real bridges
Summary
Prestressed concrete is used to reduce or offset the tensile stress of concrete under the action of loads, so as to improve the crack resistance and stiffness of components. E total prestress loss at the beam end and the stress distribution are measured by the pressure sensor at the anchorage point [11] and the electromagnetic (EM) sensor [12,13,14], respectively. It is possible for the designers and builders to determine the coefficients erroneously. E least square method [18] is the most common calculation method for estimating the friction coefficient First and foremost, such method needs to assume that the random error term obeys the zero mean and homoscedastic distribution. Based on the monitoring of the prestressed tension process of four full-scale test beams in the construction site, the above two calculation methods of friction coefficient were compared
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