Friction Loss of Externally Prestressed Concrete Beams with Carbon Fiber-Reinforced Polymer Tendons

Abstract

Friction loss is an important component of the calculation of prestressing loss for external prestress strengthening technology. Unfortunately, the test data of relevant curvature friction and wobble coefficients is scarce, especially for beams strengthened by external prestressing Carbon Fiber-Reinforced Polymer (CFRP) tendons. Through the experiment of 12 concrete beams strengthened by external prestressing CFRP tendons, this study attempts to discuss the friction loss algorithm and the reasonable value of friction coefficient. The test results demonstrated that traditional friction loss algorithm for prestressed steel tendons is also suit to external prestressing CFRP tendons, but the value of curvature and wobble coefficients should be determined by different types of CFRP tendons and saddle design. What is more, aiming at the domestic production of CFRP tendons and the adopted special saddle design in this paper, the curvature friction coefficient is 0.263 and the wobble coefficient is 0.0067 at the deviator. Results of the research provide a reference for external prestress strengthening design with CFRP tendons.

Balanced Ratio of Concrete Beams Internally Prestressed with Unbonded CFRP Tendons

“…In order to investigate the effect of friction on strain increment, a relatively conservative value of j = 0.0015/m for wobble friction and g = 0.264/rad. provided by Yu and Zhang (2011) were used. It was found that only a marginal difference of 1 % (5 %) for total strain (strain increment) was observed due to frictional loss.…”

Experimental Analysis on Pre-Stress Friction Loss of Crushed Limestone Sand Concrete Beams

“…CLS concrete with large elastic modulus is sensitive to the increase in concrete age, and the creep and shrinkage is more obvious than normal concrete [2]. When compared with long-term pre-stress loss [5][6][7][8], the instantaneous loss caused by friction also significantly affects the initial pre-stress force of the tendon [10][11][12][13][14][15]. The effective force inevitably decreases due to the friction loss between the pre-stressing tendon and duct [10].…”