ボンドなしPC部材の製作とその曲げ性質

抄録

In the process of prestressing concrete (Abbrev. PC) construction, grouting is a very cumbersome and costly job. But non-grouted PC members sometimes cause such troubles as the stress corrosion of the prestressing tendon. Viscous asphalt is an efficient anticorrosive agent for the prestressing tendon, and it prevents by virtue of its grease effect the tendons and sheath from being bonded together.
The first section of the present study describes the test results of friction coefficients of asphalted PC bars sheathed in wrapping paper. We may conclude, from the test result, that the asphalted PC bars show smaller values of friction coefficient than conventional ones in steel sheath.
The second section gives an account of the test made of the unbonded PC beams with various depths. No appreciable difference in flexural behaviors of unbonded PC beams was found between those with the asphalted PC bars and those with bare bars in the steel sheath. It was found that the larger the flatness of the section of the unbonded PC beams at failure was the greater the working tensile force in the bars was.
The third section gives an account of the test made of the effect of bars location in the section of unbonded beams. It was found that the unbonded PC beams with large eccentricities for resultant prestressing force and with concentrated location of the bars gained higher utilization of PC bar strength at failure.
In the fourth section, the flexural properties of the assembled precast unbonded PC beams were investigated. It was found that monolithic beams of lightweight concrete with large eccentricity of resultant prestressing force and with concentrated location of the bars gained higher utilization of PC bar strength.