Structural behavior of continuous two-span prestressed concrete T beams with different tendon profiles

Abstract

Approximately half-scale tests were conducted to inves­tigate the behavior of indeterminate prestressed concrete T beams with two different unbonded tendon profiles. Three T beams were employed for the tests: T beam specimen 1 (TB1) was the control specimen and had no eccentricity at the interior support and T beam speci­mens 2a and 2b (TB2a and TB2b) had eccentricity at the interior support. The results indicate that the specimens with eccentricity at the interior support had a greater number of cracks than the control specimen at the ten­sion zone of the support. This finding was explained by hyperstatic moment reducing the negative moment in the control. The trend in the slope of the strain-applied load tension relationship was different in TB1 than in TB2a due to a difference between the specimens in terms of the distance from the extreme compression fiber to the centroid of reinforcement at the support. Although the interior support was a roller with no vertical restraint, hyperstatic moment at the support occurred due to a cold welding effect, creating a partial roller condition. The hyperstatic action then decreased as the loading was increased. The authors conclude that the effect of hyperstatic moment should be accounted for in the calculation of concrete stress at the service level for continuous prestressed concrete beams with unbonded tendons and a vertically unconfined support condition.