GENERAL AND SIMPLIFIED MODELS FOR THE ANALYSIS OF PARTIALLY PRESTRESSED CONCRETE BEAMS CONTAINING FRP TENDONS OF ARBITRARY BONDED CONDITION

摘要

Two models, a general one and a simplified one, have been developed to simulate the behavior of partially prestressed concrete beams containing fiber reinforced polymer (FRP) prestressing tendons and stainless steel reinforcing bars in which the FRP tendons can be partially or fully bonded. In the general model the beam is divided into a number of segments and its section into a number of layers, and the stress increment in the unbonded tendon under incremental applied load is determined by an iterative process using the concept of compatibility of deformation in the concrete and unbonded tendon over its entire unbonded length. The simplified model assumes that any section in the beam has a tri-linear moment-curvature relationship characterized by three points, namely, cracking of concrete, yielding of non-prestressed steel, and crushing of concrete or rupture of the prestressing tendon during loading stage of the beam. Rational assumptions for determining the stress increment in the unbonded tendon and the rigidity distribution in the beam have been adopted in order to keep the analysis reasonably simple. Results, in the form of load-deflection relationships, from the two models are compared with test results from a number of beams containing unbonded FRP tendons and stainless steel reinforcing bars, and reasonable agreement is obtained indicating that the simplified model can give a satisfactory prediction of the behavior of partially prestressed, partially or fully bonded beams.