Influence of unbonded pretensioned reinforcement placed in narrow ducts to equilibrium of post-tensioned beams cross sections.

Bar elements pretensioned by unbonded steel reinforcement placed in narrow ducts are considered in this paper. Such elements find one of their main applications in the field of post-tensioned reinforced concrete. One of the main features of the post-tensioned concrete beams is an interaction between pretensioned strand and rest of the construction body which appears like a distributed balancing load. Increasing of the beam deflection leads to tensioning force change in its strands. This affects to the balancing load that in turn differs the subsequent deflection increasing. Analysis of influence of changing balancing load to equilibrium of cross sections of simply supported post-tensioned reinforced concrete beam has been made in the proposed article by methods of applied mechanics of materials. It is shown that increasing deflection of the beam and corresponding growth of balancing load are compensated by bending moment caused by eccentrical compression of the beam. [ABSTRACT FROM AUTHOR]