DESIGN METHODS OF PRESTRESSED CONCRETE PENSTOCK

A method is developed to check the fracture strength of longitudinal tensile stress of concrete during construction stage of prestressed concrete penstock. A formula is proposed to calculate the maximum distance of two consecutive strands that results in uniform distribution of concrete prestress along the penstock. The tensile steps and the tensile forces during construction stage of prestressed strands are determined for decreasing the secondary bending moment along the axis of penstock. Based on the theory of multiplayer axisymmetric plane strain model, a method is proposed to calculate the fracture strength of concrete during normal service stage. A design formula is also given to calculate the ultimate bearing capacity of prestressed concrete penstock. The work in the paper is believe to be useful for rational design and construction of prestressed concrete penstock.