circular reinforced concrete staircase

huangyhg

circular reinforced concrete staircase
can any body give me the refernce/design calculation of circular reinforced concret stair design.
           --thanks in advance--
it's an interesting flexural-torsional problem and can be difficult to engineer.  boundary/support conditions are critical as well as stiffness.
i'm not aware of any 'canned' solutions to them.
dik
check aashto on curved bridge/ramp design ref/criteria. they are similar, but the loads.
the 'reinforced concrete designer's handbook' by reynolds et al has a design method and charts for spiral stairs.
it references what is presumably a more complete guide; 'charts for the design of helical stairs' by santathadaporn & cusens, in 'concrete and constructional engineering 61(2), 1966, pp. 46-54'.