Strength and stiffness analysis of spiral casing with different embedded manners

For three typical manners of steel spiral casing(SC) embedded in concrete,i.e.,manner of SC embedded in concrete with soft cushion layer(MSCL),manner of SC embedded in concrete while holding a certain water head inside SC(MHWH) and manner of SC embedded directly in concrete(MD),the influence of setting up of expansion joint and anti-thrust ring on the stress and deformation distributions of a giant SC and its surrounding concrete was analyzed by FEM and thereafter these three manners were evaluated.Some conclusions are(1) Evaluated from decreasing concrete tensile stress and increasing SC bearing ratio of water pressure,MSCL is better than MHWH and MHWH is better than MD.Evaluated from deformation of steel structures,MD is better than MSCL and MHWH.However,evaluated from deformation of concrete,MD is worse than MSCL.(2)For MSCL and MHWH,the setting up of expansion joint and anti-thrust ring will not much affect the stress distributions of SC and surrounding concrete.Evaluated from structural integrated stiffness,MSCL is equivalent to or a little weaker than MHWH.(3) For MSCL,if setting up of expansion joint is concelled,the anti-thrust ring may be cancelled.For MHWH,if expansion joint is set up,it is suggested that the anti-thrust ring be set up.This paper can be a reference for the optimal choice of embedding manners for SC.