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  • Design of Hollow Sections

    CE Designer

    Member

    Updated: Oct 22, 2024
    Views: 4.2K
    How does the design equation vary for hollow sections such as cylindrical pipe (under tension or compression) vary from the design of solid sections. Normally you would calculate the stress using the cross-sectional area. But with pipes, is it as simple as just using the surface area provided by the wall thickness or is there some other factor to consider?
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  • ISHAN TOPRE

    Member • Jan 11, 2013

    The basic equation is T/J= G*theta/L=Tau/R.

    T=Torque,
    J=Polar Moment of Inertia
    G=Modulus of rigidity,
    theta=angle of twist,
    L=Length of beam or section,
    Tau= Shear stress
    R= Maximum/ Outer Radius
    Here everything is same but polar moment of inertia varies with cross-section.

    If, you are considering pressure vessels, try calculating Hoop stress and Longitudinal streee, (PD/2t) and (PD/4t) respectively.
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  • zaveri

    Member • Jan 12, 2013

    #-Link-Snipped-# said it all.

    but however various sections have various properties. for example I-sections have good tensile and compressive strengths, but has poor resistance to twisting moments.

    circular sections have good shear strength, and bending moment.
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  • zaveri

    Member • Jan 14, 2013

    also, if a cylindrical solid machine member acted upon by axial forces (tension or compression), is to be replaced by a hollow cylindrical member, then it is just enough to ensure that stress acting is lesser than the ultimate stress of the material.

    for a solid cylindrical member under tension, the stress equation will be:

    tensile stress = load / ((pi/4))*diameter^2

    for a hollow cylindrical member under tension, the stress equation will be:


    tensile stress = load / ((pi/4))*(outer diameter^2 - inner diameter^2)

    now it is the designer's choice to select the correct inner and outer diameters.
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