Pipes sometimes are classified as flexible or rigid pipes by checking the vertical deflection-to-internal diameter ratio in which the structural damage of the pipes subjected to parallel plate testing occurs. This control is made with unaided eyes. Do you know of any specific vertical deflection-to-internal diameter ratio associated with the beginning of the damage in which the flexible and rigid pipes are differentiated? Do you know any references for that classification?
dear Saeed
Hello
I hope that you can find your answer in the below link and attached file:
https://books.google.com/books?id=IXOKd3QSaBIC&pg=PA33&lpg=PA33&dq=how+can+determine+that+a+pipe+belongs+to+flexible+or+rigid+pipes+category?&source=bl&ots=7nYe-LeNSv&sig=UB0lzjsifdj87OYjjPqLYEWYcZo&hl=en&sa=X&ved=2ahUKEwi24u2fh5zdAhXKKlAKHeF0DBAQ6AEwCHoECAoQAQ#v=onepage&q=how%20can%20determine%20that%20a%20pipe%20belongs%20to%20flexible%20or%20rigid%20pipes%20category%3F&f=false
Yours,
You can also refer the attached link.
https://ascelibrary.org/doi/pdf/10.1061/(ASCE)0733-947X(1986)112%3A5(507)
1. rigid pipes start showing signs of structural distress before being vertically deflected 2 percent. Rigid pipes include reinforced non-cylinder concrete, reinforced concrete cylinder, prestressed concrete cylinder, vitrified clay, polymer concrete, cast iron, asbestos cement and cast-in-place pipes.
flexible pipes will deflect at least 2 percent without structural distress. Most flexible pipe material standards allow up to 5 percent deflection. Deflection is limited to 2 percent if the flexible pipe has a rigid lining and coating and 3 percent for a rigid lining and flexible coating. Flexible pipes include steel, ductile iron, thermoplastics such as Polyvinyl Chloride (PVC) and High Density Polyethylene (HDPE), thermosetting plastics such as fiberglass-reinforced polymer (FRP), bar-wrapped concrete cylinder pipe, and corrugated steel pipes.
2. To define if the behavior of a pipe is flexible or rigid, it is convenient to consider the stiffness ratio Rs as the ratio between soil stiffness and pipe stiffness:
Rs = E’ / (EI/D3) = E’D3/EI
Where:
E’ is the soil stiffness modulus of the soil (slope of a secant on the stress strain diagram);
EI/D3 = E/12(D/t)3 is the pipe stiffness, where I is the transverse moment of inertia per unit length of individual pipe wall components.
Soil stiffness E’ can vary from 100 kPa for damped soil to 50-100 Mpa for well-compacted, coarse-grained soil. Pipe stiffness EI/D3 is inversely related to pipe flexibility D/t and reduces progressively to zero for high D/t values. Usually pipe stiffness contributes significant resistance to pipe deflection if Rs is less than about 200, or D/t less than 50. Conversely, soil stiffness is crucial for flexible pipes and Rs is usually greater than 200.
Dear Bardia Roghani Shivanand Mahadeo Mali Chitaranjan Pany
Thank you so much for your reply. I have found the answer of my question from your replies.
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