Hello,

I have to analyze an FRP pipe line. I don't know how to combine the load cases. I know that we don't have to consider the Expansion load case for stress. But I don't know how to combine Wind effect: For Steel I do an operating case like L1 = W+P1+T1+WIN1 and for stress an occasional case :L1-operting(w+P1+T1)+ SUS (W+P1). But For FRP pipe we have an allowable stress for Operating case that's why I don't know if have to consider the Operating load case or occasional load case for stress analyze of FRP Lines. Samething for Earthquake.

I have another Question: For the allowable stress, if I refer to BS 7159 I have only one allowable stress (I suppose for ambient temperature) which depends on the chemical composition and the temperature of the Fluid. But I don't know If I have to define an allowable for ambient and one for 80°C for example.

Please could someone help me?

Tanks in advance.

Anojan

I believe most FRP codes evaluate the state of stress regardless of load type so there is no combination or separation of loads. Just evaluate the stress resulting for any expected load set.

The CAESAR II allowable stress for BS 7159 is based on the design strain. This strain times the axial or hoop modulus will give the axial and hoop allowable stress. Does design strain or elastic modulus change with temperature? If so, then so would the allowable stress that you enter in CAESAR II.

FRP as an elastic material and has no plastic-elastic material properties. No deviation between primary and secundairy stresses is needed like for steel.
B31.3 part A gives some rules for stress checks but these are far from complete. BS7159 and UKOOA don't give strict rules for combinations and checks. ISO14692 gives seperate allowables for SUS, OPE and HYD cases.

If I understand, we don't have to analyse the occasional Loads for FRP pipe.

Thanks to Dave and Corne

No one here said you need not evaluate occasional loads. It's just that the codes do not isolate those loads to evaluate them. I would suggest you look at the state of stress (and structural response) under operating plus occasional (e.g. T1+D1+W+P1+WIND1).

Ok, Thanks Dave