Can hetrogeneous materials be realistically modelled using B31.3 in Caesar II?

I have been engaged to analyse a filament wound fibreglass pipeline using B31.3

I know Caesar II recommends the use of BS7159, and uses the 'Eff' box to model the Ea/Eh ratio that is of primary importance to hetrogeneous analysis. Changing the code to 31.3, still with (material 20 FRP), the 'eff' box seems to be looking for a longitudinal joint efficiency (ie. less than 1) not a modulus ratio.

Yes, CAESAR can be used to model FRP pipe in a B31.3 analysis. That is the Code we (RPS) use most often. But you need to be careful with Expansion stresses. It is usually not recommended to include expansion stress cases as FRP is not a ductile material. Expansion-type stresses should be treated the same as primary stresses, so use Sustained, Operating, or Occasional as appropriate.
With regard to "Eff", I'm not sure what input you're referring to, but the "Elastic modulus/axial" is the axial modulus of the pipe; and "Ea/Eh*Vh/a" is the ratio of the axial modulus to hoop modulus multiplied by the Poisson ratio. It is common for FRP vendors to publish two Poisson ratios. Use the value that provides axial strain from hoop stress. For pipe wound at 55°, this will be the larger of the two values.

For FRP pipe analyis, you have to use the following FRP properties (to be furnished by FRP vendor)

Axial Modulus of elasticity
FRP ratio (as per casear input spread sheet)
Thermal expansion coefficent
lamination type
Some of the properties you have to enter in special execution parameters and others in the input spread sheet directly.

It is also recommended to get allowable hoop stress, axial stress, allowable bending stresses directly from the vendor for sustained, operating and occalsional loading conditions. So you need not fill up any data for allowable stress in the caesar input spreadsheet.

In the result, you can just compare the actual axial stress, bending stress, hoop stress by using 132 character print option and compare with vendor allowable for sustained, operating and occasional loading condition. Sometimes, the vendor will furnish different axial and bending allowable stresses versus hoop stresses and in such case you have to take the allowable stresses coressonding to hoop stress.

K.R.Srinivasan
Sr Engineer/ Technip Malaysia
e-mail:krsrini@pacific.net.sg

Stress analysis of FRP using B31.3 needs to input SIF at fitting. SIF values are normally provided by vendor. In absence of vendor data, the SIF values for elbow, reducer and tee are 2.3, 1.0 and 1.0 respectively may be used.