CANADIAN Z662 - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II
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CAESAR II Version
13

Calculate pressure stiffening using Z662

Pressure stiffening is not defined by default in the code. You can include pressure stiffening on bends in the analysis by including the Use Pressure Stiffening=Yes option in the setup file.

Flanged end modifications using Z662

Modifications resulting from flanged ends are permitted in the code providing the bend is not a widely spaced miter.

Pad thickness using Z662

There is no limit in Z662 for the beneficial effect of the pad on an intersection. Most codes limit the pad thickness to 1.5 times the header thickness. For Z662, CAESAR II does not limit the pad thickness.

Z662 girth butt welds default value

The default SIF value for a girth butt weld is 1.0. This is also Markl’s original basis for SIFs. In-plane and out-plane stress intensification factors for intersections are the same.

Calculate socket welds using Z662

Z662 makes no distinction between socket welds with undercut and socket welds without undercut. Codes that do differentiate use 1.3 for socket welds with no undercut, and 2.1 for all others. Unless you are specifying a fillet weld leg length, use a default SIF value of 1.3.

Calculate effective section modulus using Z662

Z662 has no provision for using an effective section modulus calculation at intersections.

Calculate the CANADIAN Z662 allowable stress limits

Use the equations below to calculate the stress allowables.

Expansion Allowable = (0.72)(T)(Sy)

Sustained Allowable = (Fac)(T)(L)(Sy)

Occasional Allowable = (Occ)(Fac)(T)(L)(Sy)

Operating Allowable = 0.9(T)(Sy), if pipe is buried and axial stress is compressive

Operating Allowable = (T)(Sy), if pipe is not buried and axial stress is compressive

Where:

Sy = Specified Minimum Yield Stress

Fac = Construction Design Factor

T = Temperature De-rating Factor

Occ = Occasional Load Factor (Default is 1.0)

L = Location Factor

CAESAR II assumes that Section 4.6.2 of the Z662 code establishes a requirement for the allowable operating stress of 0.9 x S x T whenever the net axial stress is compressive in the absence of bending stress, and an allowable operating stress of S x T when the net axial stress is compressive in the presence of bending stress.

Section 4.6.2 requires the following:

  1. The reduction of the axial expansion stress by the product of Poisson’s Ratio and the pressure hoop stress.

  2. The addition of the hoop stress to the axial stress.

The latter represents the calculation of stress intensity when the axial stress is compressive, implying that there is no longitudinal pressure stress in buried pipe (the longitudinal pressure thrust loads are transmitted directly to the soil). CAESAR II handles these requirements, in the operating load case, in the following manner:

  1. If FAC is 1.0, the piping system is fully restrained in the axial direction as described in Section 4.6.2.1, and the operating stress is calculated as:

    Sh + E a (T2 - T1) - v Sh < 0.9 S x T

  2. If FAC is 0.001, the piping system is buried, but the soil supports are modeled (rather than just assumed to be fully rigid). This setting removes the longitudinal pressure stress from the equation (as described above), and takes bending stresses into consideration, as required by Section 4.6.2.2.1. In this case, the operating stress is calculated as:

    Sh +Fax/A + Sb - v Sh < S x T

  3. If FAC is 0.0, the piping system is either not restrained, or is a freely spanning or above ground portion of a restrained line, as described in Section 4.6.2.2.1. In this case, the longitudinal pressure stress is restored, so this formula only comes into effect if the net axial stress including pressure is compressive, in which case the operating stress is calculated as:

    Sh +Slp + Fax/A + Sb < S x T

  4. CAESAR II does not do an operating code stress check for those elements for which the net axial stress is longitudinal.

  5. CAESAR II does not check for buckling, as required by Section 4.6.2.2.2.

Z662 reducer default values

The default SIF value is 1.0. The default flexibility factor value is 1.0.