	Applies To
	Product(s):	AutoPIPE Vessel
	Version(s):	45.00.02.004
	Environment:	N/A
	Area:	Lifting Lug
	Original Author:	Bentley Technical Support Group

Problem:

How AutoPIPE Vessel calculates values of C1 and C2 for local loads on cylindrical shell?

Solution:

Lug attachment loaded Area:

As you can see in the report, Ratio of ᵝ1 and ᵝ2 values should be in between 0.25 and 4.

That means ratio of c1 and c2 should be within the 0.25 and 4. Hence to meet this criteria AutoPIPE Vessel take the appropriate value of c2.
Refer below example for reference

At Loading Area:

Here half of circumferential length c1 = 17.5 mm (half of the lug thickness 35mm)
half of Longitudinal length c2 = 70 mm (4 times the c1 to maintain the maximum ratio)

At the edge of reinforcing pad:

Here half of circumferential length c1 = 240 mm (half of the RF pad width 480mm)
half of Longitudinal length c2 = 325 mm (Half of the RF pad length 650mm as the ᵝ1 and ᵝ2 ratio is within the limit)

Rectangular Loaded Area:

Please see the comments below.

1. The following is all based on WRC107, 2002 update, and AutoPIPE Vessel 46.00.00.165
2. AutoPIPE input and output report.
3. Take a moment to flip the input for Length/axis with Width /Axis
4. Notice exactly what AutoPIPE vessel is doing:
  1. The program considers the 2 values entered for Length/axis and Width /Axis.
  2. The first objective is evaluating the Ratio of B1/B2. This must meet the range given by tables 7 and 8 of the standard. (B1/B2 range = 0.25 to 4).
  3. Is the ratio of B1/B2 with in this range?

1. 1. 1. If yes use both values for C1 and C2 as entered in the program
    2. If no, take the smallest value as either C1 or C2, and program calculates the other by multiplying by 4

Notes:

From WRC107:

From AutoPIPE Vessel:

2 c1 = circumferential length ==> c1 = 1/2 circumferential length (named "half width of loaded area" in help topic)

2 c2 = longitudinal length ==> c2 = 1/2 longitudinal length (named "half length of loaded area" in help topic)

Below the equations to determine c1 and c2 for a rectangular attachment in APV:
if ( c1/c2 > 4 ) c1 = 4 * c2

if ( c1/c2 < 0.25 ) c2 = 4 * c1

Example: 1, Length/axis = 100 and Width /Axis = 6.

1. 2. Calculate the ratio 6/100 = .06 or 100 /6 = 16.6.
  3. Are both ratios outside of the range for 0.25 – 4? YES
  4. Evaluate the smaller number between 6 or 100, take 6.
  5. Set C1 = 6 and calculate C2 by multiplying by 4. C2 = 24.
  6. See report image above.

Example: 2, Length/axis = 6 and Width /Axis = 100.

1. 2. Calculate the ratio 6/100 = .06 or 100 /6 = 16.6.
  3. Are both ratios outside of the range for 0.25 – 4? Yes
  4. Evaluate the smaller number between 6 or 100, take 6.
  5. Set C2 = 6 and calculate C1 by multiplying by 4. C1 = 24.
  6. See report image above.

Example: 3, Length/axis = 23 and Width /Axis = 6.

1. 2. Calculate the ratio 6/23 = .26 or 23/6 = 3.8.
  3. Are both ratios outside of the range for 0.25 – 4? NO
  4. Use the values for C1 and C2 as entered in the dialog.
  5. See report image above.

In conclusion, as long as the ratio of the two values for Length/Axis and Width/Axis remains within the specified range of 0.25 to 4, the exact values entered in the dialog are utilized. However, if the ratio of these two values falls outside this range, AutoPIPE Vessel will take the lesser of the two values and multiply it by 4 to determine the other value as clearly demonstrated by the 3 examples above.

Q. How AutoPIPE Vessel calculates values of C1 and C2 for local loads on cylindrical shell?

Problem:

Solution:

See Also