Hi,
Good day to everyone.

The transit case is generally done for piping transported through barges with the application of barge acceleration.

In a recent stress analysis for transportation, we observed pipe lift off at some + Y supports (around 3-5 mm) during transportation. The acceleration used was 0.7 g horizontal and 0.2 g vertical.

Load cases used are:
L1 WNC SUS
L2 U1 OCC
L3 U2 OCC
L4 U3 OCC
L5 L2+L3 OCC (SRSS)
L6 L3+L4 OCC (SRSS)
L7 L1+L5 OCC (ABS)
L8 L1+L6 OCC (ABS)

Is it possible for the pipe to lift off when 0.2 g vertical acceleration is given or holddown supports need to be provided at all +Y support points during transportation to prevent liftoff.

I find this lift-off during transportation something different and need advice and thoughts on this topic if there should be no liftoff during transportation.

Regards,
SAM.

Hi,
Can anyone share their thoughts and suggestions on the above mentioned topic.
Transit Analysis case is unique in CAESAR and it is bound to generate high forces on some supports when barge accelerations are applied.

Regards,
SAM.

Hi,

The load cases had the problem and now it has been corrected.
Case 5-8 was changed to scalar, but the question is will 0.2 g force will cause the pipe to lift 2 mm.

Only a force greater than 1g can cause the pipe to lift, whereas in our analysis we have applied a 0.2 g vertical acceleration......

Is it real or any problem with the displacement values interpretation in CAESAR.

Kindly share your thoughts.

Regards,
SAM.

Hi,
Any comment on vertical lift during transportation analysis...

Regards,
SAM.

Sometimes supports lift-off during transportation therefore you need to add temporary supports (search for sea-fastening)

But if you have non-linear supports (+Y), the way you construct the load cases is not a valid approach. You apply a vertical acceleration over a system without weight and you will obtain non real vertical displacements where maybe there is no vertical displacement at all.

Change the loadcases definition or use linear supports. Observe the differences.

regards,

Dear danb,

I agree that the load case approach was not correct for +Y support during transportation. If the support is non linear and the vertical acceleration alone is applied without weight there will be definitely lift off..

The load case can be simplified to check the results.

L1 WNC SUS
L2 WNC+U1+U2+U3 SUS

Kindly share if there are other load case options available. You are correct in mentioning the two solutions.
Change the loadcases definition or use linear supports.

Many thanks for knowledge sharing.

Thanks & Regards,
SAM

linear approach:

L1 WNC SUS
L2 U1 OCC
L3 U2 OCC
L4 U3 OCC
L5 L2+L3 OCC (SRSS)
L6 L3+L4 OCC (SRSS)
L7 L1+L5 OCC (ABS)
L8 L1+L6 OCC (ABS)

Non linear approach:

L1 = WNC+U1+U2 (OPE)
L2 = WNC-U1+U2 (OPE)
L3 = WNC+U3+U2 (OPE)
L4 = WNC-U3+U2 (OPE)
L5 = WNC+U1-U2 (OPE)
L6 = WNC-U1-U2 (OPE)
L7 = WNC+U3-U2 (OPE)
L8 = WNC-U3-U2 (OPE)
L9 = WNC (SUS)
L10 = L1-L9 (OCC)
L11 = L2-L9 (OCC)
L12 = L3-L9 (OCC)
L13 = L4-L9 (OCC)
L14 = L5-L9 (OCC)
L15 = L6-L9 (OCC)
L16 = L7-L9 (OCC)
L17 = L8-L9 (OCC)
L18 = L9+L10 (OCC) scalar
L19 = L9+L11 (OCC) scalar
L20 = L9+L12 (OCC) scalar
L21 = L9+L13 (OCC) scalar
L22 = L9+L14 (OCC) scalar
L23 = L9+L15 (OCC) scalar
L24 = L9+L16 (OCC) scalar
L25 = L9+L17 (OCC) scalar

Look complicated but it is the only way when you deal with non-linear system

Regards,

Recently i done some transport analysis

my obervations :

for modular / PAR ( pree assembled rack's)

for small bore lines 3" and below:

1. provide temporary limit stop and transport hold down guide required for the end of the moduls.

2. any over hang more than 2mtrs provide metal straps.

for big bore lines 100% required transport analysis.

REGARDS,

AKULA