Dear Stress Engineers,
Our client asked us to analyze lines for Blast load in both horizontal and vertical directions.
For horizontal, everything is OK but for +Y direction, most of the lines will be failed in Code Stress Evaluation.
The question is that when I reduce the amount of pressure load there is no change in calculated stress in lines. Now I’m in doubt if the model or load cases are defined correct or not.

Is there any idea?

Many thanks.

How did you model the blast load? What load case are you talking about (where the stress didn't change)?

Richard,
I added Blast load as a Pressure vs. Elevation wind load. Then ckecked them as OCC load cases. Is this correct?

By changing the value of this Pressure, there is no change in the Code Stress Evaluation of these OCC load cases.

Hello dear Shahram.
plz write your load case which you check it as OCC. load.
check shape factor not to be off on that eleman(s).also you can mail your caesar file to my e-mail: A.MAHDIKHANI@GMAIL.COM

Dear Mahdikhani,
You can see my definition for blast load and list of load cases as below.
I checked code compliance for load cases nr. 8, 15, 16, 17, 18, 19, 20 and 21 which is failed for “+WIN3” and Code Stress value (ratio) didn't change by changing Wind Pressure. Is it normal?

Regards.


----- WIND ANALYSIS DATA

WIND LOADING #: 1
USER DEFINED WIND PRESSURE vs. ELEVATION
20400.000 N./sq.m. 50000.000 mm.

-----/ WIND DIRECTION SPECIFICATION /------------
X WIND Direction cosine (or vector) ........... 1.0000
Y WIND Direction cosine (or vector) ...........
Z WIND Direction cosine (or vector) ...........

----- WIND ANALYSIS DATA

WIND LOADING #: 2
USER DEFINED WIND PRESSURE vs. ELEVATION
20400.000 N./sq.m. 50000.000 mm.

-----/ WIND DIRECTION SPECIFICATION /------------
X WIND Direction cosine (or vector) ...........
Y WIND Direction cosine (or vector) ...........
Z WIND Direction cosine (or vector) ........... 1.0000

----- WIND ANALYSIS DATA

WIND LOADING #: 3
USER DEFINED WIND PRESSURE vs. ELEVATION
20400.000 N./sq.m. 50000.000 mm.

-----/ WIND DIRECTION SPECIFICATION /------------
X WIND Direction cosine (or vector) ...........
Y WIND Direction cosine (or vector) ........... 1.0000
Z WIND Direction cosine (or vector) ...........



--------------LISTING OF STATIC LOAD CASES FOR THIS ANALYSIS--------
1 (OPE) W+D1+T1+P1+H
2 (OPE) W+D1+T1+P1+H+WIN1
3 (OPE) W+D1+T1+P1+H-WIN1
4 (OPE) W+D1+T1+P1+H+WIN2
5 (OPE) W+D1+T1+P1+H-WIN2
6 (OPE) W+D1+T1+P1+H+WIN3
7 (OPE) W+D1+T1+P1+H-WIN3
8 (SUS) W+P1+H
9 (OCC) L9=L2-L1
10 (OCC) L10=L3-L1
11 (OCC) L11=L4-L1
12 (OCC) L12=L5-L1
13 (OCC) L13=L6-L1
14 (OCC) L14=L7-L1
15 (EXP) L15=L1-L8
16 (OCC) L16=L9+L8
17 (OCC) L17=L10+L8
18 (OCC) L18=L11+L8
19 (OCC) L19=L12+L8
20 (OCC) L20=L13+L8
21 (OCC) L21=L14+L8

Please note the blast loads can be in all three directions. The allowable stress goes upto yield value of material. In your case use hold down supports and the pipework will be safe.

Dear PKU,
Thanks for your reply. You are correct. I checked hold down support and the job passed code stress evaluation.

The problem is that all supports are installed in the field and during the detail design of the project blast load was not checked in vertical direction!
Now is the project handover time and the project manager wants to be sure there is no other way unless pipe supports' modification, which is huge extra work and I want to be 100% sure of my analysis!

Regards
Shahram

Anyone can explain more details about blast load input in Caesar II?
We input blast load in wind load edition, right?

Either that, or a uniform pressure versus elevation load (also defined on the "wind" dialog).

hi,
how can we increase the allowable stresses to yield value of the material to perform blast analysis? Is there any option in Caesar to perform using yield value?

Modify the occasional load factor.

Regards,