Structural Steel Example #2 - Design a support to limit nozzle loads - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II Version
12

Design a support to limit the loads on the waste heat boiler’s flue gas nozzle connection. The maximum allowable loads on the nozzle are as follows:

Faxial = 1500 lb.

Fshear = 500 lb.

Mtorsion = 10000 ft. lb.

Mbending = 5000 ft. lb.

In this example, create the structural steel input file, SUPP2.str, from a text file. The structural steel preprocessor converts this file to the CAESAR II model.

Check the piping and structure shown in the following four figures:

Create the structural input ASCII file using a text editor

  1. Using a text editor, type the following input parameters for the model:

    UNIT ENGLISH.FIL

    ;DEFINE SECTIONS

    SECID 1 W24X104

    SECID 2 W18X50

    ;DEFINE MATERIALS

    MATID 1 YM=29E6 POIS=0.3 G=11.6E6 DENS=0.283

    ;COLUMN STRONG AXIS ORIENTATION

    ANGLE=90

    ;VERTICAL COLUMNS

    EDIM 230 235 DY=10-

    EDIM 235 220 DY=13-10

    EDIM 200 205 DY=10-

    EDIM 205 210 DY=13-10

    ;SLOPED COLUMNS

    EDIM 245 250 DX=8.392- DY=10-

    EDIM 260 255 DX=8.392- DY=10-

    EDIM 250 220 DX=11.608- DY=13-10

    EDIM 255 210 DX=11.608- DY=13-10

    MAKE BEAMS DEFAULT SECTION

    DEFAULT SECID=2;

    EDIM 235 240 DZ=-2.5-

    EDIM 240 205 DZ=-2.5-

    EDIM 220 215 DZ=-2.5-

    EDIM 215 210 DZ= -2.5-

    EDIM 250 255 DZ=-5-

    ;THE FINAL SET OF HORIZONTAL BEAMS

    ;ALONG THE X AXIS HAVE A

    ;STANDARD STRONG AXIS ORIENTATION

    ANGLE=0

    EDIM 250 235 DX=11.608-

    EDIM 255 205 DX=11.608-

    ;ANCHOR THE BASE NODES

    FIX 200 TO=260 BY=30 ALL

    FIX 245 ALL

    • After the data is processed, this file does not display the line breaks in Microsoft's Notepad text editor, but the data remains valid. Use a more robust editor to display the individual lines.

    • For information on editing ASCII text, see ASCII Text File Rules.

  2. Name and save the file as SUPP2.str.

Import the structural input file into the Structural Steel Modeler

  1. Click File > Open from the CAESAR II main window ribbon.

  2. Change File of type to Structural (*.str) and navigate to the file you created, SUPP2.str. Then, click Open.

  3. Click Home > Input > Structural Input from the CAESAR II main window ribbon.

    The software opens the structural model for SUPP2.str.

  4. After you have confirmed that the model is correct, click File > Save, and click Yes to save the model.

  5. Select all the check boxes in the Model Generation Status dialog box, and click OK.

    CAESAR II checks the input. If the error checker does not find any fatal errors, the software writes the execution files. You can use the model in a piping analysis, or you can analyze the model singularly. For the purposes of this example, you will analyze the model with a piping model.

  6. Close the CAESAR II Structural Modeler dialog box and return to the CAESAR II main window.

Input piping data for Example #2

Next, enter the input for the piping system to be analyzed in a new piping job.

  1. Click File > New from the CAESAR II main window ribbon.

  2. Change File of type to Piping Input (*.c2) , enter the file name as PIPE2 (for the purposes of this example).

  3. Navigate and select the CAESAR II data folder, and click OK.

    The software opens the Review Current Units dialog box.

  4. Verify the current units are English, then click OK.

    The software opens the piping input for PIPE2.c2.

  5. Click the Classic Piping Input tab on the left of the graphical display.

Enter the piping input data using the Input Echo report data shown below. For more information on how to quickly enter piping input data, see Navigating the Classic Piping Input Dialog Box using the Function Keys.

PIPE DATA

From 5 to 10 DX= 6.417 ft.

PIPE

Dia = 30.000 in. Wall= .375 in.

GENERAL

T1= 850 F Mat= (186)A335 P5

Insul Thk= .000 in.

BEND at "TO" end

Radius= 45.000 in. (LONG)

RESTRAINTS

Node 5 ANC

ALLOWABLE STRESSES

B31.3 (2008)

----------------------------------------------------------

From 10 to 15 DY= -8.000 ft.

----------------------------------------------------------

From 15 to 20 DY= -13.833 ft

----------------------------------------------------------

From 20 to 25 DY= -8.000 ft.

BEND at "TO" end

Radius= 45.000 in. (LONG)

----------------------------------------------------------

From 25 to 30 DX= 10.000 ft.

RESTRAINTS

Node 30 +Y

----------------------------------------------------------

From 30 To 35 DX= 30.000 ft.

RESTRAINTS

Node 35 +Y

----------------------------------------------------------

From 35 To 40 DX= 10.000 ft.

BEND at "TO" end

Radius= 45.000 in. (LONG)

----------------------------------------------------------

From 40 To 45 DZ= -3.750 ft.

----------------------------------------------------------

From 45 To 50 DZ= -4.000 ft.

PIPE

Dia= 30.000 in. Wall= .375 in.

Insul Thk= .000 in.

REDUCER

Diam2= 36.000 in. Wall2= .375 in.

----------------------------------------------------------

From 50 To 55 DZ= -20.000 ft.

PIPE

Dia= 36.000 in. Wall= .375 in.

Insul Thk= .000 in.

----------------------------------------------------------

From 55 To 60 DZ= -20.000 ft.

----------------------------------------------------------

From 60 To 65 DZ= -10.000 ft.

RESTRAINTS

Node 65 ANC

----------------------------------------------------------

From 15 To 115 DX= -2.500 ft.

PIPE

Dia= 30.000 in. Wall= .375 in.

Insul Thk= .000 in.

RIGID Weight= .00 lb.

RESTRAINTS

Node 115 X Cnode 215

Node 115 Z Cnode 215

----------------------------------------------------------

From 20 To 120 DX= -2.500 ft.

RIGID Weight= .00 lb.

RESTRAINTS

Node 120 X Cnode 240

In this piping input example, there are two weightless, rigid elements at nodes 15 to 115 and 20 to 120 that run out from the pipe centerline to the connecting points of the structure.

The two restraint sets at the end of the data—115 and 120—are pipe nodes and their CNodes—215 and 240—are structural steel nodes in SUPP2.

Connect the pipe to the structure

  1. From the Classic Piping Input dialog box, click Environment > Include Structural Input Files.

    The software opens the Include Structural Files dialog box.

  2. Enter the name of the structural steel model to be included (in this example, SUPP2).

    You can type the name and click Add, or click Browse to search for the file (which has the .str or the compressed .c2s extension), select the file, and click OK.

  3. If the pipe and structure do not plot properly relative to one-another, then one of the following situations may have occurred:

    1. The connecting nodes were not defined correctly.

    2. The Connect Geometry Through CNodes option was not set to True in the Configuration Editor. For more information, see Connect Geometry Through CNodes in the Configuration Options.

      Refer to the Pipe2 plotted pipe and structure shown below:

  4. After the software plots the pipe and structure relative to one another, exit the Generate piping input dialog box and run the error check.

    The error checker includes the pipe and structure together during checking. The execution files that the software writes also include the structural data.

  5. Run the analysis using the default load cases.

    The following shows the restraint report for Load Case 1, W+T1 (OPE):

The loads on the anchor at 5 are excessive. The structural steel frame and pipe support structure as shown are not satisfactory.

In this example, displacement of the structure is small relative to the displacement of the pipe. The pipe is thermally expanding out away from the boiler nozzle and down, away from the boiler nozzle.

The pipe is pulling the structure in the positive X direction at the top support and pushing the structure in the negative X direction at the bottom support. These displacements result in higher loads on the boiler nozzle. The vertical location of the structural supports should be studied more closely.

You could add vertical springs at 30 and 35, which might help, along with a repositioning of the structural supports vertically. For example, the support at node 120 should be moved down so that its line of action in the X direction more closely coincides with the center line of the pipe between nodes 25 and 40.