This is an example of prestress loading in a plane frame structure.

It covers two situations:
1. From the member on which it is applied, the prestressing effect is transmitted to the rest of the structure through the connecting members (known in the program as PRESTRESS load).
2. The prestressing effect is experienced by the member(s) alone and not transmitted to the rest of the structure (known in the program as POSTSTRESS load).

This problem is installed with the program by default to C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\Sample Models\UK\UK-6 Prestress and Poststress Loading.STD when you install the program.

### Example Problem No. 6

Where:

• L1 = 4.5 m
• L2 = 6 m
• L3 = 12 m

Actual input is shown in bold lettering followed by explanation.

`    STAAD PLANE FRAME WITH PRESTRESSING LOAD`

Every input has to start with the term STAAD. The term PLANE signifies that the structure is a plane frame structure and the geometry is defined through X and Y axes.

`    UNIT METER KNS`

Defines the input units for the data that follows.

```    JOINT COORD
1 0. 0. ; 2 12. 0. ; 3 0. 6. ; 4 12. 6.
5 0. 10.5 ; 6 12. 10.5 ; 7 0. 15. ; 8 12. 15.```

Joint number followed by X and Y coordinates are provided above. Since this is a plane structure, the Z coordinates need not be provided.

Note: Semicolons (;) are used as line separators to allow for input of multiple sets of data on one line.
```    MEMBER INCIDENCE
1 1 3 ; 2 3 5 ; 3 5 7 ; 4 2 4 ; 5 4 6
6 6 8 ; 7 3 4 ; 8 5 6 ; 9 7 8```

Defines the members by the joints to which they are connected.

```    SUPPORT
1 2 FIXED ```

The supports at joints 1 and 2 are defined to be fixed supports.

```    MEMB PROP
1 TO 9 PRI AX 0.2044 IZ 8.631E-03```

Member properties are provided using the PRI (prismatic) attribute. Values of area (AX) and moment of inertia about the major axis (IZ) are provided.

```    UNIT MMS
DEFINE MATERIAL START
ISOTROPIC CONCRETE
E 21.0
POISSON 0.17
DENSITY 2.36158e-008
ALPHA 5e-006
DAMP 0.05
G 9.25
TYPE CONCRETE
STRENGTH FCU 0.0275
END DEFINE MATERIAL
CONSTANTS
MATERIAL CONCRETE ALL```

TThe DEFINE MATERIAL command is used to specify material properties and the CONSTANT is used to assign the material to all members. Length unit is changed from METER to MMS to facilitate the input.

```    LOADING 1 PRESTRESSING LOAD
MEMBER PRESTRESS
7 8 FORCE 1350. ES 75. EM -300. EE 75. ```

Load case 1 is initiated followed by a title. Load 1 contains PRESTRESS load. Members 7 and 8 have a cable force of 1350 KNs. The location of the cable at the start (ES) and end (EE) is 75 MMs above the centre of gravity while at the middle (EM) it is 300 MMs below the c.g. The assumptions and facts associated with this type of loading are explained in G.15.5 Prestress and Poststress Member Load.

```    LOADING 2 POSTSTRESSING LOAD
MEMBER POSTSTRESS
7 8 FORCE 1350. ES 75. EM -300. EE 75. ```

`    PERFORM ANALYSIS`

This command instructs the program to perform the analysis.

```    UNIT METER
PRINT ANALYSIS RESULTS```

The preceding command is an instruction to write joint displacements, support reactions and member forces in the output file. The preceding line causes the results to be written in the length unit of meters.

`    FINISH`

This command terminates the STAAD run.

## Input File

``````STAAD PLANE FRAME WITH PRESTRESSING LOAD
UNIT METER KNS
JOINT COORD
1 0. 0. ; 2 12. 0. ; 3 0. 6. ; 4 12. 6.
5 0. 10.5 ; 6 12. 10.5 ; 7 0. 15. ; 8 12. 15.
MEMBER INCIDENCE
1 1 3 ; 2 3 5 ; 3 5 7 ; 4 2 4 ; 5 4 6
6 6 8 ; 7 3 4 ; 8 5 6 ; 9 7 8
SUPPORT
1 2 FIXED
MEMB PROP
1 TO 9 PRI AX 0.2044 IZ 8.631E-03
UNIT MMS
DEFINE MATERIAL START
ISOTROPIC CONCRETE
E 21.0
POISSON 0.17
DENSITY 2.36158e-008
ALPHA 5e-006
DAMP 0.05
G 9.25
TYPE CONCRETE
STRENGTH FCU 0.0275
END DEFINE MATERIAL
CONSTANTS
MATERIAL CONCRETE ALL
MEMBER PRESTRESS
7 8 FORCE 1350. ES 75. EM -300. EE 75.
MEMBER POSTSTRESS
7 8 FORCE 1350. ES 75. EM -300. EE 75.
PERFORM ANALYSIS
UNIT METER
PRINT ANALYSIS RESULTS
FINISH
``````

```                                                                  PAGE NO.    1
****************************************************
*                                                  *
*           Version  22.08.00.***                  *
*           Proprietary Program of                 *
*           Bentley Systems, Inc.                  *
*           Date=    OCT 19, 2021                  *
*           Time=    17:54:29                      *
*                                                  *
*  Licensed to: Bentley Systems Inc                *
****************************************************
2. UNIT METER KNS
3. JOINT COORD
4. 1 0. 0. ; 2 12. 0. ; 3 0. 6. ; 4 12. 6.
5. 5 0. 10.5 ; 6 12. 10.5 ; 7 0. 15. ; 8 12. 15.
6. MEMBER INCIDENCE
7. 1 1 3 ; 2 3 5 ; 3 5 7 ; 4 2 4 ; 5 4 6
8. 6 6 8 ; 7 3 4 ; 8 5 6 ; 9 7 8
9. SUPPORT
10. 1 2 FIXED
11. MEMB PROP
12. 1 TO 9 PRI AX 0.2044 IZ 8.631E-03
13. UNIT MMS
14. DEFINE MATERIAL START
15. ISOTROPIC CONCRETE
16. E 21.0
17. POISSON 0.17
18. DENSITY 2.36158E-008
19. ALPHA 5E-006
20. DAMP 0.05
21. G 9.25
22. TYPE CONCRETE
23. STRENGTH FCU 0.0275
24. END DEFINE MATERIAL
25. CONSTANTS
26. MATERIAL CONCRETE ALL
28. MEMBER PRESTRESS
29. 7 8 FORCE 1350. ES 75. EM -300. EE 75.
31. MEMBER POSTSTRESS
32. 7 8 FORCE 1350. ES 75. EM -300. EE 75.
33. PERFORM ANALYSIS
FRAME WITH PRESTRESSING LOAD                             -- PAGE NO.    2
P R O B L E M   S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS          8  NUMBER OF MEMBERS       9
NUMBER OF PLATES          0  NUMBER OF SOLIDS        0
NUMBER OF SURFACES        0  NUMBER OF SUPPORTS      2
Using 64-bit analysis engine.
SOLVER USED IS THE IN-CORE ADVANCED MATH SOLVER
TOTAL      PRIMARY LOAD CASES =     2, TOTAL DEGREES OF FREEDOM =      18
TOTAL LOAD COMBINATION  CASES =     0  SO FAR.
34. UNIT METER
35. PRINT ANALYSIS RESULTS
ANALYSIS RESULTS
FRAME WITH PRESTRESSING LOAD                             -- PAGE NO.    3
JOINT DISPLACEMENT (CM   RADIANS)    STRUCTURE TYPE = PLANE
------------------
JOINT  LOAD   X-TRANS   Y-TRANS   Z-TRANS   X-ROTAN   Y-ROTAN   Z-ROTAN
1    1     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
2    1     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
3    1     0.1917    0.0000    0.0000    0.0000    0.0000    0.0004
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
4    1    -0.1917    0.0000    0.0000    0.0000    0.0000   -0.0004
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
5    1     0.1799    0.0000    0.0000    0.0000    0.0000    0.0008
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
6    1    -0.1799    0.0000    0.0000    0.0000    0.0000   -0.0008
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
7    1    -0.0014    0.0000    0.0000    0.0000    0.0000    0.0002
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
8    1     0.0014    0.0000    0.0000    0.0000    0.0000   -0.0002
2     0.0000    0.0000    0.0000    0.0000    0.0000    0.0000
FRAME WITH PRESTRESSING LOAD                             -- PAGE NO.    4
SUPPORT REACTIONS -UNIT KNS  METE    STRUCTURE TYPE = PLANE
-----------------
JOINT  LOAD   FORCE-X   FORCE-Y   FORCE-Z     MOM-X     MOM-Y     MOM Z
1    1    -30.59      0.00      0.00      0.00      0.00     80.49
2      0.00      0.00      0.00      0.00      0.00      0.00
2    1     30.59      0.00      0.00      0.00      0.00    -80.49
2      0.00      0.00      0.00      0.00      0.00      0.00
FRAME WITH PRESTRESSING LOAD                             -- PAGE NO.    5
MEMBER END FORCES    STRUCTURE TYPE = PLANE
-----------------
ALL UNITS ARE -- KNS  METE     (LOCAL )
MEMBER  LOAD  JT     AXIAL   SHEAR-Y  SHEAR-Z   TORSION     MOM-Y      MOM-Z
1    1     1     -0.00     30.59     0.00      0.00      0.00      80.49
3      0.00    -30.59     0.00      0.00      0.00     103.07
2     1      0.00      0.00     0.00      0.00      0.00       0.00
3      0.00      0.00     0.00      0.00      0.00       0.00
2    1     3     -0.00     62.59     0.00      0.00      0.00     121.89
5      0.00    -62.59     0.00      0.00      0.00     159.77
2     3      0.00      0.00     0.00      0.00      0.00       0.00
5      0.00      0.00     0.00      0.00      0.00       0.00
3    1     5     -0.00     10.30     0.00      0.00      0.00      50.98
7      0.00    -10.30     0.00      0.00      0.00      -4.64
2     5      0.00      0.00     0.00      0.00      0.00       0.00
7      0.00      0.00     0.00      0.00      0.00       0.00
4    1     2      0.00    -30.59     0.00      0.00      0.00     -80.49
4     -0.00     30.59     0.00      0.00      0.00    -103.07
2     2      0.00      0.00     0.00      0.00      0.00       0.00
4      0.00      0.00     0.00      0.00      0.00       0.00
5    1     4      0.00    -62.59     0.00      0.00      0.00    -121.89
6     -0.00     62.59     0.00      0.00      0.00    -159.77
2     4      0.00      0.00     0.00      0.00      0.00       0.00
6      0.00      0.00     0.00      0.00      0.00       0.00
6    1     6      0.00    -10.30     0.00      0.00      0.00     -50.98
8     -0.00     10.30     0.00      0.00      0.00       4.64
2     6      0.00      0.00     0.00      0.00      0.00       0.00
8      0.00      0.00     0.00      0.00      0.00       0.00
7    1     3   1371.41   -168.75     0.00      0.00      0.00    -326.21
4  -1371.41   -168.75     0.00      0.00      0.00     326.21
2     3   1339.41   -168.75     0.00      0.00      0.00    -101.25
4  -1339.41   -168.75     0.00      0.00      0.00     101.25
8    1     5   1287.12   -168.75     0.00      0.00      0.00    -312.00
6  -1287.12   -168.75     0.00      0.00      0.00     312.00
2     5   1339.41   -168.75     0.00      0.00      0.00    -101.25
6  -1339.41   -168.75     0.00      0.00      0.00     101.25
9    1     7    -10.30     -0.00     0.00      0.00      0.00       4.64
8     10.30      0.00     0.00      0.00      0.00      -4.64
FRAME WITH PRESTRESSING LOAD                             -- PAGE NO.    6
MEMBER END FORCES    STRUCTURE TYPE = PLANE
-----------------
ALL UNITS ARE -- KNS  METE     (LOCAL )
MEMBER  LOAD  JT     AXIAL   SHEAR-Y  SHEAR-Z   TORSION     MOM-Y      MOM-Z
2     7      0.00      0.00     0.00      0.00      0.00       0.00
8      0.00      0.00     0.00      0.00      0.00       0.00
************** END OF LATEST ANALYSIS RESULT **************
36. FINISH
*********** END OF THE STAAD.Pro RUN ***********
**** DATE= OCT 19,2021   TIME= 17:54:29 ****
FRAME WITH PRESTRESSING LOAD                             -- PAGE NO.    7
************************************************************