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EX. UK-7 Modeling Offset Connections in a Frame

This example illustrates modeling of structures with offset connections. Offset connections arise when the center lines of the connected members do not intersect at the connection point. The connection eccentricity behaves as a rigid link and is modeled through specification of MEMBER OFFSETS.

This problem is installed with the program by default to C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\Sample Models\UK\UK-7 Modeling Offset Connections in a Frame.STD when you install the program.

Example Problem No. 7

Where:

  • L1 = 4.5 m
  • L2 = 6 m
  • L3 = 178 mm
  • L4 = 152 mm

Actual input is shown in bold lettering followed by explanation.

   STAAD PLANE TEST FOR MEMBER OFFSETS

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 6. 0. ; 3 0. 4.5 
    4 6. 4.5 ; 5 0. 9. ; 6 6. 9.

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.
    SUPPORT 
    1 2 PINNED

Pinned supports are specified at joints 1 and 2. The word PINNED signifies that no moments will be carried by these supports.

    MEMB INCI 
    1 1 3 2 ; 3 3 5 4
    5 3 4 ; 6 5 6 ; 7 1 4 

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

    MEMB PROP BRITISH
    1 TO 4 TABLE ST UC356X368X129
    5 6 TA ST UB305X165X40
    7 TA LD UA200X150X12

All member properties are from British steel table. The word ST stands for standard single section. LD stands for long leg back-to-back double angle.

    UNIT MMS
    MEMB OFFSET 
    5 6 START 178. 0.0 0.0
    5 6 END -178. 0.0 0.0
    7 END -178.0 -152.0 0.0

The preceding specification states that an OFFSET is located at the START/END joint of the members. The X, Y, and Z global coordinates of the offset distance from the corresponding incident joint are also provided. These attributes are applied to members 5, 6, and 7.

    DEFINE MATERIAL START
    ISOTROPIC STEEL
    E 210
    POISSON 0.3
    DENSITY 7.6977e-008
    ALPHA 6e-006
    DAMP 0.03
    TYPE STEEL
    STRENGTH FY 0.24821 FU 0.399894 RY 1.5 RT 1.2
    END DEFINE MATERIAL
    CONSTANTS
    MATERIAL STEEL ALL

The DEFINE MATERIAL command is used to specify material properties and the CONSTANT is used to assign the material to all members.

    LOADING 1 WIND LOAD 

Load case 1 is initiated followed by a title.

    JOINT LOAD
    3 FX 225.0 ; 5 FX 112.5

Load 1 contains joint loads at nodes 3 and 5. FX indicates that the load is a force in the global X direction.

    PERFORM ANALYSIS

The above command is an instruction to perform the analysis.

    UNIT METER
    PRINT FORCES
    PRINT REACTIONS 

The above PRINT commands are instructions for writing the member forces and support reactions to the output file. The preceding line causes the results to be written in the length unit of meters

    FINISH

This command terminates a STAAD run.

Input File

STAAD PLANE TEST FOR MEMBER OFFSETS
UNIT METER KNS
JOINT COORD
1 0. 0. ; 2 6. 0. ; 3 0. 4.5
4 6. 4.5 ; 5 0. 9. ; 6 6. 9.
SUPPORT
1 2 PINNED
MEMB INCI
1 1 3 2 ; 3 3 5 4
5 3 4 ; 6 5 6 ; 7 1 4
MEMB PROP BRITISH
1 TO 4 TABLE ST UC356X368X129
5 6 TA ST UB305X165X40
7 TA LD UA200X150X12
UNIT MMS
MEMB OFFSET
5 6 START 178. 0.0 0.0
5 6 END -178. 0.0 0.0
7 END -178.0 -152.0 0.0
DEFINE MATERIAL START
ISOTROPIC STEEL
E 210
POISSON 0.3
DENSITY 7.6977e-008
ALPHA 6e-006
DAMP 0.03
TYPE STEEL
STRENGTH FY 0.24821 FU 0.399894 RY 1.5 RT 1.2
END DEFINE MATERIAL
CONSTANTS
MATERIAL STEEL ALL
LOADING 1 WIND LOAD
JOINT LOAD
3 FX 225.0 ; 5 FX 112.5
PERFORM ANALYSIS
UNIT METER
PRINT FORCES
PRINT REACTIONS
FINISH

STAAD Output File

                                                                  PAGE NO.    1
             ****************************************************        
             *                                                  *        
             *           STAAD.Pro CONNECT Edition              *        
             *           Version  22.04.00.**                   *        
             *           Proprietary Program of                 *        
             *           Bentley Systems, Inc.                  *        
             *           Date=    APR 21, 2020                  *        
             *           Time=    15:41:24                      *        
             *                                                  *        
             *  Licensed to: Bentley Systems Inc                *        
             ****************************************************        
     1. STAAD PLANE TEST FOR MEMBER OFFSETS
INPUT FILE: UK-7 Modeling Offset Connections in a Frame.STD
     2. UNIT METER KNS
     3. JOINT COORD
     4. 1 0. 0. ; 2 6. 0. ; 3 0. 4.5
     5. 4 6. 4.5 ; 5 0. 9. ; 6 6. 9.
     6. SUPPORT
     7. 1 2 PINNED
     8. MEMB INCI
     9. 1 1 3 2 ; 3 3 5 4
    10. 5 3 4 ; 6 5 6 ; 7 1 4
    11. MEMB PROP BRITISH
    12. 1 TO 4 TABLE ST UC356X368X129
    13. 5 6 TA ST UB305X165X40
    14. 7 TA LD UA200X150X12
    15. UNIT MMS
    16. MEMB OFFSET
    17. 5 6 START 178. 0.0 0.0
    18. 5 6 END -178. 0.0 0.0
    19. 7 END -178.0 -152.0 0.0
    20. DEFINE MATERIAL START
    21. ISOTROPIC STEEL
    22. E 210
    23. POISSON 0.3
    24. DENSITY 7.6977E-008
    25. ALPHA 6E-006
    26. DAMP 0.03
    27. TYPE STEEL
    28. STRENGTH FY 0.24821 FU 0.399894 RY 1.5 RT 1.2
    29. END DEFINE MATERIAL
    30. CONSTANTS
    31. MATERIAL STEEL ALL
    32. LOADING 1 WIND LOAD
    33. JOINT LOAD
    34. 3 FX 225.0 ; 5 FX 112.5
    35. PERFORM ANALYSIS
      TEST FOR MEMBER OFFSETS                                  -- PAGE NO.    2
            P R O B L E M   S T A T I S T I C S
            -----------------------------------
     NUMBER OF JOINTS          6  NUMBER OF MEMBERS       7
     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 =     1, TOTAL DEGREES OF FREEDOM =      14
   TOTAL LOAD COMBINATION  CASES =     0  SO FAR.
    36. UNIT METER
    37. PRINT FORCES
  FORCES                              
      TEST FOR MEMBER OFFSETS                                  -- PAGE NO.    3
   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    -49.14    -20.23     0.00      0.00      0.00       4.59
                 3     49.14     20.23     0.00      0.00      0.00     -95.65
      2    1     2    337.50    -25.11     0.00      0.00      0.00       0.00
                 4   -337.50     25.11     0.00      0.00      0.00    -112.99
      3    1     3    -30.77     53.79     0.00      0.00      0.00     150.98
                 5     30.77    -53.79     0.00      0.00      0.00      91.06
      4    1     4     30.77     58.71     0.00      0.00      0.00     170.67
                 6    -30.77    -58.71     0.00      0.00      0.00      93.55
      5    1     3    299.02    -18.38     0.00      0.00      0.00     -52.06
                 4   -299.02     18.38     0.00      0.00      0.00     -51.65
      6    1     5     58.71    -30.77     0.00      0.00      0.00     -85.58
                 6    -58.71     30.77     0.00      0.00      0.00     -88.07
      7    1     1   -479.29     -1.96     0.00      0.00      0.00      -4.59
                 4    479.29      1.96     0.00      0.00      0.00      -9.62
   ************** END OF LATEST ANALYSIS RESULT **************
    38. PRINT REACTIONS
  REACTION                            
      TEST FOR MEMBER OFFSETS                                  -- 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   -362.61   -337.50      0.00      0.00      0.00      0.00
      2    1     25.11    337.50      0.00      0.00      0.00      0.00
   ************** END OF LATEST ANALYSIS RESULT **************
    39. FINISH
             *********** END OF THE STAAD.Pro RUN ***********         
               **** DATE= APR 21,2020   TIME= 15:41:24 ****
      TEST FOR MEMBER OFFSETS                                  -- PAGE NO.    5
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