EX. UK-25 Analysis of a Structure with Compression-Only Members
This example demonstrates the usage of compression-only members. Since the structural condition is load dependent, the PERFORM ANALYSIS command is specified once for each primary load case.
This problem is installed with the program by default to C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\Sample Models\UK\UK-25 Analysis of a Structure with Compression-Only Members.STD when you install the program.
This example has been created to illustrate the command specification for a structure with certain members capable of carrying compressive force only. It is important to note that the analysis can be done for only 1 load case at a time. This is because, the set of "active" members (and hence the stiffness matrix) is load case dependent.
- L = 5.25 m, H = 3.5 m
- Load case 1: P1 = 45 kN & P2 = 70 kN
- Load case 2: P3 = -45 kN & P4 = -70 kN
STAAD PLANE
* EXAMPLE FOR COMPRESSION-ONLY MEMBERS
The input data is initiated with the word STAAD. This structure is a PLANE frame. The second line is an optional comment line.
UNIT METER KNS
Units for the commands to follow are specified above.
JOINT COORDINATES
1 0 0 ; 2 0 3.5 ; 3 0 7.0 ; 4 5.25 7.0 ; 5 5.25 3.5 ; 6 5.25 0
Joint coordinates of joints 1 to 6 are defined above.
MEMBER INCIDENCES
1 1 2 5 ; 6 1 5 ; 7 2 6 ; 8 2 4 ; 9 3 5 ; 10 2 5
The members 1 to 10 are defined along with the joints to which they are connected.
MEMBER COMPRESSION
6 TO 9
Members 6 to 9 are defined as COMPRESSION-only members. Hence for each load case, if during the analysis, any of the members 6 to 9 is found to be carrying a tensile force, it is disabled from the structure and the analysis is carried out again with the modified structure.
MEMBER PROPERTY BRITISH
1 TO 10 TA ST UC152X152X30
Members 1 to 10 are assigned the UC152X152X30 section from the British steel table.
UNIT MMS
DEFINE MATERIAL START
ISOTROPIC STEEL
E 210
POISSON 0.3
DENSITY 7.6977e-008
ALPHA 6e-006
DAMP 0.03
TYPE STEEL
STRENGTH FY 0.25 FU 0.4 RY 1.5 RT 1.2
END DEFINE MATERIAL
CONSTANTS
MATERIAL STEEL ALL
UNIT METER
The DEFINE MATERIAL command is used to specify material properties and the CONSTANT is used to assign the material to all members.
SUPPORT
1 6 PINNED
Joints 1 and 6 are declared as pinned-supported.
LOAD 1
JOINT LOAD
2 FX 70
3 FX 45
Load 1 is defined above and consists of joint loads in the global X direction at joints 2 and 3.
PERFORM ANALYSIS
The above structure is analyzed for load case 1.
CHANGE
MEMBER COMPRESSION
6 TO 9
One or more among the members 6 to 9 may have been in-activated in the previous analysis. The CHANGE command restores the original structure to prepare it for the analysis for the next primary load case. The members with the compression-only attribute are specified again.
In load case 2, joint loads are applied in the negative global X direction at joints 4 and 5.
PERFORM ANALYSIS
CHANGE
The instruction to analyze the structure is specified again. Next, any compression-only members that were inactivated during the second analysis (due to the fact that they were subjected to tensile axial forces) are re-activated with the CHANGE command. Without the re-activation, these members cannot be accessed for further processing.
LOAD 3
REPEAT LOAD
1 1.0 2 1.0
Load case 3 illustrates the technique employed to instruct STAAD to create a load case which consists of data to be assembled from other load cases already specified earlier. We would like the program to analyze the structure for loads from cases 1 and 2 acting simultaneously. In other words, the above instruction is the same as the following:
The analysis is carried out for load case 3.
CHANGE
The members inactivated during the analysis of load case 3 are re-activated for further processing.
LOAD LIST ALL
At the end of any analysis, only those load cases for which the analysis was done most recently, are recognized as the "active" load cases. The LOAD LIST ALL command enables all the load cases in the structure to be made active for further processing.
PRINT ANALYSIS RESULTS
The program is instructed to write the joint displacements, support reactions and member forces to the output file.
FINISH
The STAAD run is terminated.
Input File
STAAD PLANE
* EXAMPLE FOR COMPRESSION-ONLY MEMBERS
UNIT METER KNS
SET NL 3
JOINT COORDINATES
1 0 0 ; 2 0 3.5 ; 3 0 7.0 ; 4 5.25 7.0 ; 5 5.25 3.5 ; 6 5.25 0
MEMBER INCIDENCES
1 1 2 5
6 1 5 ; 7 2 6 ; 8 2 4 ; 9 3 5 ; 10 2 5
MEMBER COMPRESSION
6 TO 9
MEMBER PROPERTY BRITISH
1 TO 10 TA ST UC152X152X30
UNIT MMS
DEFINE MATERIAL START
ISOTROPIC STEEL
E 210
POISSON 0.3
DENSITY 7.6977e-008
ALPHA 6e-006
DAMP 0.03
TYPE STEEL
STRENGTH FY 0.25 FU 0.4 RY 1.5 RT 1.2
END DEFINE MATERIAL
CONSTANTS
MATERIAL STEEL ALL
UNIT METER
SUPPORT
1 6 PINNED
LOAD 1
JOINT LOAD
2 FX 70
3 FX 45
PERFORM ANALYSIS
CHANGE
MEMBER COMPRESSION
6 TO 9
LOAD 2
JOINT LOAD
4 FX -45
5 FX -70
PERFORM ANALYSIS
CHANGE
LOAD 3
REPEAT LOAD
1 1.0 2 1.0
PERFORM ANALYSIS
CHANGE
LOAD LIST ALL
PRINT ANALYSIS RESULTS
FINISH
STAAD Output File
PAGE NO. 1 **************************************************** * * * STAAD.Pro CONNECT Edition * * Version 22.12.00.*** * * Proprietary Program of * * Bentley Systems, Inc. * * Date= OCT 27, 2022 * * Time= 15: 7:53 * * * * Licensed to: Bentley Systems Inc * **************************************************** 1. STAAD PLANE INPUT FILE: UK-25 Analysis of a Structure with Compression-Only Members.STD 2. * EXAMPLE FOR COMPRESSION-ONLY MEMBERS 3. UNIT METER KNS 4. SET NL 3 5. JOINT COORDINATES 6. 1 0 0 ; 2 0 3.5 ; 3 0 7.0 ; 4 5.25 7.0 ; 5 5.25 3.5 ; 6 5.25 0 7. MEMBER INCIDENCES 8. 1 1 2 5 9. 6 1 5 ; 7 2 6 ; 8 2 4 ; 9 3 5 ; 10 2 5 10. MEMBER COMPRESSION 11. 6 TO 9 12. MEMBER PROPERTY BRITISH 13. 1 TO 10 TA ST UC152X152X30 14. UNIT MMS 15. DEFINE MATERIAL START 16. ISOTROPIC STEEL 17. E 210 18. POISSON 0.3 19. DENSITY 7.6977E-008 20. ALPHA 6E-006 21. DAMP 0.03 22. TYPE STEEL 23. STRENGTH FY 0.25 FU 0.4 RY 1.5 RT 1.2 24. END DEFINE MATERIAL 25. CONSTANTS 26. MATERIAL STEEL ALL 27. UNIT METER 28. SUPPORT 29. 1 6 PINNED 30. LOAD 1 31. JOINT LOAD 32. 2 FX 70 33. 3 FX 45 34. PERFORM ANALYSIS STAAD PLANE -- PAGE NO. 2 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS P R O B L E M S T A T I S T I C S ----------------------------------- NUMBER OF JOINTS 6 NUMBER OF MEMBERS 10 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. *** LOAD CASE 1 -- START ITERATION NO. 2 **NOTE-Tension/Compression converged after 2 iterations, Case= 1 35. CHANGE 36. MEMBER COMPRESSION 37. 6 TO 9 38. LOAD 2 39. JOINT LOAD 40. 4 FX -45 41. 5 FX -70 42. PERFORM ANALYSIS *** LOAD CASE 2 -- START ITERATION NO. 2 **NOTE-Tension/Compression converged after 2 iterations, Case= 2 43. CHANGE 44. LOAD 3 45. REPEAT LOAD 46. 1 1.0 2 1.0 47. PERFORM ANALYSIS **NOTE-Tension/Compression converged after 1 iterations, Case= 3 48. CHANGE 49. LOAD LIST ALL 50. PRINT ANALYSIS RESULTS STAAD PLANE -- PAGE NO. 3 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS ANALYSIS RESULTS STAAD PLANE -- PAGE NO. 4 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS 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 -0.0005 2 0.0000 0.0000 0.0000 0.0000 0.0000 0.0007 3 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0001 2 1 0.1609 0.0464 0.0000 0.0000 0.0000 -0.0003 2 -0.1900 -0.0132 0.0000 0.0000 0.0000 0.0003 3 0.0138 0.0030 0.0000 0.0000 0.0000 -0.0000 3 1 0.2889 0.0594 0.0000 0.0000 0.0000 -0.0003 2 -0.2889 -0.0132 0.0000 0.0000 0.0000 0.0002 3 0.0091 0.0080 0.0000 0.0000 0.0000 0.0000 4 1 0.2889 -0.0132 0.0000 0.0000 0.0000 -0.0002 2 -0.2889 0.0594 0.0000 0.0000 0.0000 0.0003 3 -0.0091 0.0080 0.0000 0.0000 0.0000 -0.0000 5 1 0.1900 -0.0132 0.0000 0.0000 0.0000 -0.0003 2 -0.1609 0.0464 0.0000 0.0000 0.0000 0.0003 3 -0.0138 0.0030 0.0000 0.0000 0.0000 0.0000 6 1 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0007 2 0.0000 0.0000 0.0000 0.0000 0.0000 0.0005 3 0.0000 0.0000 0.0000 0.0000 0.0000 0.0001 STAAD PLANE -- PAGE NO. 5 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS SUPPORT REACTIONS -UNIT KNS METE STRUCTURE TYPE = PLANE ----------------- JOINT LOAD FORCE-X FORCE-Y FORCE-Z MOM-X MOM-Y MOM Z 1 1 -0.13 -106.67 0.00 0.00 0.00 0.00 2 114.87 106.67 0.00 0.00 0.00 0.00 3 10.38 0.00 0.00 0.00 0.00 0.00 6 1 -114.87 106.67 0.00 0.00 0.00 0.00 2 0.13 -106.67 0.00 0.00 0.00 0.00 3 -10.38 0.00 0.00 0.00 0.00 0.00 STAAD PLANE -- PAGE NO. 6 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS 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 -106.67 0.13 0.00 0.00 0.00 -0.00 2 106.67 -0.13 0.00 0.00 0.00 0.45 2 1 30.22 -0.21 0.00 0.00 0.00 0.00 2 -30.22 0.21 0.00 0.00 0.00 -0.73 3 1 -6.94 0.03 0.00 0.00 0.00 -0.00 2 6.94 -0.03 0.00 0.00 0.00 0.09 2 1 2 -29.91 0.24 0.00 0.00 0.00 0.38 3 29.91 -0.24 0.00 0.00 0.00 0.46 2 2 0.15 -0.12 0.00 0.00 0.00 -0.08 3 -0.15 0.12 0.00 0.00 0.00 -0.33 3 2 -11.49 -0.03 0.00 0.00 0.00 -0.08 3 11.49 0.03 0.00 0.00 0.00 -0.03 3 1 3 0.12 -0.15 0.00 0.00 0.00 -0.46 4 -0.12 0.15 0.00 0.00 0.00 -0.33 2 3 0.12 0.15 0.00 0.00 0.00 0.33 4 -0.12 -0.15 0.00 0.00 0.00 0.46 3 3 27.79 -0.00 0.00 0.00 0.00 0.03 4 -27.79 0.00 0.00 0.00 0.00 -0.03 4 1 4 0.15 0.12 0.00 0.00 0.00 0.33 5 -0.15 -0.12 0.00 0.00 0.00 0.08 2 4 -29.91 -0.24 0.00 0.00 0.00 -0.46 5 29.91 0.24 0.00 0.00 0.00 -0.38 3 4 -11.49 0.03 0.00 0.00 0.00 0.03 5 11.49 -0.03 0.00 0.00 0.00 0.08 5 1 5 30.22 0.21 0.00 0.00 0.00 0.73 6 -30.22 -0.21 0.00 0.00 0.00 0.00 2 5 -106.67 -0.13 0.00 0.00 0.00 -0.45 6 106.67 0.13 0.00 0.00 0.00 0.00 3 5 -6.94 -0.03 0.00 0.00 0.00 -0.09 6 6.94 0.03 0.00 0.00 0.00 0.00 6 1 1 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 2 1 137.81 0.00 0.00 0.00 0.00 0.00 5 -137.81 0.00 0.00 0.00 0.00 0.00 3 1 12.51 0.00 0.00 0.00 0.00 0.00 5 -12.51 0.00 0.00 0.00 0.00 0.00 7 1 2 137.81 0.00 0.00 0.00 0.00 0.00 6 -137.81 0.00 0.00 0.00 0.00 0.00 STAAD PLANE -- PAGE NO. 7 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS 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 2 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 3 2 12.51 0.00 0.00 0.00 0.00 0.00 6 -12.51 0.00 0.00 0.00 0.00 0.00 8 1 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 2 2 53.66 0.00 0.00 0.00 0.00 0.00 4 -53.66 0.00 0.00 0.00 0.00 0.00 3 2 20.72 0.00 0.00 0.00 0.00 0.00 4 -20.72 0.00 0.00 0.00 0.00 0.00 9 1 3 53.66 0.00 0.00 0.00 0.00 0.00 5 -53.66 0.00 0.00 0.00 0.00 0.00 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 3 20.72 0.00 0.00 0.00 0.00 0.00 5 -20.72 0.00 0.00 0.00 0.00 0.00 10 1 2 -44.55 -0.31 0.00 0.00 0.00 -0.82 5 44.55 0.31 0.00 0.00 0.00 -0.81 2 2 -44.55 0.31 0.00 0.00 0.00 0.81 5 44.55 -0.31 0.00 0.00 0.00 0.82 3 2 42.29 0.00 0.00 0.00 0.00 -0.01 5 -42.29 -0.00 0.00 0.00 0.00 0.01 ************** END OF LATEST ANALYSIS RESULT ************** 51. FINISH STAAD PLANE -- PAGE NO. 8 * EXAMPLE FOR COMPRESSION-ONLY MEMBERS *********** END OF THE STAAD.Pro RUN *********** **** DATE= OCT 27,2022 TIME= 15: 7:54 **** ************************************************************ * For technical assistance on STAAD.Pro, please visit * * http://www.bentley.com/en/support/ * * * * Details about additional assistance from * * Bentley and Partners can be found at program menu * * Help->Technical Support * * * * Copyright (c) Bentley Systems, Inc. * * http://www.bentley.com * ************************************************************