Hi all,
I am modelling a simple structure as shown below and when I analysed it, warning was shown and the bending moment diagram are completely wrong.
What is the potential cause here and how to solve it?
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PAGE NO. 1
1. STAAD SPACE
INPUT FILE: C:\Users\user\Desktop\ALLPER~1\LCJ\Staadpro\Hanging Platform 1.STD
2. START JOB INFORMATION
3. ENGINEER DATE 14-AUG-20
4. END JOB INFORMATION
5. INPUT WIDTH 79
6. UNIT METER KN
7. JOINT COORDINATES
8. 1 0 0 0; 2 820 0 0; 3 2020 0 0; 4 3220 0 0; 5 4420 0 0; 6 5240 0 0; 7 0 0 1000
9. 8 820 0 1000; 9 2020 0 1000; 10 3220 0 1000; 11 4420 0 1000; 12 5240 0 1000
10. 13 0 0 2000; 14 820 0 2000; 15 2020 0 2000; 16 3220 0 2000; 17 4420 0 2000
11. 18 5240 0 2000; 19 0 0 3000; 20 820 0 3000; 21 2020 0 3000; 22 3220 0 3000
12. 23 4420 0 3000; 24 5240 0 3000; 25 0 2000 0; 26 5240 2000 0; 27 0 0 2400
13. 28 5240 0 2400
14. MEMBER INCIDENCES
15. 1 1 6; 2 19 24; 3 1 19; 4 6 24; 5 2 20; 6 3 21; 7 4 22; 8 5 23; 9 7 8; 10 8 9
16. 11 9 10; 12 10 11; 13 11 12; 14 13 14; 15 14 15; 16 15 16; 17 16 17; 18 17 18
17. 19 25 27; 20 26 28
18. DEFINE MATERIAL START
19. ISOTROPIC STEEL_275_NMM2
20. E 2.05E+08
21. POISSON 0.3
22. DENSITY 77
23. ALPHA 1.2E-05
24. DAMP 0.03
25. TYPE STEEL
26. STRENGTH FY 275000 FU 410000 RY 1.5 RT 1.2
27. END DEFINE MATERIAL
28. MEMBER PROPERTY COLDFORMED EUROPEAN
29. 1 TO 8 TABLE ST RHS100X50X2.5
30. 9 TO 18 TABLE ST SHS50X50X2
31. 19 20 TABLE ST CHS33.7X2
32. CONSTANTS
33. MATERIAL STEEL_275_NMM2 ALL
34. SUPPORTS
35. 1 6 25 26 PINNED
36. LOAD 1 LOADTYPE DEAD TITLE DEAD LOAD
**WARNING- THIS STRUCTURE IS DISJOINTED. IGNORE IF
MASTER/SLAVE OR IF UNCONNECTED JOINTS.
STAAD SPACE -- PAGE NO. 2
37. MEMBER LOAD
38. 1 TO 18 UNI GY -0.5
39. LOAD 2 LOADTYPE LIVE TITLE LIVE LOAD
40. MEMBER LOAD
41. 1 TO 18 UNI GY -0.25
42. LOAD 3 LOADTYPE WIND TITLE WIND LOAD
43. MEMBER LOAD
44. ELEMENT LOAD
45. LOAD COMB 4 DL+LL
46. 1 1.0 2 1.0
47. LOAD COMB 5 1.4DL + 1.6LL
48. 1 1.4 2 1.6
49. LOAD COMB 6 1.2(DL + LL + WL)
50. 1 1.2 2 1.2 3 1.2
51. LOAD COMB 7 DL + LL + 1.4WL
52. 1 1.0 2 1.0 3 1.4
53. PERFORM ANALYSIS PRINT STATICS CHECK
P R O B L E M S T A T I S T I C S
-----------------------------------
NUMBER OF JOINTS 28 NUMBER OF MEMBERS 20
NUMBER OF PLATES 0 NUMBER OF SOLIDS 0
NUMBER OF SURFACES 0 NUMBER OF SUPPORTS 4
Using 64-bit analysis engine.
SOLVER USED IS THE IN-CORE ADVANCED MATH SOLVER
TOTAL PRIMARY LOAD CASES = 3, TOTAL DEGREES OF FREEDOM = 156
TOTAL LOAD COMBINATION CASES = 4 SO FAR.
STAAD SPACE -- PAGE NO. 3
*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 2 EQN.NO. 4
LOADS APPLIED OR DISTRIBUTED HERE FROM ELEMENTS WILL BE IGNORED.
THIS MAY BE DUE TO ALL MEMBERS AT THIS JOINT BEING RELEASED OR
EFFECTIVELY RELEASED IN THIS DIRECTION.
*WARNING- ZERO STIFFNESS IN DIRECTION 2 AT JOINT 2 EQN.NO. 5
*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 3 EQN.NO. 10
*WARNING- ZERO STIFFNESS IN DIRECTION 2 AT JOINT 3 EQN.NO. 11
*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 4 EQN.NO. 16
*WARNING- ZERO STIFFNESS IN DIRECTION 2 AT JOINT 4 EQN.NO. 17
*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 5 EQN.NO. 22
*WARNING- ZERO STIFFNESS IN DIRECTION 2 AT JOINT 5 EQN.NO. 23
*WARNING- ZERO STIFFNESS IN DIRECTION 2 AT JOINT 7 EQN.NO. 32
*WARNING- ZERO STIFFNESS IN DIRECTION 3 AT JOINT 7 EQN.NO. 33
*WARNING- ZERO STIFFNESS IN DIRECTION 2 AT JOINT 8 EQN.NO. 38
*WARNING- ZERO STIFFNESS IN DIRECTION 3 AT JOINT 8 EQN.NO. 39
**WARNING - THERE WERE MORE THAN 12 DOF WITH ZERO STIFFNESS.
THE FIRST 12 ARE LISTED ABOVE.
TOTAL # TRANSLATIONAL= 44 TOTAL # ROTATIONAL= 0
**NOTE - NEAR INSTABILITY AT JOINT 10 DIRECTION = FX
PROBABLE CAUSE - NEAR SINGULAR K-MATRIX
K-MATRIX DIAG= 7.2966164E-01 L-MATRIX DIAG= 9.5209732E-09 EQN NO 49
**NOTE - NEAR INSTABILITY AT JOINT 16 DIRECTION = FX
PROBABLE CAUSE - NEAR SINGULAR K-MATRIX
K-MATRIX DIAG= 7.2966164E-01 L-MATRIX DIAG= 9.5209732E-09 EQN NO 85
**NOTE - NEAR INSTABILITY AT JOINT 19 DIRECTION = FX
PROBABLE CAUSE - NEAR SINGULAR K-MATRIX
K-MATRIX DIAG= 1.5838575E-01 L-MATRIX DIAG= 1.6926188E-10 EQN NO 103
*** WARNING:
Pivoting Applied for Small or Zero Pivots. Solution Successfully Completed.
STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 1
LOADTYPE DEAD TITLE DEAD LOAD
CENTER OF FORCE BASED ON Y FORCES ONLY (METE).
(FORCES IN NON-GLOBAL DIRECTIONS WILL INVALIDATE RESULTS)
X = 0.262000010E+04
Y = 0.000000000E+00
Z = 0.149999996E+04
TOTAL APPLIED LOAD 1
***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 1 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = -19480.00
SUMMATION FORCE-Z = 0.00
STAAD SPACE -- PAGE NO. 4
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 29219999.76 MY= 0.00 MZ= -51037603.01
TOTAL REACTION LOAD 1
***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 1 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = 4120.00
SUMMATION FORCE-Z = 0.00
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= 10794400.94
MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 1)
MAXIMUMS AT NODE
X = 0.00000E+00 0
Y = -1.17629E-07 24
Z = 0.00000E+00 0
RX= 3.00867E+06 1
RY= 0.00000E+00 0
RZ= 1.60326E+07 24
STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 2
LOADTYPE LIVE TITLE LIVE LOAD
CENTER OF FORCE BASED ON Y FORCES ONLY (METE).
(FORCES IN NON-GLOBAL DIRECTIONS WILL INVALIDATE RESULTS)
X = 0.262000010E+04
Y = 0.000000000E+00
Z = 0.149999996E+04
TOTAL APPLIED LOAD 2
***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 2 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = -9740.00
SUMMATION FORCE-Z = 0.00
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 14609999.88 MY= 0.00 MZ= -25518801.51
TOTAL REACTION LOAD 2
***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 2 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = 2060.00
SUMMATION FORCE-Z = 0.00
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= 5397200.47
STAAD SPACE -- PAGE NO. 5
MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 2)
MAXIMUMS AT NODE
X = 0.00000E+00 0
Y = -5.88145E-08 24
Z = 0.00000E+00 0
RX= 1.50433E+06 1
RY= 0.00000E+00 0
RZ= 8.01630E+06 24
STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 3
LOADTYPE WIND TITLE WIND LOAD
TOTAL APPLIED LOAD 3
***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 3 )
SUMMATION FORCE-X = 0.0000000E+00
SUMMATION FORCE-Y = 0.0000000E+00
SUMMATION FORCE-Z = 0.0000000E+00
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.0000000E+00 MY= 0.0000000E+00 MZ= 0.0000000E+00
TOTAL REACTION LOAD 3
***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 3 )
SUMMATION FORCE-X = 0.0000000E+00
SUMMATION FORCE-Y = 0.0000000E+00
SUMMATION FORCE-Z = 0.0000000E+00
SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.0000000E+00 MY= 0.0000000E+00 MZ= 0.0000000E+00
MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 3)
MAXIMUMS AT NODE
X = 0.00000E+00 0
Y = 0.00000E+00 0
Z = 0.00000E+00 0
RX= 0.00000E+00 0
RY= 0.00000E+00 0
RZ= 0.00000E+00 0
************ END OF DATA FROM INTERNAL STORAGE ************
54. DEFINE ENVELOPE
55. 4 TO 7 ENVELOPE 1
**WARNING: DEFAULT ENVELOP TYPE 'STRESS' FOR ENVELOP# 1 IS ASSUMED
56. END DEFINE ENVELOPE
57. FINISH
STAAD SPACE -- PAGE NO. 6
*********** END OF THE STAAD.Pro RUN ***********
**** DATE= AUG 14,2020 TIME= 10:45:58 ****
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