Good day Everyone!
I have several warnings in what I'm trying to design.
I designed this model in STAAD TRUSS since this is a truss.
Below are the details. Thanks in advance.
P R O B L E M S T A T I S T I C S ----------------------------------- NUMBER OF JOINTS 121 NUMBER OF MEMBERS 197 NUMBER OF PLATES 0 NUMBER OF SOLIDS 0 NUMBER OF SURFACES 0 NUMBER OF SUPPORTS 22
SOLVER USED IS THE OUT-OF-CORE BASIC SOLVER
ORIGINAL/FINAL BAND-WIDTH= 102/ 18/ 45 DOF TOTAL PRIMARY LOAD CASES = 4, TOTAL DEGREES OF FREEDOM = 297 TOTAL LOAD COMBINATION CASES = 5 SO FAR. SIZE OF STIFFNESS MATRIX = 14 DOUBLE KILO-WORDS STAAD TRUSS -- PAGE NO. 7
REQRD/AVAIL. DISK SPACE = 12.5/ 871950.9 MB
*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 11 EQN.NO. 1 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 1 AT JOINT 55 EQN.NO. 4*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 88 EQN.NO. 7*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 89 EQN.NO. 10*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 60 EQN.NO. 13*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 90 EQN.NO. 16*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 61 EQN.NO. 19*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 91 EQN.NO. 22*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 62 EQN.NO. 25*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 92 EQN.NO. 28*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 63 EQN.NO. 31*WARNING- ZERO STIFFNESS IN DIRECTION 1 AT JOINT 93 EQN.NO. 34 **WARNING - THERE WERE MORE THAN 12 DOF WITH ZERO STIFFNESS. THE FIRST 12 ARE LISTED ABOVE. TOTAL # TRANSLATIONAL= 84 TOTAL # ROTATIONAL= 0 ***WARNING - INSTABILITY AT JOINT 121 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 4.4049210E+02 L-MATRIX DIAG= 3.6663829E-07 EQN NO 54 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY **NOTE** STAAD DETECTS INSTABILITIES AS EXCESSIVE LOSS OF SIGNIFICANT DIGITS DURING DECOMPOSITION. WHEN A DECOMPOSED DIAGONAL IS LESS THAN THE BUILT-IN REDUCTION FACTOR TIMES THE ORIGINAL STIFFNESS MATRIX DIAGONAL, STAAD PRINTS A SINGULARITY NOTICE. THE BUILT-IN REDUCTION FACTOR IS 1.000E-09 THE ABOVE CONDITIONS COULD ALSO BE CAUSED BY VERY STIFF OR VERY WEAK ELEMENTS AS WELL AS TRUE SINGULARITIES. ***WARNING - INSTABILITY AT JOINT 8 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 4.0197194E+01 L-MATRIX DIAG= 7.1054274E-15 EQN NO 65 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 41 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 6.1183192E+02 L-MATRIX DIAG= 3.9748602E-07 EQN NO 72 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 2 DIRECTION = FX PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.2704715E+02 L-MATRIX DIAG= -4.0103032E-11 EQN NO 73 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY STAAD TRUSS -- PAGE NO. 8
***WARNING - INSTABILITY AT JOINT 2 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 1.4603033E+01 L-MATRIX DIAG= -2.4886759E-12 EQN NO 74 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 2 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.3650660E+02 L-MATRIX DIAG= -4.1524117E-11 EQN NO 75 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 4 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 1.4743329E+01 L-MATRIX DIAG= 3.5527137E-15 EQN NO 95 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 4 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.3408224E+02 L-MATRIX DIAG= -2.8421709E-14 EQN NO 96 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 118 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 4.4165583E+02 L-MATRIX DIAG= 0.0000000E+00 EQN NO 114 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 119 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 4.5418037E+02 L-MATRIX DIAG= 2.3703706E-11 EQN NO 117 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 38 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.9622196E+02 L-MATRIX DIAG= 5.6843419E-14 EQN NO 153 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 124 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 4.5490480E+02 L-MATRIX DIAG= 8.2428642E-10 EQN NO 156 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 1 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 1.4522596E+01 L-MATRIX DIAG= 1.7763568E-15 EQN NO 188 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 1 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.3057744E+02 L-MATRIX DIAG= 0.0000000E+00 EQN NO 189 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 39 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 6.1455070E+02 L-MATRIX DIAG= 1.9194886E-09 EQN NO 192 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY STAAD TRUSS -- PAGE NO. 9
***WARNING - INSTABILITY AT JOINT 6 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 3.9099370E+01 L-MATRIX DIAG= 7.1054274E-15 EQN NO 194 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 3 DIRECTION = FX PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.3288038E+02 L-MATRIX DIAG= -3.6948222E-11 EQN NO 226 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 3 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 1.4667662E+01 L-MATRIX DIAG= -2.3252511E-12 EQN NO 227 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 3 DIRECTION = FZ PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 2.3288195E+02 L-MATRIX DIAG= -3.6919801E-11 EQN NO 228 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 75 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 5.6258032E+03 L-MATRIX DIAG= 1.8189894E-12 EQN NO 242 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 54 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 5.5161260E+03 L-MATRIX DIAG= 4.9476512E-10 EQN NO 284 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY ***WARNING - INSTABILITY AT JOINT 43 DIRECTION = FY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 5.5161260E+03 L-MATRIX DIAG= -6.9212547E-10 EQN NO 296 ***NOTE - VERY WEAK SPRING ADDED FOR STABILITY 290. LOAD LIST 5 TO 8 291. FINISH *********** END OF THE STAAD.Pro RUN ***********
Hello,
I guess the model is a 3D one and you defined as a truss and hence the problem occurs. If you change it to STAAD SPACE then it may solved.
If you want more explanation please upload the staad file here.
Answer Verified By: Rex Homer C.
Wow. Thanks a lot Sir. When I changed the model into STAAD SPACE, the zero stiffness problem was indeed solved.
Can you send screen shot here dude
Hello. Thanks. But this was already solved a long time ago.The problem was solved by analyzing the structure as a 3D since it was 3D and changing the STAAD TRUSS in the command file back to STAAD SPACE.