STAAD2006的警告是什么意思，请教.急

***WARNING - INSTABILITY AT JOINT 8 DIRECTION = MY PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING K-MATRIX DIAG= 1.8595238E+01 L-MATRIX DIAG= -3.5527137E-15 EQN NO770 ***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. 请教高手，上面是什么意思啊.