ZERO STIFFNESS IN DIRECTION 1 AT JOINT    313 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.
    ZERO STIFFNESS IN DIRECTION 4 AT JOINT    313 EQN.NO.       7
    ZERO STIFFNESS IN DIRECTION 5 AT JOINT    313 EQN.NO.       8
    ZERO STIFFNESS IN DIRECTION 6 AT JOINT    313 EQN.NO.       9
    ZERO STIFFNESS IN DIRECTION 1 AT JOINT    315 EQN.NO.      19
    ZERO STIFFNESS IN DIRECTION 4 AT JOINT    315 EQN.NO.      22
    ZERO STIFFNESS IN DIRECTION 5 AT JOINT    315 EQN.NO.      23
    ZERO STIFFNESS IN DIRECTION 6 AT JOINT    315 EQN.NO.      24
    ZERO STIFFNESS IN DIRECTION 1 AT JOINT    316 EQN.NO.      25
    ZERO STIFFNESS IN DIRECTION 4 AT JOINT    316 EQN.NO.      28
    ZERO STIFFNESS IN DIRECTION 5 AT JOINT    316 EQN.NO.      29
    ZERO STIFFNESS IN DIRECTION 6 AT JOINT    316 EQN.NO.      30
  
   **WARNING - THERE WERE MORE THAN 12 DOF WITH ZERO STIFFNESS.
               THE FIRST 12 ARE LISTED ABOVE.
               TOTAL # TRANSLATIONAL=    249 TOTAL # ROTATIONAL=    741
  
里面的DIRECTION 1 2 3 4 5 6是指哪个方向？后面的EQN.NO.　又是什么意思？
我结构中没对约束释放呀？
请大家指教

1、direction 1 2 3 4 5 6分别代表fx,fy,fz,mx,my,mz。
2、EQN可能代表等式(equation)。
3、THIS MAY BE DUE TO ALL MEMBERS AT THIS JOINT BEING RELEASED OR EFFECTIVELY RELEASED IN THIS DIRECTION.  
4、ZERO STIFFNESS IN DIRECTION 4 AT JOINT 313 EQN.NO. 7  
    ZERO STIFFNESS IN DIRECTION 5 AT JOINT 313 EQN.NO. 8  
    ZERO STIFFNESS IN DIRECTION 6 AT JOINT 313 EQN.NO. 9  
表示313节点没有转动约束，如果节点作用力偶会导致失稳，如果没有转动荷载，结构分析不会产生影响。

可能是合并构件造成的问题
例如 T 型杆件连接  在模型中应是3根杆件
如果把上面的两根杆件合并成一根, 可能出现上面的问题
可查看节点313 ,315 ,316 , 是否在杆件中,而不是杆件的起点或终点
  
随便说说  嘿嘿

可能是增加或减少构件或节点，造成程序编号混乱而出错，可以在代码编辑器里进行人工修正，存盘，重新运行。我以前碰到的问题是所有构件内力都是0。

一般是精度设置的问题. 比如0.04 当精度为0.1 时及被视为0. that's it