用AWB分析一大型空间屋盖结构，在求解时出现以下错误：

A solver pivot warning or error has been detected in the UX degree of freedom of node 4776 located in Geom-1_beams. This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues.  Check results carefully. You may select the offending object and/or geometry via RMB on this warning in the Messages window.

*** ERROR ***                           CP =       2.062   TIME= 17:17:43
 There is at least 1 small equation solver pivot term (e.g., at the UX  
 degree of freedom of node 4776).  Please check for an insufficiently   
 constrained model.     

初步以为是杆件节点的连接有问题，但在Spaceclaim中检查后各节点连接均没有问题。改变多种约束方式依然提示上述错误。

以下是AWB工程文件（ANSYS 18版本），希望前辈们能够指导下，十分感谢

TEST.rar