预应力混凝土简支小箱梁分析,分离式建模，力筋节点与混凝土节点耦合，混凝土材料命令流为：

et,1,solid65$keyopt,1,1,0$keyopt,1,7,1

mp,ex,1,2.1945e10$mp,prxy,1,0.2$mp,dens,1,2551.0204$mp,alpx,1,1e-5 

FC=2.31e7

FT=1.89e6 

tb,concr,1

tbdata,,0.5,0.95,FT,-1

tb,miso,1,,11 

tbpt,,0.0002,0.19*FC

tbpt,,0.0004,0.36*FC

tbpt,,0.0006,0.51*FC

tbpt,,0.0008,0.64*FC

tbpt,,0.0010,0.75*FC

tbpt,,0.0012,0.84*FC

tbpt,,0.0014,0.91*FC

tbpt,,0.0016,0.96*FC

tbpt,,0.0018,0.99*FC

tbpt,,0.002,FC

tbpt,,0.0033,FC

运行后报错：

 *** FATAL ***                           CP =     913.812   TIME= 00:17:46

 The supplied nonlinear material properties produced an incorrect        

 material tangent matrix.  Please check your TB input carefully.  A      

 very small yield stress may cause this failure.

将混凝土修改为弹性（solid45）后可完成分析，请问是混凝土材料表命令流的问题，还是其他方面的问题？如何解决