急！！！钢筋混凝土非线性分析中出现的错误

出现以下错误：
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.
我得材料本构关系的命令流：
FC=23.1e6   
FT=1.89e6
tb,concr,1   
tbdata,,0.2,0.95,FT,-1
tb,miso,1,,11   
tbpt,,0.0002,fc*0.19
tbpt,,0.0004,fc*0.36
tbpt,,0.0006,fc*0.51
tbpt,,0.0008,fc*0.64
tbpt,,0.001,fc*0.75
tbpt,,0.0012,fc*0.84
tbpt,,0.0014,fc*0.91
tbpt,,0.0016,fc*0.96
tbpt,,0.0018,fc*0.99
tbpt,,0.002,fc
tbpt,,0.0033,fc*0.85

mp,ex,2,2.0e11  
mp,prxy,2,0.3
mp,dens,2,7850
tb,bkin,2   

请问一下，哪里有错误啊，如何修改啊！！！！
非常感谢！！

少了最后一句
tbdata,,300e6,0