Modelling fibre section with patch command

[rinchen]

Dear forum users/fmk/Silvia,
I am trying to model the thinwalled channel section using fibre section command. Four corners of channel section has round corners for which I try to use circular patch. But it does not seem to give the accurate coordinates of the centroid. Maybe my command is wrong. I have reproduced my fibreSec command here:

section fiberSec $secID {
patch quadr $matID $nft $nfL $y4 $z6 $y4 $z5 $y3 $z5 $y3 $z6 ; #Top lip
patch circ $matID $nfC $nft $y3 $z4 $r $R 0 90.0; #top right corner
patch quadr $matID $nfbf $nft $y2 $z4 $y2 -$z3 $y1 -$z3 $y1 $z4 ; #Top flange
patch circ $matID $nfC $nft $y3 -$z3 $r $R 90 180.0; #Top left corner
patch quadr $matID $nft $nfdw -$y3 -$z2 -$y3 -$z1 $y3 -$z1 $y3 -$z2 ; #web
patch circ $matID $nfC $nft -$y3 -$z3 $r $R 180 270.0; #Bottom left corner
patch quadr $matID $nfbf $nft -$y1 $z4 -$y1 -$z3 -$y2 -$z3 -$y2 $z4 ; #bottom flange
patch circ $matID $nfC $nft -$y3 $z4 $r $R 270 360.0; #Bottom right corner
patch quadr $matID $nft $nfL -$y3 $z6 -$y3 $z5 -$y4 $z5 -$y4 $z6 ;
}

I also tried to use series of patch quadr command in place of circular patch command to produce fibre section of corners but OpenSees would not allow me to use patch command more than 9 within the same fibreSec command.

So, could anyone suggest me how to correct the above errors?

Many thanks.

[fmk]

you could try inputiing the individual fibers