动力计算中监测shell单元内力报错？

远望

new
set safe on
config dyn
;
set echo off
;--- core ---
; adjust brick from rectangle to trapezoid
gen zone brick p0(0,0,0) p1(70,0,0) p2(0,30,0) p3(0,0,30) &
    p4(70,30,0) p5(0,60,30) p6(10,0,30) p7(10,60,30) size 4,3,3
;--- create whole downstream model ---
gen zone reflect dd 0         dip 90
;--- river bed ---
; adjust x position of division for new brick
gen zone uwedge p0(70.0,0.0,-30.0) p1(70.0,30.0,0.0) &
   p2(0.0,0.0,-30.0)  p3(70.0,-30.0,0.0) size 6 4 6
gen zone uwedge p0(130.0,0.0,-30.0) p1(130.0,30.0,0.0) &
  p2(70.0,0.0,-30.0) p3(130.0,-30.0,0.0) size 6 3 6
;--- now create upstream part ---
gen zone reflect dd 90 dip 90
;
sel shell id 2 range z 0.5 40
sel shell id 2 property isotropic=(1e9, 0.25) thickness=0.4 density=2000
;
set echo on
;
fix x y z
ini xv 0 yv 0 zv 0 xdisp 0 ydisp 0 zdisp 0
free x y z
range name dam z=0,30
range name foundation z=-30,0
group dam  range dam
group foundation range foundation
model mohr range=dam
prop  shea 1e8 bulk 2e8 cohes=1e10 range=dam
prop  tens 1e10 range=dam
ini   dens 1700 range=dam
model elastic range=foundation
prop  shea 5e8 bulk 1e9 range=foundation
ini   dens 2100 range=foundation
; save  dam0.sav
; rest    dam0.sav
range name left      plane dd 0 dip -45 orig (0,60,30) dist 0.5
range name right     plane dd 0 dip 45 orig (0,-60,30) dist 0.5
range name valley    left any right any
range name east_end  plane dd 90 dip 90 orig (130,0,0)  dist 0.5
range name west_end  plane dd 90 dip 90 orig (-130,0,0) dist 0.5
range name ends      east_end any west_end any
range name bottom_line z=-35.0 -29.5
apply nvel=0.0 plane dd 0 dip -45 range=left bottom_line not ends not
apply nvel=0.0 plane dd 0 dip  45 range=right bottom_line not ends not
apply nvel=0.0 range=ends bottom_line not valley not
fix y z  range=bottom_line
set dyn=off grav=0,0,-10 small
hist unbal
solve
; save dam1.sav
; rest dam1.sav
ini xdis=0 ydis=0 zdis=0
apply remove gp
free x y z
apply xvel=0 yvel=0 zvel=0 range valley any ends any
apply nstress=-3e5 grad 0,0,1e4 &
  range plane norm 1,0,2 orig 10,0,30 dist 0.5
prop tens=0 fric=30 cohes=0 range=dam
his gp xdisp 0,0,30
his gp ydisp 0,0,30
;
solve
ini xv=0 yv=0 zv=0 xdis=0 ydis=0 zdis=0
; save dam2.sav
; rest dam2.sav
set dyn=on large
define setup
omega = 2.0 * pi * freq
o_env = 2.0 * pi / env_time
end
define wave
if dytime > env_time
  wave = 0.0
else
  wave = 0.5 * (1.0-cos(o_env*dytime)) * ampl * sin(omega*dytime)
endif
end
set @freq=2.0 @ampl=4.0 ; (0.4 g)
;
set @env_time= 6.0           ; (6 sec attack & decay)
@setup
apply xacc=1.0 hist=@wave yacc=0.5 hist=@wave zacc=0 &
range valley any ends any
;
save 'dam_temp.sav'
;
restore 'dam_temp.sav'
hist id 10 dytime
hist id 11 @wave
hist id 12 gp xvel 0,0,-30
hist id 13 gp xvel 0,0,0
hist id 14 gp xvel 0,0,15
hist id 15 gp xvel 0,0,30
hist id 16 gp xacc 0,0,-30
hist id 17 gp xacc 0,0,0
hist id 18 gp xacc 0,0,15
hist id 19 gp xacc 0,0,30

hist id 1511 sel recover sres mx surfx (1 0 0) (35, 0, 15)
hist id 1512 sel recover sres mx surfx (1 0 0) ( 0, 0, 30)

plot sel geom shell on node on cid on surfsys off
plot sel geom shell on node on cid on surfsys on
set dyn damp local 0.15 ;(approx 5% damping)
solve age 1.0
; save dam3.sav
plot hist 1511 vs 10
plot hist 1512 vs 10


上面的命令流是按照FLAC3D手册中给出的大坝动力计算的例子改写的，和手册例子唯一的区别是在坝体表面添加了shell单元，
然后用hist命令监测两个shell单元的弯矩。

问题是，如果只监测一个shell单元的内力，运行正常；如果同时监测两个shell单元的内力（如上面的命令所示），
则FLAC3D(v3.00 261)软件报错“history-1511: surface system not set at node 25”

有朋友遇到过和我类似的问题吗？

附件中有使用的命令流，望版主和前辈解惑，谢谢！

慕野心舟

动力分析中的结构单元必须设置阻尼
参考陈育民《FLAC/FLAC3D基础工程实例》P198——原文"注意：……动力分析中如果存在结构单元，需要采用SEL set damp 命令，指定结构单元阻尼，否则计算会提示出错。"