结构地震反应谱分析实例
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在多位朋友的大力帮助下,经过半个多月的努力,鄙人终于对结构地震反应谱分析有了一定的了解,现将其求解步骤整理出来,以便各位参阅,同时,尚有一些问题,欢迎各位讨论!
为叙述方便,举一简单实例:
在侧水压与顶部集中力作用下的柱子的地震反应谱分析,谱值为加速度反应谱,考虑X 与Y向地震效应作用。已知地震影响系数a与周期T的关系:
a(T)= 0.4853*(0.4444+2.2222*T) 0<T<=0.04 秒
0.4853*(0.10/T)^(-0.686) 0.04<T<=0.1 秒
0.4853 0.1<T<=1.2 秒
0.4853*(1.2/T)^1.5 1.2<T<=4 秒
以下是命令流程序
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/filname,SPEC,1
/PREP7
!定义单元类型及材料特性
ET,1,45
MP,EX,1,2.8E10
MP,DENS,1,2.4E3
MP,NUXY,1,0.18
!建立模型
BLOCK,0,1,0,1,0,5
!网格剖分
ESIZE,0.5
VMESH,all
/VIEW,,-0.3,-1,1
EPLOT
FINISH
/SOLU
!施加底部约束
ASEL,,LOC,Z,0
DA,ALL,ALL
ALLSEL
!施加自重荷载
ACEL,0,0,10
!进行模态求解
ANTYPE,MODAL
MODOPT,LANB,30
SOLVE
FINISH
!进行谱分析
/SOLU
ANTYPE,SPECTR
SPOPT,SPRS,30,YES
SVTYP,2 !加速度反应谱
SED,1,1 !X与Y向
FREQ,0.2500,0.2632,0.2778,0.2941,0.3125,0.3333,0.3571,0.3846,0.4167 FREQ,0.4545,0.5000,0.5556,0.6250,0.7143,0.8333,1.1111,2.0000,10.0000 FREQ,25.0000,1000.0000
SV,0.05,0.0797,0.0861,0.0934,0.1018,0.1114,0.1228,0.1362,0.1522,0.1716 SV,0.05,0.1955,0.2255,0.2642,0.3152,0.3851,0.4853,0.4853,0.4853,0.4853 SV,0.05,0.2588,0.2167
SOLVE
FINISH
!进行模态求解(模态扩展)
/SOLU
ANTYPE,MODAL
EXPASS,ON
MXPAND,30,,,YES,0.005
SOLVE
FINISH
!进行谱分析(合并模态)
/SOLU
ANTYPE,SPECTR
SRSS,0.15,disp
SOLVE
FINISH
/POST1
SET,LIST !结果1
/INP,,mcom
lcwrite,11
LCASE,11
PRRSOL, !结果2 SET,FIRST
PRRSOL, !结果3 SET,NEXT
PRRSOL, !结果4 SET,NEXT
PRRSOL, !结果5 SET,NEXT
PRRSOL, !结果6 FINISH
!静力分析
/SOLU
ANTYPE,STATIC
!施加水压荷载
NSEL,,LOC,Y,0
NSEL,R,LOC,Z,0,5 SFGRAD,PRES,0,Z,0,-10000 SF,ALL,PRES,50000
!施加集中荷载
NSEL,,LOC,Y,0
NSEL,R,LOC,z,5
F,ALL,FY,10000
ALLSEL
EPLOT
SOLVE
FINISH
/POST1
set,last
lcwrite,12
Lcase,11
Lcoper,add,12
Lcwrite,13
LCASE,12
PRRSOL, !结果7 LCASE,13
PRRSOL, !结果8
FINISH
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以下是计算的结果
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结果1:(Results Summary)
1 21.647
2 21.647
3 121.51
4 121.51
结果2:(单独谱分析反力LCASE,11)
VALUE 2467.9 2290.1 18384.
结果3:(单独谱分析反力SET,FIRST)
VALUE 0.13334E+06-0.15785E+07-0.18819E-06
结果4:(单独谱分析反力SET,NEXT)
VALUE -0.15785E+07-0.13334E+06-0.48918E-06
结果5:(单独谱分析反力SET,NEXT)
VALUE -0.87805E+07 0.27008E+08 0.86846E-07
结果6:(单独谱分析反力SET,NEXT)
VALUE 0.27008E+08 0.87805E+07 0.79325E-06
结果7:(单独静力分析反力LCASE,12)
VALUE 0.22901E-08-0.15500E+06 0.12000E+06
结果8:(谱分析与静力分析叠加反力LCASE,13)
VALUE 2467.9 -0.15271E+06 0.13838E+06
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以下是问题的讨论
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1、模态提取数为30,即取前30阶振型数,但在谱分析时得到的是4阶,这4阶是什么意思?
2、在单独谱分析时,为何结果2、
3、
4、
5、6会相差如此之大?(其应力和位移也是如此。)
3、在进行谱分析的合并模态步骤中,模态合并方法应该选用SRSS,0.15,DISP还是SRSS,0.15,ACEL(其对结果影响很大)?