CivilFEM 钢框架结构荷载组合

实例描述

在右柱底部(A点)产生最大弯矩的临界荷载组合,同时找到右柱(A点)Y方向顶部纤维最大组合应力组合。绘制其各自的变形和荷载。

左侧上角横梁(B点)Y方向底部纤维最大应力组合,同时绘制相应的变形与荷载。

根据在AISC LRFD指定的荷载与荷载组合,在所有平面框架的所有截面的最大组合应力

需要说明的是,本例重点在于各种荷载的组合方式如何实现。

几何形状

a   =   30 ft

b   =   15 ft

截面

梁 :   W  12×50 (AISC U.S. Units)

柱 :   HP 12×63 (AISC U.S. Units)

材料

Steel A572 Fy= 50 ksi

荷载

本例中,需要定义以下几种荷载:

D:恒荷载

L:活荷载(由移动设备等产生)

Lr:屋顶活荷载

W:风荷载

S:雪荷载

E:地震荷载(基于AISC的钢结构地震规定的部分1)

R:初始的雨水或冰荷载

荷载组合

本例中假设有如下几种组合

1.4D

1.2D + 1.6L + 0.5(L r  or S or R)

1.2D + 1.6(L r  or S or R) + (0.5L or 0.8W)

1.2D + 1.3W + 0.5L + 0.5(L r  or S or R)

1.2D    1.0E + 0.5L + 0.2S

0.9D    (1.3W or 1.0E)

分析模型说明

使用2D BEAM3单元,每个单元 3 ft 长。框架的几何信息如下图所示。

命令流

FINISH
~CFCLEAR,,1

! Title
/TITLE, Steel Building Load Combinations with AISC LRFD
! CivilFEM Setup: 规范和单位
~UNITS,,LENG,FT        !单位: Foot, s, Kips
~UNITS,,TIME,S
~UNITS,,FORC,KIPS
~CODESEL,EC3,EC2,,,EC8

/PREP7
! CivilFEM Preprocessor
! ————————————————–
! 定义材料
~CFMP,1,LIB,STEEL,ASTM,A572Gr50! Mat 1: Steel A572 Fy= 50 ksi
! 单元类型
ET,1,BEAM3  ! Type 1: 2D Beam
! 定义截面
~SSECLIB,1,1,51,219           !W 12×50 Beams
~SSECLIB,2,1,54,7             !HP 12×63 Columns
~BMSHPRO,1,BEAM,1,1,,,3,1,0   !梁壳属性
~BMSHPRO,2,BEAM,2,2,,,3,1,0   !梁壳属性
! Ansys Preprocessor
! ————————————————–
! 关键点
K, 1 $ K,2,30 $ K,3,60 $ KGEN,4,ALL,,,0,15
! 连线
L, 4, 5 $ L, 5, 6 ! 第一层
L, 7, 8 $ L, 8, 9 !第二层

L,10,11 $ L,11,12 ! 顶层
L, 1, 4 $ L, 4, 7 $ L, 7,10 ! 左侧柱
L, 2, 5 $ L, 5, 8 $ L, 8,11 !中间柱

L, 3, 6 $ L, 6, 9 $ L, 9,12 ! 右侧柱
! 网格划分
ESIZE,3 ! 单元大小= 3 ft
REAL,1 $ LMESH, 1, 6 ! 梁单元划分
REAL,2 $ LMESH, 7,15 ! 柱单元划分
/DIST,,40 !视图距离
EPLOT     !绘制单元
! 定义组合
! 顶层组合
LSEL,S,,,5,6,,1
CM,ROOF,ELEM
! 底层组合
ESEL,S,REAL,,1
CMSEL,U,ROOF
CM,FLOOR,ELEM
! 顶层和底层
CMSEL,S,ROOF
CMSEL,A,FLOOR
CM,BEAM,ELEM
! 左侧柱
NSEL,S,LOC,X,0
ESLN,S,1
CM,LCOLUMN,ELEM
!中间柱单元
NSEL,S,LOC,X,30
ESLN,S,1
CM,CCOLUMN,ELEM
! 右侧柱单元
NSEL,S,LOC,X,60
ESLN,S,1
CM,RCOLUMN,ELEM
! 柱单元
ESEL,S,REAL,,2
CM,COLUMN,ELEM
ALLSEL,All

/SOLU
! Ansys Solution
! ————————————————–
! 定义约束
DK,1,ALL
DK,2,ALL
DK,3,ALL
! 荷载步
!荷载步1: 恒荷载
/TITLE,Dead Load
! 顶层恒荷载= 1.00 kips/ft
CMSEL,S,ROOF
SFBEAM,ALL,1,PRES,1.00
! 底部恒荷载= 0.90 kips/ft
CMSEL,S,FLOOR
SFBEAM,ALL,1,PRES,0.90 ! 施加荷载
ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL ! 删除所有荷载

! 荷载步 2 to 41: 活荷载(1.30 kips/ft) 独立位于每个底部单元
/TITLE,Live Load at Floor
IELEM=0
*DO,I,1,40 !底层有40个单元
CMSEL,S,FLOOR
IELEM=ELNEXT(IELEM)
SFBEAM,IELEM,1,PRES,1.30
ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL
*ENDDO

!荷载步42 to 61: 活荷载(1.30 kips/ft)位于每个顶层单元
/TITLE,Live Load at Roof
IELEM=0
*DO,I,1,20 !顶层有20个单元
CMSEL,S,ROOF
IELEM=ELNEXT(IELEM)
SFBEAM,IELEM,1,PRES,1.30
ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL
*ENDDO

! 荷载步62:风荷载+X
/TITLE,Wind +X
! 左侧柱 0.8 kips/ft
CMSEL,S,LCOLUMN
SFBEAM,ALL,1,PRES,0.80
! 顶部 0.4 kips/ft
CMSEL,S,ROOF
SFBEAM,ALL,1,PRES,-0.40
! 右侧柱 0.4 kips/ft
CMSEL,S,RCOLUMN
SFBEAM,ALL,1,PRES, 0.40
ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL

! 荷载步 63: 风荷载 -X
/TITLE,Wind -X
! 0.4 kips/ft左侧
CMSEL,S,LCOLUMN
SFBEAM,ALL,1,PRES,-0.40
! 顶部0.4 kips/ft
CMSEL,S,ROOF
SFBEAM,ALL,1,PRES,-0.40
! 右侧 0.8 kips/ft
CMSEL,S,RCOLUMN
SFBEAM,ALL,1,PRES,-0.80
ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL

! 荷载步64: 雪荷载(0.5 kips/ft)
/TITLE,Snow Load
CMSEL,S,ROOF
SFBEAM,ALL,1,PRES,0.50
ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL

! 荷载步65: 地震荷载 +X
/TITLE,Earthquake +X
! 一层水平力22.00 kips
FK, 4,FX,22.00
! 二层水平力24.00 kips
FK, 7,FX,24.00
! 顶层水平力20.00 kips
FK,10,FX,20.00
SOLVE
FKDELE,ALL,ALL

! 荷载步 66: 存水荷载(1.00 kips/ft)
/TITLE,Load due to Rainwater
CMSEL,S,ROOF
SFBEAM,ALL,1,PRES,1.00

ESEL,ALL
SOLVE
SFEDELE,ALL,ALL,ALL
/POST1
! CivilFEM Postprocessor
! ————————————————–
! CivilFEM Combinations: 定义组合规则

! 组合规则1: [D] Dead Load恒荷载
! /TITLE,Title
/TITLE,[D] Dead Load
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF ,    1, ADD     ,     1
! STSTDEF, ICMB, ISTST, Type  , ITEM1
~STSTDEF,    1,     1,LSTEP,     1
! ~STSTCFT, ICMB, ISTST, CFT1, CFT2
~STSTCFT,    1,     1, 1.00 ! [D] = 1.00 * Load Step 1

!组合规则2: [L] 活荷载
! /TITLE,Title
/TITLE,[L] Live Load
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    2, COMPATIB, 40
! ~STSTDEF, ICMB, ISTST, Type  ,ITEM1,ITEM2,ITIME,INCSTST,INCITEM1
~STSTDEF,    2,     1,LSTEP,2    ,     ,40   ,1      ,1 ! LS 2 to 41

! 组合规则3: [Lr] 顶层活荷载
! /TITLE,Title
/TITLE,[Lr] Roof Live Load
! ~CMBDEF , ICMB, Type      , NSTST
~CMBDEF,    3, COMPATIB, 20
! ~STSTDEF, ICMB, ISTST, Type  ,ITEM1,ITEM2,ITIME,INCSTST,INCITEM1
~STSTDEF,    3,     1,LSTEP,42   ,     ,20   ,1      ,1 ! LS 42 to 61

! 组合规则4: [W] 风荷载
! /TITLE,Title
/TITLE,[W] Wind
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    4, INCOMPAT,     2
! ~STSTDEF, ICMB, ISTST, Type  ,ITEM1,ITEM2,ITIME,INCSTST,INCITEM1
~STSTDEF,    4,     1,LSTEP,62   ,     ,2    ,1      ,1 ! LS 62 to 63

! 组合规则5: [S] 雪荷载
! /TITLE,Title
/TITLE,[S] Snow
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    5, COMPATIB, 1
! ~STSTDEF, ICMB, ISTST, Type  , ITEM1
~STSTDEF,    5,     1,LSTEP, 64

! 组合规则6: [E] 地震荷载
! /TITLE,Title
/TITLE,[E] Earthquake
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    6, OPPOSED , 1
! ~STSTDEF, ICMB, ISTST, Type  , ITEM1
~STSTDEF,    6,     1,LSTEP, 65

! 组合规则7: [R] 雨水
! /TITLE,Title
/TITLE,[R] Rainwater
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    7, COMPATIB, 1
! ~STSTDEF, ICMB, ISTST, Type  , ITEM1
~STSTDEF,    7,     1,LSTEP, 66

! 组合规则8: [(Lr or S or R)]

! /TITLE,Title
/TITLE,[(Lr or S or R)]
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    8, OPTION  , 3
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,    8,     1,CMB, 3 ! 规则3: [Lr] 顶部活荷载
~STSTDEF,    8,     2,CMB, 5 ! 规则5: [S] 雪荷载
~STSTDEF,    8,     3,CMB, 7 ! 规则7: [R] 雨水

! 组合规则9: [(0.5*L or 0.8*W)]
! /TITLE,Title
/TITLE,[(0.5*L or 0.8*W)]
! ~CMBDEF, ICMB, Type      , NSTST, KEYTITL,ITEM1
~CMBDEF,     9,SELECTVC , 2    ,        ,1      ! NADD = 1 (Select one)
! ~STSTCFT, ICMB, ISTST, Type, ITEM1
~STSTDEF,    9,     1,CMB, 2 ! C.Rule No.2: [L] Live Load
~STSTDEF,    9,     2,CMB, 4 ! C.Rule No.4: [W] Wind
! ~STSTCFT, ICMB, ISTST, CFT1, CFT2
~STSTCFT,    9,     1, 0.50, 0.50 ! 0.5 * [L] Live Load
~STSTCFT,    9,     2, 0.80, 0.80 ! 0.8 * [W] Wind

! 组合规则10: [(1.3*W or 1.0*E)]
! /TITLE,Title
/TITLE,[(1.3*W or 1.0*E)]
! ~CMBDEF, ICMB, Type     , NSTST, KEYTITL,ITEM1
~CMBDEF,    10,SELECTVC, 2    ,        ,1      ! NADD = 1 (Select one)
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   10,     1,CMB,     4 ! C.Rule No.4: [W] Wind
~STSTDEF,   10,     2,CMB,     6 ! C.Rule No.6: [E] Earthquake
! ~STSTCFT, ICMB, ISTST, CFT1, CFT2
~STSTCFT,   10,     1, 1.30, 1.30 ! 1.3 * [W] Wind
~STSTCFT,   10,     2, 1.00, 1.00 ! 1.0 * [E] Earthquake

!组合规则11: (A4-1) 1.4*D
! /TITLE,Title
/TITLE,(A4-1) 1.4*D
! ~CMBDEF, ICMB, Type , NSTST
~CMBDEF,   11, ADD, 1
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   11,     1,CMB, 1 ! C.Rule No.1: [D] Dead Load
! ~STSTCFT, ICMB, ISTST, CFT1
~STSTCFT,   11,     1, 1.40          ! 1.4*[D] Dead Load

! 组合规则12: (A4-2) 1.2*D + 1.6*L + 0.5*(Lr or S or R)
! /TITLE,Title
/TITLE,(A4-2) 1.2*D + 1.6*L + 0.5*(Lr or S or R)
! ~CMBDEF, ICMB, Type , NSTST
~CMBDEF,   12, ADD, 3
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   12,     1,CMB, 1 ! C.Rule No.1: [D] Dead Load
~STSTDEF,   12,     2,CMB, 2 ! C.Rule No.2: [L] Live Load
~STSTDEF,   12,     3,CMB, 8 ! C.Rule No.8: [(Lr or S or R)]
! ~STSTCFT, ICMB, ISTST, CFT1
~STSTCFT,   12,     1, 1.20 ! 1.2*[D] Dead Load
~STSTCFT,   12,     2, 1.60 ! 1.6*[L] Live Load
~STSTCFT,   12,     3, 0.50 ! 0.5*[(Lr or S or R)]

! 组合规则13: (A4-3) 1.2*D + 1.6*(Lr or S or R) + (0.5*L or 0.8*W)
! /TITLE,Title
/TITLE,(A4-3) 1.2*D + 1.6*(Lr or S or R) + (0.5*L or 0.8*W)
! ~CMBDEF, ICMB, Type , NSTST
~CMBDEF,   13, ADD, 3
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   13,     1,CMB, 1 ! C.Rule No.1: [D] Dead Load
~STSTDEF,   13,     2,CMB, 8 ! C.Rule No.8: [(Lr or S or R)]
~STSTDEF,   13,     3,CMB, 9 ! C.Rule No.9: [(0.5*L or 0.8*W)]
! ~STSTCFT, ICMB, ISTST, CFT1
~STSTCFT,   13,     1, 1.20          ! 1.2*[D] Dead Load

~STSTCFT,   13,     2, 1.60          ! 1.6*[(Lr or S or R)]
~STSTCFT,   13,     3, 1.00          ! 1.0*[(0.5*L or 0.8*W)]

! 组合规则14: (A4-4) 1.2*D + 1.3*W + 0.5*L + 0.5*(Lr or S or R)
! /TITLE,Title
/TITLE,(A4-4) 1.2*D + 1.3*W + 0.5*L + 0.5*(Lr or S or R)
! ~CMBDEF, ICMB, Type , NSTST
~CMBDEF,   14, ADD, 4
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   14,     1,CMB, 1 ! C.Rule No.1: [D] Dead Load
~STSTDEF,   14,     2,CMB, 4 ! C.Rule No.4: [W] Wind
~STSTDEF,   14,     3,CMB, 2 ! C.Rule No.2: [L] Live Load
~STSTDEF,   14,     4,CMB, 8 ! C.Rule No.8: [(Lr or S or R)]
! ~STSTCFT, ICMB, ISTST, CFT1
~STSTCFT,   14,     1, 1.20 ! 1.2*[D] Dead Load
~STSTCFT,   14,     2, 1.30 ! 1.3*[W] Wind
~STSTCFT,   14,     3, 0.50 ! 0.5*[L] Live Load
~STSTCFT,   14,     4, 0.50 ! 0.5*[(Lr or S or R)]

!组合规则15: (A4-5) 1.2*D +/- 1.0*E + 0.5*L + 0.2*S
! /TITLE,Title
/TITLE,(A4-5) 1.2*D +/- 1.0*E + 0.5*L + 0.2*S
! ~CMBDEF, ICMB, Type  , NSTST
~CMBDEF,    15,ADDVC, 4
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   15,     1,CMB, 1 ! C.Rule No.1: [D] Dead Load
~STSTDEF,   15,     2,CMB, 6 ! C.Rule No.6: [E] Earthquake
~STSTDEF,   15,     3,CMB, 2 ! C.Rule No.2: [L] Live Load
~STSTDEF,   15,     4,CMB, 5 ! C.Rule No.5: [S] Snow
! ~STSTCFT, ICMB, ISTST, CFT1, CFT2
~STSTCFT,   15,     1, 1.20, 1.20 !            1.2 *[D] Dead Load
~STSTCFT,   15,     2, 1.00,-1.00 ! (+1.0 or -1.00)*[E] Earthquake
~STSTCFT,   15,     3, 0.50, 0.50 !             0.5*[L] Live Load
~STSTCFT,   15,     4, 0.20, 0.20 !             0.2*[S] Snow

! 组合规则16: (A4-6) 0.9*D +/- (1.3*W or 1.0*E)
! /TITLE,Title
/TITLE,(A4-6) 0.9*D +/- (1.3*W or 1.0*E)
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    16,ADDVC    , 2
! ~STSTDEF, ICMB, ISTST, Type, ITEM1
~STSTDEF,   16,     1,CMB,  1 ! C.Rule No. 1: [D] Dead Load
~STSTDEF,   16,     2,CMB, 10 ! C.Rule No.10: [(1.3*W or 1.0*E)]
! ~STSTCFT, ICMB, ISTST, CFT1, CFT2
~STSTCFT,   16,     1, 0.90, 0.90 !            0.9 *[D] Dead Load
~STSTCFT,   16,     2, 1.00,-1.00 ! (+1.0 or -1.00)*[(1.3*W or 1.0*E)]

! 组合规则17: (A4-1) or (A4-2) or (A4-3) or (A4-4) or (A4-5) or (A4-
6)
! /TITLE,Title
/TITLE,Critical Combination: (A4-1) or (A4-2) or … (A4-6)
! ~CMBDEF, ICMB, Type      , NSTST
~CMBDEF,    17,OPTION   , 6
! ~STSTDEF, ICMB, ISTST, Type, ITEM1, ITEM2, ITIME, INCSTST, INCITEM1
~STSTDEF,   17,     1,CMB, 11   ,      , 6    , 1      , 1 ! (A4-1) to (A4-6)

! CivilFEM 组合: 查询结果
! 节点90的最大Z方向弯矩
~CMBINQ,17,REACT,M,Z,MAX,90, ,2,1
PLDISP,2 ! Plot Concomitant Deformed Shape and Loads
! 91单元,90节点Y顶部最大组合应力
~CMBINQ,17,BEAM,COMBS,YTZM,ABS,90,91,2,1
PLDISP,2 ! Plot Concomitant Deformed Shape and Loads
/PBC,F,0 $ /PSF,PRES,,0 ! Supress plot of loads
~PLLSSTR,SX,28,2       ! 绘制应力分布(scale factor = 2)
!45单元49节点Y底部最大组合应力
~CMBINQ,17,BEAM,COMBS,YBZM,MAX,49,45,2,1
PLDISP,2 ! Plot Concomitant Deformed Shape and Loads
/PBC,F,0 $ /PSF,PRES,,0
~PLLSSTR,SX,128,2     ! Plot Concomitant Stress Distribution (scale factor = 2)

! CivilFEM 组合: 得到所有单元的临界结果
! CivilFEM 组合: 定义目标
~TRGUPT,1,28,S,X                    ! Stress point definition
~TRGDEF,1,CROSS,SS,PT1,ABS          ! Target 1 : Y顶部最大应力绝对值
~TRGUPT,2,128,S,X                   ! Stress point definition
~TRGDEF,2,CROSS,SS,PT2,ABS          ! Target 2 :Y底部最小应力绝对值
! CivilFEM 组合: 进行组合
~COMBINE,
! CivilFEM 组合: 读取结果
~CMBDAT,2
! Y顶部应力绝对最大值
~CMB,17,,,,,1
~PLLSSTR,SX,28,2           !(scale factor = 2)
! Y底部应力绝对最大值
~CMB,17,,,,,2
~PLLSSTR,SX,128,2          ! (scale factor = 2)

 

 

 

 

 

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