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CFVR4806 - UBC 97: Seismic Analysis (design spectrum) Z-axis

Seismic Analysis on a 1 DOF beam according to UBC 97

This example compares spectrum accelerations given by CivilFEM to accelerations obtained when solving on a 1 DOF beam and to the correct UBC 97 spectum accelerations.
The model is 1 element beam with only 1 DOF, which direction the CivilFEM spectrum is set (the rest of the DOF are constrained). A different mass is applied at the free end of the beam for the beam period to be equal to the 20 CivilFEM spectrum points. After solving, the mass acceleration is obtained and compared to the CivilFEM spectrum acceleration and to the correct value. Therefore, this example checks the following results:

  • CivilFEM spectrum is defined correctly by comparing to the correct value
  • CivilFEM spectrum is applied correctly and response acceleration is equal to spectrum acceleration

Element types used in the model: BEAM4, MASS21

Needed CivilFEM Modules:
Geotechnical Module
Bridges and Civil Non Linearities Module
Advanced Prestressed Concrete Module

The example can be launched on an educational license.
KEYWORDS
Seismic
UBC 97

Model Statistics
Number of elements 1
Number of nodes 2
Number of civil materials 1
Number of cross sections 1
Number of shell vertices 0

Log file: CFVR4806.DAT


   FINISH
  ~CFCLEAR,,1
  NomFile='CFVR4806'
  /TITLE, %NomFile%, UBC 97: Seismic Analysis (design spectrum) Z-axis

! ----------------------------------------------------------------------
! Model definition
! ----------------------------------------------------------------------
! CivilFEM Setup: Code & Units
~UNITS,,LENG,CM
~UNITS,,TIME,S
~UNITS,,FORC,KP
~CODESEL,,,,,UBC97
/PREP7
! Preprocessor
! ----------------------------------------------------------------------
! Materials: A-42
 ~CFMP,1,LIB,STEEL,EA,A42
! Modify density (Rho = 0)
 ~CFMP,1,USER
 ~CFMP,1,DatGen,RHO,,0
! Element Types
  ET,1,BEAM4   ! Type 1: 3D Beam
  ET,2,MASS21  ! Type 2: Mass
! Sections
 ~SSECLIB,1,1,1,1   !IPE 80
 ~BMSHPRO,1,BEAM,1,1,,,4,,0,,

! Nodes
  L = 10              ! L    : Bar length
  N, 1
  N,10,L
! Elements
  TYPE,1
  MAT ,1
  REAL,1
  EN,1,1,10
  EPLOT
! Parameters
  *GET,AR20,EX,1         		          ! Ex   : Elastic Modulus
  ~CFGET,AR22,SECTION,1,MECHPROP,A,,2     ! Area : Bar area
  ~CFGET,AR23,SECTION,1,MECHPROP,IZZ,,2   ! Izz  : Moment of inertia
  ~CFGET,AR24,SECTION,1,MECHPROP,IYY,,2   ! Iyy  : Moment of inertia

! Spectrum definition
  ~DEFSPEC,ALL,4,A,DESIGN,A,7.5,2/3

  pi=3.141592654

! ----------------------------------------------------------------------
! DATA CHECK
! ----------------------------------------------------------------------
! Data comparision number
  NComp = 40
  NComp_ch = 0

! Matrix dim.
  *DIM,LABEL,CHAR,Ncomp,1
  *DIM,LABEL_CH,CHAR,Ncomp_ch,1
  *DIM,VALUE,,Ncomp,3
  *DIM,VALUE_CH,CHAR,Ncomp_ch,3
  *DIM,TOLER,,Ncomp,2

*DO,ARG1,1,20
   /PREP7
   ~CFGET,AR26,SEISM,,SPEC,TH,,ARG1,1   ! Period
  ! Labels
   LABEL(ARG1,1) = 'Sa(%ARG1%)z'
   LABEL(20+ARG1,1) = 'Sa(%ARG1%)z'

   AR25=12*AR20*AR24/L**3      ! Bending rigidity around Y axis
   AR27=AR25*(AR26/(2*pi))**2  ! Mass applied at end
   R,2,0,0,AR27
   TYPE,2
   MAT, 1
   REAL,2
   EN,2,10
   FINISH
   /SOLU

 ! Solution
 ! ---------------------------------------------------------------------
 ! Displacements
   D,1,,,,,,ALL
   D,10,,,,,UX,UY,,ROTX,ROTY,ROTZ
   ~MODLSOL,1
   ~CMBMOD,NONE,NONE,HORIZONT,0,0.0001
 ! Query results
   *GET,ARG5,NODE,10,U,Z
 ! Correct values
   VALUE(20-ARG1+1,1)=ARG5*AR25/AR27 ! Acceleration
 ! Obtained values
   ~CFGET,VALUE(20-ARG1+1,2),SEISM,,SPEC,SDH,,ARG1,1	 ! Y components of design horizontal spectrum
   ~CFGET,VALUE(40-ARG1+1,2),SEISM,,SPEC,SDH,,ARG1,1	 ! Y components of design horizontal spectrum
   /PREP7
   ! CivilFEM gives the spectrum Normalized by gravity.
   ! To compare it must be changed to acceleration user units.
   VALUE(20-ARG1+1,2) = VALUE(20-ARG1+1,2)*981
   VALUE(40-ARG1+1,2) = VALUE(40-ARG1+1,2)*981
   EDELE,2
*ENDDO

! Correct values
! ----------------------------------------------------------------------
 VALUE(40,1)= 172.65600
 VALUE(39,1)= 189.50049
 VALUE(38,1)= 209.98703
 VALUE(37,1)= 235.44000
 VALUE(36,1)= 267.91448
 VALUE(35,1)= 310.78080
 VALUE(34,1)= 369.97714
 VALUE(33,1)= 457.03059
 VALUE(32,1)= 597.65538
 VALUE(31,1)= 863.28000
 VALUE(30,1)= 863.28001
 VALUE(29,1)= 811.48321
 VALUE(28,1)= 759.68641
 VALUE(27,1)= 707.88961
 VALUE(26,1)= 656.09281
 VALUE(25,1)= 604.29600
 VALUE(24,1)= 552.49920
 VALUE(23,1)= 500.70240
 VALUE(22,1)= 448.90560
 VALUE(21,1)= 397.10880

! Warning and error tolerances
! ----------------------------------------------------------------------
   *DO,II,1,NComp
     TOLER(II, 1)= 0.1 $ TOLER(II, 2)= 0.1
   *ENDDO

! ----------------------------------------------------------------------
! Results Comparison
! ----------------------------------------------------------------------
  COMPARA.MAC

Results

LabelTargetCivilFEMRatioTolerance
Sa(1)z 397.11 397.111.000 0.1
Sa(2)z 448.91 448.911.000 0.1
Sa(3)z 500.7 500.71.000 0.1
Sa(4)z 552.5 552.51.000 0.1
Sa(5)z 604.3 604.31.000 0.1
Sa(6)z 656.09 656.091.000 0.1
Sa(7)z 707.89 707.891.000 0.1
Sa(8)z 759.69 759.691.000 0.1
Sa(9)z 811.48 811.481.000 0.1
Sa(10)z 863.28 863.281.000 0.1
Sa(11)z 863.28 863.281.000 0.1
Sa(12)z 597.66 597.661.000 0.1
Sa(13)z 457.03 457.031.000 0.1
Sa(14)z 369.98 369.981.000 0.1
Sa(15)z 310.78 310.781.000 0.1
Sa(16)z 267.91 267.911.000 0.1
Sa(17)z 235.44 235.441.000 0.1
Sa(18)z 209.99 209.991.000 0.1
Sa(19)z 189.5 189.51.000 0.1
Sa(20)z 172.66 172.661.000 0.1
Sa(1)z 397.11 397.111.000 0.1
Sa(2)z 448.91 448.911.000 0.1
Sa(3)z 500.7 500.71.000 0.1
Sa(4)z 552.5 552.51.000 0.1
Sa(5)z 604.3 604.31.000 0.1
Sa(6)z 656.09 656.091.000 0.1
Sa(7)z 707.89 707.891.000 0.1
Sa(8)z 759.69 759.691.000 0.1
Sa(9)z 811.48 811.481.000 0.1
Sa(10)z 863.28 863.281.000 0.1
Sa(11)z 863.28 863.281.000 0.1
Sa(12)z 597.66 597.661.000 0.1
Sa(13)z 457.03 457.031.000 0.1
Sa(14)z 369.98 369.981.000 0.1
Sa(15)z 310.78 310.781.000 0.1
Sa(16)z 267.91 267.911.000 0.1
Sa(17)z 235.44 235.441.000 0.1
Sa(18)z 209.99 209.991.000 0.1
Sa(19)z 189.5 189.51.000 0.1
Sa(20)z 172.66 172.661.000 0.1


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