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CFVR4804 - UBC 97: Seismic Analysis (design spectrum) X-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: CFVR4804.DAT


   FINISH
  ~CFCLEAR,,1
  NomFile='CFVR4804'
  /TITLE, %NomFile%, UBC 97: Seismic Analysis (design spectrum) X-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,3,D,DESIGN,A,10,2/3

  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%)x'
   LABEL(20+ARG1,1) = 'Sa(%ARG1%)x'

   AR25=AR20*AR22/L
   AR27=AR25*(AR26/(2*pi))**2  ! Mass applied at end
   R,2,AR27
   TYPE,2
   MAT, 1
   REAL,2
   EN,2,10
   FINISH
   /SOLU

 ! Solution
 ! ---------------------------------------------------------------------
 ! Displacements
   D,1,,,,,,ALL
   D,10,,,,,,UY,UZ,ROTX,ROTY,ROTZ
   ~MODLSOL,1
   ~CMBMOD,HORIZONT,NONE,NONE,0,0.0001
 ! Query results
   *GET,ARG5,NODE,10,U,X
 ! 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
   ! 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
   /PREP7
   EDELE,2
*ENDDO

! Correct values
! ----------------------------------------------------------------------
   VALUE(40,1) = 176.58000
   VALUE(39,1) = 193.80732
   VALUE(38,1) = 214.75946
   VALUE(37,1) = 240.79091
   VALUE(36,1) = 274.00345
   VALUE(35,1) = 317.84400
   VALUE(34,1) = 378.38571
   VALUE(33,1) = 467.41765
   VALUE(32,1) = 611.23846
   VALUE(31,1) = 882.90000
   VALUE(30,1) = 882.90000
   VALUE(29,1) = 829.92600
   VALUE(28,1) = 776.95200
   VALUE(27,1) = 723.97800
   VALUE(26,1) = 671.00400
   VALUE(25,1) = 618.03000
   VALUE(24,1) = 565.05600
   VALUE(23,1) = 512.08200
   VALUE(22,1) = 459.10800
   VALUE(21,1) = 406.13400

! 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)x 406.13 406.131.000 0.1
Sa(2)x 459.11 459.111.000 0.1
Sa(3)x 512.08 512.081.000 0.1
Sa(4)x 565.06 565.061.000 0.1
Sa(5)x 618.03 618.031.000 0.1
Sa(6)x 671 6711.000 0.1
Sa(7)x 723.98 723.981.000 0.1
Sa(8)x 776.95 776.951.000 0.1
Sa(9)x 829.93 829.931.000 0.1
Sa(10)x 882.9 882.91.000 0.1
Sa(11)x 882.9 882.91.000 0.1
Sa(12)x 611.24 611.241.000 0.1
Sa(13)x 467.42 467.421.000 0.1
Sa(14)x 378.39 378.391.000 0.1
Sa(15)x 317.84 317.841.000 0.1
Sa(16)x 274 2741.000 0.1
Sa(17)x 240.79 240.791.000 0.1
Sa(18)x 214.76 214.761.000 0.1
Sa(19)x 193.81 193.811.000 0.1
Sa(20)x 176.58 176.581.000 0.1
Sa(1)x 406.13 406.131.000 0.1
Sa(2)x 459.11 459.111.000 0.1
Sa(3)x 512.08 512.081.000 0.1
Sa(4)x 565.06 565.061.000 0.1
Sa(5)x 618.03 618.031.000 0.1
Sa(6)x 671 6711.000 0.1
Sa(7)x 723.98 723.981.000 0.1
Sa(8)x 776.95 776.951.000 0.1
Sa(9)x 829.93 829.931.000 0.1
Sa(10)x 882.9 882.91.000 0.1
Sa(11)x 882.9 882.91.000 0.1
Sa(12)x 611.24 611.241.000 0.1
Sa(13)x 467.42 467.421.000 0.1
Sa(14)x 378.39 378.391.000 0.1
Sa(15)x 317.84 317.841.000 0.1
Sa(16)x 274 2741.000 0.1
Sa(17)x 240.79 240.791.000 0.1
Sa(18)x 214.76 214.761.000 0.1
Sa(19)x 193.81 193.811.000 0.1
Sa(20)x 176.58 176.581.000 0.1


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