RSPEC

Bulk Data Entry Specifies directional combination method, modal combination method, excitation direction(s), response spectra and scale factors for Response Spectrum Analysis.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RSPEC RID DCOMB MCOMB CLOSE          
  DTISPEC1 SCALE1 X11 X12 X13        
  DTISPEC2 SCALE2 X21 X22 X23        
  DTISPEC3 SCALE3 X31 X32 X33        

Example 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RSPEC 35 ALG SRSS 1.0          
  7 1.3 0.5 0.5 -1.        

Example 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
RSPEC 35 SRSS CQC 0.0          
  7 1.3 0.5 0.5 -1.        
  4 2.0 -2 -0.0 -1.        
  2 17. 0.5 -2.5 -1.        

Definitions

Field Contents SI Unit Example
RID RSPEC identification number. Must be unique.

No default (Integer > 0)

  
DCOMB Directional combination method.
ALG (Default)
Algebraic.
SRSS
Square root of sum of squares.
  
MCOMB Modal combination method.
ABS (Default)
Absolute sum.
SRSS
Square root of sum of squares. 2
CQC
Complete quadratic combination.
NRL
Navy Research Laboratory's SRSS.
  
CLOSE Modal frequency closeness parameter. 2

Default = 1.0 (Real ≥ 1.0)

  
DTISPECi Response spectrum reference. Identification number of the DTI,SPECSEL entry.

No default (Integer > 0)

  
SCALEi Scale factor for excitation.

No default (Real <> 0.0)

  
Xij Components of a vector representing ground excitation i, j = 1..3  

Comments

  1. DTISPEC2/SCALE2/X21/X22/X23 and DTISPEC3/SCALE3/X31/X32/X33 are optional ground excitations for multi-directional excitation. The directions of excitation have to be orthogonal to each other and will be reported as error otherwise.
  2. When MCOMB = SRSS or NRL, natural frequencies that are close will be summed by the ABS method. The close frequencies are determined using the inequality.(1)
    F ( i + 1 ) < C L O S E * F ( i ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOraiaacI cacaWGPbGaey4kaSIaaGymaiaacMcacqGH8aapcaWGdbGaamitaiaa d+eacaWGtbGaamyraiaacQcacaWGgbGaaiikaiaadMgacaGGPaaaaa@4378@

    Where, F ( i ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOraiaacI cacaWGPbGaaiykaaaa@3908@ and F ( i + 1 ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOraiaacI cacaWGPbGaey4kaSIaaGymaiaacMcaaaa@3AA5@ are successive natural frequencies.

    Then, they are combined with other modal contributions in accordance with the specified MCOMB option. Since natural frequencies are in ascending order, CLOSE values should be greater than or equal to 1.0.

  3. Refer to Response Spectrum Analysis in the User Guide for more details.