SIMQKE program

SIMQKE1

Generation of artificial time histories compatible with a specified target spectrum.

The program was written by Dario Gasparini and Erik Vanmarke at the Massachusetts Institute of Technology, 1976. The source code and program manual are available from the NISEE at the University of California, Berkeley.

Some input and output modifications, dated October 1999, have been made by Edmund Booth Consulting Engineer, including the correction of some minor errors .

As a test of these modifications, the UBC:97 spectrum for Zone 4, soil type E was taken as a target. A 20 second record length was specified, and spectral accelerations at 300 periods, equally spaced between 0.05 seconds and 4 second, were used. 5 statistically independent time histories were calculated; 50 iterations were specified for each time history. A 'compound' envelope for the generated time histories was specified. Calculation time for all five time histories was about two hours on a PII/300 laptop, so the software is not particularly efficient.

The results are shown in graphical and tabular form below. They would satisfy Eurocode 8 and UBC:97 requirements for design motions. The statistical independence betweeen motions would satisfy USNRC requirements.

Fig 1: Typical generated acceleration & velocity time history

Fig 2: All five generated acceleration time histories

Fig 3: Ratios of spectra of generated motions to target spectrum

Table of ratios of generated to target spectral values, and cross correlation between histories
for UBC:97 target spectrum

SIMQKE

Average

5 THs

Max ratio

1.13

1.54

1.08

1.29

1.08

1.18

Min ratio

0.83

0.67

0.86

0.70

0.84

0.85

Average
ratio

1.01

1.05

0.97

0.87

1.00

0.98

Standard
Deviation

0.06

0.21

0.04

0.12

0.05

0.06

Cross correln
between THs

2.5%

15.9%

21.2%

9.5%

Fig 4: Comparison of SIMQKE with El Centro NS: accelerations

Fig 5: Comparison of SIMQKE with El Centro NS: velocities

Fig 6: Comparison of SIMQKE with El Centro NS: spectral accelerations