References that I find show the horizontal axis of the seismic repsonse spectrum to be shown as Period, in seconds. When I am looking at mode shapes, or generally conversing in dynamics, I find speaking in terms of frequency to be more useful and familiar.

In order to have a feel for what acceleration would apply to my different mode shapes (an internal caesar II cald, I know, but I wanted to check) I set about converting, then graphing the spectral acceleration curve that I had created (using the curve tool.) I found that the ASCE7 curve I had built was stored in the directory as a file named "ASCE7(02)SPECTRUM1H". I opened it and found the following data:

* ASCE 7 Spectrum Data File
* Horizontal
* Jobname = IGINAL SCOPE\STRESS\CALC FOLDERS - DELIVERABLES\BRIDGE_TRIAL
* FREQ (HZ) MULTIPLIER
0.0010000 0.1301708
0.2122016 0.3231429
1.0610081 0.3231429
1.1198947 0.3061512
1.1857020 0.2891597
1.2597259 0.2721681
1.3436081 0.2551765
1.4394583 0.2381849
1.5500344 0.2211933
1.6790125 0.2042017
1.8314034 0.1872101
2.0142183 0.1702185
2.2375784 0.1532269
2.5166545 0.1362353
2.8752646 0.1192437
3.3530576 0.1022521
4.0212893 0.0848091
5.0221567 0.0543742
6.6863327 0.0306759
10.0000000 0.0137143


What is odd is that I think that this first column should read period in seconds, not frequency in HZ. The data is the exact same as that presented when I generate the curve, but the units would then be wrong.

behold the picture from Caesar II (ver 4.5):

So, which is correct ?

The horizontal axis (in this instance) is "Period (sec)". The units label in the disk file is incorrect. I'll get that corrected.