Seismosoft | Earthquake Engineering Solutions

Hi Seismosoft,

I would like to confirm a point regarding the implementation of ASCE 41-23 in Seismosoft 2026, specifically for the horizontal response spectrum. The software notes that starting with ASCE 41-23, Sxs and Sx1 are already adjusted for site effects. However, under the Seismic Action tab, the only required inputs appear to be the MCER Sxs and Sx1 values for BSE-2N (2%/50yr).

If we want to evaluate BSE-2E and BSE-1E performance, how are the corresponding horizontal spectra obtained? Should spectral parameters for BSE-2E and BSE-1E be entered separately, or is there a built-in relationship that derives them automatically from the BSE-2N inputs?

The graphical plots of the horizontal spectra for BSE-2E and BSE-1E do not appear to match the spectra obtained when using their respective actual parameters. Could you please clarify how these spectra are generated within the software?

Thank you.

The spectral acceleration of the BSE-2E (5%/50years) seismic hazard level is 75% of the BSE-2N (2%/50years) level, according to section ASCE 41-23, C2.3.1.3. Similarly the (20%/50years) and (50%/50years) levels are 50% and 37.5% of BSE-2N.
For more details refer to section C2.3 of the Commentary of ASCE 41-23.
Seismosoft Support

Thank you for your clarification.

However, please let me know if my understanding is incorrect. Upon reviewing ASCE 41-23, Section C2.3.1.3, the statement that BSE-2E equals 75% of BSE-2N appears only in the commentary and is described as historical information rather than a prescribed or fixed factor. It is also noted that, in some cases, BSE-2E values may be capped at the BSE-2N level. This suggests that BSE-2E values can exceed the 75% relationship and that the hazard levels are not strictly proportional.

Additionally, when comparing spectral values for BSE-2E, BSE-1E, and BSE-2N obtained from the online ASCE hazard tools, the results do not appear to follow the 75% and 50% ratios.

In versions prior to 2026, we were able to input spectral values directly for each hazard level, which produced the expected spectral acceleration curves.

Since the online ASCE Hazard tool (https://ascehazardtool.org/) provides only the MCER (2%/50years) parameters, we based the other Seismic Hazard levels on the ratios provides in C2.3.1 of ASCE 41-23. Do you feel that we should provide also an option for defined parameters in the other seismic hazard levels. When can engineers find the necessary values for the other seismic hazard levels?
Seismosoft Support

Since the online ASCE Hazard tool (https://ascehazardtool.org/) provides only the MCER (2%/50years) parameters, we based the other Seismic Hazard levels on the ratios provides in C2.3.1 of ASCE 41-23. Do you feel that we should provide also an option for defined parameters in the other seismic hazard levels. When can engineers find the necessary values for the other seismic hazard levels?
Seismosoft Support

Thank you for your response.
However, the online ASCE Hazard Tool does provide spectral parameters for all ASCE 41 hazard levels (BSE-2N, BSE-1N, BSE-2E, and BSE-1E), not only MCER values. These can be accessed by selecting: ASCE 41-23 → Seismic → Summary

As an example, for San Francisco, California
(Lat: 37.780077°, Long: −122.420162°)
ASCE 41-23 / Soil Class D, the following seismic parameters are provided:
Hazard Level (Sxs, Sx1)
2N: (1.73, 1.75)
1N: (1.15, 1.16)
2E: (1.73, 1.38)
1E: (1.03, 0.66)

As shown above, these values do not strictly follow fixed proportional scaling (e.g., 75% or 50% of BSE-2N). In particular, the BSE-2E Sxs value is equal to the BSE-2N value in this case. As an additional reference, an Excel file containing OCONUS ground motion parameters is provided under UFC 3-301-01 (https://www.wbdg.org/dod/ufc/ufc-3-301-01) , which engineers commonly use for Department of Defense projects outside the United States.

For now, the practical workaround I am using is to manually generate the response spectrum externally and then import it into the software. However, this approach somewhat defeats the purpose of having the program internally generate code-based spectra, particularly since previous versions allowed direct specification of spectral parameters for each hazard level.

Thank you.

Can you please send a screenshot of the summary that you get at support@seismosoft.com?
I still get only the MCER data with both the Summary and the Full Report buttons, even when using the exact coordinates above
Thank you.
I also checked the Excel file with the OCONUS ground motion parameters, and it does not include data from the US, as you correctly pointed out.
Seismosoft Support

It may be possible that the selected standard in the Hazard Tool is set to ASCE 7, which would only display the MCER parameters.
To obtain the ASCE 41 hazard levels, the standard must be set to ASCE/SEI 41-23 before clicking “View Results”.
I have also sent an email to support@seismosoft.com with the requested screenshots for reference.
Thank you.

Thank you, Fernnie.
After your detailed feedback, we decided to include both options in SeismoBuild, i.e. (i) the current functionality with only the MCER data, and (ii) data for all spectra of all the seismic hazard levels. This will be implemented either in SeismoBuild v2026, Release-3 or in SeismoBuild v2027 that will be published next November.
Seismosoft Support

Hello, just following up on this discussion.
As mentioned earlier, my current workaround is to manually generate the response spectrum externally and then import it into the software. After running the analysis and confirming that the correct spectral values from the generated spectrum were used, I proceeded to generate the calculation report.
However, I noticed that while the report displays the correct response spectrum graph, the spectral values listed beneath it appear to be incorrect. Could you please confirm whether this issue is limited to the generated report and does not affect the actual analysis results?
We are planning to use the generated report for submission, but at the moment it still seems to contain several discrepancies.