Intro
This plug-in automates the calculation of equivalent static seismic loads in accordance with the AS 1170.4:2024 standard. It allows engineers to easily input seismic design parameters and instantly visualize story-wise lateral force distributions for both X and Y directions, significantly streamlining the seismic design workflow.
Applicable standards
- AS 1170.4:2024 (Structural design actions, Part 4: Earthquake actions in Australia)
Benefits of this plugin
- Standards Compliance: Follows the latest AS 1170.4:2024 standard for seismic design, supporting compliant and up-to-date static lateral load calculations.
- Visual Validation: Dual bar charts show story force,story shear and overturing moment distribution by direction, enabling immediate verification and interpretation of load results.
- Interactive Workflow: Instant updates of graphs based on parameter changes help reduce iteration time and increase modeling efficiency.
- Calc.Sheet Export & Integration: Apply static seismic loads directly to your structural model or export to Excel calculation sheet for documentation and further use.
How to use this plugin?
- On the left, users input seismic design parameters of your structural model .
- On the right, the plugin instantly visualizes results such as Story Force, Story Shear, and Overturning Moment in both X and Y directions using charts and tables.
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Once all parameters are set, go to the “Load Cases to Apply to Seismic Loads” tab.
Here, you can select the Static Load Cases where the seismic loads will be applied for each direction. - Finally, click the “Apply Seismic Loads” button to assign the calculated loads to your structural model.
Note
This plugin is organized into multiple functional sections, each guiding users through the process of generating static seismic loads as per AS 1170.4:2024. The seismic design parameters allows users to define the key design parameters required for seismic analysis. Each parameter is based on specific clauses from AS 1170.4:2024.
① Sub-Soil Class Selection
Begin by determining the sub-soil class of the structure's location. Choose from Ae, Be, Ce, De, or Ee, referring to Section 4.1.1 or 4.2 of the standard.
② Annual Probability of Exceedance
Set the annual probability of exceedance. This value determines the probability factor (kp). Refer to Table 3.1 for selecting kp based on different exceedance probabilities.
③ Hazard Factor (Z)
Define the hazard factor (Z) for the site. Use Table 3.2 to find Z values for specific Australian locations, or refer to Figures 3.2(A)–3.2(G) for detailed regional data.
④ kp × Z Calculation
The product of kp and Z (i.e., kpZ) is automatically computed and validated against the minimum values defined in Table 3.3.
⑤ Importance Level (2–4)
Select the importance level for the structure, restricted to Levels 2, 3, or 4 in this plugin.
Note: Refer to the NCC (National Construction Code) or AS/NZS 1170.0 Appendix F for guidance.
Level 1 structures are not required to consider seismic action and are not supported by this plugin. And, domestic structures(housing) are not supported in this plugin.
⑥ Structure Height (hn)
Input the total height of the structure (hn), measured from the base to the highest mass contributing to seismic load. The maximum story height in the modeling will be used.
⑦ Earthquake Design Category (EDC)
Based on Table 2.1, the plugin determines the Earthquake Design Category (EDC) as I, II, or III.
EDC I: Checked by Simple Static Method (Clause 5.2, 5.3) – Supported
EDC II: Checked by Static Analysis (Clause 5.2, 5.4) – Supported
EDC III: Requires Dynamic Analysis (Clause 5.2, 5.5) – Not Supported in this plugin
→ In this case, use the separate plugin: [AS 1170.4:2024] Response Spectrum Generator
⑧ Ductility and Performance Factors
Specify values for:
Structural Performance Factor (Sp) – Refer to Table 6.5
Structural Ductility Factor (μ) – Refer to Table 6.5
Different values can be set for X and Y directions individually.
⑨ Fundamental Period (T₁)
Enter the fundamental natural period for each direction (X and Y), in seconds.
To use the code-based approximate method (per Equation 6.2(7)), click the “Period Calculator” to calculate T₁ automatically.
Conclusion
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- This plugin provides a comprehensive and user-friendly environment for generating static seismic loads in compliance with AS 1170.4:2024.
- By guiding users through standardized parameter inputs and offering dynamic visual feedback, it ensures transparency in the seismic design process. Engineers can better understand how key inputs—such as soil class, structural height, and ductility—impact the story-wise load distribution, enhancing both design quality and decision-making efficiency.
- The seamless workflow from input to visualization and export significantly reduces manual effort and promotes standardized, reproducible outcomes in structural seismic design.