Model seismic demand with clear engineering inputs. Review coefficients, periods, forces, and graph trends instantly. Plan safer structures using transparent calculations and downloadable summaries.
The page uses a stacked single-column flow, while the calculator fields use 3 columns on large screens, 2 on smaller screens, and 1 on mobile.
This calculator applies a common engineering workflow for horizontal seismic coefficient and design base shear. It is useful for quick preliminary checks and documented input review.
Where:
Auto period options:
| Case | Zone | I | R | Soil | T (sec) | W (kN) | Ah | Vb (kN) |
|---|---|---|---|---|---|---|---|---|
| Mid-rise RC office | IV | 1.0 | 5.0 | Medium | 0.80 | 18,000 | 0.0408 | 734.40 |
| Essential hospital block | V | 1.5 | 5.0 | Soft | 1.20 | 24,000 | 0.0752 | 1,804.80 |
| Flexible industrial shed | III | 1.2 | 3.0 | Hard | 0.30 | 9,000 | 0.0800 | 720.00 |
It represents the fraction of seismic weight used to estimate design lateral force. A higher coefficient means greater earthquake demand on the structure.
Soil changes the response spectrum. Softer soils often amplify motion at longer periods, which can increase seismic demand for flexible buildings.
Use manual Sa/g when your governing code, project spectrum, or software model already provides a site-specific spectral acceleration value.
It accounts for ductility, redundancy, and energy dissipation capacity of the structural system. Larger R values reduce the design coefficient.
Base shear is the total horizontal design force at the foundation level. It is central to lateral force distribution and member design checks.
No. It is a preliminary engineering aid. Final analysis, detailing, drift checks, and load combinations must follow the governing code and project requirements.
It lets advanced users adjust the coefficient when a project uses damping-related modifications or calibrated spectrum adjustments beyond the default assumption.
It improves workflow by showing the computed summary immediately under the header, making exports and review faster after each submission.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.