Seismic Component (Fp) Calculator, ASCE 7-22

What it checks

The module calculates the horizontal design force Fp for a single nonstructural component in accordance with ASCE 7-22 Chapter 13. It supports both architectural and mechanical/electrical components by selecting the appropriate row from Table 13.5-1 or Table 13.6-1. The design method applies the strength-based force chain defined in Section 13.3.1 to determine the seismic demand on the component. The calculation sequence begins by determining the component importance factor Ip and the height factor Hf. It then evaluates the response modification factor Rmu and the ratio of the component amplification factor to the component response modification factor, CAR/Rpo. The module computes the base force using Equation 13.3-1 and checks this value against the lower and upper bounds specified in Equations 13.3-3 and 13.3-2. Finally, it applies any necessary doubling for vibration-isolated components with large air gaps and calculates the anchorage force.

Inputs

Site and Component - Design spectral response acceleration at short periods SDS, component operating weight Wp (pounds), and the row key for Table 13.5-1 or 13.6-1.
Geometry and Support - Attachment height z (ft), average roof height h (ft), and a flag indicating if the component is supported at or below grade.
Importance - The component importance condition per Section 13.1.3 or a direct override value for Ip.
Supporting Structure - Fundamental period Ta (s), SFRS response modification coefficient R, seismic importance factor Ie, and overstrength factor Omega0.
Component Dynamics - Component fundamental period Tp (s), vibration isolation status, and whether the isolator air gap exceeds 0.25 in.
Overrides - Manual values for CAR and Rpo, which must be provided as a pair.

What it reports

Horizontal Design Force - The final Fp in pounds, adjusted for the 13.3-2/13.3-3 bounds and any note-a doubling.
Force Ratio - The ratio of Fp to Wp, representing the fraction of component weight.
Uncapped Force - The value from Equation 13.3-1 before the application of the lower and upper bounds.
Bounds - The lower bound from Equation 13.3-3 and the upper bound from Equation 13.3-2, both in pounds.
Governing Equation - The specific equation citation that determined the final Fp value.
Factor Ratio - The CAR/Rpo value actually used, which becomes 1.0 if the Tp exception applies.
Overstrength Factor - The component overstrength factor Omega0p taken from the selected table row.
Anchorage Force - The product of Omega0p and Fp, used for anchorage design.

Code references

The engine cites ASCE 7-22 Chapter 13, specifically Equations 13.3-1, 13.3-2, and 13.3-3 for the force calculation and bounds. It utilizes Tables 13.5-1 and 13.6-1 for component factors. The module also references Section 13.1.3 for the importance factor, Equation 13.3-4 and 13.3-5 for the height factor, Equation 13.3-6 for the response modification factor, and Equation 13.3-13 for the component period.

Limits

The module designs a single component and does not account for interactions between multiple components. It assumes the supporting structure properties are provided by the user and does not calculate the supporting structure's response. Manual overrides for CAR and Rpo are refused if not provided as a pair. Results are engineering aids; the engineer of record is responsible for the design.

This module ships in the desktop app

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