What it checks
The module designs open-web steel joists against SJI K-Series load tables. It evaluates the member for uniform capacity, deflection, and bridging requirements. The design method uses Allowable Stress Design (ASD), determining the governing total load as a uniform load of equal moment or shear.
The sequence of checks begins by identifying the governing load combination, which may include dead, live, snow, or seismic effects. The module then compares the resulting uniform load against the SJI catalogue values for total safe uniform load and live load. Finally, it performs a deflection check using the moment of inertia and modulus of elasticity to ensure the span meets the L/360 limit.
Inputs
- Loads - Snow load (plf), roof live load (plf), and SJI total safe uniform load (plf).
- Properties - Moment of inertia (in^4) and the joist's own weight (plf).
- Combinations - Project load combinations and the Ev toggle (SDS) for vertical seismic effects.
- Geometry - Span (ft) and spacing, mirrored from the joist properties.
What it reports
- Governing Total Load - The uniform load (plf) of equal moment or shear that governs the design.
- Live Load Capacity - The SJI live load (plf) for L/360 deflection at the specific span.
- Deflection - The calculated deflection (inches) for a simply-supported, uniformly-loaded beam.
- Combination Label - The specific load combination that governed and the source of its factors.
- Concentrated Load Check - The governing total load (plf) when a concentrated live load is checked in place of the uniform live load.
- Placement Trials - Every placement tried with the corresponding governing total-load DCR.
Code references
The engine cites SJI K-Series load tables. It references the L/360 deflection limit for live load and the vertical seismic effect factor 0.2*SDS*D for seismic combinations. The module notes that steel has no load-duration concept, preventing the application of NDS factors to snow loads.
Limits
The module assumes the joist behaves as a simply-supported beam for deflection calculations. It does not apply load-duration factors to steel members. The concentrated live load check is only performed when explicitly switched on, replacing the uniform live load while keeping dead load constant. Results are engineering aids; the engineer of record is responsible for the design.