What it checks
The module designs simple-span wood I-joists, specifically TJI-style members, against manufacturer ESR catalog capacities. It performs checks for moment, web shear, deflection under live and total loads, and bearing stress at the supports. The design method utilizes Allowable Stress Design (ASD) combinations, applying specific load-duration factors to determine the governing demand-to-capacity ratios.
Section properties are derived from the manufacturer’s catalog or ESR rather than being embedded in the engine. The sequence of checks evaluates the worst moment and shear demands across the available load combinations. Each combination is assessed with its own duration factor, and the results identify the governing combination and the specific load-duration factor applied.
Inputs
- Loads - Dead load, floor live load, and optional snow load (plf) or roof live load (plf). Supplying optional loads activates the combination engine.
- Combinations - Project load combinations (Vec
). If absent, the module uses default dead and floor live load cases. - Seismic - Ev toggle (A4) and SDS value. If SDS is greater than zero, the vertical seismic effect 0.2*SDS*D is folded into seismic combinations.
- Geometry - Joist spacing and optional concentrated live load, using the same fields as the wood joist module.
- Properties - Allowable moment (lb-ft) and shear (lb) from the ESR at Cd = 1.0, and catalogue EI (lb-in^2).
- Supports - Bearing length at the supports (in).
- Weight - Joist weight (plf), which the beam’s Self Weight option adds to the dead load.
What it reports
- Moment DCR - The worst demand-to-capacity ratio for moment over the ASD combinations, compared against the ESR allowable moment.
- Shear DCR - The worst demand-to-capacity ratio for shear over the ASD combinations, compared against the ESR allowable shear.
- Deflection - Deflection results for live load and total load, compared against serviceability limits using the catalogue EI.
- Bearing Stress - Bearing stress at the supports, compared against allowable bearing stress based on the provided bearing length.
- Governing Combination - The specific load combination that governed the design, including where its factors came from.
- Duration Factor - The load-duration factor (Cd) actually applied to the governing combination.
Code references
The engine cites Manufacturer ESR (ICC-ES) catalog capacities. The design checks are verified against ESR-1040 and ESR-2403. The module applies ASD combinations and specific load-duration factors as defined by the manufacturer’s ESR data.
Limits
The module performs simple-span checks only; it does not model continuous spans or complex boundary conditions. Section properties are not embedded and must be provided from the manufacturer’s ESR. If no load combinations are provided and no loads beyond dead and floor live are supplied, the module behaves as a basic check without the combination engine. The Ev toggle is optional and only affects seismic combinations when SDS is greater than zero. Results are engineering aids; the engineer of record is responsible for the design.