> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/steel-i-girder-bridge-workflow/templates-for-code-check-and-load-rating-sig/floor-beam-load-rating-t-sig.md).

# Floor Beam Load Rating T \[SIG]

The floor beam load rating template collects the inputs that stay constant across every LRFR floor beam load rating — the mapped strength and service load rating combinations, the condition, system and resistance factors, the modular ratio, and the construction type. Each individual floor beam load rating object (under the Load Rating section) points at one template, so these values do not have to be repeated at every floor beam.

### General

**Strength (Load Rating Combination):** The load rating combination table serves as the basis for all finite element analysis results used in the load rating equations. Pick the Load Rating Combination Table that maps the analysis result cases (DC1, DC2, DW, and the Design, Legal, Emergency, and Permit live-load cases) and their load factors for the strength limit state. The user must provide a value.

**Service (Load Rating Combination):** The load rating combination table serves as the basis for all finite element analysis results used in the load rating equations. Pick the Load Rating Combination Table that maps the analysis result cases and their load factors for the service limit state. The user must provide a value.

**Condition Factor:** Condition factor φc per AASHTO MBE Article 6A.4.2.3, based on the condition state of the floor beam per the most recent inspection report. Typical values: 1.00 for good or satisfactory condition, 0.95 for fair condition, and 0.85 for poor condition. The value must be greater than zero for a rating factor to be computed.

**System Factor:** System factor φs per AASHTO MBE Article 6A.4.2.4, reflecting the redundancy of the floor system. The default of 0.85 corresponds to MBE Table 6A.4.2.4-1 for floor beams spaced more than 12 ft apart with noncontinuous stringers; use a higher value where the floor system provides more redundancy. The system factor is applied to flexure only; shear is rated with a system factor of 1.0 (MBE 6A.4.2.4). The value must be greater than zero.

**Resistance Factor for Flexure:** Resistance factor φf applied to the nominal flexural resistance of the floor beam. The default of 1.0 is the AASHTO LRFD Article 6.5.4.2 value for flexure of steel members. The value must be greater than zero.

**Resistance Factor for Shear:** Resistance factor φv applied to the nominal shear resistance of the floor beam. The default of 1.0 is the AASHTO LRFD Article 6.5.4.2 value for shear of steel members. The value must be greater than zero.

**Modular Ratio Comp. Method \[EsbyEc/User Input]:** Selects how the modular ratio n used for the composite section properties is obtained. *EsbyEc* computes n as the elastic modulus of the steel divided by the elastic modulus of the deck concrete. *User Input* uses the value entered in Modular Ratio. The modular ratio only matters for floor beams that act compositely with the deck.

**Modular Ratio:** The modular ratio n used in the transformed composite section calculations when Modular Ratio Comp. Method is *User Input* (default 8). It must be greater than zero. Available when Modular Ratio Comp. Method is *User Input*.

**Type of Construction \[Shored Construction/Unshored Construction]:** With *Unshored Construction*, permanent load applied before the concrete deck has hardened or become composite is carried by the steel section alone, while permanent load and live load applied afterwards are carried by the composite section. With *Shored Construction*, all permanent load is assumed to be applied after the deck has become composite.

**Use Deck Rebar in Plastic Mom. Calc. (Pos. Flex.) \[Yes/No]:** Controls whether the deck reinforcement forces (Prt and Prb) are included when computing the plastic moment of a composite floor beam in positive flexure. When set to *Yes*, the deck reinforcement contributes to the plastic moment capacity; when set to *No*, it is conservatively neglected.

### Appendix A6

AASHTO Appendix A6 covers the flexural resistance of straight composite I-sections in negative flexure and straight noncomposite I-sections with compact or noncompact webs. It accounts for the ability of such sections to develop flexural resistances greater than the yield moment My (web plastification factors, a lateral-torsional buckling resistance that includes the St. Venant torsional constant J), where Article 6.10.8 stays at the yield moment. The benefit is largest for rolled shapes and built-up sections with stocky webs, and small for webs that approach the noncompact web slenderness limit of Eq. A6.1-1.

**Use Appendix A6 Provisions? \[Yes/No]:** When set to *Yes*, the floor beam load rating objects that use this template rate flexure with the Appendix A6 moment resistances wherever the section qualifies: a straight alignment with supports skewed at most 20 degrees, flange yield strengths not above 70 ksi, I<sub>yc</sub>/I<sub>yt</sub> at least 0.3 and a compact or noncompact web (Article A6.1). The rating verifies these conditions itself and keeps the Article 6.10.8 resistances where they are not met; the report says which applied. In negative flexure it covers composite and noncomposite members; in positive flexure only noncomposite members (a composite member in positive flexure is rated per Articles 6.10.7 and 6.10.8 as before). C<sub>b</sub> is taken as 1.0, as in the code check. The noncomposite member's steel section is taken as its flange, web and cover plates (each with its section loss); flange side plates are not part of it. No lateral bending stress is applied to the discretely braced compression (top) flange of a noncomposite member in positive flexure, as in the Article 6.10.8 rating. Default *No*.


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