# Steel Tub Girder Load Rating \[STG] ## 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. It is used to map the analysis result cases and their corresponding factors to the template for strength limit state. **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. It is used to map the analysis result cases and their corresponding factors to the template for service limit state. **Condition Factor:** Condition Factor (φc) is based on the Bridge Management System (BMS) condition state of the element per the most recent inspection report. Typical values: 1.00 for BMS Condition 1-2 (Good/Satisfactory), 0.90 for Condition 3 (Fair), and 0.85 for Condition 4 (Poor). **Include Haunch for Section Properties? \[Yes/No]:** According to DOT requirements, haunch area may or may not be included in the sectional property computations. When haunch is included, it increases the inertia and section modulus and decreases the stress values, making the calculation less conservative. When set to NO, haunch dimensions are still used to determine the locations of the deck and girder sections. **Include Top Lateral Bracing for Section Properties? \[Yes/No]:** When set to YES, the contribution of the top lateral bracing system is included in the closed-section torsional and warping properties of the tub girder used in the load rating equations. **Include Web Longitudinal Stiffeners for Section Properties \[Yes/No]:** When set to YES, web longitudinal stiffeners are added to the computed cross-section properties of the tub girder. **Use Deck Rebar in Plastic Mom. Calc. (Pos. Flex.) \[Yes/No]:** Controls whether deck reinforcement is included when calculating the plastic moment capacity for positive flexure regions. **Type of Construction \[Shored\_Construction/Unshored\_Construction]:** For steel I-girder bridges, **unshored** construction is commonly employed. In this method, any permanent load applied before the concrete deck has hardened or become composite is assumed to be borne entirely by the steel section, while any permanent load and live load applied after this stage are assumed to be supported by the composite section. In the case of shored construction, all permanent load is assumed to be applied after the concrete deck has hardened or become composite, and this information should be clearly stated in the contract documents. **Support Lines for Span Definition \[All/Selection]:** Specifies the support lines to be used in span definition. **'All'** includes all support lines associated with the girder. **'Selection'** allows manual selection of support lines for span computation. **Selected Support Lines :** Specifies the support lines to be considered in span computation when **'Selection'** is selected in the *Support Lines for Span Definitions* input. Only the selected support lines will be used to define spans. ## Appendix B6 This Article shall apply for the calculation of redistribution moments from the interior-pier sections of continuous span I-section flexural members at the service and/or strength limit states. These provisions shall apply only for I-section members that satisfy the requirements of Article B6.2.These optional provisions provide a simple rational approach for calculating the moment redistribution from interior-pier sections due to the effects of yielding. This approach utilizes elastic moment envelopes and does not require the direct use of any inelastic analysis methods. The restrictions of Article B6.2 ensure significant ductility and robustness at the interior-pier sections. **Use Appendix B6 Provisions \[Yes/No]:** If the user selects "Yes" for Appendix B6 provisions, the code check component will internally verify for additional requirements and will not use it if all conditions are not met. If all conditions are met for the support stations, the code check will report the amount of major axis bending moment to be redistributed (Delta Mrd) from piers to span regions for strength and service limit states. This information can be used to determine if using Appendix B6 satisfies the AASHTO requirements for the support locations in their first run. **Mrd at Supports List (Strength) :** In the second run, the user needs to enter the Mrd values of each pier reported in the summary as an input to the code check for any span region adjacent to pier locations. This will help determine if the distributed moment can cause any problems at those locations. If the user wishes to utilize Appendix B6, they must define a separate template for each girder to correctly input the Mrd values at pier locations. **Mrd at Supports List (Service):** In the second run, the user needs to enter the Mrd values of each pier reported in the summary as an input to the code check for any span region adjacent to pier locations. This will help determine if the distributed moment can cause any problems at those locations. If the user wishes to utilize Appendix B6, they must define a separate template for each girder to correctly input the Mrd values at pier locations. {% hint style="info" %} Note that a moment value must be entered at all bearing points, even if it is zero. However, no moment should be assigned to support lines that are additionally placed solely for geometric adequacy. ![image-20250515-064738.png](https://openbrim.atlassian.net/wiki/download/attachments/2127003671/image-20250515-064738.png?api=v2) {% endhint %} **Adj. to Interior-Pier Section Stations(Str):** The user can specify the range for moment redistribution with station values along the PGL for each pier. To help users understand the behavior, the following logic can be applied: the demand will be redistributed, increasing the demand at the adjacent stations while decreasing the demand at the pier. The expected outcome is that the maximum demand value at the pier will decrease, and the maximum demand value at the adjacent stations will increase. However, the above logic is simply explained to demonstrate the behavior. For a more detailed explanation, users need to refer to the AASHTO code and OpenBrIM detailed report. **Adj to Interior-Pier Section Stations(Ser):** The user can specify the range for moment redistribution with station values along the PGL for each pier. To help users understand the behavior, the following logic can be applied: the demand will be redistributed, increasing the demand at the adjacent stations while decreasing the demand at the pier. The expected outcome is that the maximum demand value at the pier will decrease, and the maximum demand value at the adjacent stations will increase. However, the above logic is simply explained to demonstrate the behavior. For a more detailed explanation, users need to refer to the AASHTO code and OpenBrIM detailed report. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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