Rating Tab
The Rating tab allows you to specify loads and group combinations (LFR or LRFR) to be used for determining a bridge vehicle load rating. Multiple load ratings can be performed and each load rating is stored separately. Load ratings can be used to track on-going bridge condition or determine available capacity for overload permitting. The analysis is performed assuming no additional losses beyond those computed through the Final Case.
Rating combinations have a type depending on whether LFDR or LRFR is being used and consist of a number of loadings (e.g. DL, LL) with associated load factors. LFDR combinations can have a type of Inventory or Operating. LRFR combinations can have a type Design-Inventory, Design-Operating, Legal, or Permit. The following types of loadings may be added to a combination.
The Rating tab is used to add both loads and combinations to the current bridge. The tab consists of three panes or views to facilitate the creation of loads and the formation of combinations. The left-side view is referred to as the "Combination Tree" and contains the list of user-defined combinations. The right-side view is referred to as the "Load Tree" and actually contains two lists of loads: Library Live Loads obtained from the Live Load Library and user-defined project loads. The bottom view displays either a summary of results from a load rating analysis or a graphical representation of the loads on the bridge.
The list of Library Live Loads in the Load Tree can only be viewed; they cannot be edited. To view a Library Live Load, double-click or select it using the right mouse button and then select View Library Live Load. The Library Live Loads are intended to be placed into combinations or into the project loads by selecting them with the left mouse button and then dragging them to the appropriate combination or into the project loads. Library Live Loads may be edited once they are in the list of project loads.
Combinations are added by right-clicking in the Combination view and selecting Add Combination. Combinations contain references to loads on the bridge. You may create loadings on the bridge by right-clicking on load categories on either the project load tree or the combination tree. Adding loads by right-clicking on the combination tree performs two activities: first, a loading is created on the bridge and second, a reference to it is added to the combination. You may add combination items to a combination by dragging loads, either from the list of library live loads or from the list of project loads currently defined for the bridge to a particular combination.
Deleting a combination item from a combination merely removes the reference to the loading from the combination; the actual loading is still on the bridge. Deleting a loading from the list of project loads removes all references to it for all combinations and then deletes it from the bridge.
Loads and combinations are created for each load rating. After defining loads and/or combinations, you can perform an analysis of the structure by clicking the Rating Analysis button. After performing the analysis, the rating summary text report displays in the bottom frame of the screen.
Bridge ratings are conducted on the Full Width Only, even if you selected the Optional Girder Analysis.
Load ratings can be performed using ASSHTO Standard (LFDR) or ASSHTO Load Resistance and Factor Rating (LRFR). The rating specification is chosen by selecting AASHTO Standard or LRFD on the Project Tab.
