Load Rating Combination Table [CUG]

Each row defined in this section serves as an input to load rating templates and enables mapping of the analysis results to load rating objects.

To utilize this object, or in other words, to assign related factors to the appropriate vehicles for the bridge load rating, users must ensure that the related Result Extraction Cases and Live Load Cases are properly defined.

As stated in the related specifications, "Strength is the primary limit state for load rating; service limit states are selectively applied." For simplification purposes, it is recommended that users define two separate Load Rating Combination Tables—one for Strength coefficients and one for Service coefficients. The results will be combined for Strength Limit States and Service Limit States to streamline the load rating process. These two definitions can then be assigned to the Concrete Girder Load Rating object as the Strength (Load Rating Combination) and Service (Load Rating Combination) parameters.

Refer to the tables below to see the factors used in load rating calculations:

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Table 6A.4.4.2.3a-1

Permanent Loads

Bridges that will undergo load rating should also have a Permanent Loads Rating. Such definitions can be made using the parameters provided below.

γDC (max): Specifies the maximum load factor for composite and non-composite dead load cases. Typically set to 1.25 for strength limit states, as per AASHTO Table 3.4.1-2 or DOT amendments.

γDC (min): Specifies the minimum load factor for composite and non-composite dead load cases. Typically set to 0.9 for strength limit states, as per AASHTO Table 3.4.1-2 or DOT amendments.

DC1: Used for setting non-composite dead load result extraction cases. Includes loads applied during the non-composite state of girders, such as self-weight of the steel girder, cross frame load, formwork load, and deck load.

DC2: Used for setting composite dead load result extraction cases. Includes loads applied to the composite state of girders, such as barrier loads.

γDW (max): Defines the maximum load factor for wearing surface and utilities load cases (DW). Typically set to 1.5 for strength limit states, as per AASHTO Table 3.4.1-2 or DOT amendments.

γDW (min): Defines the minimum load factor for wearing surface and utilities load cases (DW). Typically set to 0.65 for strength limit states, as per AASHTO Table 3.4.1-2 or DOT amendments.

DW: Used to specify the result extraction case for wearing surfaces and utilities. Loads applied in the composite state, such as these, should be mapped here.

γP (max): This parameter specifies the maximum load factor to be used for the Permanent Loads case (permanent loads other than dead loads).

γP (min): This parameter specifies the minimum load factor to be used for the Permanent Loads case (permanent loads other than dead loads).

Permanent Loads: This parameter sets the Permanent Load Case previously created in the Result Extraction (from Stages) object.

PS Loads

Prestressing Loads can be taken into account for load rating, where the related definitions can be made using this section of the Load Rating Combination Table object.

γPS: This parameter can be used to specify the factor for the Prestressing Load Case.

PS: This parameter can be used for assigning the Prestressing Load Case to be considered for load rating.

γPS Loss (Relaxation): This parameter can be used to specify the load factor for the relaxation case.

PS (Relaxation): The relaxation case can be assigned by this parameter.

γPS Loss (Elastic Shortening): This parameter can be used to specify the factor for the Elastic Shortening case.

γCR: This parameter can be used to specify the factor to be used in the case of creep.

PS (Creep): This parameter can be used to assign the case associated with creep.

γSH: This parameter can be used to specify the factor for shrinkage.

PS (Shrinkage): This parameter can be used to specify the case associated with shrinkage.

Design Load

Design Load Rating can be performed by defining the parameters in this tab. The design load rating must use HL-93 loading and comply with LRFD standards, utilizing the bridge's current dimensions and properties.

γLL (Inventory): This parameter can be used to define the load factor for live loads when calculating the inventory rating of the bridge.

γLL (Operating): This parameter can be used to define the load factor for live loads when calculating the operating rating of the bridge.

LL: This parameter can be used to specify the live load case in the load rating calculations for the design load rating.

Legal Load

Legal Load Rating should be conducted for bridges that do not have sufficient capacity under the design load rating, with the purpose of addressing the need for load posting or strengthening.

Legal Load Rating can be applied to all legal trucks (the Notional Rating Load/state legal loads), considering the maximum weights and configurations specified by regulatory authorities.

Up to 20 different factors and 20 live load cases can be used to define the legal load rating, providing flexibility in evaluating the bridge's capacity to safely support legally permissible vehicle loads.

γLL 1:

LL 1:

γLL 2:

LL 2:

γLL 3:

LL 3:

γLL 4:

LL 4:

…

γLL 20:

LL 20:

Emergency Load

Up to 10 different factors and 10 live load cases can be used to define the emergency load rating, enabling the assessment of the bridge's capacity to handle vehicles during emergency situations.

γLL 1:

LL 1:

γLL 2:

LL 2:

γLL 3:

LL 3:

…

γLL 10:

LL 10:

Permit Load

Permit Load Rating is associated with permit applications for the passage of vehicles that exceed the legally established weight limitations. It is recommended that users define the permit load rating for bridges that have sufficient capacity for legal loads. Actual permit trucks can be used.

Up to 10 different factors and 10 live load cases can be used to define the permit load rating, facilitating the evaluation of the bridge's capacity to accommodate vehicles requiring special permits.

γLL 1:

LL 1:

γLL 2:

LL 2:

γLL 3:

LL 3:

…

γLL 10:

LL 10: