AASHTO LRFD Specific Parameters

Used to input parameters for loading per the AASTHTO LRFD Bridge Design Specifications.

Setting	Description
Live Load Impact Factors	Multiplier accounting for imperfection in road surface resulting in additional dynamic loading. These factors vary depending upon the bridge component being designed. The default value of 1.33 is specified for bridge components (other than deck joints) for limit states other than fatigue or fracture (AASHTO LRFD table 3.6.2.1-1). Separate values may be specified for the Design Tandem vehicle and the Design Truck (HS).
Multiple Presence Factors	Multipliers for design vehicles based on the number of design lanes in the transverse section of a roadway. The multiple presence factors, m, account for the statistical improbability of three or more adjacent lanes being loaded simultaneously with the design vehicle. The default values are taken from AASHTO LRFD table 3.6.1.1.2-1.

Setting

Description

Live Load Impact Factors

Multiplier accounting for imperfection in road surface resulting in additional dynamic loading. These factors vary depending upon the bridge component being designed. The default value of 1.33 is specified for bridge components (other than deck joints) for limit states other than fatigue or fracture (AASHTO LRFD table 3.6.2.1-1). Separate values may be specified for the Design Tandem vehicle and the Design Truck (HS).

Multiple Presence Factors

Multipliers for design vehicles based on the number of design lanes in the transverse section of a roadway. The multiple presence factors, m, account for the statistical improbability of three or more adjacent lanes being loaded simultaneously with the design vehicle. The default values are taken from AASHTO LRFD table 3.6.1.1.2-1.