Function
- AASHTO LRFD states, "For negative moment between points of contraflexure under a uniform load on all spans, 90 percent of the effect of the two design trucks combined with 90 percent of the effect of the design lane load." Additionally, force components other than negative moment also need to be determined based on the two-truck rule in some projects.
- Assign the elements or links to apply the two-truck rule for all force components, including negative moment.
- AASHTO LRFD Design Load
This function also automatically considers the requirement of the effect of 90% of two design trucks spaced at 50 ft and 90% of the design lane load for negative moment in accordance with AASHTO LRFD when specified. The requirement of 14 ft distance between the 32 kip axles is also maintained.
- PennDOT Design Load (PHL-93TRK)
This function considers the Pennsylvania DOT requirements. For the negative moment between points of dead load contraflexure, the effect of two design trucks spaced a minimum of 50 ft. between the lead axle of one truck and the rear axle of the other truck, combined with the effect of the design lane load; the distance between the 32 kips axles of each truck shall be taken as 14 ft.. The two design trucks are placed in adjacent spans to produce maximum force effects. (PUB 15M (5-12) 3.6.1.3.1.)
- PennDOT Tandem Load (PHL-93TDM)
For the negative moment between points of dead load contraflexure, the effect of two tandems with axle weights of 25 kips spaced from 26 ft. to 40 ft. apart, combined with the effect of the design lane load. The two tandems should be placed in adjacent spans to produce maximum force effects. (PUB 15M (5-12) 3.6.1.3.1.)
- AASHTO legal load (The Manual for Bridge Evaluation)
This function also automatically considers the requirement of the effect of a lane load of 0.2 klf combined with two AASHTO Type3-3 vehicles or state legal loads multiplied by 0.75 spaced at 30 ft for negative moment in accordance with the Manual for Bridge Evaluation by AASHTO .
In addition, for span lengths greater than 200ft, critical load effects shall be created by the AASHTO Type3-3 vehicles or state legal loads multiplied by 0.75 and combined with a lane load of 0.2klf.
- Each State DOT legal load
This function also automatically considers the requirement of the effect of a lane load of 0.2 klf for both negative moment and for span lengths greater than 200ft in accordance with DOT Legal vehicles when specified using the LRFR method.
Call
From the main menu, select [Load] tab > [Type : Moving Load] > [Advanced] group > [Lane Supports All Forces/Moments]
Input
Option
Add : Enter the selected elements or links to apply the two-truck rule for all force components, including negative moment.
Delete : Select and delete previously entered elements.
Type
Select the element type, i.e. Truss, Beam, Plate, Elastic Link, General Link.
Select Two Nodes
Select the two end nodes of an Elastic Link or General Link to choose the Links. The link itself cannot be selected directly. Multiple links can be selected simultaneously by selecting multiple nodes that correspond to the i-end and j-end of the links.