[LOAD] Braking Load Application
BRAKING LOAD APPLICATION
According to AASHTO 3.6.4
Braking Force (BR) can be calculated as greater of the following:
25% of the axle weight if the Design Truck or Design Tandem
5% of (Design Truck/Design Tandem + Lane Load)
So,
So, 25% of Design Truck governs: 18kips
So the number of lanes in a model be: n
Multiple presence factor for the lanes be: m
Then the Braking Force will be maximum of:
So, the maximum force should be applied horizontally at the deck level in the longitudinal direction which in turn will generate forces on the columns and other substructures.
EXAMPLE:
The bridge shown here is a 3 span PSC Box Girder bridge having 2 lanes.
Total Span: 410 ft, so can easily fit complete HL-93 Truck and Tandem Load.
The current bridge has 2 lanes:
So, for 2 Lanes Max Braking Load: 36 kips
We have a single line element representing the bridge:
Total Span 410 ft, so a uniformly distributed load of 36/410 = 0.9 or 1 kips/ft has to applied.
Go to Load > Static Load > Static Load Cases:
Name: Braking Load
Type: Braking Load
Click Add
Then Go to Load > Static Loads > Element Beam Loads
Load Case Name: Braking Load
Load Type: Uniform Loads
Direction: Global X
Value: Relative, x1:0, x2:1, w:1
Select All the elements
Click Apply
According to AASHTO 3.6.4
Braking Force (BR) can be calculated as greater of the following:
25% of Design Truck | 0.25*72 | 18 kips |
25% of Design Tandem | 0.25*50 | 12.5 kips |
5% of (Design Truck + Lane Load) | 0.05*(72+412*0.64) | 16.8 kips |
5% of (Design Tandem + Lane Load) | 0.05*(50+412*0.64) | 15.7 kips |
So, 25% of Design Truck governs: 18kips
So the number of lanes in a model be: n
Multiple presence factor for the lanes be: m
Then the Braking Force will be maximum of:
Number of Lanes | Multiple Presence Factor | Calculation | Braking Force |
1 Lane | 1.2 | 18 x 1.2 x 1 | 21.6 kips |
2 Lanes | 1 | 18 x 1 x 2 | 36.0 kips |
3 Lanes | 0.85 | 18 x 0.85 x 3 | 45.9 kips |
4 Lanes | 0.65 | 18 x 0.65 x 4 | 46.8 kips |
So, the maximum force should be applied horizontally at the deck level in the longitudinal direction which in turn will generate forces on the columns and other substructures.
EXAMPLE:
The bridge shown here is a 3 span PSC Box Girder bridge having 2 lanes.
Total Span: 410 ft, so can easily fit complete HL-93 Truck and Tandem Load.
The current bridge has 2 lanes:
So, for 2 Lanes Max Braking Load: 36 kips
We have a single line element representing the bridge:
Total Span 410 ft, so a uniformly distributed load of 36/410 = 0.9 or 1 kips/ft has to applied.
Go to Load > Static Load > Static Load Cases:
Name: Braking Load
Type: Braking Load
Click Add