24 
BULLETIN I486, U. S. DEPARTMENT OF AGRICULTURE 
case 2. straight grade lines, either level or inclined 
In this case, the bridge grade is raised parallel to itself a distance 
a and an arbitrary camber placed on the structure. The approach 
vertical curves should be not less than one-fourth of the length of 
the structure, unless this length exceeds 200 feet, in which case the 
.. V5E _ : 
L 
APPROACH VERTICAL CURVE 
NOT LESS THAN £ L 
ON GRADES OF 3 PER CENT AND UNDER C = I INCH PER 40 FEET OF SPAN LENGTH.- 
ON GRADES OVER 3 PER CENT REDUCE CAMBER 50 PER CENT FOR EACH ADDITIONAL 
PER CENT OF GRADE. 
Pig. 21. — Grade-line treatment of bridge located on a continuous grade 
approach vertical curve should be kept at 200 feet and the camber c 
should be given a value equal to 1 inch for every 40 feet of span 
length. Where the grade is more than 3 per cent, the camber should 
be reduced as shown in Figure 21. 
CONCAVE GRADE INTERSECTION 
A flat bridge grade should be laid to intersect the two intersecting 
approach grades, as shown in Figure 22, and connected to the profile 
THE CURVE V 2 MAY BE SHORTENED 
TO NOT LESS THAN 50 FT, PREFERABLY 
NOT LESS THAN 100 FT. 
■ •:v:-: 7 t t t t :-:-> / :<x ^ 
Fig. 22.— Grade-line treatment on a bridge located on a concave grade intersection 
grades with vertical curves. The treatment between points A and B 
should be exactly the same as for the flat grade line (fig. 21), except 
that the camber c should be taken as 50 per cent of the camber out- 
lined under case 2 and the vertical curves V 2 may be shortened to not 
less than 50 feet if necessarv. 
