Straight and curved steel I-girder bridges - Computational Analysis and Design of Bridge Structures - page 213

of their respective influence lines are used to multiply the fraction of vehicular
loading to that girder, and areas under their respective influence lines are used
to multiply the fraction of lane loading to their respective girders.
To determine the extreme live load locations and corresponding extreme
values, influence lines are obtained from the influence surface for each
girder. Figure 7.17 shows the 3D perspective views for exemplar positive
and negative moment influence surfaces. Their exemplar 2D views for all
four girders from the DESCUS-I program (2012) are shown in Figures 7.18
and 7.19. Placement of live loads on one influence surface is shown in

900.0

800.0
700.0
600.0
500.0
400.0
300.0
200.0
100.0
0.0

G G1
G3
G4

7 8 9 10 11

1 2 3 4 5 6

−100.0
−200.0

Figure 7.18 DESCUS-I example—positive moment influence lines of girder 2.

1 2 3 4 5 6 7 8 9 10 11

0.0

100.0

200.0

300.0

G2

G G G4

400.0

Figure 7.19 DESCUS-I example—negative moment influence lines of girder 2.