Redundancy analysis - Computational Analysis and Design of Bridge Structures - page 468

To maximize the live loading effect, live loading positions are dependent
on the locations of cutting members. If the cutting member is close to the
center of the bridge, the truck is positioned at the centerline. Both truck and
lane loads are such transversely positioned that truss panel A will be more
heavily loaded.

15.3.1 loading cases
The full dead load (DL) and live loading plus impact (LL + I) were applied
as specified by AASHTO LRFD (AASHTO 2013) and Penn DOT Design
Manual (Penn DOT 2000) for extreme cases III and IV. They are summa-
rized as follows:

1. All DL intensities were computed from the actual weights of the indi-
vidual components of the bridge, and their load factors are listed in
Table 15.3.

2. (LL + I) was determined by applying a full PHL-93 or P-82 live load
longitudinally to obtain maximum tension and compression effects
for all members. The impact and distribution factors specified by
AASHTO were utilized. The Penn DOT vehicular live loading on
the roadways of bridges or incidental structures, designated as PHL-
93 (similar to AASHTO HL-93, except higher-design tandem), shall
consist of a combination of the following:

a. Design truck (HS-20 as shown in Figure 15.6a) or design tandem
(two axles of 31.25 kip or 139 kN)

b. Design lane load (0.64 kip/ft or 9.3 kN/m) and the P-82 permit
truck is shown in Figure 15.6b. Note that the loading HL-93 or
PHL-93 used here can be replaced by any other design vehicles
of any code and P-82 can be replaced by permit vehicles of any
jurisdiction.

Two load combinations are considered in either extreme event III (no cut)
or extreme event IV (cut) case. Computer-run cases in relation to element-
cut and load cases are listed in Table 15.4. Load factors in relation to load
combinations and load cases are shown in Table 15.5.

Table 15.3 Dead load factors for extreme events III and IV
Load fact ors

Extreme event III Extreme event IV

Maximum 1.25 1.05 γ DC

Minimum 0.90 0.95

Maximum 1.50 1.05

γ DW

Minimum 0.65 0.90