The cyclic loading program was designed to generate
large horizontal shear force ranges within the composite
connection between the girder and the deck. A four-stage
loading program was used (Fig. 6). The first three stages
subjected each test specimen to more than 2 million cycles
of structural loading. The final stage subjected each test
specimen to more than 5 million additional cycles of structural
loading. The vertical shear force range was increased
by approximately one-third at each stage, resulting in the
final stage applying twice the vertical shear force range as
the initial stage. In this final stage, the vertical shear force
range was 94 kip (418 kN).
The design of the composite connection in a slab-onstringer
bridge is frequently driven by service-level fatigue
load considerations. Section 6.10.10 of the AASHTO
LRFD specifications provides guidance on the design of a
shear stud composite connection. These provisions were
used to determine the amount of steel crossing all of the
girder-to-haunch composite connection interfaces. The
goal was to simulate the resistance of the design bridge
while imparting loads exceeding those that the bridge
may experience. Figure 7 shows that the horizontal shear
fatigue load range per unit length generated in the first