Dynamic Test of Span A3
The maximum measured midspan dynamic and static strains for all girders with vehicles loaded to 100 kips; and traveling 55 MPH traveling speed was collected.
Figure 6(a) shows a typical time vs. midspan strain relationship at 55 MPH. The fundamental natural frequency of the bridge was calculated by the power spectrum of measured time-strain or time-acceleration data as shown in Figure 6(b). The dominant natural frequency of this test was about 10.5 Hz (cps).
BRIDGE B: SR-55 OVER SUWANNEE RIVER
Bridge B is located on SR-55 over the Suwannee River at Fanning Springs, Florida. The bridge consists of one-66 ft simple span and two-121 ft continuous spans. The bridge was designed for two lanes of HS20 loading. The first span (66 ft) consists of 5 AASHTO type III girders, spaced at 8'-8" while the remaining two spans consist of AASHTO type IV girders spaced at 5 ft. The instrumentation locations are at quarter span (L/4) and midspan(L/Z) for spans 131 (type III girders) and B2 ( type IV girders).
Static Test of Span B1
The static load test was performed on span 1. Figure 7 shows the load position of the testing vehicles during the static test. Figure 8 presents the midspan deflections at different loading stages during the static test. A linear relationship exists between the applied load and the measured deflection and, also, between the applied load and the measured girder strain. These results indicated maximum measured deflection and strain of 0.385 inches and 195 microstrain respectively for girder 3. Neither cracking nor other signs of distress were observed at the maximum applied load.