sponse will also be compared with selected field observations and these may be used to improve on or calibrate the analytical models of the test structure. This calibrated model can then be used to investigate a broader range of wind and geometric conditions. Preliminary testing Data from one short-term field monitoring test is presented in this section. In Figure 3 a downstream view of the I235 Euclid test structure is shown as a large truck passes under the instrumented truss and DMS cabinet during testing. The Euclid test structure has a span of 21.0 m between support centerlines. The truss is 1.50 m wide and varies in height from 1.80 m at the supports to 2.40 m at mid span (measured center to center of chords). The truss was fabricated is two symmetric segments. The main top and bottom chords were fabricated from 152 mm diameter by 7.9 mm thick circular hollow welded aluminum tubes. Major web struts were fabricated from 76.0 mm diameter by 7.9 mm thick circular hollow welded aluminum tubes. The total height of the steel support frames are 8.55 m at the shoulder and 7.60 m at the median. The support frames are 2.0 m wide and are fabricated from 254 mm diameter STD. steel pipe. Web struts are fabricated from 76 mm diameter STD steel pipe. The structure has a near east-west orientation. The 8.0 m wide by 1.50 m high by 1.0 m deep DMS cabinet is mounted to the truss structure with a slight offset to the median support. All major structural elements are of welded construction. Field instrumentation setup The field monitoring period for the Euclid test was accomplished over a three day period. Installation and tear down of instrumentation was done at night using moving lane closures during the first and third test day. The second test day was used to collect multiple response time windows that were associated with varying combinations of passing vehicle traffic plus quite periods to measure ambient response to background wind conditions. . The instrumentation setup for the Euclid test was made up of 47 data channels that included a common time channel, two DMS panel pressure gage channels, wind speed and direction channels, 36 dynamic strain channels that were configured in paired orientations to measure average and bending stains in individual components, and 6 acceleration channels that were configured in pairs to measure horizontal, vertical, and transverse combinations of the global acceleration response of the structure. All channels were synchronously sampled at 250 Hz using triggered time window of approximately eight seconds that included a pre-event buffer period. Dynamic strain measurements were recorded using BDI full-bridge strain transducers. In Figure 4 gage installations on the two east support columns of the Euclid structure are shown. Each BDI gage in the photograph uses an active full-bridge gage configuration to measure average longitudinal dynamic strain over a 76 mm gage length. Paired strain gage installations on the two lower truss chords and on a transverse strut are shown in Figure 5. Also shown in Figure 5 is the bi-axial accelerometer installation on the lower south chord near mid span. Fig 3 Truck in lane 2 passing under Euclid 4-chord arched support structure during short term field test Fig 4 View of strain instrumentation attached near the base of the two steel support columns on the shoulder or east end of the structure. Note the use of 4 gage configuration for bi-axial measurements. BDI 76 mm single axis strain gage 414
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