In July 1979, field tests were conducted on the Fremont Bridge on the Willamette River in Oregon to obtain strain and temperature measurements that would provide information on in situ and service load stress conditions. The behavior of the bridge was more dependent on temperature than on traffic. On a hot day when the temperature reached 100 F, the temperature differential between the exposed top and shaded bottom flange plates was 50 F. The maximum daily stress range in the tie girders due to the temperature differential was about 10 ksi. Where local bending occurred in the web plates, the maximum daily stress range was about 20 ksi. Comparison of strain readings on two days of comparable temperature, with light and heavy traffic, indicated that the stress range due to traffic was about 1-2 ksi. Dynamic recordings of strain were made at 12 selected category E details during typical traffic conditions. The passage of heavy vehicles typically caused stress ranges up to 1000 psi. The largest measured stress range of about 3000 psi was associated with the passage of a heavy mobile crane. The frequency of these stress ranges was estimated to be about 50 percent of the average daily truck traffic of 5400 vehicles. The bridge was also subjected to a controlled loading of four heavy vehicles weighing a total of 177 100 lb. The maximum stress range occurring on an instrumented cross section near the junction of the arch rib and tie girder was 750 psi. The maximum stress range at any other instrumented location was 2150 psi.

A comprehensive postconstruction evaluation study of the Fremont Bridge on the Willamette River in Oregon (ll was conducted for the Oregon State Highway Division (OSHD). The purpose of this study was to assess the long-range performance of main loadcarrying, nonredundant tensile members and components of the structure.