Temperature Effects On Box Bridge Caused By Hot Asphalt Mixture During Paving

The duration of paving hot asphalt mixture(HMA) on bridge is relatively short, it raises conscerns of negative effects of strain/stress that will be big enough to cause cracks on deck, web, roof and its flange of girders, especially of continuous bridges. In the project, a laboratory study was conducted to understand the temperature effects of HMA during paving on the beidget girder. A standard concrete box model girder of 2 meters long and1.2 meters wide was made at a scale of 1:2 in the laboratory. 117 concrete strain gauges, steel bar strain gauges and 120 temperature sensors were embedded in the reinforced concrete box girder. Stone Matrix Asphalt(SMA) layer of 4 cm was paved on the deck of concrete grider at 155℃. The distribution of the temperature and strain were collected on the deck, flange, web and its roof at different time after paving.This research made the following conclutions:(1)The temperature distribution curve along the height of the girder is roughly in hyperbolic shape. At the most unfavorable condition, temperature T1 is 38 ℃ on the top of the deck. The turning point is 16 cm from the top of the deck. The temperature in the roof is 0 ℃;(2) The most unfavorable condition was found at 50 minutes after paving the HMA. The strain distribution along the height of the girder is in a curve. The maximum tensile strain is-127.6uε, which appeared at 16 cm to the top of roof. Mostly a compressive strain in the deck was observed on the roof. The maximum compressive strain is 240uε. Tensile strain in the web, and compressive strain in the floor were observed;(3) The strain distribution of the girder is similar to that in(2). The corresponding maximum tensile stress is-2.80 MPa, and the maximum compressive stress is 5.27 Mpa.