ABSTRACT
Orthotropic steel decks with closed ribs (trough ribs) have been widely used in suspended bridges, cable-stayed bridges, or urban viaducts. In Japan, however, numerous orthotropic steel decks are suffering from the initiation of fatigue cracks. In these, the root-deck cracks shown in Fig. 1 are one of the most serious fatigue damages that can happen in orthotropic steel bridges. So far, there is no effective method to improve fatigue strength of weld root between orthotropic steel decks and trough ribs as an after-construction procedure. One reason for this is because the fatigue cracks tend to initiate inside the closed ribs and they are difficult to find out. Deck through crack from the weld root. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig115_1.tif"/>
In this study, the authors propose one technique to improve the fatigue strength of weld root between orthotropic steel deck and trough rib. The technique is conducted with the peening at the weld toe outside trough rib. Namely, this technique can be applied from outside the closed ribs. The residual compressive stress will be introduced to the weld root inside the closed rib by peening from outside the closed rib. Therefore, the purpose of this study is to investigate the effect on fatigue strength improvement of weld root between orthotropic steel deck and trough rib by peening from outside the trough rib.
Test specimen used in this study, which simulates the welding between deck plate and trough rib, is shown in Fig. 2. In this figure, the peening procedure is also indicated. Two lines near the weld toe are peened one after another. Plate bending fatigue tests were carried out with the specimen. Test specimen and peening procedure. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig115_2.tif"/>
Fatigue test results are shown in Fig. 3 with the fatigue strength classified by JSSC. As can be seen in this figure, the fatigue life of the peened Specimen P is about 4 times longer than that of the as-welded Specimen AW. Therefore, it might be possible to improve fatigue strength of weld root in orthotropic steel deck by peening from outside the closed trough rib. Fatigue test result in S-N diagram. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig115_3.tif"/>
