ABSTRACT
In recent years, fatigue cracks have been detected in the orthotropic steel decks of numerous highway bridges due to the repetitive loading of heavy traffic. In decks with trough ribs, almost half of all fatigue cracks originate in the weld root between the deck plate and the rib. Hence, the thickness of the deck plate and the weld quality of the rib have been improved in newly built bridges. In contrast, various countermeasures have been proposed for the decks of bridges in service. As a method applied to the upper side of the deck, the replacement of the existing asphalt pavement with steel fiver reinforced concrete (SFRC) can be conducted to improve the stiffness of the deck plate. However, this requires long hours of lane closure and good weather conditions for construction. As for methods applied to the lower side, emergency measures such as crack-stop holes and re-welding have been conducted for existing cracks; there is a great need for a permanent measure.
The authors propose a method of retrofitting existing orthotropic steel decks using plates and stud bolts, as shown in Figure 1. This method has the feature of changing the welding joint between the deck plate and the trough rib to the bolted connection; thus, the existing joints are cut to reduce the risk of crack initiation in the future. Proposed retrofit method. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig118_1.tif"/>
In this study, the slip and fatigue characteristics of the retrofitted connection are confirmed. The obtained slip coefficients are sufficient for the friction joint. The tensile fatigue strength of the fastened plate satisfies the standard strength which is defined by Japan Road Association. And the stress experienced by a full-scale steel deck specimen is investigated experimentally by a static loading test as shown in Figure 2. It is found that a large strain occurs at the deck plate and the transverse rib under the proposed retrofit method. The expansion of the bending span of the deck plate above the trough rib was considered to be the cause of the increase of the strain. A dynamic loading test for the specimen is also conducted to evaluate the durability improvement. Fatigue cracks were not observed around the weld zone of the fastened stud bolt and the transverse rib after two million repetitions of wheel loading. However, fatigue cracks are found at the weld zone of unfastened stud bolts. It is considered that insufficient fastening of the stud bolt will lead to the occurrence of fatigue cracks. Actual truck loading on the full-scale specimen. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig118_2.jpg"/>
