Structural assessment and strengthening measures for a cantilevered road deck

摘要

Starting from the investigation of the simple case of a cantilevered road deck, this paper attempts to demonstrate that deeper investigations of a structural safety problem may lead to significant modifications of the goals of the investigation. The assignment by the owner authority consisted of assessing the bending moments due to traffic loads, above all from axle loads, at the clamping of a cantilevered slab and to propose appropriate measures if needed. The slab carries the road deck, being the hard shoulder of the Swiss North-South motorway close to the Italian border. In a first step, the regular axle loads of the new Swiss action code are applied to calculate the inner forces by simple hand calculations. It is found that the shear resistance is noticeably more critical than the bending resistance, considering both the new Swiss structural concrete code as well as, for reasons of comparison, Eurocode 2. In a second step, the reduction of the axle loads is investigated considering actualised load models developed for the assessment of existing road bridges. It is found that applying these models achieves structural safety in large parts of the structure, but that other parts still exhibit insufficient structural safety. In the third part, the possible range of strengthening measures is investigated. It is pointed out that every strengthening method should be carefully checked for its application conditions and the corresponding consequences. Qualitative criteria are adequate to judge a specific strengthening method in a certain situation. The last part of the paper discusses the effectively executed measures. Conclusions on the application of the findings from the paper to other assessment situations are drawn.