Investigation of Settlement at Bridge Approach Slab Expansion Joint: Numerical Simulations and Model Tests (0-4147-2)

Researchers propose a new approach slab, which has a one-span slab after reviewing the existing knowledge and the existing practice, performing numerical analyses, and conducting model scale simulations. Some of the most important conclusions from the numerical analyses are listed below: 1. The presence of the abutment wall founded on piles creates a difference in settlement between the abutment wall and the embankment. 2. This differential settlement is drastically reduced in the absence of the wall. 3. The transition zone is about 40 ft with 80 percent of the maximum settlement occurring in the first 20 ft for a uniform load case. 4. The size of the sleeper slab and support slab influences the settlement of the slab when load is applied to the slab. The optimum width of both slabs is about 5 ft. The height of the embankment is influencing the settlement of the embankment. Based on the work done in this research project, the new recommended approach slab is at least 20 ft long and has one span from the abutment to the sleeper slab. It should be designed to carry the full traffic load without support on the soil except at both ends; the support slab used in the current solution is removed and the wide flange is kept on the embankment side as a temperature elongation joint. This new approach slab will simplify construction, be less expensive, and place less emphasis on the need for very good compaction close to the abutment wall. The BEST (Bridge to Embankment Simulator of Transition) device, which is a l/20th scale model of the typical transition, was used to simulate the existing approach slab and the new proposed approach slabs. The results indicate the following: 1. The proposed new approach slab (one-span) with a 20 ft simulated span length gave a smaller bump than the current two-slab approach slab. 2. The soil with the higher compaction level developed less bump at the sleeper slab than the lower compaction soil. 3. The bump size increased with the number of cycles in a straight line on a log-log plot. The maximum vertical acceleration of the simulated car was 32 mlsec2 at a velocity of 13.78 km/hr.