Page - 152 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 4 Typical reinforcing bar and anchor bar configurations The chute slab included both formed and unformed transverse contraction joints. The as-built drawing details show formed transverse contraction joints including a 19.1-cm (7.5-in) deep key, in which the downstream edge of the upstream slab overlaps the upstream edge of the downstream slab, as shown in Fig. 3. Construction records and photographs indicate that much of the chute slab was constructed using slip-form methods. Although the as-built drawings show 12.2 m (40 ft) wide by 15.2 m (50 ft) long chute slab panels, it is believed that the slip-forming used to construct the chute concrete allowed the contractor to place more than one 15.2 m (50-ft) long concrete chute slab panel at a time. It is further believed that the contractor created unformed contraction joints by cutting shallow grooves in the freshly placed concrete to initiate a crack at intermediate design joint locations within the slip-form length, rather than stopping the slip-forming operation to construct a formed contraction joint. Formed contraction joints would have been constructed at the ends of the slip-form runs. The as-built drawings show that all longitudinal contraction joints were to be keyed. The specific key configurations varied for different longitudinal contraction joints. According to the as-built drawings, all contraction joints were completed with 0.4-cm (1-in) deep by 0.098-cm (0.25-in) wide filler material, placed in a groove formed at the top of the joint, and 15.9 mm (No. 5) dowel bars at 45.7 cm (18-in) spacing were constructed across all of the chute slab formed joints (see Fig. 3). These dowel bars were embedded and bonded for a length of 45.7 cm (18 in) on one side of the joint, and were wrapped to prevent bond for 25.4 cm (10 in) on the 152