Shear and disturbed regions in high performance concrete bridges

Based on the extensive literature review, parametric study and four full-scale 23.8 m (78 ft) long NU-1100 I-beams with a composite deck slab shear testing results, the following conclusions can be made on shear. (1) An integrated and simplified shear design model has been developed. It has been found that the proposed model results in a much simpler design without sacrificing the shear capacity of the prestressed concrete members and without significantly impacting the cost. (2) For properly detailed prestressed concrete bridge I-beams, one can approach $\rm 0.25f\sbsp{c}{\prime}bd\sb{v}$ for maximum shear reinforcement. A key factor is the anchorage of the longitudinal reinforcement. (3) The horizontal wires of the orthogonal welded wire fabric have been found to be extremely effective to control shear cracking and increase the shear capacity. Based on the strut-and-tie model analysis and eight 3.1 m (10 ft) long NU-1100 post-tensioned I-beams testing, the following conclusions are made on post-tensioned anchorage zone. (1) Two optimized anchorage zone details have been developed. The reduced tapered anchorage zone details are recommended to be used for all sizes of the NU I-beams. (2) Modification of the current available I-beam forms is not needed except an additional small form of about 1.0 m (3.3 ft) long. (3) Reinforcement in the anchorage zone is designed to resist post-tensioning bursting force in combination with vertical shear. Based on the analysis and three 12.2 m (40 ft) long NU-1100 I-beams with 203 mm (8.0 in.) deck slab testing, the following conclusions are made on beam continuity for negative moment. (1) Making the beams continuous before casting the deck can increase the span capacity and help increasing the composite action between the deck slab and the beam. (2) The continuity method using Grade 634 MPa (92 ksi) threaded rods has been developed. The developed connection details have performed well and are recommended as a standard non-prestressing beam continuity method. (3) The bulky bottom flange of the NU I-beam has been found to have at least 1.51 times the designed ultimate negative moment capacity