Aziz Saber

Full-Scale Test of Continuity Diaphragms in Skewed Concrete Bridge Girders

Continuity diaphragms used in prestressed girder bridges on skewed bents have caused difficulties in detailing and construction. The results of the field verification for the effectiveness of continuity diaphragms for skewed, continuous, and prestressed concrete girder bridges are presented. The current design concept and bridge parameters that were considered include skew angle and the ratio of beam spacing to span (aspect ratio). A prestressed concrete bridge with continuity diaphragms and a skewed angle of 48° was selected for full-scale test by a team of engineers from Louisiana Department of Transportation and Development and the Federal Highway Administration. The live load tests performed with a comprehensive instrumentation plan provided a fundamental understanding of the load transfer mechanism through these diaphragms. The findings indicated that the effects of the continuity diaphragms were negligible and they can be eliminated. The superstructure of the bridge could be designed with link slab....

Impact of Higher Truck Loads on Remaining Safe Life of Louisiana Bridge Decks

Evaluation of the load capacity of existing bridge decks is a major concern for the Louisiana Department of Transportation and Development. Available funds must be expended in a rational strategy, which would allow for inspection, maintenance or rehabilitation. This paper presents the results of the study on the proposed higher truck loads and their economic impact to the state and to the industry. The impact of adapting such regulations on the existing Louisiana bridge decks is determined based on a deterministic load capacity evaluation as well as a reliability assessment. The target reliability level is derived from bridge deck structures designed to satisfy AASHTO standard design specifications and to satisfy safe and adequate performance levels. Fatigue analyses are performed using finite element modeling with detailed load capacity evaluations and reliability analyses on a representative sample of bridge decks to provide specific examples of expected changes in rating and safety levels.

Stability of Long-Span Pretensioned High-Performance Concrete Girders

Development of high performance concrete has increased the span length of given size precast prestressed girders up to 40 percent. While the designer’s main concerns were the safety and stability of the bridge once construction was completed, attention should also be given to the temporary stresses and stability of these precast girders during handling and erection along with girder stability during bridge deck construction. Bulb-tee, NU (developed by the University of Nebraska) and AASHTO sections were considered. The effects of intermediate diaphragms on the behavior of long span prestressed high performance concrete girder bridges were evaluated using finite element analysis. The limit on diaphragm spacing as stated in AASHTO were found to be conservative. Different methods to improve the lifting spans of long high performance concrete girders were also recommended. The outcome of this research will expedite and help assure safety in the construction of high performance concrete long-span girders.