| For several years, the most common application of high-performance concrete (HPC) has been in the building industry where concrete strengths of 100 MPa and more have been frequently used in the lower columns of high-rise buildings. In comparison, strengths of about 60 MPa have been considered the maximum achievable in the precast, prestressed concrete industry; this appears to be very timid especially considering that several research studies have indicated that the potential advantages from the utilization of HPC with its increased strength and improved durability for precast, prestressed concrete highway bridges are quite promising. In spite of this, there is still some disagreement within the industry that HPC is beneficial. The misconception that the benefits of the material do not justify its higher cost and the increased quality control requirements associated with its production seems to deter most designers and precast concrete producers from exploiting it. The use of HPC in bridges is unlikely to advance quickly without a clear economic incentive for precasters to utilize the material widely. This study is intended to help provide such an incentive.; The overall objective of the study is to assess the potential economic benefits from the utilization of concretes with compressive strengths of up to about 100 MPa for continuous, precast, pretensioned I-girder highway bridges. These were chosen because they represent the most common type of precast, prestressed concrete bridges constructed in North America. The problem is formulated as an optimal design problem. Refined computer-oriented structural analysis methods combined with modern computational design optimization techniques are used to develop an optimization system that is utilized to perform extensive economic studies on this type of bridges. The results of these studies are presented, interpreted and discussed. It is shown that the cost savings with HPC can far outweigh its additional material and production costs, particularly for the longer span bridges. Sensitivity analyses of the obtained results with respect to the major assumptions made in developing the optimization system are performed. These analyses suggest that the findings of this study are applicable to a wide range of practical values surrounding those assumed. |
