Prefabricated Steel Bridge Systems: Final Report
The main objective of the present study was to identify and assess the use of new and innovative prefabricated steel bridge systems/elements and methods in bridge construction, rehabilitation and replacement. To this end, the study was divided into three phases: (i) the background and knowledge building phase, (ii) the concept development phase, and (iii) the optimization phase.
In the first phase, a literature review was first performed on the history of steel bridges. The current practice and applications of prefabricated systems were then discussed, including innovations that are currently being implemented, as well as several designs schemes that are still in the experimental phase of development. Review and synthesis of such an endeavor led to identification of problems hindering the wide spread use of these systems for accelerated bridge construction and developing possible enhancements by establishing the minimum system requirements (criteria) for rapid construction. It was found that in order to become competitive with "in-place construction" of steel and/or concrete bridges, prefabricated systems must aesthetics acceptable and provide benefits such as:
- Cost Effectiveness / Standardization
- Faster Installation
- Design Flexibility
- Easy Handling and Transportation of Components
- Reduced Superstructure Depth
- Greater Durability
- Reduced Maintenance
In the second phase of the study, two steel bridge concepts are developed and detailed, using innovative prefabrication and construction techniques. Both concepts are based on modular units made of steel girders and concrete deck. The first concept is made of all-prefabricated system including the deck slab, whereas the second is made of prefabricated steel girder system and cast-in-place concrete deck. These two concepts, in addition to adhering to the rapid construction philosophy, address the current needs, including system adaptability, connection details between components, use of innovative materials, standardization of components, design and construction specifications, transportation weight and size limits, and limits to standard erection cranes and equipment.
In the third (optimization) phase, the two concepts were optimized using Genetic Algorithms (GA) and Surrogate Based Optimization (SBO) techniques taking into account objective constraints such as weight limitation due to transportation, and LRFD code requirements. In particular, the optimization was implemented to study the effects of the following parameters: span length, slab thickness, concrete strength, and concrete type (light weight versus normal weight). Performance and Cost analyses were also carried out to compare between systems and assess the influence of the different parameters on cost.
Finally, the main findings of the study are presented, followed by recommendations for future research work.