About the research
Given their advantages over conventional construction techniques, Accelerated Bridge Construction (ABC) methods have been increasingly used not only for the rehabilitation/replacement of existing structures but also for the construction of new structures. Such methods can greatly reduce on-site construction time, improve safety of the traveling public and workers, improve bridge components quality, and enhance durability and longevity of the overall bridge structure. As a result, several Departments of Transportation (DOTs) have successfully developed and implemented ABC procedures for superstructures and to some extent for substructure systems when rehabilitating or replacing structurally deficient or functionally obsolete bridges.
Attempts at implementing ABC techniques for abutments in past projects by the California DOT (Caltrans) have been challenging. In a typical ABC methodology, the abutment is cast in pieces at a precast yard, transported to the project site and assembled using adequately detailed connections that generally require cast-in-place concrete closure pour. Limits imposed on individual precast pieces by the size and weight restrictions of the transportation routes and lifting equipment commonly available at project sites result in the need for several precast pieces and associated connections to achieve standard abutment sizes used in California. As a result, longer on-site construction time is required to connect the pieces, which negates some of the benefits associated with precast construction.
Moreover, the development of ABC for substructure systems, especially abutments, requires careful consideration of seismic performance and Soil-Foundation-Structure interaction (SFSI). In the current design philosophy, the abutment shear keys and backwall are frequently used seat-type abutments are sacrificial elements and part of the bridge energy dissipation system. They are designed to provide longitudinal and transverse resistance under service loads and small to moderate earthquakes, but fail under design level seismic events in order to limit the forces experienced by the abutment and its foundation elements. It is therefore important that the ABC methodology be developed to meet this design criterion and that the expected performance be verified through a comprehensive experimental testing.
To overcome the aforementioned challenges, this research aims to develop an improved ABC technique for abutments that will utilize hollow core prefabricated elements, which can be filled with concrete on-site to complete the system. The use of more efficient materials such as high strength concrete (HSC), ultra high-performance concrete (UHPC), and fiber reinforced polymer (FRP) will be investigated to increase the size of individual elements while minimizing their weights in order to facilitate transportation and assembly of the abutment system. In addition, any delays associated with curing of onsite concrete or grout will be minimized by using rapid set materials and/or temporary hardware that can be mounted to the prefabricated elements. The PI of the project has significant expertise in developing ABC techniques to successfully achieve the goal of the research.
The main objectives of this research include:
- Developing a cost-effective and lightweight prefabricated bridge abutment modular system that consists of light weight prefabricated hollow elements (shells) made from HSC, UHPC, and/or FRP that are infilled with concrete to form a complete abutment
- Developing simple and reliable details for the shell-to-footing, shell-to-pile, and shell-to-wingwall connections that minimize on-site working days, construction challenges and delays, and ensure adequate seismic performance of the overall system
- Developing analysis techniques that can quantify the expected performance of the abutment system with consideration of the developed connection details
- Verifying the performance of the system and its connections under service and seismic loading through scaled testing in real world conditions that will account for soil-abutment-pile interaction effects
- Developing construction techniques for quickly constructing abutments using the new concrete-filled shell system