|Principal Investigator: ||Rigoberto Burgueño, Ph.D.|
|Research Assistant: ||Pimpida (Grace) Surakomol, P.E.|
|Period: ||May 2001 – Present|
Longitudinal splicing of precast/prestressed (pc/ps) girder bridges has recently gained increasing support as an effective method to increase the spanning capabilities of pc/ps concrete bridges, typically limited to shorter lengths due to transportation limits. The concept has thus gained the support of several highway agencies as an alternative to steel plate girder designs. However, the modifications typically required for "pier" or "negative" spans over intermediate supports and the intricate interdependence of system design parameters, particularly splice location and construction staging, can limit the economic advantage of spliced girder construction. The objective of this research work is to implement multi-objective structural optimization algorithms for the optimization of spliced pc/ps girder bridges. The specific aims is to implement a of a multi-objective design optimization approach to (i) develop optimal component and system designs for different construction procedures, (ii) investigate optimal construction sequences for maximum efficiency, (iii) development of optimal pier segments for continuous systems, and (iv) develop design recommendations and aids for spliced girder bridge design based on optimized results.
|Figure 1. Multi-Span Spliced Girder Bridge and Custom Pier Segment|
A multi-objective optimization procedure is currently under development to achieve the above-mentioned research goals. The procedure is being developed within the Matlab software utilizing gradient-based optimization algorithms in combination with custom routines for analysis of the bridge system. Multi-objective functions under consideration include a) economics (i.e., minimum costs due to materials, construction, etc.), b) geometric requirements (including superstructure depth, clearances, and aesthetic quality), and c) optimal performance (reserved capacity, deformations, dynamic response, etc.). The bridge system analysis will consider staged construction and time-dependent material effects. Constraints for the optimization procedure consist mainly on stress limits for serviceability and allowable stress design, as well as ultimate capacities according to the load-resistance-factor-design method. The optimized results will be used to create design examples and design aids (i.e., charts and tables).
|Figure 2. Components of a Spliced Precast/Prestressed Concrete Girder Bridge System|
Preliminary studies considering only one construction method have shown that a spans of 210 ft are feasible for Michigan DOT 1800 mm deep I-girders in a three-segment single-span arrangement, while 300 ft spans are feasible for two-span continuous systems composed of two positive segments and a pier segment.
Increasing the spanning capabilities of precast/prestressed concrete bridges is expected to have a large impact in reducing the bidding cost of current superstructure options for medium span bridges as it will provide a competitive alternative to steel solutions. With optimized design examples, charts, and tables developed from this research, designers and owners will feel more comfortable to use and select SGB system as an option for their projects, which should gradually lead to their increased use in the design of highway bridges. Optimized details of spliced girder design and construction will allow achievement of the technical and economical benefits of this efficient bridge system.