Majority of substandard bridges needing replacement are under 100 ft. long and are simple spans. FSPGBS provide an economical short span steel bridge alternative for bridges less than 60 ft. long. The feedback from contractors and consultant is that developing modified version of FSPGBS, with maximum span lengths approaching 100 ft. will significantly help the bridge industry. In fact, inspection of U.S. bridge inventory indicates that majority of substandard bridges are less than 100 ft. long and are simple spans. FSPGBS have many advantages for both steel fabricators and bridge owners. Folded plate girders suitable for different span lengths differ only by their cross-sectional dimensions. The different top and bottom flange widths and web depth can easily be accommodated by changing the bend locations so fabricators can build folded girders very quickly while only stocking two plate thicknesses (1/2 and 3/8 inches).
The shape of the cross section for the FSPGBS has several key advantages in its design and construction. Following are brief descriptions of some of the advantages. The inverted tub shape produces a very stable bridge girder configuration that does not require internal or external cross frames for either local or global stability. A typical box section needs top lateral bracing, during construction and during replacement of deck. The FSPGBS does not internal or external bracing, which has proven to cause many fatigue cracking challenges. Casting the deck on top of folded plate girder could use conventional construction equipment and practices, if needed. The top flange of the folded plate girder is wide enough (about 25 in. to 35 in.) to serve as a work platform. Because of the torsional stiffness of the folded plate girder, there is no need for providing internal or external bracing during construction. Perhaps the major advantage of FSPGBS over tub or box bridges, is the opening from the bottom side that allows easy inspection of the girder and prevents accumulation of moisture. For longer span bridges the depth of a closed box is large enough to enter inside and inspect and clean if needed. Hot Dip Galvanizing the FSPGBS is a very good option for corrosion protection. Hot dip galvanizing can provide more than 75 years of service life at a very economical cost. Typical cost of hot dip galvanizing ranges between 18 to 22 cents per pound of steel.
The main objective of the proposed project is to develop improved version of FSPGBS, suitable for ABC and maximum span lengths, exceeding 100 ft, with allowance for incorporating camber.
The following sections describe the work plan in detail.
- Task 1- Developing Ideas for Extending the Maximum Length of FSPGBS to more than 100 ft. with capability to Incorporate Camber if needed: The main approach to extend the maximum length of FSPGBS to more than 60 ft will be in the form of developing a splice detail that could be used to connect segments of the folded plate girders with maximum lengths of 60 ft.
- Task 2 – Conducting Non-Linear Finite Element Analysis to Comprehend Performance of Splice Connection: The first step in the research project, following envisioning the connection detail, will be to carry out parametric studies using non-linear finite element analysis to fully comprehend the behavior and force transfer mechanism for the splice connection detail.
- Task 3 – Experimental Test: Following completion of numerical work and finalizing the connection detail, an experimental work will be carried out to verify the adequacy of splice connection design and detail.
- Task 4 – Development of Design Provisions: Using the results of numerical and experimental work, complete design provisions for the splice connection and other aspects of FSPGBS will be developed.
- Task 5 – Development of ABC-UTC Guidelines for FSPGBS: The project deliverable will be in the form of all the essential information that bridge owners and designers will need to utilize FSPGBS in practice.
Principal Investigators: Dr. Atorod Azizinamini