ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306198
The historic 70-ft-long Big Chickies Bridge over Big Chiques Creek in Lancaster, Pa., was replaced with a precast concrete tied-through- arch bridge that replicated the appearance of the original while upgrading the design to current loading, flooding, sight, and safety requirements. 46 | ASPIRE , Winter 2010 S TAT E P ennsylvania has a long history of building precast, prestressed concrete bridges, going back to the first structures to use that concept beginning in the late 1940s. Today, a high percentage of the state's bridges continue to be constructed from prestressed concrete. That total has jumped substantially in recent years, led by the passionate support for infrastructure improvements directed by Governor Edward G. Rendell. The Keystone State has a large number of bridges, but a high percentage of them are less than 100 ft long, owing to the state's rugged terrain and many streams and rivers. Some of them also have deteriorated from long service and a gap that was growing between the need for maintenance and the capabilities to fund that work. Most projects fall into the category of "Bridge Rehabilitation or Replacement," which encompasses everything from repairs to the existing structure to building a completely new bridge. The other categories of projects comprise "Bridge Preservation" and "Bridge Maintenance." Funding for bridge projects took a dramatic leap in 2008 with Governor Rendell's Rebuild Pennsylvania initiative. Bridges benefit from those efforts through the Accelerated Bridge Program (ABP) portion. The goal is to repair or replace 1145 structurally deficient bridges over a 3-year period. The Pennsylvania Department of Transportation (PennDOT) exceeded its first- year goal of 411 bridges by opening bids on 470 contracts by June 30, 2009. In addition to the ABP bridges, PennDOT is working toward awarding contracts to fix 105 structurally deficient bridges with federal money from the American Recovery and Reinvestment Act (ARRA). Contract spending for bridges also has been rising, from $259 million in 2002 to $787 million in 2008. For fiscal year 2009, thanks to these additional funding sources, contract spending is expected to reach nearly $1 billion. In fact, the state has finally turned the corner on the backlog of bridge maintenance needs. In March, for the first time in memory, the number of structurally deficient bridges in the state declined, from 6034 to 5911. As of last September, the number had been lowered further to 5846. Concrete Bridges Dominate Most of the bridges—as many as 90%— will be constructed using concrete materials. Prestressed concrete I-beams and box beams are the most common solutions, primarily because of the excellence of precast concrete fabricators in the area who can supply the necessar y components on a fast response and competitive basis. Many projects in Pennsylvania have presented challenges to designers and fabricators alike. Even small projects can create unique designs. A typical example is the Big Chickies No. 2 Bridge on Auction Road (T-875) over Big Chiques Creek in Lancaster, Pa. The historic concrete tied-arch bridge had degraded, lowering the maximum allowable load. Maintaining the aesthetics and contextual sensitivity for the 1920s structure, while upgrading to meet new loading, flooding, sight, and safety constraints, were key concerns. These were exacerbated by the need to widen the Pennsylvania by Tom Macioce, Pennsylvania Department of Transportation Infrastructure Focus and Close Relationships Work in ASPIRE_Winter10.indb 46 12/18/09 2:30:37 PM