Case Study - Treichler's Bridge

Even though the prestressed alternate was handicapped by the variance allowing less than four steel stringers and the need to absorb design and core boring costs, all of the top ten bidders chose the concrete alternate.

Project Review

The irony is not lost on the casual observer. Less than 20 miles upstream from Bethlehem Steel on the scenic Lehigh River stands a new prestressed concrete bridge at Treichler's. Where Bethlehem Steel today remains stationed as a silent monument to Pennsylvania's once-dominant steel industry, the new river crossing at Treichler's shouts the promise of a very competitive and solution oriented prestressed concrete industry poised for the 21st century.

Built by Nyleve Bridge Corporation, of Emmaus, Pennsylvania as a contractor alternate design to the weathering steel structures originally planned and designed for this site, the Treichler's bridges speak volumes about the prestressed concrete industry's team-based approach to bridge design and construction. The sanded aesthetic and low maintenance function of each of the structure's nine spans represent the kind of cost-saving partnering and quality management that PennDoT, the bridge owner, strives for.

The alternate prestressed concrete design absorbed additional up-front costs for a new preliminary as well as final design, additional core borings, the inclusion of one extra pier for each bridge and engineering review fees. Yet, the prestressed concrete alternate design at Treichler's saved the taxpayers of Pennsylvania more than $2 million over PennDoT estimates for its steel bridge design. In fact, all of the ten low bidders on the $10.1 million project chose the prestressed concrete alternate while the five highest bids were based on the as-designed steel structure. As an added bonus, the bridge connecting northern Lehigh and Northampton counties in the foothills of the Pocono Mountains will be essentially completed six months ahead of schedule.

The story of the Treichler's Bridge begins well before bid opening with a value engineering process initiated by the prestressed concrete industry. That team exercise would ultimately prove that prestressed concrete beams were feasible for the 1,200 foot long crossings at Treichler's.

Early TS&L (type, size & location) estimates by PennDoT engineers were based on the once-traditional notion that prestressed concrete could not compete with steel in such long-span projects. Nevertheless, as the project proceeded through almost ten years of preliminary engineering, archaeological digs and final design, the prestressed industry was laying the foundation for efficiency that would allow it to win highly contested bridge projects such as this one.

Advances in concrete technology and ever-increasing concrete strengths have stretched prestressed concrete beam capabilities beyond the 150-foot lengths that would be required for this job. But longer beams would mean nothing, if they could not be produced, transported, and erected efficiently. After all the contractor selection process is, in the end, only bottom-line oriented.

Recognizing the ever-changing technologies and marketplace PennDoT had the wisdom to have a Contractor Alternate Design policy that allowed the contractor to base a bid on a team value engineered design.

So, while the prestressed concrete industry's engineers used their imagination to create a total solution using prestressed concrete beams and a newly developed proprietary precast diaphragm system, the contractor's integrated supply team sharpened the pencils. This team approach - selling solutions, not just products - brought to the table an efficient alternate design for the Treichler's Bridge that used prestressed concrete beams in place of steel girders.

Cost savings reflected in the successful bid packages were found in several additional market factors.

Simple laws of supply and demand likely affected the contractor's overall pricing for the options. Schuylkill Products, Inc., the prestressed concrete beam fabricator, assured speedy delivery and with the use of the precast diaphragms speedy erection of the superstructure. This quick delivery allowed Nyleve to devise a construction plan that saved time and money: Not only would they open the upstream structure by the November 1997 target date, they also would have the downstream twin in place at the same time, lacking only its wearing surface. It too would carry traffic as soon as the ready mix paving plants reopened the following spring. This plan beat the PennDoT target completion of the fall of 1998.

Falling market prices for high strength concrete mixes also would affect bid prices. Cost-per-yard economies, when spread over the beams, decks, piers, and foundations of the 1,200 foot twin structure, represented a significant benefit for those bidding on the alternate prestressed concrete design.

Overall concrete savings first were reflected in costs to fabricate the alternate's 75 prestressed concrete members, where a total of about 3,418 cubic yards of concrete was used. In addition, the wider top flanges of the prestressed concrete beams required smaller, less expensive deck pans, less total deck reinforcing steel and fewer yards of deck concrete to purchase and to place.

These total savings in shipping, deck steel, speed of construction as the result of using precast diaphragms, and total concrete were enough to offset the costs of engineering the prestressed concrete beam alternate design as well as the expense of the alternates' additional piers. As with any prestressed concrete beam bridge, the investment at Treichler's carries residual maintenance and environmental benefits. The brushed finish of a prestressed concrete superstructure will not flake, over time, tiny bits of rust or paint into the river far below. It does not require repainting and its associated costs for encapsulation, sandblasting and disposal. And it will not mark its piers with the running, russet stain of oxidation as it serves the public's best interests 20 miles upstream from a now silent fortress of steel.