‘Stan Span’ Hits Home Run Over Mississippi River

August 2014 » Exclusive
Unaffordable $541 million bridge design transformed into a $230 million cable-stayed structure.
Randy Hitt and Hans Hutton, P.E., S.E.
The cable-stayed design features two, 400-foot-tall delta-shaped towers. Photo: © Debbie Franke 2014, courtesy HNTB

Stanley Frank Musial, one of the greatest hitters in baseball history, was known to St. Louis Cardinals fans as “Stan the Man.” Now, those fans have an enduring symbol in which to honor their hero. The new Stan Musial Veterans Memorial Bridge sails over the Mississippi River like one of his trademark home runs and is affectionately nicknamed the “Stan Span.” Like its namesake, the bridge is a record-holder. The 2,772-foot-long, three-span unit has a main span of 1,500 feet, making it the third-largest cable-stayed span in the country.

At an overall bridge length of nearly 1.2 miles including approaches, the cable-stayed unit design features two, 400-foot delta-shaped towers and four lanes that carry 55,000 vehicles per day. The 6,500 feet of total bridge structure include concrete girders on the Missouri approach and steel plate girders on the Illinois approach that fly over 21 railroad tracks overseen by four railroad companies.

Successful delivery of the project was made even sweeter by the fact that it was a bi-state effort. The main span and the two approaching spans were jointly funded by the Missouri Department of Transportation and the Illinois Department of Transportation. It is the first bridge to be built in 40 years between downtown St. Louis and St. Clair County, Ill.

The Stan Span relieves traffic on nearby bridges, primarily the Congressman William “Bill Clay Sr. Bridge. That bridge was the only urban interstate bridge between Illinois and Missouri and one of only two bridges in the United States that carries three interstates — I-55, I-64, and I-70. The new bridge allowed the DOTs to realign and reconstruct portions of I-70 and numerous load roads on both sides of the state line, resulting in less congestion, reduced fuel consumption, and fewer accidents.

Effort is nearly scrapped

In Roads & Bridges’ 2012 Top Bridges List, the cable-stayed structure ranked fourth, a far cry from seven years earlier, when the project was nearly scrapped. A previous concept for the bridge resulted in a project costing nearly $2 billion. Right-sizing the original design, which featured eight lanes and a 2,000-foot main span, required MoDOT (the lead agency), IDOT, and HNTB (lead designer) to identify what was essential to the project and pare away the rest.

The resulting bi-state agreement set boundaries. For example, U.S. Coast Guard restrictions required a 1,500-foot main span and the most economical bridge type for that span length was the cable-stayed bridge. The agreement also identified pier locations and set lane requirements at two in each direction, with the ability to restripe to three lanes on each side. Once the agreement was signed in February 2008, the project moved forward rapidly.

The 2,772-foot-long, three-span unit has a main span of 1,500 feet, making it the third-largest cable-stayed span in the country. Photo: © Debbie Franke 2014, courtesy HNTB

Redesigned in 11 months

HNTB began design in July 2008, relying heavily on its experience to accelerate the process. With recent projects that include the Huey P. Long Bridge in Louisiana, the cable-stayed bridge in Cape Girardeau, Mo., and the cable-stayed bridge in Greenville, Miss., HNTB had more Mississippi River bridge experience than any other firm in the country. Combining its deep understanding of the effects of wind, river currents, and soil on Mississippi River bridges with its well-respected cable-stayed bridge work, the firm produced a landmark design in 11 months and had reduced the price to $230 million.

Through much coordination with both states, HNTB’s trimmer design featured four lanes with full shoulders, the required 1,500-foot main span, and additional width and load capacity to handle two more lanes by restriping. And, if the time comes when traffic volumes exceed capacity, the bridge is designed to accommodate an adjacent, companion structure.

The redesign was supported across two states, meeting the goals and budgets of each agency while fulfilling the public’s expectations.

Unorthodox seismic analysis

One of the keys to shrinking the project’s size and price tag was HNTB’s approach to seismic analysis. Drawing from the expertise of top researchers at the University of Illinois and the University of California-Berkeley, the firm applied the conditional mean spectrum approach to seismic analysis. The conditional mean spectrum considered the most expected (or mean) response spectrum, conditioned on the occurrence of a target spectral acceleration value at the period of interest for the most likely scenario of potential earthquakes in the region.

Until the Stan Musial Veterans Memorial Bridge project, the conditional mean spectrum had been used on buildings, mainly in California — never on a bridge — but the analysis has evolved. The project team, with the Federal Highway Administration’s permission, felt confident the conditional mean spectrum would provide a more realistic picture of demands on the structural system than the aggregated design spectrum typically used on highway bridges.

They were right. The application stripped away unnecessary conservatism and helped HNTB produce a more economical design by reducing the bridge’s seismic loading, the size of its structural components, and the amount of rebar needed. It also eliminated a costly ground improvement program anticipated under the original design.

Alternative technical concepts

In an attempt to further reduce the project cost, MoDOT implemented an innovative contracting method known as alternative technical concepts (ATC). ATCs are suggested changes to the baseline design submitted confidentially by prequalified contractors. Proposed changes provide a solution that is equal to or better than the requirements in the request for proposals. If the alternative technical concept is acceptable to both owners, the concept could be incorporated as part of the proposing team’s technical and price submittal.

Cost-Saving Plays

  • MoDOT selected experienced, professional, capable project members, who worked well together.
  • Key team members co-located to produce the design faster and beat the $1.2 million in monthly inflation costs.
  • The team had decision-making authority, giving it the ability to sidestep layers of bureaucracy.
  • Team members created a risk registry and reviewed it every week to ensure they were focusing on aspects most critical to successful delivery.
  • MoDOT let the main span and the approaches as three separate projects so the main span — the critical path to timely delivery — could go under construction as quickly as possible.
  • Steel anchor boxes eliminated the need for complex forming of concrete inside the bridge’s delta-shaped pylon legs.
  • The bridge’s structural elements are made of weathering steel, which has a 100-year design life and saves the cost of maintenance, materials, and interruption to traffic.

Part of HNTB’s contract was to guide MoDOT in developing an ATC process and then assist the two short-listed contractors in evolving their concepts. In November 2009, the project was awarded to the joint venture of Massman Construction, Traylor Brothers, and Alberici Constructors. By leveraging equipment to install larger-diameter drilled shafts, and thus reducing the number of drilled shafts, the contractor was able to efficiently utilize equipment that it already possessed.

The contractor also proposed load testing the shafts during construction to ensure the rock sockets were only as deep as necessary for the soil conditions. As a result, the project set a world record for load testing at 36,000 tons without the failure of the test shaft.

Adopting the ATC approach, MoDOT and IDOT were able to achieve the cost savings of a design-build job without using design-build procurement. The alterative contracting method heightened competition, introduced efficiency at the most appropriate time in the design process, and optimized constructability.

The project marks the first completed design-bid-build ATC in the United States and MoDOT’s first application on a large-scale design-bid-build project. The DOT plans to use the method again.

Like its namesake, construction of the Stan Musial Veterans Memorial Bridge drew crowds. Demand for public tours offered on the construction project outpaced available slots. In addition, many stakeholders in the community were quoted in various publications, praising the project for its iconic nature and seamless delivery:

  • “It’s been fun to watch …”
  • “It’s a beautiful structure. It’s cool to see the merging of engineering and aesthetics.”
  • “It’s exciting to see these projects that are still getting done.”

A smooth construction process delivered the project on time and on budget with minimal change orders, reflecting the high quality of the design plans for such a complex structure. The Stan Musial Veterans Memorial Bridge opened to traffic on Feb. 9, 2014, nearly one year after Musial’s death at age 92. It received the International Bridge Conference’s George S. Richardson Medal, presented for a single, recent outstanding achievement in bridge engineering.

Randy Hitt, project director for the Missouri Department of Transportation, oversaw delivery of the Stan Musial Veterans Memorial Bridge. During his 26-year career, he has been involved in the construction of 14 major river crossings. Contact him at randy.hitt@modot.mo.gov. Hans Hutton, P.E., S.E., HNTB Corp. engineer of record for the Stan Musial Veterans Memorial Bridge project, is chief engineer of the firm’s Kansas City bridge department. Contact him at hhutton@hntb.com.


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