For more than half a century, the Paseo Bridge over the Missouri River has linked Kansas City, Mo.’s downtown with the city’s northland, carrying more than 100,000 vehicles each day. Even before the structure — which is the longest self-anchored suspension bridge in North America — suffered a structural failure that forced its closure for emergency repairs in 2003, the Missouri Department of Transportation (MoDOT) had conducted a major investment study that confirmed the bridge’s structural obsolescence, as well as the need for a new structure that could accommodate the city’s traffic growth.
Considering either a major overhaul or a replacement, MoDOT hired HNTB to conduct an environmental impact study (EIS) that began in April 2004, “in case future funding came along,” said MoDOT project director Brian Kidwell. Even at this early stage, MoDOT knew it wanted considerable project flexibility, a fact that required HNTB to craft the EIS looking at how the project might affect the environment and people without restricting options for proposers if the project were to become a reality.
Just seven months after the EIS began, Missouri voters approved Amendment 3, which provided MoDOT with funding for several major bond-financed projects. A statewide priority-setting process unfolded quickly, designating the Paseo Bridge as the highest-ranking unfunded project and allocating $195 million for its replacement.
The existing Paseo Bridge, which was designed by HNTB in the 1950s, is a Kansas City landmark, and therefore the community wanted to replace it with another signature span — an implausible option with the original funding amount alone. Soon after, a supplemental $50 million legislative earmark, secured with the help of Missouri Senator Christopher Bond, allowed the project to move forward with improvements to the I-35/I-29 corridor, plus the construction of a signature span.
At the same time, MoDOT also had received authority for three pilot design-build projects — a process that had never been used in Missouri. HNTB had been hired as the general engineering consultant for the first of those projects — reconstruction of I-64 near St. Louis. The Paseo Bridge replacement — dubbed kcICON — for which HNTB was selected to provide program management assistance, would be MoDOT’s second design-build effort.
Maximizing innovation “We wanted to create a new model for design-build,” Kidwell said. “Instead of telling proposers what we wanted them to build and then asking how cheaply and quickly they could build it, we wanted a non-prescriptive, fixed-price, best-value approach.”
With a design-build vision in mind, MoDOT looked to outside consultants to help implement a new, innovative approach for project delivery. That team, which was led by David Downs, the current program management professional services leader for HNTB, helped develop the design-build procurement process in place today. (See an outline of MoDOT’s new design-build procurement process.)
MoDOT’s approach to design-build was immediately put to the test. “The funding was in place and there were hurry-up desires from leadership and the community,” Kidwell said. “We worked with HNTB to get the project off the ground because they were so familiar with the pieces and parts of this corridor, and already were so active in the EIS process. We wrote a broad, all-encompassing, on-call contract to tap into HNTB’s expertise for anything we might need on the project. It was hard to project what we’d get into, since we hadn’t done it before, but HNTB’s size, experts, and desire to partner with MoDOT on this new model made it a great fit.”
Using the EIS and values from a community advisory group that represented both sides of the river, and without defining what the completed bridge would entail, the following goals were set to guide the design-build process:
“MoDOT’s approach had never been done before, anywhere,” said HNTB Project Manager Rachel Lunceford. “MoDOT had nowhere near the dollars needed to build the desired project, but asked the industry to be as creative as possible.”
Most design-build projects follow a far more prescriptive process. “For the kcICON project, we had concepts and the right-of-way corridor, but didn’t require a specific design,” Kidwell said. “We also opened up our design standards, allowing contractors to use any standard already accepted by the Federal Highway Administration. Opening our standards got competing teams to cherry-pick the best value design options from around the country and bring them all into one project. The fixed price made this work. We found a way to get every high-priority item into the job within one fixed price, which allowed us to come up with a project that has the highest value for the people paying for it. We modified all kinds of our own typical procedures to get a project that really reflected citizens’ goals.”
“MoDOT has its own design manual and its own specs, but they threw all that out,” Lunceford said. “The approach turned previous processes on their heads — it was that different — and we got beautiful aesthetics and all of the things we wanted for much less than the anticipated cost.”
The project is currently under construction through the Paseo Corridor Constructors Joint Venture, which includes Clarkson Construction Co., Massman Construction Co., and Kiewit Construction Co.
Project challenges Among the project challenges was creating as much room as possible for innovation without eliminating standards that still were necessary to conform to the EIS.
“The new bridge is being built over one of the world’s fastest flowing rivers, adjacent to five railroads and is 1.5 miles from Kansas City’s downtown airport,” Lunceford said. “That limits a certain amount of creativity — you can’t eliminate coordination with these agencies, for example put a pier in the middle of a railroad. HNTB reviewed the standards that the contractors would bring in from other parts of the country and evaluated how those standards would be applied to the project.”
HNTB also assisted in prioritizing project goals, developing the request for proposals, developing a scoring system for proposal review that awarded higher technical points for greater creativity, and participating in the contractor selection process.
Model for the long term MoDOT is sold on the best-value approach of its new design-build method. “The model will work well going forward,” Kidwell said. “The whole nation is suffering from construction budget reductions, and everybody must do what they can with the money available. Because every project is different, bright people have to come up with best-value solutions. Contractors bring varying expertise and designers have encountered other solutions. When agencies look to them to offer up all these experiences, we really stretch our dollars.
“As an industry of engineers, we like following convention, getting really good at the process of knowing how to do something. We can easily deliver that type of job. But what MoDOT found is that by involving more people and leaving more options for the design-build team, really good ideas and huge benefits will emerge.”
Form factors The new Paseo Bridge will be a 260-foot-high, dual-span cable-stayed structure. Anchored by a single delta-shaped concrete pylon, the top of the new bridge will be 316 feet above the river in a fanned, cable-stay assembly. The bridge will include three through lanes in each direction, and a merge lane for northbound traffic to enter and exit the bridge. It will also have a southbound bicycle and pedestrian crossing that will be separated from roadway traffic by a barrier. The roadway deck is divided in half by a concrete median with 2-foot concrete guard rails on the sides to provide drivers with a clear view from the bridge.
The aesthetic design has indentations in each edge of the pylon, reducing its visual bulk and the amount of concrete required to cast the structure. The legs of the pylon are compact and were designed to appear as if they dissolve into the river bed. The designer, Bradley Touchstone with DodStone Group, had a distinct architectural view in mind for this bridge. As a result, the contractor, Paseo Corridor Constructors, needed a formwork solution to meet the challenges of constructing the new Paseo Bridge.
Doka was selected to provide the engineering solutions and formwork for the top half of the bridge pylon. It was essential that the formwork solution facilitate the 20-foot concrete pours using self-climbing formwork. Doka provided two sets of formwork — one for each pylon — and incorporated all of the formwork systems to provide customization to meet the contractor’s unique needs.
The outside face of the bridge pylon is inclined at a 20-degree slope with four outside faces. The Top 50 form system used here can be configured for fast and safe stripping of the formwork, after which the interior forms can be immediately reconfigured and rapidly re-set into the next casting.
MF 240 support brackets created an 8-foot working surface and were used on each side of the pylon. The dam formwork, D22, was used on the short angle faces because of its load capacity and ability to facilitate tall pours. The pours were 5 feet by 8 feet and were 20 feet tall, which is top-heavy for a 70-degree inclined pylon. On the sloping side of the bridge pylon, SKE 100 in conjunction with Top 50 was used to support the vertical dead weight of the concrete.
Source: Doka
This article is reprinted from Designer magazine with permission from The HNTB Companies.
Susan Rhode is communications manager in the Corporate Communications and Brand Stewardship group for HNTB Corporation. She can be contacted at srhode@hntb.com.
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