In 2015, Burns & McDonnell proposed an innovative bridge raising program that utilized a progressive design-build (PDB) approach to improve efficiency and speed up the schedule for raising low-clearance bridges spanning the Kansas turnpike.
Upon receiving notice to proceed, Burns & McDonnell served as a turnkey design-build contractor and developed a bridge raising plan that could safely and efficiently raise the bridges over interstate traffic while minimizing disruptions to regular traffic on the turnpike.
Under this plan, construction teams deploy up to 10 hydraulic pumps on each bridge project, carefully pushing as much as 500,000 pounds of steel girders and concrete deck upward 1 inch at a time. After about a day of pumping, shimming, inspecting and repeating, the bridges are raised to the specified height, where they are placed on new bearings and secured with steel anchor bolts.
While the bridges are raised, the construction team also inspects and performs a range of routine maintenance, ranging from substructure concrete repairs to expansion joints, slab repairs and deck overlays. This value-added feature to the program has resulted in significant cost savings, while minimizing further disruptions to highway traffic. Significant safety improvements also are performed during the raisings, including median barrier improvements, bridge pier protection, guardrail and end terminal upgrades, and drainage and erosion improvements.
These value-added project elements have addressed and mitigated risks through contingencies to the project budget that cover any additional costs as needed. With the design-build method, these costs have typically been negligible because crews already mobilized to the site can complete tasks quickly and without change orders. In most cases, unspent contingency funds are returned to the KTA as overall budget savings that have helped improve program economics.
The program utilizes an assembly-line approach, where one crew executes the same or similar project tasks before moving on to another project underway at another site to tackle the same tasks. The method allows the overall program to move forward steadily with no downtime in the schedule.
As an additional efficiency, the program sources the new steel bolsters needed on the raised bridge decks from AZCO, a Burns & McDonnell construction division specializing in fabrication of structural steel components. With AZCO fabricating these long-lead components to precise specifications well before they are needed on the project site, additional schedule risk is mitigated.
Thanks to this schedule optimization and sourcing efficiency, six to seven projects have been started and completed on average each year since the program began.