James J Hill

Minnesota Department of Transportation Overload Field Tests of Standard and Standard Installation Direct Design Reinforced Concrete Pipe Installations

The design, manufacture, and installation of concrete pipe have changed significantly under the new standard installation direct design (SIDD) beddings. The Minnesota Department of Transportation (MnDOT) initiated a research project to evaluate the benefits of these new installations in conjunction with state-of-the-art means for determining soil stiffness and, thereby, its effect on concrete pipe performance. The methodology used to develop the test installations, how the pipes were instrumented, and the significance of soil stiffness relative to soil density is described. The performance of concrete pipe under both the SIDD and MnDOT standard installations, the resulting variability found with specific soils, and recommendations for concrete pipe design and installation are also addressed.

Reconstruction of a Damaged Steel Beam Bridge Using an Overhead Support System

Reconstruction of a bridge damaged by a backhoe on Interstate 494 and Xerxes Avenue in Minneapolis, Minnesota, in 2006 is discussed. The backhoe was extended above the clearance height of the bridge and, after extensively damaging the first five beams, became hung up under the bridge. The backhoe bucket had to be cut off before the truck and backhoe could be removed from under the bridge. The conventional method of supporting a bridge during reconstruction is reviewed and is then compared with the unique system that was used to support the remaining steel beams during reconstruction. The main design features and actual field methods are highlighted as well as a special lifting capability that was used to deal with a difficult field problem that arose.

STRUCTURAL MODELING FOR RECONSTRUCTION OF ARCH BRIDGE

When a 70-year-old multiarch concrete bridge was to be reconstructed by removing the deck and vertical spandrel columns down to the arch, analysis was necessary for unloading and reloading. The arch bridge, located on TH-55 over the Minnesota River, was of world-record length for such a structure when it was originally constructed in 1926 through 1928. The amount of steel reinforcement in each of the two support arches was only 32 No. 9 bars of 28.6-mm (1.125-in.) diameter. The deck, which was 18.3 m (60 ft) wide and supported at 9.1 m (30 ft) by columns, was designed as a patented panel system. This involved the use of only 250 kg (550 lb) of reinforcement in each deck panel. The slab did not possess upper reinforcement in the center areas, so removal operations could not allow the slab to cantilever in these areas. As a result of the minimal steel reinforcement in the deck and arches, removal operations needed to be planned safely and effectively. At no time during the removal process could the arches be placed in flexural stress above their very limited carrying capacity. Prospective contractors were advised of this condition and were given 2 weeks beyond the original deadline to submit bids accordingly. The proposal and plans given to each prospective contractor for bidding showed a possible deck removal method using a crane. Structural modeling by the contractors consultant and the Minnesota Department of Transportation using Staad III finite element analysis was necessary for the contractors bridge deck removal and replacement method. The existing slab removal and replacement with a wider, 27.4-m (90-ft) deck was successful and the bridge was reopened to traffic in October 1994.