For the first time in its eight-year history, the Top 10 Bridges list has a light-rail project on its tail. The structural design of the Tempe Town Lake Light Rail Bridge is an innovative, continuous 11-span triangular steel truss with a 30-ft-wide cast-in-place concrete deck. 

 

Truss fabrication proved to be a challenging process because diagonal truss members and cross members connecting the tip pipe chords required 1,760 and 880 welds, respectively. Of the 880 pieces of diagonal bracing, 722 were unique in terms of angles, lengths and beveled cuts. 

 

The project team proceeded with an innovative approach using specialized CAD software and CNC thermal-cutting equipment. This system cut and rotationally aligned the pipes and cut each diagonal to length.

 

During construction, high-voltage power lines got in the way. Since the large drill rigs on the barge could not fit under the power lines and the lines could not be de-energized, the abutment design switched from its original design of using drilled shafts to using a spread footing. 

 

A major water line below posed another problem. The underground 72-in.-diam. pipeline was encased with concrete reinforcement to withstand the weight of the south abutment and support structures.