WARREN WITH POLYGONAL TOP CHORD PONY TRUSS
1909 Craig 18E0230N4340002 Illinois Steel Br.
1911 Muskogee 51E0930N4140009 Vincennes Br.
1914 Muskogee 51E0950N4130009 Missouri Valley Br.
1916 Osage 57N3533E0300002 Missouri Valley Br.
Engineers altered the Warren truss as they did the Pratt, through their sucess, as measured by use within Oklahoma, did not reach the same proportions as with the Pratts. The most common change saw the curving of the top chord to achieve greater length and more economy without sacrificing strength; a polygonal chord Warren could be built to 140 feet as a rule. Never a standard state design, most of this type originated in the counties between 1909 and 1920 (Figure 56). The oldest documented example was built northwest of Vinita in 1909 by Illinois Steel Bridge, a 133-foot riveted span with verticals. The typical structural plan employed channel beams for the top chord, braced angle in the bottom chord, and laced angles for diagonals. Gusset plates reinforced the joints on most of these spans.