The Illinois State Fairgrounds Coliseum in Springfield, Illinois, was designed in 1901 by architect W.H. Reeves of Peoria, Illinois, and opened the same year for horse shows and livestock competitions. Over the course of its 118 years, the Coliseum has remained a significant attraction for Illinois. It has welcomed a variety of events and entertainment; maintaining its 46,000-square-foot presence on the fairgrounds is of considerable importance to the people of Illinois and the Illinois Department of Agriculture.
In 2016, an engineering study revealed corrosion in the Coliseum’s support columns and bolts missing from roof connections, as well as roof leaks and wood-framing rot. Officials closed the arena for the 2017 and ’18 state fairs. After the state secured renovation funds, Hanson served as a subconsultant to architecture firm Bailey Edward Design Inc. to provide structural and ancillary electrical and mechanical engineering design and construction administration services for the project, which included replacing the existing shingled roofing system, wood roof deck and purlins; strengthening selected primary structural members, including steel columns and truss members; and replacing the clerestory windows in the approximately 46,000-square-foot, circa-1901 and -1903 Coliseum facility on the fairgrounds.
The new roofing system includes rigid insulation and shingles that mimic the appearance of the original roofing material. Hanson conducted a detailed evaluation of the building’s steel and wood structural members, including comprehensive modeling to assess the structure’s response under the self-weight of the new, heavier roof deck, snow and wind loads.
The in-situ and laboratory evaluation of existing systems, conducted by other specialty consultants, included the identification of timber species, grade and condition; steel yield and tensile strengths and composition; and in-situ brick masonry compressive and shear strength testing. Hanson used the results of these evaluations to consider the capacity of the existing structural components and prepared details for strengthening selective components.
Structural analyses showed that loads imparted to the low roof system from the high roof system substantially exceeded the calculated lateral capacity of the low roof wood diaphragm. It is believed that this loading was a primary contributor to the poor condition of the low roof deck. Hanson and the project architect developed a method for strengthening the lateral capacity and stiffness of the low roof structure with a steel truss positioned within the insulation layer atop the replacement low roof deck. The truss delivers lateral loads imparted by the high roof to the perimeter masonry walls around the eave of the low roof. Roofing materials were applied to plywood sheathing that caps the insulation and conceals the truss assembly.
This solution provided the necessary strength to resist the lateral loads with little impact on the structure’s appearance and was accepted by the Illinois Historic Preservation Division.