The existing structure was assessed based on the original 1966 drawings prepared by Lev Zetlin and Associates (see Appendix A). The current roof structure consists of a 6 in. reinforced concrete slab supported by steel trusses that span 84 ft across the Great Hall. The trusses are made up of teeshaped chord members and double-angle web members. Secondary wide flange beams spaced at approximately 21 ft span between the trusses and create two-way action in the slab. Analyses conducted during Phase 1 of this Feasibility Study showed that the secondary components (roof slab and beams) do not have sufficient capacity to support the added load of the photovoltaic array. Consequently, support systems were conceptualized that would deliver the new loads directly to the trusses. Analyses conducted during Phase 2 therefore focused on the roof trusses.

Loads and stresses on the trusses were determined using the American Society of Civil Engineers (ASCE) 7-10 design loads and typical material weights. Taking into consideration the dead loads (truss members, roofing materials, concrete slab, catwalks, and ceilings) and snow loads, the total load on the roof structure is estimated to be 130 lbs per sq. ft (see table below). With a distance of 21 ft-4 in. between trusses, this equates to approximately 2,800 lbs per lineal foot applied to the truss.

• Existing Load Summary - Load (lb/ft2)
• Truss (Self)                                     10
• Slab                                                   75
• Catwalks and Ceilings                   13
• EPDM Roof                                       5
• Insulation                                          3
• Live Loads (Snow)                         25
• Total                                                131 lb/ft2

Using structural analysis software and hand calculations, it was determined that the members of the existing roof trusses labeled T-3 in the original drawings do not meet the current structural steel code for compression capacity under these load conditions. At the time of original construction, the members met requirements called for by the applicable code, the American Institute of Steel Construction (AISC) 6th Edition Steel Construction Manual. The AISC Steel Construction Manual has since been updated to account for torsional and flexural-torsional buckling and strength limitations of slender elements within members.

The trusses were also analyzed for the addition of the PV cells and accompanying concrete knee walls. The weights of these materials and associated snow drifting loads would apply an additional 30 lbs per sq. ft (see table below), or approximately 665 lbs per lin. ft to the T-3 trusses at the locations of the new walls.

• Additional Load Summary - Load (lb/ft2)
• Concrete Wall                                    18.75
• Photovoltaic Cells                               5
• Snow Drift                                            7        
• Total                                                    31 lb/ft2

These loads would introduce an additional sixty thousand pounds (approximate) into each of the steel chord members, causing four additional chord members to be stressed beyond code-prescribed limitations

In the words of Valerie Oliveiro, Assistant to the Senior Associate Director of the Krannert Center for the Performing Arts, KCPA is “dedicated to the advancement of the education, research, and public engagement mission of the University of Illinois through the pursuit of excellence and innovation in the performing arts.”[1] These words exemplify the importance of KCPA to the campus community. A hub of social interaction and innovation, Krannert has a unique role as a leader and innovator in sustainability initiatives at the University of Illinois. This unique importance is what drove KCPA to the idea of implementing LED lighting in its lobby. After more than two years of research and experimentation, consideration to the developing goals of the Illinois Climate Action Plan (iCAP) and joint funding from the Student Sustainability Committee (SSC) and the Illinois Clean Energy Community Foundation, KCPA finally decided to pull the trigger on The University’s largest LED lighting project.

[1] Oliveiro, Valerie. ICECF Funding Proposal for the KCPA LED Lobby Lighting Retrofit Project. Krannert Center for the Performing Arts, University of Illinois, September 17th, 2009