Wrigley Field renovations in Chicago. Elaine Shapiro / Thornton Tomasetti.
The 1060 Project aims to preserve Wrigley Field’s beauty, charm and historic features while updating and improving the iconic ballpark for fans, players and the community. Thornton Tomasetti is providing structural engineering and construction engineering services for the multiyear renovation of the iconic ballpark, one of the last old-time major league ballparks still in regular use in the United States.
The plan is being implemented in phases during off seasons. Phase 1 strengthened the left field grandstand foundations; rebuilt the ballpark’s outfield bleacher seating sections, adding 300 seats and 300 standing positions along with new concessions under the bleachers; and installed two large video boards, one 3,990 square feet in left field and the other 2,400 square feet in right field; among other improvements. Phase 2 renovations included new amenities at the upper-level concourse, a large new 30,000-square-foot clubhouse connected by a new tunnel to the dugout and structural strengthening and repairs to the left field grandstand.
The clubhouse, the second largest in the Major League, is located in the basement levels of a new steel-frame mixed-use office and retail building adjacent to the ballpark that is targeted for completion by year-end 2016. The tunnel that links the clubhouse to the dugout was strategically dug to avoid the foundations of the stadium seating under which it extends. A micropile-based earth retention system was used for the tunnel. Jet grouting with a soil and concrete mixture was used to improve the soil along the tunnel’s walls to protect against groundwater during construction since the tunnel is located partially below the water table. The floor, walls and ceiling were then constructed with concrete.
The most challenging aspect of Phase 2 was strengthening the grandstand, including existing columns, trusses and foundations to accommodate future expansion of the upper deck. The original stadium was built in 1914 and was not designed for current code wind loads. To provide for new gravity loads−as well as the wind loads− required augmenting the grandstand’s lateral system with the addition of new columns and bracing.
Repairs were undertaken to correct concrete corrosion and deterioration, including addressing the spalling concrete on the underside of the stands. Thornton Tomasetti saved the owner millions of dollars by coming up with an alternate approach to replacing the precast and cast-in-place spalled areas. By encasing the stands’ steel rakers in cast-in-place concrete, it encapsulated the ends of the precast section to eradicate the spalled ends, reinforced the rakers flexurally for the live loads required, introduced drag strut strength through rebar in the cast-in-place rather than utilizing steel, and worked with the existing diaphragm, locking it together to provide the diaphragm reinforcement necessary for the augmented steel frame.
Phase 3 continued the strengthening and repair work of the prior phases primarily in right field. This work included reconstruction of the mezzanine and ramps, and the addition of new bracing. Additionally, extensive reinforcement of the main roof trusses was undertaken to accommodate future party decks and suite expansions scheduled for upcoming phases.
A new basement structure under the seating bowl behind home plate was also constructed as part of phase 3. This underground structure will be extended into left and right field in Phase 4 and will accommodate a new club, suites, and ultimately, team support spaces including new dugouts. On the field, the former bullpens were infilled with new seats with the relocation of the bullpens to spaces below the bleachers.
Phases 4 and 5 are planned to include modification of the existing suites, new party decks, and expansion of the underground structure constructed in Phase 3. Strengthening and repair work is scheduled to continue throughout the final phases.
Follow these topics: