‘Green Screen’ Parking Structure Features a ‘Living’ Exterior
By Dan Weinheimer and Jared Plank
When Cummins Inc. announced it would be expanding the offices of its corporate headquarters and adding a new parking structure in downtown Columbus, IN, the city had concerns about the impact on the downtown aesthetics of its impending footprint.
However, with help from the architects and engineers of the Indianapolis-based consultant firm American Structurepoint, both corporation and city were able to find a mutual solution.
The project team worked with Cummins to design a 954-space 291,300-square-foot parking structure incorporating many sustainable design principles and maintaining the architecture and historical features of the exterior to blend into its surroundings.
The facility encompasses the essential features of a modern parking garage, while simple enhancements allow it to complement the architecture of the downtown area along Jackson Street, between Sixth and Seventh streets.
A unique feature of the $10 million parking garage is the installation of 7,000-square-foot of so-called Basic Wall container system of live vines by GSky Plant Systems.
A 20-foot-tall white precast concrete trellis on the structure’s west side mirrors the iconic trellis featured across Jackson Street. The garage is topped with a continuous concrete band, which cantilevers at the corners, visually tying the structure together, creating spaces in the four corners, one for a stair /elevator and one for a stairway. Due to a restrictive site, the other two corners provided an opportunity to place a screened electrical transformer and below-grade stormwater equipment.
Self-contained planters support long-term mass vine growth to soften the north and south façades, filtering out some sunlight, while shielding views of vehicles from the street. The insulated containers feature a wire heat tracing system, designed to prevent root damage during cold temperatures, as well as an automatic irrigation system that detects when the growing medium is dry.
The Basic Wall vines will eventually grow to fill the galvanized 3-by-5-foot frames attached to the front of the container system.
The materials palette was confined to exposed natural concrete, white precast concrete, galvanized steel, clear anodized aluminum, clear glass and brick. Glass stairs and the glass elevator tower maximize natural lighting. The glass cube-like façades engage the concrete cantilevered beams and are topped with floating concrete roofs, providing a distinctive, finely detailed beacon to promote wayfinding.
The southwest corner staircase cantilevers from the solid concrete elevator tower, appearing to float between the glass and the elevator.
An open parking structure is designed to allow for natural ventilation, eliminating the need for mechanical ventilation. Appropriate levels of lighting and the use of energy-efficient LED and indirect light fixtures meet minimum foot-candle requirements and allow for a soft, even distribution of light throughout the facility.
Poor on-site soils required rammed aggregate piers to improve bearing for the foundations. The structural system was a typical one-way post-tensioned concrete frame, with moment frames providing all the lateral resistance.
The typical span for the 5½-inch one-way slab was 22 feet, with 14-by-36-inch beams spanning 60 feet, with 24-by-24-inch columns. The long spans and moment frames (instead of shear walls) helped to create a wide-open feeling and a greater sense of security in the garage.
Parking garages in this climate are susceptible to freezing, heat, precipitation, de-icing salts, etc., similar to a bridge. To address these issues, American Structurepoint implemented a multi-pronged approach to maximize building life, including providing higher concrete strength, epoxy-coated reinforcing, post-tension tendon and anchorage protection, higher prestress levels to reduce cracking, and admixtures and sealers to inhibit corrosion.
With all of these pieces taken together, the design life of the structure is considered significantly greater than a typical precast or mild reinforced parking garage.
The garage was designed to operate during business hours, with controlled access for Cummins employees through entrance/exit off Sixth and Seventh streets.
All required ADA parking is accommodated on the first level, as is motorcycle parking, with an area planned for future bicycle storage units. In keeping with Cummins’ principles of sustainable design, two electric-vehicle charging stations are also located on the first level.
With aggressive pricing, efficient geometry, streamlined architecture, and repeatability, the per-space cost for the structure came in at around $10,500, significantly lower than the national average (about $16,300/space). And all this was accomplished using an intricate “green screen,” trellis and attractive aesthetics.
The garage opened in September 2012, after only nine months
of construction, and is now part of the evolving character of downtown Columbus.
The “Green Screen Parking Structure” for Cummins Inc. was designed by American Structurepoint, in consultation with KRJDA (Kevin Roche John Dinkeloo Architects) and Todd Williams & Associates, and was built by F.A. Wilhelm Construction Co. The project has already won two awards: a 2013 Award of Merit in the Parking Structure category from the Post-Tensioning Institute; and a 2013 Outstanding Achievements in Concrete Award in the Transportation 2 category from the American Concrete Institute, Indiana Chapter.
Dan Weinheimer, AIA, NCARB, is a Senior Architectural Manager, Architecture Group, for American Structurepoint. Contact him at DWeinheimer@structurepoint.com. Jared Plank, PE, a Project Engineer in the firm’s Structural Group, can be reached at email@example.com.
Article Abstract from June, 2013