Dealing with existing low floor-to-floor heights is a complex challenge for those designing the structure for a new hospital addition tied into an original building built in the 1950s and ’60s. With modern medical facilities requiring taller ceilings for procedure rooms with advanced medical equipment, new additions must squeeze space out of every system above these ceilings. Conventional structural framing systems are the first to be considered. A composite steel system may be preferred by the client due to its flexibility for future adaptability, if the project allows for the system’s required 24 inches of space to meet 100 PSF floor live loads. Concrete flat slabs with closely spaced columns, which uses as little space as possible, is a logical choice for many projects. Concrete also is a viable option in certain situations. Such was the case at the McDonough District Hospital expansion project in Macomb, Ill.
From the perspective of the lead construction manager, Harold O’Shea Builders, many challenges were presented by the use of a concrete system for this hospital in a rural region of Illinois. Finding qualified concrete contractors without having to bring in a company from a larger city many miles away was one of the main concerns. The higher cost of the concrete structural system on an already tight project budget was the other major concern for the team. Since the region had an ample supply of erectors and steel fabricators, a steel framing solution was preferred.
Peikko’s DELTABEAM system was easy to work with on the construction side. The steel fabricator only needs to coordinate the bolt spacing for the connections to the columns, which was provided by Peikko in the DELTABEAM shop drawings. No other special requirements were needed. The erector only needed to learn a few special conditions required for shoring the DELTABEAM Composite Beams when precast is erected on one side of the Beam. Otherwise the DELTABEAM Composite Beams erected just like any other steel beam on the project. During the design process, the construction manager conducted several cost comparisons to evaluate the system’s cost efficiency compared to other conventional steel systems using composite metal deck. The DELTABEAM system with a precast floor deck was found to cost $14 per square foot less than a steel frame system. The main reasons for this reduction in cost were threefold: lower fireproofing costs of the system, a reduction in the building cladding due to the reduced floor-to-floor height, and a lower expenditure on elevated concrete decks. Another benefit, the clean and unobstructed ceiling plenum provided by the system, was not included in the structural system cost analysis but was clearly evident in the total construction cost comparisons.
