36 | SUMMER 2019 ADVANTAGE STEEL Case Study 2: Reliance Metalcenter Reliance Metalcenter located in San Antonio, Texas, is constructing a new administrative office adjacent to its existing facility. The modular office building will be one storey with a floor area of 760 m² (8,150 ft²). The office will comprise 22 modules with structural steel frames using the Z Modular system that are supported on site-built reinforced concrete foundations. Modular clerestories above the roof are attached on-site and, by spanning end-to-end with integrated trusses, enable an open-plan office with an abundance of natural light. Trellises and other architectural elements are also prefabricated and attached on-site to achieve the architectural intent for the building while respecting maximum module dimensions for efficient shipping. FEATURE CASE STUDIES The following two projects demonstrate how the advantages of modular construction outlined herein have been realized in a residential and commercial building application. Each project had unique challenges that were overcome using intelligent modular solutions, and by leveraging the strengths of structural steel. Case Study 1: Cheatham Street Flats Cheatham Street Flats, located in San Marcos, Texas, will be a 143-unit, 234-bed student housing mixed-use development. This innovative project features site-built foundations and a reinforced concrete parking structure that will support four levels of prefabricated modular construction using the Z Modular system. The building comprises habitable modules, non-habitable modules for vertical access and services, and planar hallway modules. A rendering of the building is shown in Figure 5. Amenity and public space at the main entrance requires a transfer structure compatible with the unique modular system. Structural steel proved ideal for this transfer structure, as custom connections with a high degree of adjustability allowed the modules to be supported with tight tolerances. Web openings in the wide flange shapes will be used to run services while maintaining a high ceiling. The model used for structural analysis and design is shown in Figure 6, which was important not only for the design of the modules but also for assessing the impact relative deflections in the steel and concrete support structures had on the modules. Cheatham Street Flats is currently being fabricated at a rate of up to four habitable modules a day while the site-built portions of the building are under construction. Modules in the fabrication facility are shown in Figure 7. Residents are expected to move in August 2019. FIGURE 5: Cheatham Street Flats. Rendering courtesy of Forge Craft Architecture + Design. FIGURE 7: Modules at various stages of completion. Image courtesy of Z Modular. FIGURE 6: Analytical model for Cheatham Street Flats. CONCLUSION Prefabricated prefinished volumetric construction is not a solution for every building project, but represents an opportunity for the construction industry to further innovate and shorten construction schedules, achieve a greater degree of cost certainty, improve building quality, reduce building waste, and increase worker safety and comfort. However, this form of construction has specific challenges that require consideration at the very beginning of a project by a competent and experienced design team. A collaborative approach is required to ensure all architectural, engineering, and manufacturing design decisions are holistic and work toward the goal of a successful, high-performance modular building. FIGURE 8: BIM for Reliance Metalcenter