40-Storeyed Building Built with Cold-Formed Steel Construction
Overview
How tall can a building constructed with cold-formed steel (CFS) framing go? Lets take a look at 40-Storeyed Building Built with Cold-Formed Steel Construction. While many believe the limit is around 10 stories, structural engineering advancements have pushed these boundaries much further. The Steel Framing Industry Association (SFIA) decided to challenge this notion by commissioning a design for a 40-story CFS-framed high-rise building, the SFIA Matsen Tower.
Unveiled in April 2016, the SFIA Matsen Tower was designed by Patrick Ford, P.E., of Matsen Ford Design in Waukesha, Wisconsin. This innovative project showcases the potential of CFS framing for high-rise buildings, proving that CFS can rise much higher than previously thought.
The Need for Vertical Expansion
The world’s urban population is growing rapidly. According to the United Nations, 54% of the global population lived in cities in 2014, and this is expected to increase to 66% by 2050. This growth will add 2.5 billion new urban dwellers, creating a need for vertical construction as space in cities becomes limited.
Cold-formed steel is often perceived as a material only suitable for interior drywall partition framing or as a framing backup for exterior finishes. However, the SFIA Matsen Tower demonstrates that CFS is a viable option for load-bearing support in mid-rise and high-rise structures.
Design Features of the SFIA Matsen Tower
The SFIA Matsen Tower, a residential R3 apartment building, utilizes common CFS profiles and thicknesses without the need for specialized CFS framing products. The design parameters included standard 10-foot story heights and 25’6” center-to-center demising wall spacings, creating clear spans of about 25 feet. Here are some of the key design details:
Typical Floor Assembly: Lightweight gypsum concrete on a 0.6 C deck supported by CFS joists.
Corridor Walls: These also function as bearing walls, supporting corridor framing.
Exterior Walls: Made of CFS studs, gypsum board (GWB), and sheathing with options for rigid insulation and architectural metal panels, EIFS, or cement panels.
Aluminum Balconies: Supported by wing walls or brackets connected to double studs or corner posts in the exterior walls.
Vision Areas: Openings provided in the front and rear, with smaller openings in the bearing walls.
Strength Factor: Repetitive C Studs
The tower's structural stability relies on repetitive C studs and joists for the primary gravity load-carrying frame. The main exception to CFS use is the concrete shear cores at the elevators and stairs, which provide primary bracing. The tower is designed to withstand wind gusts up to 115 mph, making it suitable for most areas in the United States.
The design ensures that each stud assembly can handle the worst-case combination of uniform lateral, eccentric live, and total loads from the joists. Spacing adjustments are critical to the structure's stability:
Stud Offsets: Spacing transitions occur at two main points—24” on-center to 16” on-center at the 34th story and 16” to 12” on-center at the 30th story. Reinforced tube elements (HSS) are required at these locations.
Prefabrication and Assembly
Prefabricating the walls is crucial to the tower’s design, ensuring proper seating of studs and secure welded connections. This prefabrication method would handle bridging forces within the walls, assisted by intersecting and reverse-oriented CFS members, as well as occasional tee braces.
Despite axial forces exceeding 60 kips per member, double studs would function effectively without bracing at the lower levels. The SFIA Matsen Tower's design is conservative, with few load reductions considered, suggesting even more efficient possibilities.
Potential for Taller CFS Structures
While the SFIA Matsen Tower is an innovative use of CFS framing, the design could theoretically extend up to 48 stories with optimized load calculations. This demonstrates that CFS has far greater potential than most architects, engineers, and contractors currently realize.
Conclusion
The SFIA Matsen Tower has redefined the possibilities of cold-formed steel framing in high-rise construction. While further exploration is needed to determine the most efficient methods, the project has set a new benchmark for CFS’s capabilities in the construction industry. As urban populations continue to grow, CFS could become a critical material for building the vertical cities of the future.
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