Establishment of Future A-Shape Geometry for Residential Construction

Steel buildings utilizing steel-concrete composite construction typically have large floor depths due to the concrete deck cast above wide-flange beams. Stay-in-place formwork is placed on the bottom flange to achieve shallower composite floor systems. This formwork comprises either concrete precast panels or steel deep decking, which supports a concrete topping slab that encases the steel beam. The goal is to minimize the floor depth, reducing the building’s overall height or increasing the floor-to-floor height. Currently in the United States, no readily available hot-rolled steel shapes allow for easy placement of stay-in-place formwork on the bottom flange. This necessitates intensive fabrication to create asymmetric beams and facilitate rapid placement of stay-in-place formwork on the wider bottom flange. This study aims to develop standardized hot-rolled asymmetric steel I-beams (A-shapes) for potential large-scale production in the United States. Utilizing A-shapes decreases the required manufacturing time and allows for increased speed and efficiency of residential building construction. The research presented herein includes beam sizing constraints established from interviews with three US steel mills. Utilizing the beam sizing constraints for manufacturing, a wide range of possible cross sections were investigated for three structural load cases. Each cross section iteration was analyzed for a total of 16 limit states to establish efficient and effective standardized A-shapes. Parametric studies were conducted to investigate sensitive limit states when altering assumed parameters. As a result of this study, two primary cross sections with a depth of 203 mm (8.0 in.) (A8s) were established for a 6.1-m (20-ft) square grid for a live load of 1.9 kPa (40 psf) and 4.8 kPa (100 psf). The heavier A8 cross section [when supporting 1.9 kPa (40 psf) live loading] satisfies all limit states for a beam length of 6.1 m (20 ft) and spacing of 8.5 m (28 ft), which allows for large open spaces between columns. The methodology developed was also utilized to size four additional A-shapes (two A10s and two A12s) and can be used to size A-shapes for other facilities.