Vibration Behavior of Composite Cold-Formed Steel Floors with Concrete Topping due to Heel-Drop Loading

Human-induced vibration is an important serviceability issue of modern structural designs, especially for light long-span structures. The common heel-drop impact is usually considered in evaluating the vibration of cold-formed steel (CFS) floors. This paper proposes a simplified equation for determining the peak accelerations under transient impacts, based on the Duhamel integral. The analytical results were validated with a comparison with the results from the heel-drop test results on a CFS floor of 3 900$$mm × 5 600$$mm (at both construction and completion stages). The dynamic responses of the floor, including peak acceleration, maximum transient vibration value (MTVV), and crest factor (a ratio of MTVV-to-peak acceleration) were analyzed in detail. The natural frequencies of the floor were obtained from the FFT and FRF analysis of heel-drop and hammering test results. The investigated on-site composite CFS floor with concrete topping was found to have a high fundamental frequency: 17$$Hz at the construction stage and 21$$Hz at the completion stage. In determining the fundamental frequency of the CFS floor, the hammering was thought to be more effective than the heel-drop owing to the phenomenon of human-structure interaction (HSI). Moreover, finite element analyses were performed to study the effects of profiled steel sheeting type (Types 28-100-800, 21-180-900, and 14-80-640) and concrete thickness (40, 50, 60, 70, 80, 90, and 100$$mm). With the SCSC condition (two opposite edges clamped and the other two edges simply-supported), the peak acceleration decreased by 50% when the concrete thickness increased from 40$$mm to 100$$mm.