Floor live load survey by forced vibration test using human-induced excitation

Abstract

The design value of floor live load is critical for structural design and reliability analysis. The use of statistical load modeling to determine this value requires large amounts of field measurement samples. The traditional “walk-in plus objects weighing” load survey scheme is labor-intensive, less efficient, and requires special weighing devices, which limits the availability of samples. To address this problem, this study proposes a new approach for floor live load surveys without the need for weighing objects on-site. The modal mass of the floor is first identified through a forced vibration test using the measured human-induced excitation and floor responses. The total physical mass (or weight) of the floor is then derived from its modal mass using conversion coefficients for eight different floor boundary conditions. Finally, the live load on the floor is obtained by subtracting the self-weight of the floor from its total weight. Numerical simulations were conducted to prove the feasibility of the proposed method and to design a condition-based application strategy. The proposed approach was applied to a floor model with various live-load distribution patterns. A person wearing an ergometer insole was employed to excite the floor through bouncing activity, and an accelerometer was used to measure the floor’s dynamic responses. Floor live loads were successfully obtained with a maximum error of approximately 12%. The new approach is proved to be a convenient, effective, and low-cost method for live load surveys.