Effects of Nonstructural Floor Layers on the Dynamic Characteristics of Structures and the Simplified Modeling Method

Abstract Vibrations induced by railways, road traffic, and human activities can affect the serviceability of buildings. In the prediction and assessment of structural vibrations, the vertical vibration of floor slabs is a primary concern. Previous studies have experimentally confirmed the influence of nonstructural floor layers, primarily leveling layers, surface layers, and other horizontal architectural layers, on the vertical dynamic characteristics of structures. These layers alter the mass, stiffness distribution, and damping of slabs, which significantly impact the results of serviceability assessment. Therefore, nonstructural layers should not be either neglected or oversimplified in floor slab modeling. Otherwise, existing studies have not theoretically discussed the effects of nonstructural layers with different properties (stiffness, mass, and thickness) on the natural frequency of floor slabs. To this end, this study established a laminated plate theoretical model of floor slabs and proposed a simplified modeling method to consider the nonstructural layers by adjusting the properties of floor slabs. The applicability of the proposed method was examined through experiments and simulations of a full-scale three-story frame structure. Subsequently, the proposed theoretical model was employed to investigate the influence of nonstructural floor layers on the modal properties of floor slabs. The findings suggest that the existence of nonstructural floor layers may either increase or decrease the vertical natural frequency of floor slabs. Generally, the natural frequency can be reduced after the construction of nonstructural floor layers when the floor slab type uses a ribbed floor with deep beams or steel truss-concrete composite floors. This reduction occurs because the deep beams or trusses provide substantial additional stiffness, which greatly exceeds that of the nonstructural layers. The findings provide a practical modeling technique and theoretical framework for structural analysis.