Abstract
The large-span floor system being lightweight with low frequency and low damping is prone to suffer severe vibration under human excitations. In this research, the vibration performance of an innovative large-span U-shaped steel-concrete composite hollow waffle (CHW) slab was studied based on field testing and theoretical analysis. First, the modal properties of CHW slab including mode shapes, frequencies, and damping ratio were captured by on-site tests and validated by the finite element method, indicating the CHW slab is a low-frequency floor system with a low damping ratio. Second, the vibration responses of CHW slab under heel-drop and jumping excitations were studied considering the impacts of spatial position, tester number, and activity types. Third, the CHW slab shows excellent vibration serviceability proved by the frequency, accelerations, and human perceptions threshold with the current codes. Meanwhile, the paper gives appropriate threshold values for the CHW slab under impulsive excitation. Finally, the natural frequency formula for the CHW slab derived by the Rayleigh–Ritz energy method agrees well with the measurements.
Highlights
Owing to the growing demand for large space and flexible layout of the buildings, large-span floor structures have been widely used in gymnasiums, open buildings, and industrial buildings. e floor height and self-weight increase significantly with the rising spans in traditional floors, such as reinforced concrete (RC) floors, steel-concrete composite floors [1, 2], prestressed concrete floors [3], and waffle slab [4], yielding high material usage and poor economic efficiency
E composite hollow waffle (CHW) slab is an innovative floor system (Figure 1) containing the RC slab, upper beams, lower beams, and web members. e three-dimensional floor system presents excellent mechanical performance, where the upper beams and slab are in pressure, and the lower beams are in tensile when suffering vertical load. e U-shaped steel plates that wrap at the side and bottom of the lower beams enhance the tensile strength, enlarging the span length
Summary and Conclusions e vibration performance of an innovative long-span U-shaped steel-concrete composite hollow waffle floor is studied based on experimental and theoretical analysis. e conclusions and suggestions are described as follows: (i) e CHW slab shows the behavior of a plate in free vibration with low frequency (6.25 Hz) and low damping ratio (2.35%). e mode shapes and frequencies from the operational modal analysis (OMA) and EMA method match well
Summary
Owing to the growing demand for large space and flexible layout of the buildings, large-span floor structures have been widely used in gymnasiums, open buildings, and industrial buildings. e floor height and self-weight increase significantly with the rising spans in traditional floors, such as reinforced concrete (RC) floors, steel-concrete composite floors [1, 2], prestressed concrete floors [3], and waffle slab [4], yielding high material usage and poor economic efficiency. Researchers have studied new types of long-span floor systems with the good structural performance [5,6,7]. E CHW slab is an innovative floor system (Figure 1) containing the RC slab, upper beams, lower beams, and web members. E three-dimensional floor system presents excellent mechanical performance, where the upper beams and slab are in pressure, and the lower beams are in tensile when suffering vertical load. E U-shaped steel plates that wrap at the side and bottom of the lower beams enhance the tensile strength, enlarging the span length. E upper and lower beams are connected by large shear stiffness web members with a small height-width ratio (less than 1), which makes the floor form good integrity. Typical vibration sources are vehicles on nearby roads, large machinery in nearby construction sites, and human activities.
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