Analysis of the Mechanical Properties of a Bidirectional Laminated Slab with Shear Keys

Abstract

The load-bearing capacity of a bidirectional laminated slab with shear keys arranged in a rectangular grid (BCSWSK) was investigated to determine its mechanical properties, using load tests on a fabricated laminated slab and finite element models. The shear force distribution across the shear keys was measured and analysed, and the effects of different parameters were identified. The interfaces between the cast bottom slab and the shear keys were strongly bonded, as was the interface between the precast bottom slab and the cast-in-place upper slab, despite it being a secondary concrete pouring. The shear force was distributed similarly along the X direction (columns) and the Y direction (rows) of the shear key arrangement. The shear forces along the Y direction were greater and reached a maximum value sooner, but the differences between columns were mostly less than 10%. A square cross-section is recommended for the shear keys. The number of rows, number of columns, and the cross-sectional area of the shear keys are the main factors influencing the mechanical properties of the composite slab, but as they individually increased, they reached a point at which further increase had little effect. Similarly, after a certain number of shear keys were used, the concrete grade cast in situ, the shear key concrete grade, and the friction coefficient between the precast bottom slab and the cast-in-place upper slab had little influence on the BCSWSK.

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“…When the cast-in-place layer thickness was greater than 60 mm, the laminated slab could be considered as castin-place slab based on the plane section assumption and enough bonded strength at the interface between cast-in-place concrete and precast concrete in the laminated slab [22]. Increasing the shear keys in the one-way or two-way laminated slab to improve the bonding strength was an effective measure [23,24], but it has limited effects on the yielding strength and deformation. Li et al [25,26] proposed a new laminated pouring technique for the composite slabs, and investigated the influence of bonding strength on the structural behavior.…”