Local Interface Displacement and Global Response of Two-Layer Reinforced Concrete Slabs under Concentrated Loading
Authors
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T. Q. K. Lam 
Faculty of Civil Engineering, Mien Tay Construction University, Vinh Long 85119, Vietnam
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Chi-Hieu Dang
Faculty of Civil Engineering, Mien Tay Construction University, Vinh Long 85119, Vietnam
DOI:
https://doi.org/10.30564/jbms.v8i4.117235Abstract
Two-layer reinforced concrete (RC) slabs are commonly used in staged construction, repair, and strengthening, yet the relationship between local interface displacement and global slab response remains insufficiently understood. This study investigated six slabs measuring 1,200 × 1,600 × 120 mm under monotonic concentrated loading. The series comprised one monolithic reference slab and five two-layer slabs with different layer arrangements and reinforcement configurations. The second layer was cast 14 days after the first layer using cement slurry at the interface and without mechanical connectors. Load, deflection, average surface strain, crack development, and local relative displacement in the long-span and short-span directions were recorded. The first visible cracks were observed at the 38 kN loading stage. The highest recorded test load was 50 kN for S1 and S2 and 63 kN for S3–S6. S4 showed the largest long-span interface displacement of 6.88 mm, whereas S3 showed the largest short-span value of 3.36 mm; S5 and S6 recorded smaller short-span values of 0.69 and 0.50 mm, respectively. The results show that global stiffness and local interface compatibility may evolve differently after cracking. These findings provide experimental evidence of partial composite action in two-layer slabs and highlight the importance of combining local interface measurements in both principal directions with global load–deflection and crack observations when assessing staged-cast or repaired reinforced concrete slabs.
Keywords:
Local Interface Displacement,Two-Layer Reinforced Concrete Slab,Concentrated Loading,Global Response,Partial Composite ActionReferences
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