Experimental investigation on flexural behavior of one-way fixed-support concrete composite slabs for precast nuclear power plant buildings

Concrete shear wall structures are the primary structural systems for nuclear power plant (NPP) buildings, characterized by thick, heavily reinforced concrete slabs with fixed supports. The incorporation of concrete composite slabs (CCSs) can significantly accelerate project timelines of the cross-construction between slab construction and equipment installation. To investigate the flexural behavior of one-way CCSs with fixed ends, static tests were conducted on four 1/4-scale slab specimens (two CCSs and two cast-in-place (CIP) controlling specimens) with consideration of the effects of mid-span joint and slab end configurations. Experimental results demonstrated that the failure mode of the four specimens was governed by flexure, with three plastic hinges forming at two slab ends and midspan, followed by concrete crushing. The existence of the new-to-old concrete interface had a minor influence on the load-carrying capacity of CCSs (8.4% difference from CIP’s capacity). The mid-span closely attached joint lowered the load-carrying capacity of the CCS by 12.3% compared to the specimen without a joint, but it was still 109.8% stronger than the CIP slab with the same thickness as its CIP layer. The ductility coefficients of CCSs with and without a joint were 5.27 and 5.11, respectively, higher than that of the CIP specimen (4.82). Finally, the influence of the joint on load-carrying capacity and stiffness is investigated, and the effective slab thickness of the joint zone and corresponding length are identified by fitting the test data, providing insights for the internal force and stiffness calculations of two-way CCSs with fixed support conditions.