Flexural Behavior of Lattice Girder Slabs with Different Connections: Experimental Study

Lattice girder slab (LGS) is a precast composite slab that serves as an alternative to conventional concrete-in-place (CIP) slabs. The load-bearing capacity of joints for the LGSs is essential for large-span slabs with precast constructions, while limited connections could achieve both free-of-formwork construction and higher flexural bearing capacity. In order to enhance the flexural behavior of LGSs with free-of-formwork joints, the straight bar lapping connection away from the midspan, loop connection, and straight bar lapping connection within keyway for midspan joints were proposed in this study. Seven full-scale one-way LGSs with different transverse connections were tested under the four-point bending tests to investigate the joint behavior. The overall response and failure mode were observed during the test. The load versus midspan deflection, deflected shape, and characteristic load capacity were analyzed and discussed. The study showed that all the slabs’ deformability could reach as high as l/50 without load reduction. The LGS with the straight bar lapping connection in the midspan had the lowest flexural capacity (70% of the capacity for LGS without joints), while the flexural resistance of the slabs with other connections could be increased by 21.4% to 44.6% compared to LGSs with the traditional straight bar lapping connection in the midspan. The LGSs with the connections having keyways had the most significant improvement and could achieve high flexural capacity and 110% of deformability of the LGS without joints. The findings could enrich the connection types for LGSs for construction convenience and mechanical efficiency and further provide reference for the design of the two-way LGSs.