Experimental study on group effect of perfobond strip connectors encased in UHPC

• Published in: Engineering structures 2022-01, Vol.250, p.113424, Article 113424
• Main Authors: Tan, Xingyu, Fang, Zhi, Xiong, Xuanwei
• Format: Article
• Language: English
• Subjects: Bearing capacity; Concrete; Connectors; Fibers; Group effect; Hybrid structures; Perfobond strip connector (PBL); Push-out test; Reinforced concrete; Reinforcing steels; Row spacing; Shear connector group; Shear strength; Steel; Steel fibers; Strip; Ultimate loads; Ultra high performance concrete; Ultrahigh performance concrete (UHPC)
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2021.113424

•Push-out tests on 26 local full-scale encased PBL specimens are conducted to examine the shear performance of UHPC-based PBL groups in the steel–concrete joints of hybrid structures.•Influences of the concrete type, row number and row spacing on the shear behavior of UHPC-based PBL shear connector groups are identified experimentally, and the mechanism is discussed in detail.•With a reduction coefficient accounting for the group effect introduced, a simplified and reliable equation for the ultimate capacity of multirow PBLs embedded in ordinary concrete or UHPC is proposed and verified.•A simplified evaluation of the shear safety of PBLs encased in UHPC is performed based on the existing design codes and the proposed equations, and certain suggestions for the structural design of steel–concrete joints using the UHPC are provided. The group effect on the shear capacity of perfobond strip (PBL) connector group embedded in ultrahigh performance concrete (UHPC) in the steel–concrete joints of hybrid structures was studied experimentally. Push-out tests were performed on 26 encased PBL specimens parameterized by the concrete type, row (or hole) number, and row spacing of connectors. The test results revealed that the failures of all the connections were characterized by the shear fracture of the reinforced concrete dowels. The average ultimate capacities per row of shear connectors in UHPC without steel fibers and with 2% volume fraction of steel fibers were approximately 19% and 42% higher, respectively, than those in C55 normal concrete, owing to the high shear strength of the matrix in UHPC and further enhancement by steel fibers. The effect of increasing the row number from 1 to 3 was a decrease of approximately 17% in the average ultimate load per row of connectors. Similarly, a decrease in row spacing from 3.85 to 2.0 times the hole diameter caused an approximately 14% decrease in the average ultimate load per row. With a reduction coefficient accounting for the group effect introduced, an alternative equation for the ultimate capacity of multirow PBLs was proposed, verified, and adopted in the simplified shear safety evaluation.