Composite materials are widely preferred for various applications owing to their unique properties for instance the wide use of steel-concrete composite beams in structures. Shear connectors, the most crucial components of these materials, are generally used in transferring longitudinal shear forces between the steel boxes and concrete slabs. Their deformation will thus cause serious effects on the structural stiffness and load-bearing capacity of the beam. Consequently, the complicated nature of shear connectors with perforated steel plates is attributed to the influence of various factors including the depth of the steel plate, the hole diameter on the steel plate and the concrete compressive strength that considerably influence the mechanical behavior of shear connectors during loading. Therefore, it is of great importance to understand their load-bearing capacity and load-slip relationship.
Perfobond shear connectors were recently proposed to improve the binding between the steel boxes and concrete plates. Perforated steels in perfobond shear connectors are constrained by both hoop and concrete dowel thus have superior mechanical properties as compared to shear connectors with perforated steel plates. Despite these promising results, the bearing capacity and load-slip relationship of perfobond hoop have not been fully explored. To these end, experimental investigation of crucial parameters influencing their bearing capacity and load-slip relationship is highly desirable.
In a recent research, scientists at Wuhan University of Technology: Xiao Li, Zhijian Hu and Yasir Ibrahim Shah together with Liang Fan from Chongqing Jiatong University investigated mechanical behavior of perfobond hoop via push-out tests conducted under static loading. They determined the corresponding bearing capacity, failure modes and load-slip relationship taking into consideration the effects of the crucial parameters. Finally, shear-friction theory and linear regression methods were explored to analyze the experimental results based on the eighteen specimens to develop a simplified formula for determining the perfobond hoop bearing capacity. The work is published in the Engineering Structures journal.
The slip failure at the interface of the steel box and concrete was identified as the main failure mode. An empirical equation for the load-slip relationship of perfobond hoop within the whole loading process was obtained from the fitted normalized experimental results. They were in good agreement with the bearing capacity results of the validated experiments. Based on the load-slip curves, the established formula could be used in calculating the load slip, thus a promising tool for engineering design. Additionally, the main phases of the load-slip curves were also in good agreement with both the exponential form and the validated specimens.
In a nutshell, the study presents an experimental investigation of perfobond hoop shear connector’s bearing capacity and slip. Based on the findings, the ultimate slip was attributed to the deformation of concrete dowels and perforated steel hoops which could be evaluated by the proposed formula. Therefore, in a statement to Advances in Engineering, Xiao Li explained that the proposed formula will provide good references for perfobond hoop related design and applications.
Li, X., Hu, Z., Fan, L., & Shah, Y. (2019). Experimental investigation of perfobond hoop shear connector’s bearing capacity and slip. Engineering Structures, 198, 109461.