Effect of fiber type on pull-out and shear strengths of various cast-in connectors in thin UHPFRC panels of different thicknesses

Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) enables a reduction in the overall volume of concrete required to satisfy structural requirements, leading to lightweight thin structural elements suitable for a variety of applications. This paper investigates the pull-out ( P u ) and shear strength ( V u ) of 48 cast-in connectors in ultra-thin UHPFRC panels ranging from 15 to 38 mm in thickness and reinforced with 2% steel fibers. Results were compared with counterparts reinforced with 2% polyoxymethylene (POM) fibers, which could be advantageous in terms of fire resistance and reduction in concrete spalling in building wall applications due to the increase in gas permeability under higher temperatures reaching up to 600 ℃ ℃ . The study examined three types of connectors, namely headed and L -shape bolts and headed inserts. It was shown that pull-out and shear strengths of cast-in connectors in panels with steel fibers range from 2.1 to 2.4 times those with POM fibers. Head diameter of the connector directly affects pull-out strength but not shear strength. As edge distance increased from 2.6 to 6.7 times the connector diameter, the shear capacity increased by 69%. Panel thickness directly affects pull-out and shear strengths of connectors that are fully embedded. For example, a 50% increase in panel thickness increased pull-out and shear strengths by 135% and 49%, respectively. New design equations have been developed for cast-in connectors in thin UHPFRC panels with steel fibers.