Effects of stud aspect ratio and cover thickness on push-out performance of thin full-depth precast UHPC slabs with grouped short studs: Experimental evaluation and design considerations

Steel-precast ultra-high-performance concrete (UHPC) composite beams containing grouped short studs in thin full-depth slabs are an economical and eco-friendly alternative for accelerated bridge construction (ABC). Nevertheless, there is limited information on the push-out performance of thin full-depth precast UHPC slabs with grouped short studs. To this end, this study examined the impacts of stud heights disturbing from 35 mm to 85 mm, stud diameters ranging from 16 mm to 22 mm, and cover thicknesses varying from 15 mm to 65 mm on the push-out performances of such members. The test results indicated that increases in stud height yielded insignificant enhancements in the shear stiffness, strength, and ductility of grouped short studs embedded in thin full-depth precast UHPC slabs. Similarly, variations in the stud height and cover thickness exerted negligible influence on the structural performance. Notwithstanding, larger cover thicknesses or larger stud diameters allow the stud to exhibit attractive shear behaviors. Based on these results, a lower limit of 1.84 for stud aspect ratios (i.e. the ratio of stud height to stud diameter) and 15 mm for cover thickness were recommended. Finally, more accurate formulas were developed to predict the shear capacity of studs by capturing weld collar contributions and to simulate the load-slip relationship of grouped short studs embedded in thin full-depth precast UHPC slabs by considering the effects of slab thickness.