Shear testing of glass fiber–reinforced polymer (GFRP) bars can be considered for material specifications, quality control, quality assurance, and structural design purposes. ASTM and the Canadian Standards Association (CSA) specify the testing apparatus and the procedure to test fiber-reinforced polymer (FRP) matrix composites, in which the principal variables are the size (diameter) and type of the FRP bars. This study develops a device to test GFRP bars in shear based on both ASTM and CSA standards. The paper provides information about the significance of shear testing of GFRP bars and the potential outcomes of this type of test. For that purpose, different types of GFRP bars (straight and bent) provided by two different suppliers are studied. Two test series are considered. The first examines straight and bent bars from two different companies, and tests two different diameters of the GFRP bars. The straight bars are tested with and without their outer coating (provided by the companies) and the bent bars are tested in their straight portion. The same bars are tested in shear after being in an alkaline solution (pH 13) for 5 months (150 days) at 60°C. The second test series considers GFRP bars of various diameters (original GFRP bars are shaved). The main objective of this work is to propose a shear testing protocol for GFRP bars of various diameters by reducing the number of cutting blades of the shear testing device. Finally, the failure modes and the significance of stiffness are discussed.

Eccentric punching shear can occur in concrete slab–column connections when the connection is subjected to shear and unbalanced moments. Unbalanced moments occur in all floor slabs at the edge and corner columns. As such, this problem is of practical relevance. However, most punching experiments in the literature deal with concentric punching shear at internal columns. This paper presents a developed database of 128 experiments of flat slabs under eccentric punching shear, including a summary of the testing procedure of each reference and a description of the slab specimens. Additionally, a linear finite element analysis of all the specimens is included to determine the relevant sectional shear forces and moments. Finally, the ultimate shear stresses from the database experiments are compared to the shear capacities determined with ACI 318-19, Eurocode 2 and the Model Code 2010. The comparison shows that the Model Code 2010 is the most precise in the predictions with an average tested to predicted ratio of 0.82 and a coefficient of variation of 29.63%. It can be concluded that improvements to the current design methods for eccentric punching shear are necessary.

Many times, existing RC flat slabs must be retrofitted to enhance their structural performance and service life. Among other retrofit techniques, concrete flat slabs can be strengthened with a top thin layer of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Since UHPFRC is a relatively expensive material compared to conventional concrete, an optimized investigation regarding the location and thickness of the UHPFRC layer may be necessary. This study examines the punching shear performance of isolated RC flat slabs retrofitted with various layouts of UHPFRC. Two optimal retrofitting configurations are proposed and evaluated using three-dimensional (3D) nonlinear finite-element analysis, where both regular concrete and UHPFRC are simulated using a combined damaged plasticity–based model. The model is verified by analyzing previously tested slab–column connections from the literature. Then the predictive capability of the model is further verified by conducting parametric studies to investigate the effect of varying the thickness and area of the UHPFRC layer on the punching shear performance of the slabs. The maximum shear resistance, deformation, and crack propagation patterns of the composite slabs with different thicknesses, areas, and orientations of the UHPFRC layer are examined. The increase in thickness of the UHPFRC layer increases the punching shear capacity. However, the displacement at the maximum resistance decreases when the thickness of the UHPFRC layer increases. The use of a UHPFRC layer only on the critical areas of a slab can be more effective and economical since the amount of UHPFRC is reduced and the ductility of the slab is increased.