Behaviour of Embedded Plates Under Eccentric Shear Loading in Reinforced Concrete
Creators: Smithaniuk, Caine
Publisher: name: University of Alberta Library
Year: 2022

<p>Embedded plates (embeds) are a common method of joining steel and concrete members in structures. Research at the University of Alberta emphasized the lack of consideration in the Canadian concrete design standard CSA A23.3:19 Annex D for the effect of reinforcement on anchorage capacity, as well as the treatment of combined loading for common shear-type connections. Conservatism in design and confusion for designers are manifestations of the current limitations of the design standard. There is currently no practical approach, codified or otherwise, that can accurately describe the behaviour of embeds in reinforced concrete. This research project aims to improve the design of embeds by identifying limitations in current design practices, and then testing previously standardized embedded plates to assess<br>
the effects of supplementary reinforcement and common shear connections, parameters that are inadequately addressed by CSA A23.3:19 Annex D. One four-stud embed standardized by Chin(2021) was tested in eccentric shear towards a free edge at a constant edge distance of 150 mm to the nearest row of anchors. Eight full-scale tests were conducted with shear reinforcement (10M stirrups) spaced at 250, 215, or 175 mm on centre with two different shear connection details (double angle and shear tab) that are commonly used in practice. From the test results, A23.3:19 was conservative in its calculation of concrete breakout strength in shear especially when tension-shear interaction effects due to eccentricity of the shear load (distance between top of concrete to bolt line on the shear connection) are considered. An average test-to-predicted ratio of 3.75 was<br>
found when comparing test results that failed by concrete breakout to A23.3:19 predictions as they would be calculated by designers (i.e., including material resistance factors and the<br>
5% fractile which is an additional safety factor that reduces capacity by ~25%), whereas this ratio is 1.17 when the material resistance factor is omitted and the 50% fractile (i.e., the mean or average expression) is used to calculate concrete breakout strength. The latter test-to-predicted ratio is closer to unity because the failure mode shifted from shear to tension concrete breakout as shear reinforcement density increased, meaning that shear reinforcement was unable to increase capacity due to a lack of rotational restraint in the test system. Tension effects on embeds loaded in eccentric shear are significant and must be considered in<br>
design. When increasing shear breakout strength by adding supplementary reinforcement, tension breakout strength must also be increased to properly utilize shear reinforcement.<br>
When tension effects associated with a lack of rotational restraint are properly accounted for, expressions from Eligehausen et al. (2019) provide good estimates of capacity for the tests, with test-to-predicted ratios of 0.98 to 1.07. Interaction curves for the standardized four stud embed from Chin (2021) are also provided for ease of calculating shear capacity.</p>