Citation: Jebara, K.; Sharma, A.; Ožbolt, J. Design Recommendations for Concrete Pryout Capacity of Headed Steel Studs and Post-Installed Anchors. CivilEng 2023, 4, 782–807. https://doi.org/10.3390/ civileng4030044 Academic Editor: Francesco D’Annibale Received: 27 March 2023 Revised: 20 June 2023 Accepted: 5 July 2023 Published: 10 July 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article Design Recommendations for Concrete Pryout Capacity of Headed Steel Studs and Post-Installed Anchors Khalil Jebara 1 , Akanshu Sharma 2, * and Joško Ožbolt 1 1 Institute for Construction Materials, University of Stuttgart, 70569 Stuttgart, Germany; khalil.jebara@hotmail.com (K.J.); josko.ozbolt@iwb.uni-stuttgart.de (J.O.) 2 Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USA * Correspondence: akanshu@purdue.edu; Tel.: +1-765-496-8368 Abstract: Current formulas to assess the shear capacity of headed steel stud anchors and post-installed (PI) anchors in case of pryout failure (sometimes known as pull-rear failure) have been derived either based on the indirect-tension resistance model or are fully empirical based on push-out test results. In both cases, the predicted pryout capacity is clearly conservative and underestimates the true pryout capacity of anchorages, especially for stiff anchors with low embedment-to-diameter ratios (h ef /d < 4.5). This paper proposes an empirical and a semi-empirical formula to predict the concrete pryout capacity of headed steel studs and PI anchors. They were derived based on an improved indirect-tension model which accounts for the stud diameter and the stud spacing in a group of anchors. Furthermore, a database of 214 monotonic shear tests from the literature, including own tests (push-off and horizontally shear tests), is reevaluated and compared to the provisions of EN1992-4. The scope of this assessment proposal includes single and group of headed steel studs and PI anchors attached to a stiff steel plate as well as shear connectors in composite structures without metal deck embedded in normal-weight concrete. Keywords: pryout capacity; pryout failure; anchor group; welded studs; shear load; design formula 1. Introduction Concrete capacity design method (CCD method) [1] is currently the most frequently used for calculating the concrete breakout capacity of anchors or a group of anchors. Current design codes, such as EN1992-4 [2], ACI 318-19 [3], EOTA-ETAG001 [4] and fib Bulletin 58 [5], which are based on the CCD method, treat concrete cone breakout behind a single anchor or an anchor group under shear load in a way comparable to tension pull-out failure based on the indirect-tension resistance model [6]. Accordingly, the characteristic concrete pryout resistance V Rk,cp is calculated using the following modified mean tensile pull-out capacity equation of an anchor group away from edge effects: V Rk,cp = k 8 · N Rk,c (1) N Rk,c = A c, N / A 0 c, N · N 0 Rk,c (1a) N 0 Rk,c = k 1 · f 0.5 ck · h 1.5 ef (1b) where k 8 empirical factor indicated in the corresponding technical specifications, N Rk,c characteristic concrete breakout strength of anchor group in tension, A c, N / A 0 c, N projection area ratio of anchor group in tension, N 0 Rk,c characteristic concrete breakout strength of single anchor in tension away from edge influence, k 1 empirical factor indicated in the corresponding technical specifications for cracked and uncracked concrete, f ck characteristic cylinder compressive strength of concrete and h ef effective embedment depth. CivilEng 2023, 4, 782–807. https://doi.org/10.3390/civileng4030044 https://www.mdpi.com/journal/civileng