Browsing by Author "Jebara, Khalil"

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Open Access
Design recommendations for concrete pryout capacity of headed steel studs and post-installed anchors
(2023) Jebara, Khalil; Sharma, Akanshu; Ožbolt, Joško
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 (hef/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.
Open Access
Pryout capacity and bearing behavior of stocky headed stud anchorages
(2018) Jebara, Khalil; Ožbolt, Joško (Prof. Dr.-Ing. habil.)
Concrete pryout failure mode, which occurs for relatively short and stocky cast-in headed studs or post installed anchors, has been investigated only to a limited extent in the past. The increasing use of such anchorages in engineering practice emphasizes the need to clarify the pryout failure mechanism and to formulate design rules that assure safe and economical structural design. Currently used design provisions to predict the pryout capacity are conservative and based on the so-called indirect-tension model, which applys the CC-Method for anchors loaded in tension to predict the pryout capacity of anchors loaded in shear and fail in pryout. The aim of this dissertation is to get more understanding into the load bearing behaviour and the pryout mechanism of shallowly embedded anchors and anchor groups, which are likely fail in concrete pryout. Furthermore, it aims at extending the CC-method to account for the pryout failure mode and improving current design recommendations. This dissertation covers experimental and numerical investigations. The experimental investigation aims at clarifying the bearing bahavior and influencing parameter of stocky cast-in single welded headed studs, which fail in concrete pryout. On the other hand, the numerical investigation aims at parametric study and pryout failure simulation of single anchor and anchor group. The results of the experimental and numerical investigation are evaluated and discussed. Finally, based on the obtained results a pryout capacity prediction equation for anchors under pure shear load is presented. An extended CC-method for pryout failure mode, which accounts for single anchor and anchor group as well as for edge and corner influence, is proposed and compared with current design formula.