## 6 Discussion and Conclusions  
Short head anchors are a modern way to create compact joints in precast reinforced concrete structures. Experimental research and subsequent numerical simulations indicate several interesting facts that can be summarized in the following points:  
* A short-headed anchor's resistance can be increased by more than 70% by using supplementary reinforcement in the form of stirrups and longitudinal rebars, proving the performed experimental measurement. Supplementary reinforcement can also prevent brittle failure of the anchorage.
* It is possible to create a numerical model by using suitable specialized software that credibly simulates the action of a tensile-loading anchor with or without supplementary reinforcement.
* The mechanism of failure, the way of crack propagation, and the predicted value of the anchorage resistance determined by the numerical analysis correspond to the experiments. The correlation coefficient reaches a value of more than 0.95.
* According to the numerical analysis, the influence of concrete strength on anchorage resistance is non-linear, and it is higher for anchors without supplementary reinforcement.
* The use of supplementary reinforcement, although small in diameter (\(\mathcal{O}\) 6 mm), can significantly increase the anchorage's final resistance (+55%). However, further increasing the supplementary reinforcement diameter (area) does not cause such a significant increase in the anchorage resistance.  
The investigation of anchorages in reinforced concrete structural elements is relatively demanding due to the large number of input parameters affecting their stiffness and resistance. In further work, it will be necessary to examine other parameters, such as the embedment depth of anchorage, the global stiffness of the concrete members in which the anchorage is installed, the distance of the anchor from the edges, the shape and size of the anchor, or the arrangement of supplementary reinforcement. Based on real experiments, numerical simulations also appear in this case as a suitable solution for the preparation of test programs and their appropriate complementation. The investigation results can also be used for practical optimization and the preliminary design of particular anchorage systems, especially in some particular cases when the standards and recommendations give inaccurate results.  
The future aim of the research is to improve the numerical models (e.g., implement the more sophisticated material model of the steel, the more precise definition of boundary conditions) and combine numerical simulations with analyses based on probabilistic methods.  
Conceptualization, M.F. and R.H.; methodology, M.R.; software, M.F.; validation, J.J. and M.R.; formal analysis, R.H.; investigation, M.F.; resources, J.J.; data curation, J.J.; writing--original draft preparation, M.F.; writing--review and editing, R.H.; visualization, M.R.; supervision, M.F.; project administration, M.F.; funding acquisition, R.H., M.F. and J.J. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Research Project No. 1/0343/18 of the Slovak Scientific Grant Agency VEGA.