# The Behaviour of Half-Slabs and Hollow-Core Slab in Four-Edge Supported Conditions
## 6 Conclusions  
The crucial element of qualitative tests was comparing the deflection performance of the selected slabs exposed to short- and long-term loading. A common feature was the lack of joint reinforcement. The presented conclusions are limited to the range of serviceable loads of the selected precast or semi-precast slabs. The slab panels maintained the possibility of load redistribution based on their interaction, despite the work of the longitudinal joints occurring only through the concrete cross-section. A more significant reduction in the stiffness in the lateral direction indicated by shift of the displacement curves towards the centre of the maximum load zone can be attributed to the lack of joint reinforcement. The precast panels connected with topping showed better parameters of the lateral interactions than the elements connected only in shear key (HC). The lack of traversal reinforcement on the LGR and LGF model significantly affected the cracking morphology and the maximum deflections under the long-term loading conditions.  
The simply supported beam model included in the calculations seems to be an overly conservative approach that does not allow accurate evaluation of the effects. A deflection overestimation of almost threefold cannot be considered a proper estimate. This approach does not take into account the plate behaviour of the model. The Marcus method produced significantly underestimated results, up to 99%. The simplified FEM approach to computations of spatial arrangement was also proposed. In that case, the level of underestimated deflections under the short-term loading did not exceed 42%. Similar results were obtained for the long-term loading. The opposite situation was observed for the model with hinge connections used for the HC slab. Calculated deflections each time were greater than the measured ones. Such results are at the acceptable level due to being the safe estimation. The hinge connection approach generates significantly less error than the current commonly used simply supported beam methods. The deflection of the FEM models can be precisely calculated by reducing the thickness of the joints. However, this approach requires a calibration procedure. Establishing the relationship with joint thickness reduction requires further research. Considering the research presented in the introduction, the analysis of displacement charts and numerical calculations, it could be formulated that the hinge model of the joint could be the answer for a design model of the presented slabs.  
Based on the short- and long-term studies, it can be concluded that the simplified calculation methods provide an unsatisfactory level of accuracy. Therefore, there is room for developing guidelines and unifying codes to design and calculate half-slabs without transverse reinforcement. Currently, we are conducting a laboratory test of half-slab models to fulfil a cognitive gap with respect to the calculation approach. The major aspect of research is the concrete-concrete interface and crack pattern at the ultimate load of slabs without transverse reinforcement. The conducted study will allow for more precise numerical representations of slab performance and the development of comprehensive guidelines.  
Conceptualisation L.D. and A.K.; methodology J.Z., L.D., R.J. and M.W.; software [PERSON] and W.M.; formal analysis [PERSON] and M.W.; investigation [PERSON], L.D., R.J., M.W., W.M. and K.G.; resources A.K.; data curation [PERSON] and R.J.; writing--original draft preparation J.Z.; writing--review and editing L.D., R.J. and K.G.; visualisation J.Z.; supervision L.D. and A.K.; project administration L.D. and A.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
We thank [PERSON] for his invaluable help in preparing research, particularly in the field of technical support. We want to thank the KONBET company for providing materials and space for research.  
The authors declare no conflict of interest.