## 4 Conclusions  
In summary, a simplified method for designing timber-concrete composite roof and floor structures with posi-joisted beams was generalized and validated through laboratory experiments and FE model analysis. The method relies on the transformed section method and \(\gamma\)-method, and its applicability was tested on a structure comprising posi-joisted beams, OSB sheets joined with screws, and a layer of concrete bonded to the OSB sheets using epoxy glue and granite chips.  
The findings indicate that the simplified method is suitable for preliminary design purposes of timber-concrete composite structures with posi-joisted beams and for determining structural parameters essential for developing FE models. A similar approach has previously been tested in the case of timber-concrete composite structures with cross-laminated timber panels, which highlights the potential versatility of suggested method across various configurations.  
The mean difference in maximum vertical displacement between the simplified method and laboratory experiments did not exceed 11.6%. An FE model of the timber-concrete composite structure with posi-joisted beams, developed using Ansys R2 2022 software, was validated through laboratory experiments, with BEAM 188 and SHELL FE types recommended for modelling timber chords and OSBs, concrete layer, and steel webs, respectively.  
Moreover, the addition of a concrete layer with a thickness of 50 mm and mechanical properties close to C25/30 strength class concrete resulted in a significant enhancement, increasing the load-carrying capacity of the investigated structure with posi-joisted beams, OSB sheets, and screws by 32.28%.  
While the method exhibits promise as a preliminary design and parameter estimation tool, design practitioners should be aware of its limitations, particularly regarding loading conditions, material properties, and the absence of considerations for concrete creep and shrinkage effects. Further research is imperative to validate the method across a broader spectrum of conditions, enhancing its accuracy for practical design applications. The ongoing pursuit of validation with field data is crucial for bridging the gap between theoretical advancements and real-world structural behaviour. As long-term behaviour is essential, future research should incorporate extended experimental periods with the monitoring of structures over an extended period to gain insights into the effects of creep, shrinkage, and other time-dependent phenomena.  
Conceptualisation, A.R., D.S. and K.B.-V.; methodology, A.R., D.S., K.B.-V. and P.A.; software, P.A. and A.R.; investigation, A.R., D.S., G.S. and E.B.; data curation, A.R., D.S. and P.A.; writing--original draft preparation, D.S., K.B.-V. and V.L.; writing--review and editing, D.S., K.B.-V. and V.L.; visualisation, A.R. and K.B.-V.; project administration, D.S. and V.L. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Latvian Council of Science funded project \"Method of Correlation of Coaxial Accelerations in 6D Space for Quality Assessment of Structural Joints (COACCEL)\" (Nr. lzp-2020/1-0240) and by \"ZM-2024/9 Behaviour analyses of different types of timber-concrete beams type panels\".  
Not applicable.  
The data that support the findings of this study are available from the first author ([PERSON]) upon request.  
The authors declare no conflicts of interest.