**4. Conclusions**

This paper describes a WRMS-based ultrasonic non-destructive testing approach based on the scanning laser Doppler vibrometry technique. The damage identification and imaging in composite steel–concrete beams were performed. Based on the results of the experimental investigations evaluated by numerical FEM simulations and supported by theoretical analysis, the following final remarks can be formulated.


The leading conclusion of the presented research is that the guided wave propagation method supported with WRMS calculation can be successfully applied for damaged imaging in steel–concrete composite beams. However, considering the complexity of guided wave propagation phenomenon, it is important to perform some initial analysis, including dispersion curves determination and FEM numerical calculations. Further works will be directed to develop the proposed method to be applicable for non-destructive diagnostics of real-scale engineering structures.

**Author Contributions:** Conceptualization and Methodology, E.W. and M.R.; Experimental Investigations, M.R. and E.W.; FEM Calculations, E.W. and M.K.; Formal Analysis, E.W.; Visualization, E.W.; Writing—Original Draft Preparation, E.W. and M.K.; Writing—Review and Editing, MR.; Supervision, M.R.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** Abaqus calculations were carried out at the Academic Computer Centre in Gda ´nsk.

**Conflicts of Interest:** The authors declare no conflict of interest.
