**7. Conclusions and Final Remarks**

Interdisciplinary and comprehensive non-destructive diagnostic tests of final bridge inspection and acceptance of a soil-steel bridge made of corrugated sheets, being the European span length record holder (25.74 m), done in the year 2017 and 2018, were described. Non-standard program of bridge loading was used during the inspection. On the one hand, classically, static loads were applied to the bridge by appropriate arrangement of trucks. On the other hand, the bridge response was studied under moving loads, to reduce permanent deformations when it was unloaded.

Because of the large dimension of the structure and also because its deformations under standard traffic loads are very small (a few mm only), sophisticated terrestrial laser scanning was done in order to measure short-term response of the bridge. Its accuracy was significantly increased by additional correction of results based on total station surveying and inductive sensors vertical displacement control. The resulting 3D deformation images of the steel shell sections, with the achieved precision (X, Y ~0.1 mm; Z ~0.01 mm; for the 2 mm × 2 mm grid of measurement points) and accuracy of the laser scanning ~0.3 mm, can be considered as a unique achievement. Such a high precision and accuracy of the geodetic measurement allowed to reliably identify bridge displacements, which under maximum loads were not more than 1.7 mm. Moreover, this image satisfies the conditions of the reference state in the case of structure monitoring, and possible periodic diagnostics during its life cycle.

A control of the structure geometry shape was done one year after the final inspection. In effect, maximum total displacement of the bridge, which occurred in one-year period, determined in terrestrial laser scanning equaled 7 mm. The scan accuracy in this case was ~2 mm. This is typical for structures of this type. Thus, we can say that the bridge experienced a change of its shape, which however does not affect its response and load bearing capacity.

A computational model of the bridge was built in order to verify the appropriateness of the design process. In situ short-term response measurements were compared with the numerical calculations resulting from FEM analyses. Calibration of the backfill elastic modulus based on the measured response of the bridge was done and the resulting accuracy of the displacements predictions was at the level of 95%. The model reflects the real response of the structure in the field of both quality and quantity of displacements and its strain. This confirms that the approach to modelling proposed in this paper was appropriate and that the bridge was correctly designed. In effect it can be used for the purpose of the bridge diagnostics or support interpretation of SHM data.

The bridge underwent all the required final acceptance tests and inspections and currently there are no doubts about its behavior during the designed lifetime. Moreover, its accurate periodic diagnostics is also possible.

**Author Contributions:** Conceptualization, M.M.; data curation, M.M., B.S. and P.T.; formal analysis, M.M., B.S. and P.T.; investigation, M.M., B.S. and P.T.; methodology, M.M., B.S. and P.T.; resources, M.M.; supervision M.M.; visualization, B.S., P.T.; writing—original draft, B.S., P.T.; writing—review and editing, M.M., B.S. and P.T. All authors have read and agreed to the published version of the manuscript.

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

**Acknowledgments:** The authors acknowledge the support provided by: the main contractor Budimex S.A., subcontractor ViaCon Polska Ltd. and research teams from Aspekt Laboratorium Ltd. and Gda ´nsk University of Technology (Department of Mechanics of Materials and Structures, Department of Geodesy) in conducting presented studies. Abaqus calculations were carried out at the Academic Computer Centre in Gda ´nsk.

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