An integrated approach for the analysis of historic timber structures combining enhanced photogrammetry and finite element modeling

Vision-based 3D Deformation Reconstruction of a Composite–Wood Hybrid Structure under Transient Load Release

Accurate reconstruction of complex structural deformation is essential for understanding transient mechanical responses in hybrid and multi-material systems. This study presents a vision-based approach for three-dimensional deformation reconstruction of a composite–wood hybrid structure subjected to transient load release. The investigated specimen consists of a U-shaped carbon-fiber-reinforced composite beam connected perpendicularly to a wooden cantilever beam, forming a configuration that exhibits strong coupling between bending and torsion during load removal. A single-camera imaging system was employed to capture the structural response throughout the release process. Surface motion was extracted from image sequences using feature tracking and temporal filtering techniques. Based on the known structural geometry and camera calibration parameters, the three-dimensional deformation field was recovered from single-view data. This method enables non-contact and full-field reconstruction without requiring embedded or attached sensors, making it well suited for hybrid or geometrically irregular structures. Preliminary experiments demonstrate that the proposed approach can effectively capture the evolution of deformation and reveal coupled twisting and bending behaviors during the transient release event. The reconstructed deformation patterns qualitatively agree with visual observations, highlighting the capability of single-view vision methods to characterize dynamic structural responses. The proposed framework provides a practical and low-cost solution for dynamic deformation monitoring of complex and multi-material structures. It underscores the potential of vision-based sensing as a valuable complement to conventional techniques in structural health monitoring applications where sensor deployment or accessibility is limited.

Integrated Photogrammetric, Petrographic, and Mechanical Assessment of Plutonic Rocks as Dimension Stone Resources

UAV Photogrammetry and Geodetic Techniques for Concrete Dome Deformation Assessment

Historic reinforced concrete domes represent valuable cultural and architectural heritage that requires accurate geometric assessment to ensure their structural stability and support long-term conservation. This study proposes an integrated methodology for assessing the geometric deviations of a historic reinforced concrete dome at St. Mary and St. Joseph Church in Alexandria, Egypt. The proposed methods combine UAV close-range photogrammetry, terrestrial laser scanning (TLS), and total station observations to generate high-resolution three-dimensional models and evaluate the as-built geometry against the theoretical design. Cross-sectional and geometric analyses were performed to investigate radial, vertical, horizontal, and centric deviations, while the reliability of the photogrammetric data was verified through camera calibration and comparison with independent geodetic measurements. The results demonstrated that the integrated methodology successfully identified geometric irregularities and deformation patterns with a high level of consistency among the three surveying techniques. The validation process confirmed the reliability of UAV photogrammetry for structural deformation assessment when integrated with TLS. The proposed framework provides a practical and accurate solution for the geometric evaluation and long-term monitoring of historic concrete domes, contributing to improved structural condition assessment and supporting maintenance, conservation, and heritage preservation programs.

Comparative analysis of concrete constitutive models in flexural beams using digital image correlation

This study investigates the influence of constitutive model parameters on both the global and local response of reinforced concrete beams. Advanced numerical simulations require appropriate material models to represent the specimen behaviour, so this research compares simplified engineering procedures with the concrete damage plas - ticity (CDP) model. A single representative specimen was analysed using a high-resolution digital image correlation (DIC) system to provide dense experimental data for precise calibration. The investigation focuses on identifying the specific tension stiffening description that best reflects the fracture kinematics recorded by the optical system. Results indicate that the strain-dependent approach (specifically the Massicotte model) offers superior consistency with experimental crack patterns and load-deflection curves. In contrast, models based on fracture energy exhibited unphysical blurring of damage zones and poorer crack localization. The study concludes that broad validation extending beyond global load-deflection curves, utilizing local displacement fields from DIC, is essential for an objective assessment of numerical model quality and the optimization of concrete structure design.

Integrated Laser Scanning and Image-Based Topology Optimization Techniques for Detection and Quantification of Visible and Subsurface Structural Defects

Reliable characterization of structural defects requires methods capable of resolving both directly observable surface damage and damage that is not visible from the inspected surface. This study presents two complementary non-contact, vision-based approaches for the detection and quantitative characterization of defects in structural components. The first approach employs high-resolution laser scanning to generate three-dimensional (3D) point clouds of damaged steel specimens. Comparative processing of measured and reference point clouds is used to localize damaged regions, quantify geometric loss, and transfer the measured defect geometry to a finite element representation. The second approach combines full-field surface deformation measurements obtained using three-dimensional digital image correlation (3D-DIC) with finite element model updating and topology optimization. In this inverse framework, measured surface response is used to infer subsurface abnormalities through their influence on the spatial distribution of structural response. Experimental steel-beam specimens containing controlled smooth defects and randomly distributed defects are used to evaluate the approaches. Comparisons with milling-based ground-truth measurements demonstrate that both methods can identify and quantify defect geometry, while providing complementary information for visible and subsurface damage assessment. The combined framework establishes a pathway toward high-fidelity, non-contact structural condition assessment and model updating for components with complex and irregular damage.

Three-dimensional reconstruction and crack measurement of cultural monuments using UAV-based photogrammetry

Abstract. Three-dimensional (3D) modeling for the documentation, preservation, and management of cultural heritage is indispensable. To achieve this goal, a low-cost unmanned aerial vehicle (UAV) combined with the Structure from Motion (SfM) photogrammetric technique was utilized to build a 3D model and conduct surface crack measurements of cultural monuments. The results showed that, under simple conditions, non-specialists can easily generate accurate 3D models from UAV-acquired imagery. In this study, the statistical errors of checkpoints between 3D reconstruction and field measurements, expressed as total RMSE, ranged from 0.103 m to 0.848 m. However, the mean absolute errors of surface crack measurements between tape-based methods and 3D reconstruction ranged from 0.002 m to 0.099 m. Furthermore, UAV-SfM was applied to measure surface crack lengths on an inaccessible cultural monument. The findings demonstrated that employing the UAV-SfM photogrammetric technique for 3D reconstruction of cultural monuments is both feasible and reliable.