Abstract

Prestressed structures are a key to the realization of the boldest architectural ideas, regardless of shape complexity, great height and large span. A characteristic feature of the prestressed structure is the better use of concrete material properties by insertion of internal forces. The internal forces are opposed to external loads effects (forces and deformations of structure). Prestressed reinforced concrete beams are characterized by lower demand for conventional reinforcing steel and provide protection against cracks occurrence in bending and shear zones. However, their most important feature is the high strength. Controlled failure of prestressed reinforced concrete beam was carried out in a Regional Laboratory of Civil Engineering by Concrete Structures Department at the Gdansk University of Technology, as a part of research focused on optical methods development for the diagnosis of concrete structures. Assessment of geometry changes of prestressed concrete beams was performed using synergy in terre trial laser scanning (TLS) and registration with a use of synchronous photography, photogrammetric methods. At the same time, classical measurement methods with the use of strain gauge electrometer and clock deflectometer were performed. Measurement data from laser scans have been processed in dedicated to working with point cloud software. The analysis allowed describing the methods for assessing changes in geometry and structure of prestressed concrete elements. Simultaneous use of terrestrial laser scanning and synchronous cameras photogrammetry led the authors to a creation of common ground for cooperation between these two different technologies. Application of both methods provided to obtain the more accurate representation of geometry than in laser scanning result. Moreover, the authors specify the areas in which remote sensing methods have significant advantages over conventional methods (mechanical methods). Failure process of prestressed concrete elements, especially with high-strength concrete and very strong compression, might be rapid and violent. Extremely fast and violent nature of prestressed concrete failure causes a limitation of study capabilities, which lead to a conclusion that standard method is insufficient. The authors referred to this problem by propose of High-Speed cameras that allowed recording images at speeds up to 25 000 frames per second.

Citations

Authors (3)