Photogrammetric and Stereo Vision Techniques for Evaluating Material Properties in Timber and Timber-Based Composite Structures

A fundamental requirement for efficient use of a glulam beam is an accurate knowledge of its mechanical behaviour and the material properties characterising that behaviour. It becomes extremely important to obtain accurate measurements of material properties of glulam, but this can be challengeable, especially for commonly used properties, such as the modulus of elasticity and shear modulus. Experiment testing is the way to determine elastic properties, however, the problem of experimentally determining appropriate values of these properties for timber-based composite is not as simple and straightforward as in isotropic materials, and care must be taken in the experimental methods used in determining their values. There is a need to develop an appropriate method in order to evaluate these properties. Unlike the traditional methods in which contact devices such as inclinometers or linear variable differential transducers are used to identify the material properties of glulam by utilizing their measurements of displacements and rotations at specific points, the optical methods provide an efficient and accurate approach for measuring these properties at multi-location so that more regions of interest can be monitored simultaneously without contact. Moreover, the traditional devices are limited to give measurements in one or two dimensions whereas the optical methods can be used to gain measurements in three dimensions. Although the optical techniques were successfully applied to different structural applications, little work has been done on the area of evaluating material properties of timber, especially modulus of elasticity and shear modulus. Therefore, the primary motivation of this project will be allocated to evaluate those properties utilizing the stereo vision approach.This thesis describes the research work in which a stereo camera system combined with a photogrammetric approach was proposed to evaluate material properties of timber and timber-based composite joists. A series of experiments were conducted to investigate the applicability of the approach to evaluate different material properties of glulam beams under different types of tests, including the torsion and the compression.Remarkable findings were obtained which might help for developing an outline for a future research programme in the field of evaluating material properties of glulam, allowing investigating the relationship between these properties. The results also showed that the optical system not only allowed assessing performance and reliability of the traditional sensors, but also allowed monitoring the deformation of the samples at various locations by providing more information which would not be possible to obtain using the traditional techniques