3D Modeling and section properties of ancient irregular timber structures by means of digital Photogrammetry

This article deals with the application of low-cost Close Range Digital Photogrammetry to obtain an accurate three-dimensional (3D) re-construction of irregular geometry structures in the field of building construction, with special attention to the evaluation of old structures. Photogrammetry can be used as a non-destructive toot to give precise 3D information about the size and shape of some elements of a structure, quickly and with no risk to the surveyors. The geometric data achieved can be used by engineers and architects to obtain the section properties, and also to estimate the influence of geometric variations in the distribution of stress. This allows us to compare areas subject to higher stress, and could be of special interest regarding some historic and cultural heritage constructions - such as the timber roof structure included as a case study in this work-from two points of view: On the one hand, Photogrammetry makes it possible to obtain precise 3D models of highly irregular elements, as old timber purlines and trusses in the case of ancient constructions; on the other, Photogrammetry is a non-contact method that minimizes the measurement time and allows its to obtain the section properties, which can be used together with some material testing characterization to evaluate the structural safety of the construction.