A Non-contact Monitoring System for Investigating As-built Membrane Roof Structures

A monitoring system that uses applied geomatics techniques, including terrestrial laser scanning and videogrammetry, has been developed in order to determine the behaviour of as-built membrane roof structures. To accommodate the constraints involved in measuring such structures, for example uniform surface texture and unreachable height, the system adopts a non-contact targeting methodology to substitute for traditional control techniques. This paper reports on experiments conducted to prove that the monitoring system is capable of satisfactorily measuring a typical membrane roof structure. Firstly, in the scheme of investigating the discrepancy between the original design for the membrane roof and the finished version, terrestrial laser scanning is used to produce an as-built model of the membrane structure. The as-built model is then statistically compared with the designed mathematical model using a surface matching approach. The results revealed significant differences between the finished structure and the designed model. Secondly, a sequential 3D surface model was generated from a videogrammetric monitoring scheme, thereby allowing the displacement of the observed area of the membrane surface to be investigated over time. The information acquired from the system is proving to be of great value to structural engineers involved in designing such membrane structures. * Corresponding author.