Structural investigations by infrared thermography and SPR
by
Patrizia Capizzi
CFTA Department, University of Palermo, Via Archirafi n°26, 90123 Palermo (Italy)
Coauthors: Cosentino P., Fiandaca G., Messina P and Terranova L.

The aim of this paper discusses two recent geophysical methodologies for purposes of civil engineering, namely the application for structural analysis of ancient buildings.

Infrared thermography is a non-destructive and non-contact technique to convert the target temperature related infrared heat energy into visible images. An IR scanner converts heat energy into an electrical signal, which is then turned into thermal picture by a microprocessor. Thermal images are displayed on computer screen in either a grey or colour scale, in which each different shade represents a temperature range. A limitation of this method is that the thermal images show only a global view (the location of the subsurface anomaly can be described only by 2D image of external surface). Other restraint is that the thermographic surveys are much influenced by climatic conditions. The infrared thermographic images, here presented, have been acquired using the P40 thermocamera by FLIR System.

The georadar is one of the recent geophysical techniques and is used in different fields. It can be successfully used to examine building walls, structural defects, floors, roads, railways, cavities or to carry out buried object detection. The higher frequencies (from 400 MHz to 2 GHz) can be successfully used for non-destructive evaluation (NDE) of building structures.

The NDE objectives for using SPR are:

 quality assurance to confirm the structure has been built in accord with the design specification;

 monitoring to assure the structure's component materials have not degraded with time (to detect possible structural failure);

 developing as-built drawings where none exist.

SPR has emerged recently as an alternate technique to X-raying concrete structures prior to cutting and coring. Historically, X-ray technology created a photographic image of the concrete interior but it required access to both sides of the structure and involved the use of hazardous X-ray sources.

Measurements have been carried out with a GSSI SPR system, namely SIR 3000. The high frequency antennas are best suited for the type of research here discussed and the depths which we plan to reach.

During restructure works of “G. Di Cristina” hospital in Palermo, it was necessary to recognize building typology, detecting and locating structural components.

Infrared thermographic images have been acquired in external front of building in order to obtain an immediate image of structural elements. In particular, building structural characteristics have been pointed out. The first two levels show a masonry structure with reinforced – concrete pillars in the corners. The upper storeys (built on later) show a carrying structure by pillars and beams.

SPR data have been acquired on a structural elements inside the building in order to obtain more detailed information.

Finally, possible integrations of two methodologies is discussed.

Date received: September 14, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caon-53.