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A scaled model of a two-span masonry arch bridge has been built in order to investigate
the effect of the central pile settlement due to riverbank erosion. The bridge model has been
equipped with different Non Destructive Testing (NDT) instruments and subjected to incremental
settlement of the pier. The evolution of the pier scour has been investigated experimentally by
means of a hydraulic model and reproduced accordingly. The numerical interpretation of damage,
carried out by finite element analyses, has been compared with the results of the Acoustic
Emissions (AE) monitoring. Several ultrasonic emissions have been detected and main damage
source areas have been localized.
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Masonry arch bridges are outstanding masterpieces which embody a priceless historical and
architectural preciousness. These structures exploit their stiffness and geometric shape to sustain
high gravity loads but are very vulnerable with respect to the loss of the bearings. Multi-span arch
bridges crossing rivers are particularly exposed to this danger because of the flood peaks. The
erosion of soil at the piers foundations due to scour leads to differential settlements which result to
serious structural damage. In the last few years, several approaches have been attempted to detect
the occurrence of scour and to monitor its evolution. However, most of the proposed monitoring
technologies are concerned with the measure of the scour depth at the piers foundations and they
provide poor information about the overall integrity of the bridge.
Structural and hydro-geological monitoring can be effectively integrated in a wider diagnostic
framework, which could provide early warnings for the safety of the structure and its occupants in
the cases of real danger. A further requirement for the monitoring and protection of historical
structures is the minimum intervention on the original construction in order to respect their
architectural and cultural value. This reason explains the choice of the sensing equipment which has
been used to investigate the effect of the pier settlement introduced in the scaled model of the
masonry arch bridge. The common characteristic of the accelerometers, fibre optic sensors, strain
gauges and AE transducers employed in the experimental study is their slightly invasive nature.
Moreover, the different NDTs acquisitions performed and coupled with the results of the numerical
analyses allowed to increase the robustness of the integrity assessment.
The prototype the bridge model has been derived from is not a real existing bridge, but it has been
designed according to the historical rules and the geometric proportions of ancient bridges. The
theory of models has been employed to scale down the geometry to half of the prototype
dimensions. The model is characterised by a length of 5.90m and it is 1.60m wide. It has been built
with handmade clay bricks also scaled to 130x65x30mm to respect the adopted modelling scale law.
Advanced Materials Research Vols. 133-134 (2010) pp 301-306
© (2010) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.133-134.301
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the
publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 130.192.29.89-27/08/10,11:04:18)