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System identification to monitor civil engineering structures

Objective



Service loads, environmental and accidental actions may
cause damage to structures. Regular inspection and
condition assessment of engineering structures are
necessary so that early detection of any defect can be
made and the structure's updated safety and reliability
can be determined. Early damage detection and location
allows maintenance and repair works to be properly
programmed. This minimizes not only the annual costs of
repair (e.g. for bridges estimated at 1,5% of their
value) but also avoids a long out of use time which can
represent an even higher economic cost (e.g. traffic
delay due to major bridge repair). Vibration monitoring
of civil engineering structures (e.g. bridges, buildings,
dams) has gained a lot of interest over the past few
years, due to the relative ease of instrumentation and
the development of new powerful system identification
techniques. In this project special attention will be
paid to techniques making use of operational data
(service loading testing).
There remains some debate whether the measured deviations
of dynamic properties (eigenfrequencies, modeshapes) are
significant enough to be a good indicator of damage or
deterioration. The comparison of original and new dynamic
properties can also be hampered by natural changes caused
by environmental influences (e.g. temperature changes).
Another still unresolved issue is the localisation of
damage starting from any observed difference in dynamic
properties.
To convince the engineering community that vibration
monitoring is a valuable technique for structural
assessment a proof of feasibility is essential.
Therefore it is of paramount importance to setup a long
term test on extensively instrumented existing structures
(e.g. bridges) for quantifying the degree of variance due
to environmental influences and also due to differences
induced by the parameter choice of the selected system
identification methods.
To complement the longterm test, a short term loading
failure test on existing structures (not only on
laboratory beams) should prove that changes in dynamic
properties are not only large enough (i.e. statistically
relevant) but can also be linked to damage in a
particular part of the structure.
The main objective is to prepare for the development of a
methodology for vibration monitoring of civil engineering
structures by integration of the following research
activities:
establishment of an optimum dynamic testing procedure
in order to obtain high quality experimental data,
application to civil engineering structures of adapted
time and frequency domain system identification methods
to extract the required dynamic information from the
data,
development of FE programs to model the dynamic
behaviour of damaged structures,
updating based on models derived from operational data,
use of damage patterns as parameters in the updating
process of the finite element model,
development of a method to incorporate information from
vibration monitoring into techniques revising safety and
reliability,
proof of feasibility by full scale, long duration tests
and progressive failure tests of representative
structures (e.g. bridges).
Estimation methods for models from operational (service)
data have multi sectorial applicability (trains,
motorcars, airplanes, offshore platforms, pumps, machines
in general ...) because traditional input/output models
may be based on irrealistic boundary conditions or on
loading not representative for real operational
behaviour. Therefore the scope of the proposed Brite
Euram project is surpassing the strict domain of Civil
Engineering.

The consortium comprises three universities (BE, DK, AT),
a research institute (CH), a software and engineering
company (BE), an integrated engineering and management
consultancy company (GB) and a company specialized in
control and monitoring of highway and railway
infrastructures (IT). Complementary experience and
competence is available in artificial and ambient testing
of large civil engineering structures, system
identification, numerical modelling of damaged
structures, updating techniques, safety evaluation.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Katholieke Universiteit Leuven
Address
2,W. De Croylaan
3001 Heverlee
Belgium

Participants (6)

Laboratoire Fédéral d'Essai des Matériaux et de Recherches
Switzerland
Address
129,Überlandstraße 129
8600 Dübendorf
Leuven Measurements and Systems (International) Numeral Technologies NV
Belgium
Address
68,Interleuvenlaan 68
3001 Heverlee
Sineco SpA
Italy
Address
Via Felice Casati 1/A
20124 Milano
Technische Universität Graz
Austria
Address
25,Lessingstraße 25
8010 Graz
W S Atkins Consultants Ltd
United Kingdom
Address
Woodcote Grove Ashley Road
KT18 5BW Epsom
Ålborg Universitet
Denmark
Address
57,Sohngårdsholmsvej
9000 Ålborg