1 INTRODUCTION: PERFORMANCE
MONITORING OF STRUCTURES
Performance monitoring of as-built, full-scale struc-
tures has become increasingly popular due to devel-
opments in design philosophy, changes in perform-
ance requirements and developments in structural
health monitoring (SHM). Performance is measured
either as displacement or acceleration resulting from
wind or seismic actions and design aims to provide
adequate resistance against various degrees of fail-
ure.
Full-scale monitoring has been used to calibrate
wind codes (Lam & Lam 1979, Littler & Ellis,
1990), to provide information about structural and
foundation system performance that can be used for
other designs and to provide indication of changes to
structural state, including damage (Jeary et al., 2001,
Stewart et al., 2005).
There has been long experience of performance
monitoring of tall buildings, but generally long span
bridges have been the subjects of the greatest ad-
vances in monitoring technology. They are mostly
public owned, accessible, visible and high profile.
Their designs have usually resulted from elaborate
experimental and numerical simulation exercises and
there is still much to be learnt about load and re-
sponse mechanisms. They also have large mainte-
nance requirements and performance monitoring via
SHM systems is now seen as the way forward in as-
sisting lifetime management of these major assets.
Bridge SHM systems have become very elaborate
(Wong, 2003, Le Diourion, 2005) and also provide
opportunities to evaluate newly developed sensors
and conduct research.
A major target for bridge monitoring is the mo-
tion of the deck structure, which for long span sus-
pension bridges can be of the order of a metre. Ver-
tical,
lateral,
torsional and even longitudinal
response is driven by a combination of wind, traffic
and thermal actions Brownjohn et al. 1994) and
measurement of ‘static’ and ‘dynamic’ components
provides information on structural and loading
mechanisms. ‘Dynamic’ implies modal respons