Abstract
Vibration-based condition identification of bolted connections can benefit the effective
maintenance and operation of steel structures. Existing studies show that modal
parameters are not sensitive to such damage as loss of preload. In contrast, structural
responses in the time domain contain all the information regarding a structural
system. Therefore, this study aims to exploit time-domain data directly for condition
identification of bolted connection. Finite element (FE) model updating is carried out
based on the vibration test data of a steel frame, with various combinations of bolts
with loss of preload, representing different damage scenarios. It is shown that the
match between the numerically simulated and measured acceleration responses of
the steel frame cannot be achieved. The reason is that time-dependent nonlinearity
is generated in bolted connections during dynamic excitation of the steel frame. To
capture the nonlinearity, a virtual viscous damper is proposed. By using the proposed
damper alongside the updated system matrices of the FE model, the time domain
acceleration responses are estimated with great consistency with the measured
responses. The results demonstrate that the proposed virtual damper is not only
effective in estimating the time domain acceleration responses in each damage case,
but also has the potential for condition identification of bolted connections with such
small damage as just one bolt with loss of preload. It can also be applied to other
challenging scenarios of condition identification, where modal parameters are not
sensitive to the damage.