The last two decades have
revealed an enormous development of computers and computer software. This
development
has given structural engineers very powerful tools such as finite
element (FEM) programmes which allow very detailed analyses of new as well as
existing structures. FEM analyses are based on
assumptions to some extent e.g.
static boundary conditions often has to be assumed or the loading is based on
codes or qualified assumptions. The tremendous development of computers and
computer software have fortunately also been to the benefit of hardware and
software for monitoring and measurement equipment such as dataloggers.
Performing measurements on complicated structures, which has previously been
analysed by FEM, can provide valuable information to verify whether calculation
assumptions. Adjustments to the structure or the service manual can be
implemented before the structure is taken into service. Performance tests on
new structures can help prevention of unexpected interruptions of the
structural service. Performing short and uncomplicated measurement routines on
existing and new structures exposed to fatigue can give a more reliable
prediction of fatigue life. The increase in transport by railway as well as
automobile has been the reason for the
strengthening of many existing bridges.
By performing measurements, strengthening can in some cases be avoided or
postponed due to a clarification of the structural behaviour and/or the
loading. Measurements can also serve as documentation for the efficiency of a
performed strengthening. This paper will be based on the following three case
stories, which illustrate the benefit from measurements:
1. New railway expansion joints
on the Great Belt Bridge before being put to service.
2. Fatigue life predictions
on a bascule bridge which had failed due to fatigue
3. Efficiency of a
strengthening of a 90 years old riveted railway bridge will be demonstrated.
Integrated use of three
dimensional non-stationary dynamic FEM analyses will be presented in relation
to the performed measurements.