Introduction - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 29

an appropriate numerical model of the bridge. The authors concluded that
the deflection of the main girder chords results from the overlapping of both
global and local behaviors. Also, the rotations do not reproduce the global
behavior of the structure. Therefore, the fundamentals about rotations in a
beam and the derived methods to estimate the bridge deflection using rota-
tions are not applicable to this structure. In addition, the external prestress
system has a significant influence on the response of the structure to the tem-
perature changes. Furthermore, observing the effectiveness of the top
chords' strengthening, the internal forces estimated using a multiple linear
regression model agree well with the internal forces obtained with the
numerical model. Overall, it was concluded that the study provided valuable
information regarding the installation of a permanent monitoring system for
the surveillance of the bridge.
The effect of local damage on the behavior of steel bridges is also a current
research area. Brunell and Kim [ 1.53 ] investigated the effects of local damage
in steel trusses on the overall behavior of the bridge. The study comprised a
combined experimental and numerical investigation. The experimental
results of a scaled model bridge were used to validate the developed numer-
ical model. The numerical model was used to perform analyses investigating
the relationship between damage and bridge failure. The behavior of 16
damage scenarios was compared with that of a control truss. A static analysis
was carried out which utilized a damage index to quantify the level of damage
present in the bridge, to examine the load transfer relationship between truss
members, and to quantify the failure load for various scenarios. In addition, a
dynamic analysis was carried out to highlight the effect of damage on mode
frequency and changes inmode shape. The authors mentioned that, since the
dynamic behavior of the test specimen was not measured in the laboratory,
the findings reported could be experimentally verified in future research.
A simple reliability analysis was conducted to assess the safety of the truss sys-
tems. The authors showed that the results and conclusions of the study were
based on laboratory-scale research, and thus a size effect might exist when
implemented in practice. Also, the technical findings reported could be con-
servative to a certain extent because the contribution of a RC deck was not
included in the analyses. The authors concluded that the presence of local
damage in the truss system significantly influences the serviceability of the
system. Also, the current AASHTO load rating method was reasonably
applicable to the truss bridge system. From a dynamic analysis perspective,
a higher mode shape and corresponding frequency were useful to detect
the presence of local damage in the truss systems. Finally, it was concluded