Introduction - Finite Element Analysis and Design of Steel and Steel-Concrete Composite Bridges - page 24

shown that the proposed method reasonably estimated the individual
buckling limit of each member by introducing a fictitious axial force in
the geometric stiffness matrix during the iterative system buckling analysis.
The optimum design of steel truss arch bridges was investigated by
Cheng [ 1.40 ] using a hybrid genetic algorithm. In the study, the weight
of the steel truss arch bridge was used as the objective function, and the
design criteria of strength (stress) and serviceability (deflection) were used
as the constraint conditions. All design variables were treated as continu-
ous/discrete variables. The author considered different methods, analysis
types, and formulations and their effects on the final designs were studied.
It was shown that the proposed algorithm integrated the concepts of the
genetic algorithm and the finite element method. Also, the proposed algo-
rithmwas compared with the first-order method and proved to perform bet-
ter than the first-order method. In addition, it was concluded that when the
proposed optimum design was used for a steel truss arch bridge, the weights
can be considerably reduced compared with those of the traditional design.
Finally, it was concluded that the geometric nonlinearity is not significant for
the investigated application. Hamidi and Danshjoo [ 1.41 ] studied the effects
of various parameters comprising velocity, train axle distance, the number of
axles, and span lengths on dynamic responses of railway steel bridges and
impact factor values. The study replaced the traditional method specified
in current codes of practice, which considered traffic load as a static load
increased by an impact factor. In the traditional methods, impact factor
was represented as a function of bridge length or the first vibration frequency
of the bridge. The authors investigated dynamic responses and impact factors
for four bridges with 10, 15, 20, and 25 m lengths under trains with 100-
400 km/h velocity and axle distances between 13 and 24 m. It was shown
that, in most cases, the calculated impact factor values are higher than those
recommended by the relevant codes. It was also shown that the train velocity
affected the impact factor, so that the value of impact factor has risen con-
siderably with the train velocity. In addition, it was shown that the ratio of
train axle distance to the bridge span length affects the impact factor value
such that the impact factor value varies for the ratio below and above unity.
Finally, it was concluded that the train number of axles only affected the
impact factor under resonance conditions. The authors have proposed some
relations for the impact factor considering train velocity, train axle distance,
and the bridge length.
The performance of high-strength bolted friction grip joints com-
monly used in steel bridges was investigated by Huang et al. [ 1.42 ]. The