Abstract:
Structural engineers, faced with the challenge of designing reliable structures at a
minimum cost, continue to seek formal techniques to assist them in obtaining cost-optimal
designs. A key feature of the design process is identification of alternative designs for solving
the given problem., which is iterative and time consuming, and may involve the consideration
of many alternatives. In case of arch bridge, options are thrust arch bridge & Bow string
Girder Arch Bridge. Normal arches need high horizontal restrains from the foundation and
may be uneconomic where such restraints are not present. Such problem is solved by
introduction of Tie, which provide the horizontal restraint and bridge is known as Bow
String Girder Arch Bridge.
The economy of the steel Bow String Girder bridge superstructure, used extensively
in medium and long span ranges, is affected by many factors such as the cost of material,
dictated by the configuration, Rise of Arch, number of suspenders, shape and size of
members, and cost of fabrication.
Design of such structures is done in various software packages available and the Rise
, Number of suspenders , shape and size of members for preliminary design is based on the
experience of engineer and is mostly on the conservative side. However, with the use of
parametric study involving different variables can be used to reduce the cost of the structure
to great levels by optimizing the topology. Apart from cost, a significant amount of time can
also be saved as the erection and fabrication required is less.
The study presents the weight of structure, topology and standard cross-section
optimization of steel Bow String Girder Bridge. The considered structures are consisted from
deck (orthogonal stringers & cross-beams), which is connected to arch by mean of
suspenders. A parametric Study is done with main focus on variables - span, rise & Number
of suspenders. The proposed study minimizes the structure’s weight, determines the optimal
topology with the optimal rise, number of suspenders as well as the optimal cross-sections of
steel members.
