Materials
Structural Steel
(EU Grade)
Yield Strength
(MPa)
Modulus of
Elasticity (GPa)
Density
(kg/m^3)
Cost
($/metric ton)
S235 235 235 7850 720
S275 275 270 8010 810
S355 355 355 8090 955
Include a free body diagram for each joint of the bridge. You are not required to solve them by hand, but they must be drawn out
Your bridge must span 24 meters and a load of 80 kN must be placed at
the center.
2) You can select from 3 different materials (see section 1), each with their
own yield strength, density, and cost. You can select from 5 different I-
Beam configurations (section 2) with different cross-sectional areas.
These are independent of each other so there are 15 different
configurations to choose from for any given bridge member. You can use
different materials/cross sections for each bridge member.
a. The Modulus of Elasticity is the value that iTruss asks for under
the “Properties” tab. Along with cross sectional area. Assuming
you are in SI units (you should be), the value is the same as what
is provided in section 1 for the given material you choose.
b. The cross-sections are not necessarily meant to be realistic.
3) Notice the example bridge is not symmetrical. This is also a design
consideration! i.e. Symmetry is “beautiful.”
4) You must calculate the stress in each member using the equation.
5) You must calculate the factor of safety in each member. You are
required to achieve a factor of safety of 2 for each member. Members
that are below or greatly exceeding that factor of safety are not
optimized and need to be redesigned.
6) You can calculate the length of each member given the node locations
and the member connection. Use the distance formula.
7) Given the length and cross-sectional area, you can calculate the
volume.
8) Given volume and density, you can calculate the member mass.
9) Given the mass of each member, you can calculate the cost