Assignment #3 Method of Finite Elements II

ethod of Finite Elements II
Assignment #3
Method of Finite Elements II
Consider the arch truss structure presented in the following figure. The arch consists of two
parabolic chords with a total span of 12m.
Using Abaqus/ CAE create a finite element model of the structure implementing truss elements.
Remember that in Abaqus/ CAE, the following modelling steps need to be implemented:
1. Geometry Definition – Define the geometry in Part module
2. Material Definition – Define the material properties in Material Module
3. Instance and Mesh – Instanse the part in the Assembly module, then choose
appropriate elements and mesh the instance.
4. Analysis module definition (e.g. Step in Abaqus terminology)
5. Load definition and Boundary condition definition.
Choose the following material parameters: E = 210 GPa, n = 0.3
the following questions:
, A = 0.01 m 2 and answer
1. Perform a linear elastic static analysis considering a nodal load P=1000 KN applied at the midnode
of the bottom chord. Record the vertical displacement at the same node.

2. Taking into account geometrical nonlinearities (Remember to check the Nlgeom checkbox in
step definition), and choosing an incremental-iterative procedure (i.e. Static Riks Method)
record the load path of the structure. Appropriate values for fields such as number of
increments, error tolerances and stopping criteria should be chosen and justified accordingly.
3. Considering a von-Mises type material with an initial yield stress of 235 MPa and an ultimate
strength of 360 MPa (achieved at a plastic strain ε p,u =6%), define an elasto-plastic material in
the material definition and perform a nonlinear inelastic analysis, neglecting geometrical
nonlinearities. Record the derived load path (uncheck the Nlgeom checkbox in step definiotion).
4. Finally, perform an incremental analysis where both material and geometrical nonlinearities
are considered. Present a graph where all four derived solutions are plotted.
4i. Try to explain the differences, if any, between the derived load-paths.
4ii. Which load-path should be appropriate for design purposes and why.
5. Without performing any computation at all, would the solution of the problem be any
different if beam elements with end releases have been used instead of truss elements?