Computational Engineering / module 8
Modelling structural systems
Trusses, frames, floors and cores — the usual model for each, its usual failure, and the hand check that catches it.
What you will understand
- Say what the pin-jointed truss idealisation gets right and what it omits
- Sweep a connection from pinned to rigid and locate where the change actually happens
- Compare four models of the same floor panel against an exact plate solution
- Decide when a core needs more than a stick model
- Name the hand calculation that validates each system
- Recognise a peak that is a singularity rather than a result
Lessons
Trusses and frames
What the pin-jointed idealisation omits, and where a connection stops being pinned.
Floors and cores
Four models of one floor panel against the exact answer — and when a core needs more than a stick.
The validation calculation
One hand check per system — the only kind that actually gets done.
Module summary
- The pin-jointed truss gets the chord force within 1 % and omits the bending entirely
- A stiffer chord attracts more secondary bending, not less
- Rigid and pinned are the ends of one parameter, and half the rigid moment arrives at about 1.65 EI/L
- A one-way model of a square panel over-predicts the moment by 183 %, and of a 3:1 panel by 6 %
- The one-way idealisation is always conservative and gets better as the panel lengthens
- A squat core's shear deformation is a fifth of its movement, not a refinement
- Every system has a hand check that takes minutes; that is the only kind that gets done
Teaching basis and review status
These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.
Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.
Read the lesson register and outstanding review notesCheck your understanding
Check yourself
A shell model of a flat slab reports a moment over a column that doubles each time the mesh is halved. What should be done?
Practice
A portal's eaves moment is 135.8 kN·m and its beam carries 15 kN/m over 12 m. What is the midspan sagging moment?
Practice
A 5 m × 5 m panel is modelled as a one-way strip, giving 31.25 kN·m/m against an exact 11.05. If the reinforcement is proportional to moment, by what factor is the short-direction steel over-provided?