# FEA model : comparing Warren and Vierendeel trusses

These Warren and Vierendeel truss Finite Element Analysis models have
as much in common as possible

- length = 16m
- heights similar : Warren Truss 3.46m, Vierendeel Truss 4m
- material = rectangular (square) box section of 0.2m (200mm) width
and height, and 0.005m (5mm) thickness, of steel
- load is in the centre, of 100,000N downwards (10 Tonnes force)

(Previous simulations,
Warren-truss and Vierendeel-truss,
were not "otherwise identical" - so could never be compared. This
Vierendeel Truss here is the same as previously presented. The Warren
Truss here now matches in its material - 200mm square 5mm thick steel
box-section)

## Presentation of the models and simulation results

- Presentation order in each section is
- Warren Truss
- Vierendeel Truss
- (where present:) Observations I offer in comparing the two models

- Exaggerated deformation / displacement is always
- 10X for Vierendeel Truss
- 200X for Warren Truss

Note therefore that for similar as-displayed deflections, in reality
the Vierendeel Truss is much more deflected than the Warren Truss.

## FEA Model

## Tensile force

The tensile forces are probably slightly lower for the Vierendeel
Truss than for the Warren Truss because the Vierendeel Truss has a
slightly greater height, therefore separation of the tension and
compression chords, than the Warren Truss.

## Bending moment

The bending moments are small in the Warren Truss - about a 100th
part - compared to the Vierendeel Truss, which uses resisted bending
moments in its load-bearing design strategy.

## Displacement in vertical direction ("y")

Deflection of the Warren Truss at about 3.2mm is much less than the
deflection of the Vierendeel Truss at about 90mm.

(R. Smith, 15Jun2016, 15Nov2016)