Bridge analysis, design + assessment

Case Study

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Falkirk Wheel

  • unique steel rotating boat lift
  • linear and nonlinear analysis
  • solid element modelling of movement sensitive connections

Falkirk Wheel and Visitor Centre (Image: famine, Source: wikipedia)

LUSAS Bridge analysis software was used as the primary analysis tool by Tony Gee and Partners (TGP) for preliminary and subsequent detailed design work on the Falkirk Wheel. The Wheel (as it is known) is a unique lifting bridge designed to reconnect the Forth & Clyde and Union canals between Glasgow and Edinburgh in Scotland. It is the world’s first rotating boat lift and the first boat lift to be built in the UK since 1875.


The project is part of a 78m British Waterways scheme to restore the two canals to their former glory. Construction of the interchange section, which comprises the Wheel, an elevated aqueduct at its upper end and a holding basin at its lower, is being led by a joint venture of Morrison and Bachy-Soletanche. Butterley Engineering, designers and manufacturers of the wheel, Tony Gee and Partners, structural engineering specialists and Bennett Associates, M&E engineering specialists and architects RMJM Scotland Ltd. complete the team.

The Wheel has an outside diameter of 35m, and comprises two 1.4m wide steel, clawed arms rotating on a 3.5 m diameter axle. A pair of 25m long, 300 m3 water filled caissons (or "gondolas") act as containers for boats which are lifted through the 24m vertical distance between the two canals. Drive is provided at one end of the axle through a system of hydraulic planetary gear units, with stability of the caissons ensured by a network of synchronised gears. It is capable of carrying a total payload of 600 tonnes in winds of Beaufort Force 6 (25-31 miles per hour). Boat transfer time is about 15 minutes.

Falkirk Wheel cog mechanism (Image Lowattboy, source wikipedia)

The uniqueness of the structure required TGP to employ some innovative and unconventional design methods. UK design codes for bridges, buildings and floating vessels were utilised, as well as Norwegian, German and American codes for such criteria as thin walled cylinder behaviour and constrained ice loading. A 1:50 scale model was used in a wind-tunnel for testing aerodynamic effects. Finite element analysis using LUSAS Bridge aided the structural design and included nonlinear solid continuum modelling of movement sensitive connections.

Falkirk Wheel and Visitor Gallery (Image: AndyW, Source: wikipedia)

Modelling with LUSAS

Detailed analysis made use of three separate LUSAS models: 

  • A 3D linear elastic shell element model allowed for analysing the axle and arms of the main structure. 
  • A 3D linear elastic model using a combination of shell and beam elements modelled one of the gondolas (shown below).

Both these models, as well as being the basis of the material design (via the stress outputs), were particularly useful in estimating deflected shapes and displacements, which can have a critical influence on the moving parts of the structure.

Falkirk Wheel stresses in axle and arms

Gondola model showing exaggerated deformed shape

A 3D nonlinear solid continuum model was used to analyse a small part of a joint in the main axle situated just inside the clawed arm. Richard Prosser, project engineer of Tony Gee and Partners, said: "We needed assurance that the axially loaded joint would not prise apart, and the results from the LUSAS model formed a vital part of this assurance."


Nonlinear analysis of joint on main axle

Nonlinear analysis of joint on main axle

Falkirk Wheel and Visitor Gallery

"We needed assurance that the axially loaded joint ( in the main axle situated just inside the clawed arm) would not prise apart, and the results from the LUSAS model formed a vital part of this assurance."

Richard Prosser, Project Engineer, Tony Gee and Partners.

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Other LUSAS Bridge case studies:

Forsmo Bridge, Sweden

Kingston Bridge widening project

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