IDAC Case Study - System 160/Mk3 Soldier Buckling Analysis


Mabey Hire

System 160/Mk3 Soldier Buckling Analysis

Mabey Hire Company Profile and Background on System 160/Mk3 Soldier
Mabey Hire designs, manufactures and supplies an extensive range of groundwork and formwork systems for hire and sale throughout the United Kingdom. The company has a rolling program of research and development for improving existing products and introducing new ones. An example of such a new product is the Mk3 Soldier of the System 160 product range. System 160 was originally introduced as a wall formwork system capable of sustaining loads up to 160 [kN]. Amongst its many applications, it is used to provide temporary support for bridges requiring replacement parapets and to stabilise and jack motorway sign gantries. It can create access platforms for city centre developments, where space is an issue, and form raking props for single-sided earthwork wall supports. The introduction of an extensive range of accessories has enabled the system to be used for a much wider range of applications.
	For example, during refurbishment of buildings, it is used as a temporary internal steel frame - when internal walls and floors have to be removed - for shoring party walls and gable ends and for retaining the facades of listed buildings, the interiors of which are often completely removed. Scope of Project The design of a component such as the Mk3 Soldier requires a high second moment of area to minimise deflection and negate buckling conditions.

The specification for the product allows varying lengths to be manufactured and the new accessories introduce a variability in end constraints.

The project consisted of the creation of an ANSYS macro that is capable of modelling the differing lengths and end constraints, as well as the specification of the number of reinforcing plates and plate thicknesses throughout the model. The ANSYS analysis produces equivalent second moment of area values about the major and minor axes through the cross-section of the soldier and performs a linear eigenvalue buckling analysis followed by a full nonlinear static structural buckling analysis.

Simulation Details

All aspects of the analysis are controlled by parameters specified at the top of the macro listing. Thus, all dimensions can be specified, as well as which - and how many - analyses are performed and whether the material plasticity should be considered.

The FE model consists of 3-D solid and shell elements. Extensive use is made of specialised and advanced contact technology that allows the edges of shell elements to be "welded" to the surfaces of solid elements or the faces of other shell elements. This allows for considerable freedom in the creation of the FE mesh and results in a high-quality solution.

The equivalent second moment of area values are calculated by placing the soldier under a cantilever load and using the ANSYS Parametric Design Language (APDL) to retrieve the displacement solution and evaluate the figures according to classical beam bending theory.

The results of the eigenvalue buckling analysis are used to "seed" the start of the nonlinear buckling solution by modifying the original "perfect" geometry - as modelled in ANSYS - to mimic the shape of the lowest buckling mode.

The Benefits

The macro now allows Mabey to investigate the buckling loads of a virtually infinite number of design configurations consisting of changes to, amongst others:

plate thicknesses
cross-sectional geometry
soldier lengths
number of reinforcing plates
material properties
end support conditions

Due to the parametric nature of the macro, all of these design variables can be used in the design optimisation routines available within ANSYS, allowing an automated investigation into the best design configurations.

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