Tank

Software Tour

Tank model and analysis types supported

Easily create 2D and 3D tank models from common tank definition data. This allows for preliminary studies to be done using any of the 2D tank modelling options that are available, before moving on developing and investigating the suitability of designs in more detail using 3D shell or 3D solid models. Design checks are performed using 3D shell models. 3D solid models are used for spillage analysis. Comparative studies can be achieved by copying tank definitions, making adjustments, and re-creating models from that revised data. 

For preliminary analysis:

  • 2D axisymmetric structural

  • 2D axisymmetric staged construction

  • 2D axisymmetric coupled thermal/structural

  • 2D beam-stick seismic

For detailed analysis:

  • 3D shell structural

  • Steel roof-only

  • 3D solid coupled/thermal structural

Examples of models created by the wizards are shown below.

2D Axisymmetric Structural

Model features are defined in individual groups for easier updating of the model and processing of results. For concrete tanks, only the outer  tank is modelled, and is investigated using 16 static loadcases.

2D Axisymmetric Staged Construction

In addition to the groups of features defined in the 2D axisymmetic structural model, extra groups are set-up to simplify the activation and deactivation of features when modelling the construction stages. Up to thirteen construction stages are automatically created by the wizard, and the nonlinear analysis sequence used ensures that the stresses and strains from a previous stage are inherited in the following stage.

2D Axisymmetric Coupled Thermal/Structural

Used to obtain the temperature variation through the thickness of the structure and to obtain the thermal stress and strains induced by the temperature gradient. Typically followed by a structural analysis that uses the temperature distribution as its input loading - commonly known as a coupled themal/structural analysis.

2D Beam-Stick Seismic

A lumped mass beam-stick model is used to perform a dynamic analysis under earthquake conditions. The adopted arrangement of components captures the complex seismic behaviour of the liquid tank system in a simplified but accurate model. A response spectrum corresponding to ASCE is defined by the wizard by default, but others and user-defined spectrums are available.

Some loadings specified or generated from some 2D analyses (such as applied loading, live loadings, thermal or seismic effects) may be converted into equivalent structural or temperature and used in a 3D model.

3D Shell Static Structural 

Used when tank loadings are not axisymmetric, and used to create design results. All loading defined for the 2D axisymmetric structural is also used for this model, and wind loading can also be applied. Half and full models may be created.

3D Shell roof-only

Used for generating half or full models of a steel tank roof (if that is of sole interest) for a linear structural analysis with all loading as defined in the tank definition.

3D Solid Coupled/Thermal Structural

Used to create a coupled thermal-structural, full, half or quarter sized 3D solid tank model, with explicitly modelled wall reinforcement, ringbeam reinforcement and spillage scenarios.


Models created

Models created by the wizards are generated with all mesh, geometric properties, attributes, supports and loadings assigned to the model, and with features grouped according to type.

Results

Once solved:

  • View results for all or selected parts of a model using separate layers for diagram, contour, vector and discrete value data.
  • Select loadcases individually for each view window, and display multiple views of the model, with each window showing results for different loadcases.
  • Manually specify basic load combinations, defining loadcases to be included and load factors to be used.
  • Use Smart Combinations to generate maximum and minimum results, reducing the number of combinations and envelopes required.
  • Define envelopes of multiple loadcases to provide maximum and minimum results.
  • Plot bending moment and shear force diagrams and visualise structural deflections.
  • Display results in global or local directions, in element directions, or at any specified orientation.
  • Selectively output results to spreadsheet applications for additional calculation and graphing uses.
  • For concrete modelling, plot crack width contours, crack patterns and values for supported design codes.
  • Use inspection locations to obtain results for user-defined positions of interest on a model.
  • Transform and display results in global or local directions, in element directions, or at any specified orientation.

Transformed results plots of component Nx and Ny are shown below.

Graphs showing, for example, the variation of moment Mx with wall height can be generated from selections made on the model.


Exporting of forces to spreadsheets

In addition to on-screen viewing of results, exporting facilities also exist to automatically convert stress distributions at chosen slicing locations on models into section forces and output to a spreadsheet. For example, for a 2D axisymmetric model, slices taken through a wall section for component SY can be used to compute vertical axial forces and bending moment.

For a 3D shell model, similar section forces based upon angular values are extracted by that wizard and exported to a spreadsheet

 


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Any modelling, design and analysis capabilities described are dependent upon the LUSAS software product, version and option in use.