Stiffness in Boundary Conditions of Masonry Walls in Prokon SUMO

When analyzing or designing Masonry Walls, boundary conditions significantly impact stiffness and structural behavior under applied loads. Proper understanding and adjustments to boundary conditions, geometry (size and thickness) and material (E-value and Poisson’s ratio). Altering any of these parameters will have a proportional influence on the behavior. 

Key considerations:

  • Role of Boundary Conditions

Boundary conditions define how a wall is supported or restrained at its edges and determine the way forces and moments are transferred through the structure. The stiffness is adjusted based on whether the boundary conditions are:

  • Fixed: Both rotational and translational movement are restrained, resulting in highest stiffness. This condition often simulates rigid connections like those found in walls attached to strong beams or slabs.
  • Pinned: Allow rotational movement while restraining translational movement, resulting in moderate stiffness. This setup often simulates walls resting on foundations without strong lateral ties.

In Prokon SUMO:

  • Shells elements default to fixed ends conditions.
  • Pinned conditions can be modelled by introducing rotational springs with low stiffness values.
  • Stiffness Parameters in Masonry Walls

Masonry wall stiffness depends on specific deformation resistances:

  • Axial Stiffness (Cxx, Cyy): Resistance to elongation or compression along x- and y-axes.
  • Shear Stiffness (Cxy): Resistance to shear deformation.
  • Flexural Stiffness (Dxx, Dyy): Resistance to bending along x- and y-axes.
  • Coupling Stiffness (Dxy, Dxz, Dyz): Interaction between different modes of deformation.
  • Adjusting Stiffness in Prokon SUMO

Prokon SUMO provides tools for fine-tuning stiffness parameters through stiffness modification factors in the Properties Palette.

Steps to Adjust Stiffness:

  • Access the Properties Palette:
    • Select the masonry wall in the model.
    • Open the Properties Palette to view the wall’s property settings.
  • Modify Stiffness Factors:
    • Modify Cxx, Cyy, Cxy, Dxx, Dyy, and Dxy based on the expected boundary conditions.
    • Ensure realistic values are used, considering the wall’s material properties and support conditions.

Note: Excessive adjustments or too many zeros in stiffness factors may render the model unsolvable.

Accurately modeling stiffness and boundary conditions is essential for predicting the structural performance of masonry walls. By carefully setting these parameters, engineers can:

  • Optimise Design Efficiency: Avoid overdesign and save resources.
  • Improve Load Distribution Understanding: Gain better insights into load-carrying behavior.
  • Mitigate Errors: Reduce inaccuracies in structural performance predictions.

Prokon SUMO enables iterative adjustments to stiffness settings, providing a reliable platform for accurate structural analysis and design.

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