📄 Pier Contribution to Out of Plane Lateral Capacity in Non-AYLA (Standard) Walls vs AYLA
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Pier Contribution to Out of Plane Lateral Capacity in Non-AYLA (Standard) Walls vs AYLA


In some cases it is possible that adding piers to the Masonry leaf has no positive contribution to the out of plane lateral load capacity of the wall. This is true when the wall is not using AYLA (advanced Yield line analysis) and is 

  1. Two way spanning - has horizontal and vertical edge supports and H/L aspect ratio > 0.3, or
  2. Horizontally spanning - has vertical edge support only

The effect of pier on lateral load capacity is only considered when the wall (or it's sub panels in opening cases) is determined to be vertically spanning.

For two way spanning wall one might expect the the piers to have a positive effect on the lateral load capacity, which in really they do. However due to a limitation in the stand design code methodology the effect of pier are not readily accommodated in the methods used to develop the two way spanning applied moment. The codes use tables of coefficients (for example Annex E in BS EN 1991-1-1:2005), which uses the ratio Î¼ to express the orthogonal ratio. The Î¼ is a ratio of the design flexural strengths fxd1/ fxd2, which are bead on material strength and do not consider the effect of the pier.

When the wall or it's sub panel is vertically spanning, then bending occurs about the he axis perpendicular to the pier, and therefore the design lateral resistance relies entirely on the fxd1,app x Zpier, where Zpier is the distributed effect elastic modulus of the pier stiffened wall per m run. The two way spanning limitation of Annex E and the the calculation of Î¼ do not affect the vertically spanning design

In the two way spanning walls the contribution of the pier is still present in the calculation of the effective thickness teff, which is used in limiting slenderness checks and also the Φ vertical buckling capacity reduction factor.

Where AYLA is used the lateral load analysis is much sophisticated in that the local effect of the piers contribution to the plastic moment capacity is considered, and the limitation of the simplified lateral moment calculation methods is no longer imposed. the AYLA feature are only available in full version MasterKey Masonry and not in the PowerPad version.