Divide the EA and EI to the out-of-plane spacing

Dear John,

Plates and geogrids are surface elements whereas piles, soil nails and anchor rods are line elements. So though dividing EA and EI by the out-of-plane spacing would give you the on average correct stiffness, the behaviour would still not be very accurate.
Generally piles and soil nails are modelled using embedded beam rows and anchor rods using node-to-node anchors for the free length and embedded beam rows for the bonded length.

With kind regards,

Dennis Waterman