Correction needed to Compliance Document B1 Structure

A printing error has been detected in Amendment 8 of the Compliance Document B1 which relates to structure.

This will affect geotechnical and structural engineers who have designed short free head piles in accordance with Verification Method B1/VM4 since 1 December 2008 when the amendment became effective.

In Verification Method B1/VM4, Paragraph 4.3.2 (a) (i) the formula for the ultimate lateral strength of a short free head pile should read:

In the current paper and web versions of Amendment 8 an additional f was inserted after the square root component in the equation. For a free head pile, f is defined as the distance above the ground surface at which the horizontal shear is applied. This additional f was inadvertently added when preparing the document for publication.

The ultimate capacity of the pile to resist lateral load calculated using the incorrect formula would be:

• a negative capacity (which is not possible) where f is less than one metre;
• a conservative estimate of capacity when f is almost one metre; and
• an overestimate of the capacity when f is greater than one metre, which could lead to a non- conservative design.

As far as the Department has been able to determine the number of buildings likely to have been adversely affected by this error is very small, if any. It is asking engineers who may have used the formula as published to review their design calculations. Any queries about this matter may be emailed to info@dbh.govt.nz.

The Department intends to correct the error in the next amendment of the Compliance Document B1. In the meantime if you have a copy of Amendment 8 of the Compliance Document B1 you will need to delete the additional f after the square root component in the equation.