Retaining walls - Today Tonight horror stories from Brisbane

This reinforced keystone wall was built without the reinforcement geogrid

Retaining walls exposed on Today Tonight Channel 7

Whilst conducting a structural inspection on a sub-standard failing retaining wall at a property north of Brisbane Friday last week, the client mentioned watching this program story from Today Tonight (see link above).

Property managers and owners should be aware of the risks retaining walls can pose to their structures.
Domestic pre-purchase building inspectors typically write-out in their disclaimers ."..the condition of retaining walls that may be present at this site are outside the limits of our inspection expertise.  We refer the buyer to seek further advice.."  This note may be embedded in the reports back page fine print and more often than not its passed over or noted and then just ignored.

Ex-cyclone Oswald damage in Brisbane

This outer Brisbane suburban shopping centre car-park shade structure failed

 during the ex-cyclone passage.  Given the relatively low 125km/hr gust speeds when

compared to the structures intended higher design gust speeds

we suspect a poor connection design has initiated early tube buckling failure.

 Water retention within the roof membrane (failed) was also noted as a potential contributor.

Ex-tropical cyclone Oswald moves through southeast Queensland

Gusts of approximately 125km/hr are quite noticeable in Brisbane (as predicted by the passing of ex-cyclone Osward ) but are well below the design cyclonic wind speeds that our houses are designed to withstand.  In a residential area of a typical Brisbane suburb set in flat surrounding terrain the Australian design standards would allow gust wind speeds to peek up to 144km/hr.  Exposed house sites on ridge lines or adjacent to open parks may be designed for gusts of 180km/hr.

Large exposed structures in a public places should also be designed to withstand significantly high wind speeds.  The early beam buckling failure of the shade structured pictured above suggests that its performance has been adversely reduced by a poor connection design detail.

The well known fact that most structural failures originate from poor connection design appears to be proven yet again in this instance.  From my experience connection design was given very little treatment in undergraduate course structural subjects.  There is something quite wrong about this lack of specific course treatment.