The NSW Government has released the preliminary findings of an interim report produced by independent engineers investigating structural issues in Opal Tower.
While the engineers have declared the building “structurally sound and not in danger of collapse”, they identified a number of issues that will require “significant rectification works”.
Most issues were found to be with the hob beams, where in many cases the construction differed from the original design drawings, resulting in bearing capabilities that are below minimum safety standards.
On level 10 for example, the precast concrete panels were found to be wider than the hob beam they were sitting on by 20mm, despite original design drawings dictating that they should be the same size. There was also less grouting between the panel and hob beam than indicated in the design.
Other issues include inadequate concrete cover in the vicinity of the connection between the hob beam and some of the columns, an incomplete dowel bar between the hob beam and panel, and inadequate tensile capacity in one of the panels.
The engineers have concluded that it is likely that a combination of some of these design and construction issues led to the structural damage on level 10.
“In regards to the timing of the observation of damage, it is likely that the damage occurred after progressive build-up of load on the structure as apartments became occupied, culminating with the observed failure at level 10 on 24 December,” reads the engineers’ report.
The cause of the damage on level four is still being investigated by the engineers, who at this point have suggested that significant rectification works will be needed to repair and strengthen the damaged hob beams and panels on level 10.
“While we have isolated the probable cause to localised structural design and construction issues, we need more information to make definitive conclusions about the cause or causes of the damage to this structure and the proposed rectification,” reads the report.
“The viability of residents re-entering the building extends beyond the structural issues considered here and hence beyond the scope of our investigation. Nevertheless, before residents re-occupy the building the designers must ensure that no structural member is overloaded as a result of any load redistribution likely to have occurred as a consequence of the observed damage to the structure of the building.”
“More work is also needed before we can provide recommendations on what needs to happen to avoid incidents like this in future,” the engineers added in a statement to the NSW Government.
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