This could have led to structural failure of an element and a possible disproportionate collapse. The peer review indicated several areas of the critical transfer slab which were considerably under-reinforced. This is clearly significant when considering a concrete framed structure, where about 80% of the load was as a result of self-weight. The structure above the transfer slab would either not have been constructed, or would not have sufficiently cured, to provide the stiffness required for such an effect to occur. It is the opinion of the reporter’s firm that generation of alleviating load paths was not possible at least when considering the self-weight of the structure. It was clear that the global model had generated alternative load paths within the structure by 'hanging' of columns above the transfer structure the columns being hung from frames above, proportionate to the frame stiffness, through a catenary or other action. The analysis showed loads in columns supported by the transfer slab were only about one third of those that would be obtained from a conventional load take down. As such the analysis gave loads on the transfer slab much reduced compared to that of a conventional 'hand' load take down, or indeed what would be replicated by undertaking individual slab design models. The design model assumed that the complete building structure was in-situ and fully cured. The designer had undertaken their reinforcement design for the critical first floor transfer slab using a 'global' or 'whole building' 3-dimensional design model.

In undertaking the review, it became apparent that the original design had not appropriately considered the construction sequence of the frame. The frame was several storeys in height and supported by a critical transfer slab at first floor.

A reporter’s firm had recently been involved in undertaking a peer review of another consulting engineer's design for a reinforced concrete flat slab frame.

18 year old framer construction