AN ALTERNATIVE approach to providing resistance to progressive collapse is being pioneered on a new block of flats in London.
Storey-height vertical precast concrete ties will link floors on the five storey project in Bennett Street, Chiswick, where developer/builder Martin Grant Homes started work this week.
Structural engineer Tully De'Ath associate Pete Davies said a load bearing brickwork with precast concrete hollowcore floor solution had been chosen for the structure as it was more economic than a framed alternative.
'A conventional solution to progressive collapse issues would be to use hollow blocks for the inner leaf, reinforced and filled with concrete and tied into the floors, ' Davies said.
'But in our experience it is difficult to ensure that the concrete will penetrate the voids all the way down to the bottom of the wall, so we looked for a more effective alternative.'
Measuring 150mm thick by 440mm wide, the 2.3m long units are erected at 2.5m to 5m centres and built into the blockwork inner leaf. Bars from the ties are bent down above the floor units and mechanically connected into the reinforcement of the 75mm topping screed. Tully De'Ath claims the ties can resist an impact loading of 34kN/mm