CROSS Safety Report
Inadequate of biomass fuel stores
This report is over 2 years old
A reporter raises concerns over designs they have come across for biomass storage structures where the appropriate lateral loads have not been considered.
Key Learning Outcomes
For civil and structural design engineers:
Be aware that biomass storage structures need to be designed for the appropriate lateral loads, noting that wood pellets give a significantly higher loading than wood chips
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A reporter was recently asked to provide a structural design for a freestanding wood fuel store and boiler house for a biomass boiler system. The same client and architects had previously designed to similar layouts and various reputable structural engineers had been employed on these schemes.
The units are all masonry construction with timber flat roofs. It became clear during the course of the design that the previous designers had used differing design loadings for the masonry. In at least one case, only wind loading had been considered for what is a retaining structure. In other cases, active pressures had been used as for a freestanding retaining wall. None of the designs had considered 'silo' pressures as codified by the Eurocodes.
Wind loading is clearly not adequate as the sole design case for a retaining structure and the active pressure design basis is also very questionable because the wall is not able to deflect significantly. Whilst it appears obvious, designers should be aware that biomass storage structures need to be designed for appropriate lateral loads, noting also that wood pellets give a significantly higher loading than wood chips.
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