Industry-leading fire research with useful implications for steel structures
Recently, researchers at HERA have been looking into the robustness and response of steel car park structures in the event of vehicle fires.
This investigation is one part of wider research to support their focus on reviewing structural fire performance to develop advanced technical solutions that improve structural fire steel building design best practices in Aotearoa New Zealand.
Structural Fire Research Engineer, Fanqin Meng says, “In accordance with the New Zealand design guide, a minimum fire resistance rating (FRR) of 30 or 60 minutes is required for structural components in sprinklers or unsprinklered buildings, respectively.
“These requirements are based on the assumption of a uniform-burning fire scenario within car park structures.
“However, research conducted by Linus Lim and Martin Feeney (reference1) suggests this assumption may not hold true, as it is far more likely for a fire involving a single vehicle to occur in a car park structure with a sprinkler system, resulting in a localised fire scenario.
This is further supported by statistical data from New Zealand (reference 2), which suggests “In the case of car park buildings equipped with sprinkler systems, a class three-vehicle fire (a singular vehicle with a combination weight [GCW] of more than 12,000kg but less than 25,001kg), may be a more probable fire scenario than a multivehicle fire.
“To evaluate the structural response, two representative vehicle fire scenarios were investigated using ABAQUS (software for advanced engineering simulations). The overall results from the simulated structures demonstrated that although the structural beams experienced plastic deformation in both fire scenarios, none of them reached failure during the simulation.
” Fanqin says the research indicates the main reason for the limited deflection of the beam is the utilization of a more realistic fire scenario, which significantly reduces the amount of heat transferred into the structural elements.
As a result, the neighbouring steel beams are at a lower temperature and exhibit greater stiffness and are able to sustain the load from the directly heated beam.
As a result, fewer fire protection materials are required.
He says, “Moreover, the research indicates that the localised fire put the compartment under a non-uniform fire scenario, where only one beam was directly exposed to the vehicle fire.
“Beams away from the fire centre were under a less severe fire scenario, or even at ambient temperature.
“As a result, the neighbouring steel beams are at a lower temperature and exhibit greater stiffness and are able to sustain the load from the directly heated beam.
“Thus, the overall vertical deflection of the steel beam was not that significant in the simulation.
” This advanced structural design methodology applies to both new buildings and retrofitting existing car park buildings with sprinkler systems safely.