Updates to Passive Fire - Calculated Capacity
Posted on 15th November 2023 at 15:03
With our sister company, MESS Ltd and a panel of Fire Engineers we are now able to exclusively offer calculated fire capacities for LGS
Working with academics and other experts in the field for the last five or six years we have developed calculated fire ratings and capacities for light gauge steel studs under design loads.
This is required as EN 1365-1 clause 13 which states that we cannot increase the design load from that tested and test rigs are only able to apply a finite load, which wouldn't be an issue till we realise how low that load is.
“The test rig had a load of 135kN overall and a 3m wide panel - giving 45kN/m - studs were 200*50*10*1.2 - G450 @ 600c B2B (300mm centres effectively) with 1 noggin at mid height.”
The table above demonstrates the need for the ability to calculate as opposed to testing. Based on test capacity and real design case loads the test rig is only able to test upto three floors.
Historically we have developed algorithm’s developed from academic research papers based on test data we have been able to develop guidance for three scenario's:
Single board to both sides
Double boards to both sides
Double boards to both sides with insulation between the studs
The calculation required data from the manufacturers in terms of the fire rating tested in terms of time and the load per stud applied so that the tool could pro rate according to the algorithm's developed.
Phase two of the project required more specific test data from manufacturers in the form of flange temperatures measured during testing so that a reduced yield strength can be calculated and a 'hot' stud capacity check be run based on this annealed yield strength.
The next phase of the project came when we realised that their actually existed TWO standards, and had done for around ten years, that allowed us to CALCULATE member capacity to ratified and approved British and European Standards. Namely, BS 5950-8 Annex A and EN 1993-1-2 Clause 4.2.4, Table E.1.
These calculation's to BS 5950-5 with elements of BS 5950-8 and BS EN1993-1-2 to allow for passive fire design. To this end the section properties declared have been re calculated based on the reduced yield strength, then used for the calculation
In addition, we have used reduced load factors for accidental loading taken from the relevant BS and EC's.
The calculation does not offer a ‘fire rating’ and nor do MMCEngineer, however we do have a panel of Fire Engineers who work with us and will under a parallel appointment provide reports to provide a fire rating. Costs for the Fire Engineer's report start at £5,000 with additional fee due to MMCEngineer for the project specific 'hot state member checks'.
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