pre cast concrete hollow core slabs in fire

Pre cast concrete hollow core slabs in fireTom LennonPrincipal Consultant, Centre for Structural Engineering

BackgroundNatural Fire Safety Concept - adverse press reportsSpallingShear failure - European research Consultation with industryRevised experimental programme

Revised test schedule

Slab A All joints filled. Structural toppingconsisting of 50mm (minimum) depth ofconcrete and a mesh reinforcement (A98mesh with 300mm lap between sheets)

Slab B All joints filled. Hooked reinforcing barsplaced in the joints over the supports.

Fire design scenarioDesign fire load of 570MJ/m²thermal inertia of 945J/m²s½Kopening factor of 0.065m½ based on a single opening 3.6m wide by 2m highapplied static load of 3.66kN/m²floor and walls lined with a single layer of fire resistant plasterboard

Predicted time-temperature response for fire tests on hollowcore slabs (b=945, O=0.065)

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Results from test 1 - slab AMaximum temperature in excess of 1200ºCmaximum vertical displacement of 100mmresidual deflection of 32mm

precast hollowcore fire test 17.9.01 - average compartment temperature

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comparison between average measured temperature and Eurocode prediction - test number 1

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average prediction

precast hollowcore fire test 17.9.01

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Test 2

Results from test 2 - slab BMaximum vertical deflection of 115mmresidual displacement of 40mmMaximum temperature in excess of 1200ºC

precast hollowcore fire tests - average atmosphere temperatures

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average test 1 average test 2

precast hollowcore fire tests - comparison of central deflection

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ConclusionsNo evidence of significant spallingLimited cracking along the length of the slab for test 2No integrity failureNo insulation failureNo premature shear failure of the units