Fire Performance Concerns of Lightweight Engineered Lumber (LEL) Systems

Transcription

1 Fire Performance Concerns of Lightweight Engineered Lumber (LEL) Systems Brian J. Meacham, PhD, PE, FSFPE Associate Professor, Fire Protection Engineering IRCC Workshop on Increasing Use of timber in Larger Buildings Challenges for Regulators and Industry 7 June 2013, Vienna, Austria

2 Overview & Acknowledgement Overview Briefly identify fire performance issues with lightweight engineered lumber (LEL) systems Briefly overview test series and outcomes conducted at Underwriters Laboratories Acknowledgement Many of the photographs were provided by Steve Kerber of UL. His contribution is greatly appreciated.

3 Fire and LEL Systems Less material (mass), less density, and less robust connections results in reduced resistance to fire

4 Fire and LEL Systems Insulation concerns Movement to eliminate fire retardants if fire barrier provided LEL systems can fail quickly in fire fire barrier performance is critical

5 Fire and LEL Systems Larger LEL buildings can mean larger fires

6 Fire and LEL Systems LEL buildings vulnerable during construction Hampshire Fire and Rescue Service chief officer John Bonney issued a warning about the danger of timber framed buildings. "When these buildings catch fire the actual structure burns. It often leads to total collapse and that puts the safety of our firefighters at risk. He added that fire spread was a major concern at the incident, and that the Chief Fire Officers Association "was right to be increasingly concerned about the number and severity of fires in timber framed buildings under construction".

7 Fire and LEL Systems Combination of high density housing, LEL systems and combustible insulation may increase community fire risk

8 Fire Tests of LEL Systems Various tests have been conducted in North America on unprotected and protected LEL systems in recent years National Research Council, Canada Series of furnace and scale model tests Underwriters Laboratories, Inc., USA Series of furnace, laboratory mock-up, and full building tests Focus of this talk on UL tests of LEL systems

9 UL Fire Tests of LEL Systems Four different set-ups Furnace (element) Laboratory mock-up (full span) Field mock-up (full span) Full building

10 UL Furnace Testing Test Assembly Supports (Unprotected) Time to Failure 4 Dimensional Lumber (2 x 10) w/ 100% Loading 7:00 5 Old Dimensional Lumber (2 x 8) w/ 100% Loading 18:05

11 UL Furnace Testing Test Assembly Supports Time to Failure 1 Dimensional Lumber (2 x 10) - Unprotected 18:35 2 Dimensional Lumber (2 x 10) - Gypsum Wallboard (1/2 44:40 in) 3 Dimensional Lumber (2 x 10) - Plaster and Lath 79:00

12 UL Furnace Testing Test Supports Time to Assembly failure 1 Engineered I Joists Unprotected (12 in.) 6:00 2 Engineered Wood and Metal Hybrid Trusses (12 in.) 5:30 3 Engineered I Joists with Openings (16 in.) 8:10 4 Engineered I Joists w/ Fire Retardant Coating (12 in.) 8:40 5 Engineered I Joists w/ Intumescent Coating (12 in.) 17:50 6 Engineered I Joists w/ 100% Loading (12 in.) 2:20 7 Engineered I Joists w/ gypsum wallboard (1/2 in.) 26:43

13 UL Lab Tests (Full Span) Experiment Floor System Description Collapse Times 1 Wood I-Joist Repeat of Field Experiment 3, 6:20 Max Ventilation 2 Wood I-Joist Max Ventilation, Torch Ignition 31:25 (5:30 after ignition) 3 Parallel Chord Wood Truss 4 Parallel Chord Wood Truss Gypsum ceiling, Void Ignition 44:46 Gypsum ceiling, 80 ft 2 exposed 13:10

14 UL Field Tests (Full-Span) Series of 10 experiments conducted in collaboration with NIST to examine four residential flooring systems

15 UL Field Tests (Full-Span) Experiment Floor System Load Ventilation Collapse 1 Dimensional Lumber 2 Dimensional Lumber 65% of design stress Maximum 11:09 65% of design stress Sequenced 12:45 3 Wood I-Joist 65% of design stress Maximum 6:00 4 Wood I-Joist 65% of design stress No / Sequenced 6:49 5 Wood I-Joist Smaller Fuel Load 65% of design stress No / Sequenced 8:27 6 Wood I-Joist Modified Maximum 6:49 7 Steel C-Joist 65% of design stress Maximum 6:11 8 Steel C-Joist 65% of design stress Sequenced 10:08 9 Parallel Chord Wood Truss 10 Parallel Chord Wood Truss 65% of design stress No / Sequenced 6:08 65% of design stress Maximum 3:28

16 UL Full Building Tests

17 Representative Outcomes Legacy Construction, Unprotected 2 x 10 Floor Joist - Collapse Time = 18:45

18 Representative Outcomes Unprotected 14 Finger Jointed Trusses - Collapse Time = 13:00

19 Representative Outcomes 14 Finger Jointed Trusses - Gypsum Ceiling - Collapse Time = 26:45

20 Representative Outcomes Metal Gusset Truss Floor with Chord Slice Plates, Wood I Joist Ends and a Framed Floor Opening - Collapse Time = 13:25

21 Representative Outcomes 14 Gusset Plated Floor Truss - Gypsum Ceiling - Collapse Time = 29:00

22 Summary Performance 22

23 Summary Lightweight engineered lumber (LEL) systems provide benefits in terms of adequate strength with less material; however, fire performance of LEL is lower than traditional timber with no protection. While thermal barriers can provide adequate protection, loss of protection can result in very short times to failure during fire. 23

24 Thank You