Fire performance banner Photo: Annabel Shephard

Mass timber panels being removed from the furnace during an ASTM E119 fire test. Photo: Annabel Shephard


2021   Fundamental Behavior of Timber Concrete-Composite Floors in Fire. 

           ASCE Journal of Structural Engineering, Vol. 147, No. 2, February 2021

           Annabel B. Shephard, Erica C. Fischer, Andre R. Barbosa, and Arijit Sinha

2019   Fire performance of timber-concrete composite floors. 

           3rd International Fire Safety Symposium, Ottawa, Ontario, Canada. 

           Erica C. Fischer, Annabel B. Shephard, Andre R. Barbosa, and Arijit Sinha

2019   Fire Performance of Timber-Concrete Composite Floors 

           Mass Timber Conference 2019

           Annabel B. Shephard, M.S. Civil Engineering

Standards Used: ASTM E119

Project Duration: 2018 – 2020
Economic Development Administration

TallWood Design Institute (TDI)

National Research Council Canada (NRC)
Research Team:
Erica Fischer - Oregon State University (OSU), School of Civil and Construction Engineering
André Barbosa - OSU School of Civil and Construction Engineering
Arijit Sinha - OSU Department of Wood Science and Engineering
Design Advisory Group:
SOM, KPFF, Aspect Engineers
Research Advisory Group:
TallWood Design Institute, Katerra, ARUP, Cairn Pacific, Forest Products Laboratory (FPL)


Cross-laminated timber (CLT) and Nail-laminated timber (NLT) floors are sometimes designed with a concrete topping that improves structural, acoustic and vibration performance. Recently, engineers are taking advantages of these concrete toppings to increase spans. There has been minimal research to examine the effect of the concrete topping on the fire performance of the composite system. Preliminary studies suggest that these composite floors may provide higher fire resistance, which could open up new market opportunities for mass timber products in buildings.


The inside of the furnace at the NRC, with CLT (left) and NLT (right) floors installed.

A view of the furnace from the outside, with distributed load being applied to the CLT and NLT floors.


Annabel Shephard--M.S. Civil and Construction Engineering, OSU--takes notes on deflection rates during fire testing at the National Research Council in Ottawa, Canada.


Project Overview
The primary stages of this project include:

  • Testing the fire performance of loaded CLT- and NLT-composite floor assemblies (preliminary test: February 2019). Data from this phase will be used to improve products, generate design guidelines, and to benchmark numerical modeling techniques that can test additional parameters for the fire performance of timber-concrete composite floor systems.
  • Validating a new fire testing setup at Oregon State University that could allow for better experimental flexibility and lowered costs. 

In order to develop a comprehensive analysis of such composite systems, the fire-tested assemblies matched those being tested by Dr. Andre Barbosa (Project: Seismic Performance of Cross-Laminated Timber and Cross-Laminated Timber-Concrete Composite Floor Diaphragms, 2017-2020) and Dr. Chris Higgins (Project: Composite Concrete-CLT Floor Systems for Tall Building Design, 2017-2020).


Erica Fischer--Assistant Professor of Civil and Construction Engineering, OSU--observes and discusses the remains of the CLT panel after fire testing. Part of the destroyed concrete diaphragm has flopped over the upper edge, and after nearly three hours of burning, only a portion of the last wooden ply remains. 


Above: Concrete-composite NLT after fire testing. The edges remain as a result of being protected from direct contact with the fire.
Below: Concrete-composite CLT after fire testing. The edges remain as a result of being protected from direct contact with the fire. After nearly three hours of burning, only a portion of the last wooden ply remains. 


Research Details
Fire exposure: ASTM E119 fire
Loading: 80 lb/ft2 sustained load
Failure criteria: Loss of load-carrying capacity
Mass timber products being tested:

Cross laminated timber (CLT):
Grade of lumber: Spruce-Pine-Fir (SPF), V2 Grade
Panel dimensions: width 4’-0”, length 16’-0”
Topping: 2.25” concrete, connected with self-tapping screws 

Nail laminated timber (NLT):
Grade of lumber: Spruce-Pine-Fir, No. 2,
Panel dimensions: width 4’-0”, length 16-0”, 2”X6” nominal lumber
Topping: 3” concrete, connected by Mitek truss plates

Future work: 

  • Shear connector tests to quantify the force-slip behavior of the shear connectors in both systems
  • Benchmark finite element modeling techniques
  • Develop testing capabilities at Oregon State University