Fire Performance of CLT and NLT Timber-Concrete Composite Floors

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)

Project Duration:

2018 – 2020

Facilities:

National Research Council Canada (NRC)

Abstract

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.

Introduction

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).

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

 

contacterica.fischer@oregonstate.edu