Durability and Mechanical Performance of Differently Treated Glulam Beams during Two Years of Outdoor Exposure

Davor Kržišnik,Bogdan Šega,Milan Šernek,Samo Grbec,Denis Plavčak,Aleš Straže,Miha Humar,Boštjan Lesar

doi:10.5552/drvind.2020.1957

Abstract

The performance of the composites is influenced by the service life of input raw wood material and used adhesives. The aim of the study was to assess the durability and mechanical performance of glulam beams treated in a different way (thermally modified and/or treated with copper-based wood preservative) and exposed in an outdoor application. Glulam beams (83 mm × 68 mm × 1100 mm), made of three layers of Norway spruce (Picea abies) with PUR adhesives used have been exposed in use class 3.2 in a horizontal position since 4th November 2016. Part of the specimens was equipped with MC sensors. Every year, the degradation was evaluated visually. The dynamic modulus of elasticity was determined by longitudinal vibration, and the static modulus of elasticity using a 4-point bending test. On the smaller specimens, cut from glulams, compressive strength, delamination, and shear strength of adhesive bonds were determined. After two years of exposure, the results indicate that the performance of glulams is determined by the wood modification and applied wood preservative.

Highlights

After two years of exposure, the results indicate that the performance of glulams is determined by the wood modification and applied wood preservative
It has to be considered that initial stages of decay are difficult to assess because there is no visible evidence of damage to the wood by incipient brown-rot decay shortly after brown-rot fungi initiate colonization and release enzymes (Clausen and Kartal, 2003)
Higher dimensional stability of thermally modified wood can be ascribed to lower equilibrium moisture content (EMC) associated to the chemical modification of organic functional end-groups (Willems et al, 2015), and to the fungal durability (Altgen et al, 2014)

Summary

Introduction

Wood is one of the earliest construction materials, and the structural use of wood and wood-based composites continues to steadily increase. The primary driving force behind the increased use of wood-based composites is the ever-increasing need to provide economical housing. Wood composites include a range of derivative wood products, which are produced by binding the fibres, strands, particles, veneers or boards of wood with adhesives, or other methods of fixation. All of these components form composite materials. As well as wood composites in outdoor applications, are exposed to biological degradation and weathering (Humar et al, 2019). In order to increase the potential of wood composites, their performance in outdoor applications has to be determined

Objectives

Methods

Results

Conclusion