Publication detail

The effect of long and short term elevated temperatures on the behaviour of lap glued joints of load-bearing spruce elements

VANĚREK, J. BÁLKOVÁ, R. ŠMAK, M. BĚŤÁK, A. VEJPUSTEK, Z.

Original Title

The effect of long and short term elevated temperatures on the behaviour of lap glued joints of load-bearing spruce elements

Type

journal article in Web of Science

Language

English

Original Abstract

The paper deals with the behaviour of glued joints of wooden sections exposed to long and short term elevated temperatures. If the adhesive is not sufficiently temperature resistant, the glued joint may lose adhesion, which could result in a change in behaviour of the glued element cross-section when exposed to fire. Moreover, detailed knowledge of the behaviour of bonded joints under such long and short term thermal exposures will enable us to make informed decisions about the need for major structural intervention in structures post exposure. Three types of adhesives: phenol-resorcinol-formaldehyde (PRF), polyurethane (PUR) and emulsion polyisocyanate (EPI), commonly used in load bearing wooden structures, were chosen for the experimental work. Thermal analysis showed that the PRF and PUR were not sufficiently cured, especially the PRF. Calorimetric analysis showed the point at which thermal degradation of all three adhesives began, at 135 degrees C for EPI and at about 160 degrees C for PRF and PUR. Spruce lap joints, with a cross section of 40 x 48 mm, bonded using these adhesives were exposed to temperatures of 140 and 170 degrees C. To properly distinguish the effect of thermal exposure duration on the lap joints, different thermal durations were used: 20, 40, 60 and 80 min, plus 3 h and 1 day. The thermal resistance at each of the elevated temperatures was investigated through measurement of the reduction in tensile shear strength. At an elevated temperature of 140 degrees C there was no significant strength reduction in all of the tested adhesives, it was only a longer duration (1 day) that produced a reduction in the tensile shear strength properties (31.0% for PRF, 16.2% for PUR and 34.1% for EPI). A temperature of 170 degrees C produced a greater decrease in strength, a significant drop (more than 15%) was found for PRF and EPI after an exposure of 40 min; for PUR after 60 min. Moreover, the longer duration exposures to a temperature of 170 degrees C resulted in a total loss in strength for PUR and a half loss of strength for EPI; for both these isocyanates adhesives this was confirmed by the total loss of wood failure criterium. On the contrary, a strength reduction of 50.0% and a sufficient wood failure criterium for a 1day temperature exposure at 170 degrees C was found for PRF.

Keywords

Wood bonds; Thermal exposures; Structural adhesives; Polyurethane; Emulsion polyisocynate; Phenol resorcinol formaldehyde

Authors

VANĚREK, J.; BÁLKOVÁ, R.; ŠMAK, M.; BĚŤÁK, A.; VEJPUSTEK, Z.

Released

1. 2. 2024

Publisher

ELSEVIER SCI LTD

Location

London

ISBN

0143-7496

Periodical

International Journal of Adhesion and Adhesives

Year of study

129

Number

February 2024

State

United Kingdom of Great Britain and Northern Ireland

Pages count

10

URL

https://www.sciencedirect.com/science/article/pii/S0143749623002555?via%3Dihub

BibTex

@article{BUT186999,
  author="Jan {Vaněrek} and Radka {Bálková} and Milan {Šmak} and Adam {Běťák} and Zdeněk {Vejpustek}",
  title="The effect of long and short term elevated temperatures on the behaviour of lap glued joints of load-bearing spruce elements",
  journal="International Journal of Adhesion and Adhesives",
  year="2024",
  volume="129",
  number="February 2024",
  pages="10",
  doi="10.1016/j.ijadhadh.2023.103575",
  issn="0143-7496",
  url="https://www.sciencedirect.com/science/article/pii/S0143749623002555?via%3Dihub"
}