The influences of moisture content variation, number and width of gaps on the withdrawal resistance of self tapping screws inserted in cross laminated timber

Published Date
doi:10.1016/j.conbuildmat.2016.09.008

Author 

Catarina Silva ^a,,

Jorge M. Branco ^a,

Andreas Ringhofer ^b,

Paulo B. Lourenço ^a,

Gerhard Schickhofer ^b,

aISISE, Univ. of Minho, Dept. of Civil Engineering, Portugal

bInstitute of Timber Engineering and Wood Technology, Graz Univ. of Technology, Austria

Received 30 December 2015. Revised 30 August 2016. Accepted 2 September 2016. Available online 9 September 2016.

Highlights

• Withdrawal resistance   of self-tapping screws inserted in CLT is presented.
• •
  Effects of moisture content (MC) variation and existence of gaps were analyzed.
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  Increase of MC causes the reduction of   for almost all test configurations.
• •
  Relative humidity cycle results in high decreases of  .

Abstract 

A large experimental campaign comprised of 470 withdrawal tests was carried out, aiming to quantify the withdrawal resistance of self-tapping screws (STS) inserted in the side face of cross laminated timber (CLT) elements. In order to deeply understand the “CLT-STS” composite model, the experimental tests considered two main parameters: (i) simple and cyclic changes on moisture content (MC) and (ii) number and width of gaps. Regarding (i), three individual groups of test specimens were stabilized with 8%, 12% and 18% of moisture content and one group was submitted to a six month RH cycle (between 30% and 90% RH). Concerning (ii), different test configurations with 0 (REF), 1, 2 and 3 gaps, and widths equal to 0 mm (GAP0) or 4 mm (GAP4), were tested. The influences of MC and number of gaps were modeled by means of least square method. Moreover, a revision of a prediction model developed by Uibel and Blaß (2007) was proposed.

The main findings of the experimental campaign were: the decrease of withdrawal resistance for specimens tested with MC = 18% in most configurations; the unexpected increase of withdrawal resistance as the number of gaps with 0 mm increased; and, the surprising increase of withdrawal resistance for REF specimens submitted to the RH cycle.

Keywords

Cross laminated timber

Self-tapping screws

Moisture content variation

Withdrawal resistance

Axial loading

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  Corresponding author at: Campus de Azurém, 4810-058 Guimarães, Portugal.
  
  

For further details log on website :
http://link.springer.com/article/10.1007%2Fs10570-016-0933-y