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Doctoral project: Connections and compression perpendicular to the grain in cross-laminated timber

The main aim of the project is to predict in a combined experimental-numerical study the mechanical behavior of wood, specifically in the transverse plane, in order to better understand the influence of the annual ring structure on load dispersion. This will help to investigate the structural response of engineered wood-based products such as cross-laminated timber (CLT) under compression perpendicular to the grain, as well as connections in CLT structures.

Image: Comparison of shear strain distribution from experiment and numerical modeling.

Project information

Doctoral student
Shaheda Tahmina Akter
Supervisors
Thomas K Bader and Jan Oscarsson, Linnaeus University; Erik Serrano, LTH, Lund University, Sweden
Participating organizations
Linnaeus University; LTH, Lund University, Sweden
Project start
Febr 2017
Subject
Building technology (Department of Building Technology, Faculty of Technology)

More about the project

Experimental strain distribution by an advanced deformation measurement system.
Experimental strain distribution by an advanced deformation measurement system.

Modern engineered wood-based products are gaining importance as load bearing elements in structures. Particularly the share of Cross-laminated timber (CLT) in timber structures is increasing considerably, also in the Nordic European countries, due to the renewable characteristics of timber and its load carrying potential. CLT is a composite structure of wooden lamellas glued together in a cross-wise, layered manner.

The PhD project aims at investigating the material properties and cylindrically orthotropic effects of wood on its load bearing behavior by establishing a relationship between material properties of wood and CLT at the product and structural level. A computational model, able to describe and predict the behavior of CLT under compressive loading perpendicular to the grain, will be developed in this project. The computational model can save time and effort required for experimental tests of CLT at the product and structural scale. Moreover, the computational model will allow accomplishing a parameter study to observe the effects of material properties and annual ring orientations in lamellas, the effect of numbers of layers, lamination thickness, thus it can be used for product optimization.

The project consists of a combined experimental and numerical approach in order to provide experimental evidence for model development, validation, and calibration. Experimental investigations will be performed using advanced deformation measurement systems to visualize and quantify the effects of annual ring structures as well as load distribution effects. The effect of a globally superimposed shear load, in addition to compression perpendicular to the grain, on the local stress and strain field will be studied to gain a better understanding of the mechanical response of CLT under compression loading.

Besides the mechanical response of the CLT product, the load-bearing characteristics of connections in CLT structures constitute an important design issue that will be dealt with in this project. This encompasses the behavior of CLT in contact situations, inducing relative deformations due to compression perpendicular to the grain stresses, as well as connections with mechanical fasteners. This is expected to lead to enhanced design concepts for connections in CLT structures.

The doctoral project is part of the Compression perpendicular to the grain in cross-laminated engineered wood-based products research project.

Application of a numerical model in a CLT connection.
Application of a numerical model in a CLT connection.