Shear Properties of Cross Laminated Timber (CLT) under in-plane load - Test Configuration and Experimental Study

Sep 14, 2026

The study investigates shear properties of cross laminated timber (CLT) subjected to in-plane loads, focusing on how geometry-dependent layups and test configurations influence mechanical behavior. It addresses limitations of current approval methods that rely heavily on single-node testing, which cannot represent the full stress state of diaphragm elements. The work frames in-plane shear behavior through three failure scenarios—gross shear, net shear, and torsion in gluing interfaces—and examines experimental strategies to realize pure shear and reproducible failure mechanisms.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages21

Reading Time53 min

AccessFree to download

Introduction

CLT under in-plane loading and in-plane shear

Failure scenarios and characterization challenges

Limitations of single-node testing

Efforts toward full-scale diaphragm testing

Alternative test configurations and evaluation approaches

Shear Properties of Cross Laminated Timber (CLT) under in‐plane load: Test Configuration and Experimental Study Reinhard Brandner, Graz University of Technology *) Philipp Dietsch, Technische Universität München *) Julia Dröscher, Graz University of Technology Michael Schulte‐Wrede, Technische Universität München Heinrich Kreuzinger, Technische Universität München Mike Sieder, Technische Universität Braunschweig Gerhard Schickhofer, Graz University of Technology Stefan Winter, Technische Universität München *) joint first authorship Keywords: cross laminated timber; CLT; shear in‐plane; diaphragm; test configura‐ tion; experimental study; parameter study; shear strength; shear modulus; failure mechanisms; characteristic properties; design concept 1 Introduction Cross laminated timber (CLT) is a two‐dimensional laminated engineered timber product, commonly composed of an uneven number of orthogonally and rigidly con‐ nected layers. High resistances in‐ and out‐of‐plane predestines it for numerous ap‐ plications, e.g. for floor and wall elements, shear walls, folded panels and beams. With respect to its resistances and properties as a structural product, it is differenti‐ ated between out‐of‐plane and in‐plane loading. For CLT under out‐of‐plane loading, test configurations and characteristic values are well agreed. For CLT under in‐plane loading, some properties are still under discussion, presently resulting in conservative regulations, e.g. tension and compression in direction of the top layers. The same is valid for CLT under in‐plane shear. To fully profit from the high capacities of CLTin‐plane, a detailed knowledge of all relevant mechanical properties, which are dependent on the geometrical layup of the elements, as well as the development and verification of practicable test configurations to determine these properties are indispensable. Consolidated knowledge of CLT properties under in‐plane shear is crucial for typical structural applications such as wall and floor diaphragms, cantilevered CLT walls and CLT used as (deep) beams, in all cases potentially featuring holes or notches. The cur‐ rent technical approvals for CLT products contain differing regulations to determine their load‐carrying capacities in‐plane. Generally they imply a verification of the tor‐ sional stresses in the cross‐section of the cross‐wise glued elements as well as a veri‐ fication of the shear stresses proportionally assigned to the boards of the top and cross layers. The basis of theoretical and practical considerations are the following three basic failure scenarios for a CLT‐element under in‐plane shear: (i) gross‐shear (longitudinal shearing in all layers),(ii) net‐shear (transverse shearing in all layers in weak direction), and (iii) torsion failure in the gluing interfaces between the layers (Bogensperger et al. 2007, 2010; Flaig and Blaß 2013; Brandner et al. 2013) . All failure mechanisms can be achieved if a corresponding test configuration is applied. Properties for the mechanism (iii)“torsion”, based on Blaß and Görlacher (2002), Jeit‐ ler (2004) and Jöbstl et al. (2004) are well accepted (DIN EN 1995‐1‐1/NA) . In con‐ trast, the determination of the properties (i) gross‐shear and (ii) net‐shear by testing is challenging, as it is practically impossible to secure larger fields of pure shear. Up to now, the properties for in‐plane shear provided in technical approvals are based on testing single nodes. The resulting strength values are partly seemingly high and fea‐ ture a higher variability than expected for diaphragms. Associated investigations in‐ clude Wallner (2004), Jöbstl et al. (2008) and Hirschmann (2011) . After re‐evaluating and summarizing previous findings Brandner et al. (2013) propose fv,net,05 = 5.5 N/mm² as 5 %‐quantile of net‐shear strength for a reference CLT node in conjunction with the test configuration “EN” of Hirschmann (2011) . Board thickness, gap width and annual ring pattern were identif

FAQs

Why are shear properties of CLT under in-plane load still under discussion?

Some in-plane properties remain debated, leading to conservative regulations in technical approvals. This also applies to in-plane shear, where reliable characterization is difficult.

What three failure scenarios are used to describe CLT under in-plane shear?

The text distinguishes gross shear, net shear, and torsion failure in the gluing interfaces between layers. A suitable test configuration can trigger each mechanism.

What are the main challenges when testing CLT diaphragm shear properties using full-scale configurations?

Key challenges include realizing a continuous load introduction, obtaining a field of pure shear, and achieving failure under in-plane shear. These issues can also arise with standardized racking-strength test setups.

Sep 14, 2026

Uploaded by Quinn Holloway