Gap CLT - A study of modelling approaches and material savings
(2026) In TVSM-5000 VSMM01 20261Structural Mechanics
Department of Construction Sciences
- Abstract
- Cross laminated timber (CLT) is a sustainable alternative to concrete in multi-storey buldings. This project examines ”Gap CLT”, a modified version in which certain lamellas are removed to reduce material use. The reduction of material usage would decrease the CO2 emissions and therefore contribute to the prevention of global warming. However, the structural behavior of Gap CLT is not yet fully understood. For a one way spanning plate, it would be very suitable to remove some of the transverse lamellas as it would theoretically be a good way to save material without drastically affecting the structural capacity in the span direction.
The project aims to evalute the Gap CLT and to assess different design methods in ultimate limit state... (More) - Cross laminated timber (CLT) is a sustainable alternative to concrete in multi-storey buldings. This project examines ”Gap CLT”, a modified version in which certain lamellas are removed to reduce material use. The reduction of material usage would decrease the CO2 emissions and therefore contribute to the prevention of global warming. However, the structural behavior of Gap CLT is not yet fully understood. For a one way spanning plate, it would be very suitable to remove some of the transverse lamellas as it would theoretically be a good way to save material without drastically affecting the structural capacity in the span direction.
The project aims to evalute the Gap CLT and to assess different design methods in ultimate limit state and serviceability limit state. Analytical methods such as, the gamma method, Timoshenko theory and the shear analogy method are used along with finite element models in FEM-design and Abaqus. By introducing a reduction factor, reduced stiffness parameters are used to represent the gaps. Results from the analytical and numerical methods are compared to identify the possibilities and limitations of Gap CLT, supporting its development as a more efficient and sustainable structural solution.
For the examined design case, a CLT plate with a width of 2 meters and a length of 5 meters is studied. Along with a variable load of 2.0 kN/m2, a permanent load of 1.5 kN/m2 and the self weight is considered. It was shown that frequency of the CLT plate was the governing design check. According to the analytical methods, a material saving of 21 % could be achieved for optimized configurations. However, the methods utilizing the reduction factor could not correctly take gaps into account, as shown by the 3D finite element models in Abaqus and FEM-design, which are assumed to give the most realistic results. For these methods, the effect of the gaps was underestimated in serviceability limit state. For the ultimate limit state, only Abaqus managed to take the gaps into account. According to FE-analysis with Abaqus, a material saving of 10 % could be achieved for the examined design case. (Less) - Popular Abstract
- Cross laminated timber (CLT) is a prefabricated engineered wood product, consisting of various layers of timber lamellas which are stacked and glued upon each other crosswise. A common use for cross laminated timber is to act as a slab in a floor system, offering a more sustainable alternative to a concrete slab in a multistory building. In ongoing research, a modified version of a cross laminated timber slab is being studied. This version removes transverse and/or longitudinal members of the lamellas in order to reduce material usage. However, the influence on the mechanical performance is still relatively unknown. Therefore, the possibilities and the limitations of this “gap clt” needs to be studied further.
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/student-papers/record/9243773
- author
- Kristensen Lindberg, Anton LU
- supervisor
- organization
- alternative title
- KL-trä med hålrum - En studie av modelleringsmetoder och materialbesparing
- course
- VSMM01 20261
- year
- 2026
- type
- H3 - Professional qualifications (4 Years - )
- subject
- keywords
- CLT, Gap CLT, Cross laminated timber, Material optimization, air gaps, homogenization, RVE-models, FEM, Shear analogy method, Timoshenko theory, Gamma method, Material savings, Modelling approaches
- publication/series
- TVSM-5000
- report number
- TVSM-5284
- ISSN
- 0281-6679
- language
- English
- id
- 9243773
- alternative location
- http://www.byggmek.lth.se/english/publications/tvsm-5000-present-2014/
- date added to LUP
- 2026-06-26 10:30:27
- date last changed
- 2026-06-26 12:04:29
@misc{9243773,
abstract = {{Cross laminated timber (CLT) is a sustainable alternative to concrete in multi-storey buldings. This project examines ”Gap CLT”, a modified version in which certain lamellas are removed to reduce material use. The reduction of material usage would decrease the CO2 emissions and therefore contribute to the prevention of global warming. However, the structural behavior of Gap CLT is not yet fully understood. For a one way spanning plate, it would be very suitable to remove some of the transverse lamellas as it would theoretically be a good way to save material without drastically affecting the structural capacity in the span direction.
The project aims to evalute the Gap CLT and to assess different design methods in ultimate limit state and serviceability limit state. Analytical methods such as, the gamma method, Timoshenko theory and the shear analogy method are used along with finite element models in FEM-design and Abaqus. By introducing a reduction factor, reduced stiffness parameters are used to represent the gaps. Results from the analytical and numerical methods are compared to identify the possibilities and limitations of Gap CLT, supporting its development as a more efficient and sustainable structural solution.
For the examined design case, a CLT plate with a width of 2 meters and a length of 5 meters is studied. Along with a variable load of 2.0 kN/m2, a permanent load of 1.5 kN/m2 and the self weight is considered. It was shown that frequency of the CLT plate was the governing design check. According to the analytical methods, a material saving of 21 % could be achieved for optimized configurations. However, the methods utilizing the reduction factor could not correctly take gaps into account, as shown by the 3D finite element models in Abaqus and FEM-design, which are assumed to give the most realistic results. For these methods, the effect of the gaps was underestimated in serviceability limit state. For the ultimate limit state, only Abaqus managed to take the gaps into account. According to FE-analysis with Abaqus, a material saving of 10 % could be achieved for the examined design case.}},
author = {{Kristensen Lindberg, Anton}},
issn = {{0281-6679}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVSM-5000}},
title = {{Gap CLT - A study of modelling approaches and material savings}},
year = {{2026}},
}