Published on: 2026-09-29
Source: Saint Petersburg State University of Architecture and Civil Engineering –
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Modern timber construction is increasingly using engineered wood – materials whose properties allow them to be applied in the structures of mid-rise and multi-storey buildings. One such material is LVL (Laminated Veneer Lumber), made from unidirectional glued veneer. Scientists at SPbGASU studied how LVL structures behave under long-term load exposure and developed an approach for a more accurate assessment of their load-bearing capacity considering the material’s characteristics.
The research work “Development of a method for assessing the bearing capacity of elements and joints of LVL building structures under long-term effects considering anisotropy” was carried out by an associate professor of the Department of Metal and Wooden Structures, Candidate of Technical Sciences Pavel Koval and assistant of the Department of Reinforced Concrete and Masonry Structures Anna Kushnir.
Why it is important to consider LVL anisotropy
When designing structures made from LVL, approaches used for solid and glued wood are applied. However, LVL has characteristics that must be taken into account when assessing its performance. In particular, the strength and deformation properties of the material depend on the direction of the applied load relative to the grain.
This feature – anisotropy – is especially noticeable under prolonged loading. Researchers have found that the behavior of LVL under compression in the radial and tangential directions differs significantly.
Significant highly elastic and irreversible creep deformations arise under radial loading. In the tangential direction, failure occurs comparatively more brittlely and is closer in nature to failure under compression along the fibers.
At the same time, the boundary of resistance regions on the diagram of LVL strength dependence on the force inclination angle had not been previously identified. Determining this boundary became one of the key objectives of the study.
From theory to experiment
To solve the assigned tasks, scientists from SPbGASU combined theoretical calculations with experimental studies. During the work, analytical relationships of the limit of forced highly elastic deformations of LVL depending on the angle of force application relative to the fibers under compression were proposed.
Sample preparation process for testing
In addition, the researchers obtained experimental relationships of the limits of forced high-elastic deformations under compression at various angles relative to the fibers, depending on the loading rate.
Based on the obtained data, an experimental-theoretical method was developed that made it possible to determine the position of the boundary of resistance regions on the diagram of LVL strength dependence on the angle of force inclination under long-term loads.
An additional outcome of the work was the recommendations for designing joint nodes of building LVL structural elements under long-term effects, taking into account the anisotropy of the material.
“We managed to approach the task comprehensively: to theoretically describe the behavior of LVL through analytical dependencies and confirm them experimentally. It is precisely the combination of diagrammatic calculation and field test data that made it possible to determine the position of the boundary of resistance areas. The obtained results are a step towards a more reliable assessment of the load-bearing capacity of LVL structures under long-term loads,” notes Anna Kushnir.
The practical significance of the study is related to the possibility of increasing the reliability of the load-bearing capacity assessment of LVL structures. The proposed method can be used in the design and inspection of buildings and structures, in making changes to the current regulatory documentation, as well as in the educational process.
The obtained results simultaneously demonstrate the need for further study of the anisotropy of strength and deformations of LVL and its impact on the performance of structural elements and joints under prolonged loads.
Following the results of the research work, articles have been prepared for publication in journals included in the VAK list.
The project is implemented within the framework of the grant competition for conducting R&D by scientific and pedagogical staff of SPbSASU in 2026.
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