INFLUENCE OF REINFORCEMENT ON THE STRESS-STRAIN STATE OF A CURVED GLUED-LAMINATED TIMBER STRUCTURE

Abstract

Timber is widely used in construction, particularly as elements subjected to bending and combined compression with bending. One of the main disadvantages of timber structures is their insufficient stiffness under bending, which leads to significant deformations. Reinforcement of solid and gluelam timber provides an effective solution to this issue. However, current Ukrainian standards for the design of solid and glued timber structures lack guidelines for the calculation of reinforced elements, despite their proven effectiveness in reconstruction, strengthening, and new construction projects. To validate the modeling methodology of timber deformation, a numerical analysis was conducted using the LIRA-SAPR software package, which applies the finite element method. This software enables the determination of displacements and the stress-strain state of structures using different types of finite elements. The results obtained can be used to verify the modeling process and compare it with deformation-based analytical methods, which supports the relevance of their application. The efficiency of LIRA-SAPR has also been confirmed through multiple studies and expert evaluations. The aim of the study is to improve the design process of reinforced solid and glued timber structures by numerically modeling reinforced and non-reinforced curved laminated timber elements in LIRA-SAPR and comparing the results with those from deformation-based analytical approaches. The study involved the creation of a numerical model of a curved gluelam timber structure used as a roofing element. The structural geometry, physical and mechanical properties of timber and reinforcement, and loading conditions were defined based on existing research. Modeling was conducted using volumetric finite elements with orthotropic material properties, and reinforcement was simulated through embedded bars in tension and compression zones. Results showed a significant reduction in timber stress due to reinforcement, which also led to decreased displacements in both vertical and horizontal directions. A comparative analysis of internal stresses obtained via LIRA-SAPR and those calculated using deformation methods indicated that the software tends to yield slightly higher values in timber stress, while the reinforcement stress was found to be lower in analytical calculations. Overall, the study highlights the effectiveness of reinforcing curved timber structures, particularly in areas subjected to the highest bending moments. Modeling with LIRA-SAPR enables detailed assessment of the stress-strain state, supports the adoption of rational reinforcement strategies, and helps identify zones of shear stress concentration. The results confirm the importance of using advanced finite element modeling tools for the accurate analysis and design of complex timber structures.