Wooden Elements Research Articles

Evaluation of Tensile and Compression Bending Moment of L-Type Joints With 3D Printed Connectors

The paper investigates the bending moments under diagonal tensile and diagonal compression loads of L-type corner joints made of three wooden parts corresponding to the leg and the two stretchers used in chair construction. The wooden parts were jointed together with a 3D printed connector made of polylactic acid (PLA) filaments using Filament Fused Fabrication (FFF) as additive manufacturing technology. Larch (Larix decidua Mill.) wood was used to manufacture the wooden elements. In order to assess how the model orientation on the build platform influences the mechanical performance of the printed connector, two print positions were taken into account during the additive manufacturing (AM) process, namely horizontal and vertical. Mechanical testing under diagonal tensile and compression loads of the L-type corner joints, followed by the microscopic investigation of the fractured connectors with magnifications 50X, 80X, 100X were employed in this study. The results were compared with those of the reference L-type corner joint consisting of common mortise-tenon jointed wooden elements. The results show that the vertical orientation of the model on the build platform of the 3D printer is preferred for a better mechanical performance. The microscopy of the fractured connectors revealed the interlayer delamination of the filaments, especially in the case of the horizontal orientation of the model, which caused the wooden parts to slide out of the connector and record low values of the maximum failure loads.

The effect of heat flux on the fire and chemical properties of oak wood (Quercus petraea)

Selected fire properties of oak wood (mass loss, burning rate, and charring rate) and its chemical composition (extraction substances, lignin, cellulose, hemicellulose) were assessed. Oak wood samples with dimensions of 50 × 40 × 50 mm (l × w × t) were thermally loaded by a heat flux of 15, 20, 25, and 30 kW·m-2, using a ceramic infrared heater with a power of 1000 W. At the given thermal loading, the mass loss ranged from 26% to 47%, whereas the burning rate ranged from 0.0365 to 0.0584%·s-1. The maximum thickness of charred layer was 20 mm, and the charring rate reached values from 0.65 to 0.87 mm·min-1, in a time interval of 1800 s. With increasing thermal loading, the content of extraction substances increased by 30% and the content of lignin increased slightly as well. In contrast, the content of hemicelluloses decreased by 10.3%. This indicates that hemicelluloses are the least thermally resistant wood component. The obtained results can be used as basic data for future testing using medium-sized tests. Subsequently, they can be compared with the input parameters for calculating the fire resistance of wooden constructions elements, which will be the subject of further research.

Chemical Resistance of Modified Wood Veneers in Sustainable Load Bearing Elements.

In the pursuit of sustainable engineering solutions, material selection is increasingly directed toward resources that offer functional efficacy, economic feasibility, and minimal environmental impact. To replace environmentally damaging materials like aluminum with more sustainable alternatives like wood-based materials, it is essential to improve the durability and longevity of wood. This study explores the potential suitability of modified veneers as an outer protective layer for unmodified wooden load-bearing elements, providing a cost-effective and resource-efficient alternative to bulk modification. Unmodified, acetylated, furfurylated, and physically densified birch rotary-cut wood veneers were exposed to liquid chemical reagents (acids, base, solvents, and water) and characterized thereafter in tensile tests. The chemical resistance was evaluated based on the deterioration of tensile strength. Additionally, infinite focus microscopy, infrared spectroscopy, and contact angle measurements were performed to track morphological and chemical changes in the veneers. The results demonstrated that acetylation and furfurylation significantly enhanced chemical resistance against the tested reagents.

Numerical Methods for Topological Optimization of Wooden Structural Elements

Timber represents a building material that aligns with the environmental demands on the impact of the construction sector on climate change. The most common engineering solution for modern timber buildings with large spans is glued laminate timber (glulam). This project proposes a tool for a topological optimized geometry generator of structural elements made of glulam that can be used for building a database of topologically optimized glulam beams. In turn, this can be further used to train machine learning models that can embed the topologically optimized geometry and structural behavior information. Topological optimization tasks usually require a large number of iterations in order to reach the design goals. Therefore, embedding this information into machine learning models for structural elements belonging to the same topological groups will result in a faster design process since certain aspects regarding structural behavior such as strength and stiffness can be quickly estimated using Artificial Intelligence techniques. Topologically optimized geometry propositions could be obtained by employing generative machine learning model techniques which can propose geometries that are closer to the topologically optimized results using FEM and as such present a starting point for the design analysis in a reduced amount of time.

Numerical analysis of 3D printed joint of wooden structures regarding mechanical and fatigue behaviour

This paper presents numerical models of a 3D printed plastic joint applicable to the connection of wooden structures. The research presented provides a comparison of two alternative solutions for the geometry of the joint and results from several loading schemes and boundary conditions. Included are analyses evaluating the mechanical behaviour in a simple axial tensile test, a three-point bending test and, finally, a sensitivity analysis of the location susceptible to fatigue damage. The models include a 3D printed polycarbonate joint, wooden elements and steel shear pins. The combined model allows a deeper understanding of the interactions. Finite element method (FEM) software was used to develop the numerical models and suitably defined boundary conditions, and material properties of all parts were adopted. The simulation results show that the 3D joint exhibits a high resistance to tensile loading, while in the case of three-point bending, a higher susceptibility to fracture of the printed joint is observed. The sensitivity fatigue analysis identified critical areas on the 3D printed component that need to be improved before further development. These analyses provide important information for optimizing the design of 3D printed plastic joints intended for wooden structures.

Additive technologies for improving the strength and deformation characteristics of plastic washer joints of wooden structures

Introduction. Modern wooden structures are mostly connected by mechanical working joints. To increase the reliability of nodal joints, various kinds of washers can be pressed, inserted, or glued into the wood of the elements, thus ensuring the transmission of forces from one element to another. Joints on glued washers can transfer significant forces on a relatively small area of mutual contact, which is due to their high loadbearing capacity. Thus, the gluing of steel washers in places of increased stress concentration during force transfer ensures a significant redistribution of buckling/cracking stresses over a larger area of the connected parts. However, steel washers are highly corrosive, so additional measures are required to protect metal parts from corrosion or to replace the material with the composites. The results of full-scale tests of the samples with glued-in plastic washers are used to consider the ways of increasing the strength and deformation characteristics of the plastic washer material by applying additive technologies.Aim. To increase the load-bearing capacity of the wooden structure joints by increasing the strength and deformation characteristics of the glued washer material.Materials and methods. A method for full-scale tests of wooden specimens with glued fiberglass washers is presented. The wooden elements are made of second grade pine, while the washers are of REC Formax and REC Friction plastics. The test was performed in compression along the fibers, with control of vertical shear deformations. The methods of increasing the strength and deformation characteristics of plastic washers by using additive technologies are considered.Results. Using the data of full-scale tests the diagrams of sample deformations on glued plastic washers are drawn, the obtained results are analyzed. The sufficiently high plasticity of washer materials is established. The ways for increasing the strength and deformation characteristics of plastic washers, particularly by reinforcing the plastic washers is suggested.Conclusions. In order to increase the load-bearing capacity of the joints on the glued fiberglass washers, the reinforcement of plastic using additive CFC printing technologies and the use of different reinforcing fiber materials is adopted.

Experimental Studies on Joints of Wooden Elements with Proposed “CM Insert”

The article examines the results of testing a series of samples, where the joint operation of wooden elements is ensured by a composite material based on fiberglass. A method for ensuring joint operation is adopted according to the insert scheme on the contact surfaces. The strength and deformation characteristics of the samples are obtained, and the calculated bearing capacity is established. Statistical processing of the obtained parameters is performed.

Simulation of creep of a rectangular wooden beam under prolonged static load

Objective. Depending on the stress level, the operation of wooden beams under prolonged load is characterized by both linear and nonlinear creep. This has been shown by numerous experimental studies of wood. The theoretical description of these processes is poorly studied or presented extremely rarely. One of the priority areas in the calculations of wooden structure elements is the derivation of resolving equations of linear or nonlinear creep for various types of stress-strain state. Method. The Maxwell-Thomson equations are used as relations establishing the relationship between stresses and deformations. The technique was tested by comparing the solution with the calculation of well-known researchers. An example of calculation is given for various boundary conditions for fixing a beam of rectangular crosssection loaded with a uniformly distributed load. The deflection value is determined by the grid method. Result. A program has been developed for calculating in the MATLAB package with the possibility of varying the initial data and displaying a graph of the dependence of displacement, bending moment on time. The comparison of the maximum deflection value with the analytical solution is given. It is noted that the stresses practically do not change during creep. Conclusion. The proposed approach can be applied to the analysis of the stress-strain state and bearing capacity of wooden beams of arbitrary cross-section. There are no restrictions on boundary conditions and loading type, and the beam material can be not only wood, but also fiberglass.

Comparision of the Effectiveness of Fire-proof Impregnation Methods for Scots Pine Wood Used in Buildings Construction

The fight for a healthy and clean climate forces many restrictive changes to European law. Wooden construction fits very well into these changes, as it is able to store carbon dioxide for years. Unfortunately, many regulations, e.g. fire regulations, still hinder the development of this type of structures in Poland. Wooden elements used that have class D must achieve class B of fire resistance. For this purpose, they are modified with flame retardant agents. Three salt flame retardants based on: 1-phosphorus and iron, 2-phosphorus and nitrogen and 3-ogranic componds including benzoates, were used in the tests. The amount of applied fire retardants was compared depending on the impregnation technology used: surface immersion and pressure, as well as the reaction to fire of impregnated wooden elements. As a result of the tests, no impregnation used improved the fire properties, as shown by a small-scale cone calorimeter test. The project results indicate the need to conduct new basic research on the possibility of permanently improving the fire properties of wooden elements, which would allow the widespread use of wood in construction.

DEVELOPMENT OF METHODOLOGY AND STUDY OF THE INFLUENCE OF TECHNICAL, ORGANIZATIONAL AND TECHNOLOGICAL FACTORS ON THE DURATION OF THE PROCESS OF LIQUIDATION AND LOCALIZATION OF THE DEVELOPMENT OF DESTRUCTIONS

Analysis of the influence of technical, organizational and technological factors on the duration of the process of liquidation and localization of the development of destruction is an important stage of research into the process of liquidation of the consequences of accidental destruction. In order to compare options for liquidation and localization of the development of destruction of an emergency building, three options for reinforcement systems were analyzed: metal typical, wooden individual and combined. The work uses the method of analysis of hierarchies - a mathematical tool of a systematic approach to complex decision-making problems. The method does not impose the "correct" option, but allows you to interactively find an alternative (rational reinforcement option) that best matches the requirements for solving optimization tasks. To reduce the subjectivity of making a justified optimization decision in the conditions of complex multi-criteria optimization problems, a solution to the local problem of finding the optimal alternative according to the duration criterion, or a group of alternatives, taking into account the ratio of advantages based on the vector criterion, is proposed. To indicate the influence of advantages in quantitative expression, a pairwise comparison scale was used, which consists in a qualitative and quantitative assessment of relative advantage: equal in importance - 1; weak advantage – 2; average degree of preference ‒ 3; preference above the average degree ‒ 4; moderately stronger advantage ‒ 5; strong advantage ‒ 6; much stronger advantage ‒ 7; the most significant advantage is 8; absolute advantage ‒ 9. Initial data for choosing a temporary reinforcement option were obtained by comparing the estimated duration of dismantling and restoration works and optimizing the sequence of their execution for three options using wooden individual, metal typical and combined temporary reinforcement systems. It was established that it is impossible to ensure complete unification of reinforcement elements using only typical elements, therefore it is effective to use combined reinforcement systems using typical metal and individual wooden elements.

Basic Concepts of the Yin-Yang Story and Five-Element Doctrine and Their Implications in Business

This paper explores the fundamental principles of the Yin-Yang story and the five-element doctrine, both of which have their roots in ancient Chinese culture—one of the oldest continuous civilizations in the world. These philosophical concepts have profoundly influenced the Chinese people throughout their history, shaping their mentality, business practices, and social pursuits. The aim of this paper is to examine how the dualistic nature of Yin and Yang, representing opposing yet interconnected forces, and the five-element doctrine, categorizing the physical world into the elements of wood, fire, earth, metal, and water, continue to impact modern business strategies and decision-making processes in China. Through a detailed analysis, this paper reveals the complex relationships of unification, opposition, interdependence, mutual consumption, and transformation inherent in these philosophies. The findings demonstrate how these ancient doctrines still play a vital role in contemporary Chinese thought, offering valuable insights for global business interactions and contributing to the enrichment of the world’s cultural heritage.

Reframing the Conservation: A Case Study in using 3D Imaging Technology to Restore Carved Wooden Elements on a Painting Frame

Reframing the Conservation: A Case Study in using 3D Imaging Technology to Restore Carved Wooden Elements on a Painting Frame

Fire Resistance in Screwed and Hollow Core Wooden Elements Filled with Insulating Material

This study looks at wall partition panels with hollow core wood elements and gypsum board as protection in fire conditions. In addition to our previous research, this study on wall partitions considers the effect of steel screws in the assembly of the elements, as well as the filling of the cavity with insulating material. The goal of this work is to calculate the fire resistance time and compare the results using different numerical models. The discussion of the results analyzes the effect of steel screws and the introduction of insulating material inside the cavities. The steel screws are verified with and without threads. The numerical models are based on the finite element method, using thermal and transient analysis with nonlinear materials. The thermal insulation criterion for measuring fire resistance is referenced by the EN 1363-1:2020 standard. The steel screws allow more heat to be concentrated and, therefore, distribute it throughout the wooden wall partition members. Based on the results obtained, the use of steel screws reduces fire resistance by 71.75 min, regardless of whether the wall partition is filled with or without insulating material.

Hygrothermal assessment of three bio-based insulation systems for internal retrofitting solid masonry walls

The present project investigated the hygrothermal performance and risk of mould growth in solid masonry walls retrofitted internally with three diffusion-open bio-based insulation materials (two loose-fill cellulose and one hemp fibre), installed in test containers with controlled indoor climate. Focus was on bio-based insulation materials, as these are upcoming due to necessary CO2 reductions and because the hygroscopic properties of bio-based materials are different from traditional insulation materials like mineral wool therefore, some manufacturers claim a vapour barrier is unnecessary, even in relatively cold climates. The project was a large experimental study in two reefer containers with reconfigured facades, in which solid masonry walls with embedded wooden elements were constructed. The study focused on the conditions in the masonry/insulation interface and in the embedded wooden elements. The effect of hydrophobization and different indoor moisture loads were also investigated. Moreover, the bio-based insulation systems were compared with a wall insulated with the traditional mineral wool and vapour barrier system. Relative humidity and temperature were measured at several locations in the test walls for 1 year and 9 months. Measurements show that exposed masonry walls retrofitted internally with diffusion-open bio-based insulation materials resulted in unacceptably high moisture levels (>80% RH over longer periods). Lower moisture levels were observed when the internal insulation was combined with hydrophobization against wind-driven rain, but unacceptably high moisture levels still occurred (60%–70% in summer and 95%–100% in winter in the interface). Hydrophobization reduced the moisture levels in the interface and embedded wooden elements only in walls facing southwest, which is the direction with the most wind-driven rain. Mould growth tests showed no growth in the interface in walls insulated with cellulose insulation (mycometer surface value <25). Meanwhile growth was found in all four walls insulated with hemp fibre matts (mycometer surface value >400).

Performance of ANN, Random Forest and XGBoost methods in predicting the flexural properties of wood beams reinforced with carbon-FRP

ABSTRACT Wooden material can be used in different areas due to its various positive properties. Glued Laminated wooden elements (glulam) are wood composite materials widely used especially in the construction industry. Carbon fiber-reinforced polymers (FRP) are widely used to increase the bearing capacity values of glulam beams and improve their overall load-displacement behavior. This study was carried out in two stages. In the first stage, the bending properties of glulam timbers of different sizes with wide spans reinforced with carbon fiber-reinforced polymers were experimentally examined. In the next stage, the obtained data were predicted with three different machine learning techniques (ANN, Random Forest and XGBoost). As a result of the study, it was determined that as the section dimensions increased, the bending properties increased, and the reinforcement was effective by approximately 22%. All three different prediction techniques used could make predictions with high accuracy. However, it was determined that the best prediction was made with Random Forest (R2: 0.9892). Therefore, the bending properties of reinforced beams of different sizes can be predicted with machine learning (ML) techniques.

Experimental Analysis of Bonding in Steel Glued into Pine Timber.

Combining steel with wood has been practised for many years. The issue is related to two main areas, i.e., bonding steel elements with wood so that they serve as connectors facilitating the assembly of wood elements and bonding steel elements to wood beams to improve their load-bearing capacity. In the first case, the adhesives used may be relatively expensive and more difficult to apply, whereas in the second one, especially when steel elements are glued inside the glulam (GL) beams, it is better if the adhesives used are more accessible to apply and cheaper. As it seems rational to reinforce wood with high-modulus ties, research has been carried out to compare the connection quality of commercially available adhesives that can be used for this purpose. Moreover, thermosetting adhesives have been applied as an alternative and cheaper solution. Thermostat adhesives also have a high pH of the bond, which prevents the steel from rusting. The research shows that the load-bearing capacity of the bond depends on whether the bars are ribbed or sheet metal. Moreover, among thermosetting adhesives, the most favourable load-bearing values were obtained using a mixture of PF/pMDI (phenol formaldehyde resin/polymeric diphenylmethane diisocyanate) and powder from recycled tyres. The shear strength of these joints was 1.63 N/mm2 and 3.14 N/mm2 for flat specimens and specimens with ribbed bars, respectively.

Non-destructive Testing of Wooden Elements in Historic Buildings - An Example of Testing a 19th Century Roof Truss Structure

Destructive tests are not usually allowed in historic buildings; only non-destructive tests can be performed there. The obtained results should deliver the repair solutions that do not interfere into the historic layout of the church architecture and structure. One of the rarest areas subjected to non-destructive testing is diagnostic testing of wooden structures. However, calculations of strength verification cannot be performed if the wood class and quality are not determined. This paper describes in situ non-destructive testing of timber structural components of the roof truss system in the 19th century church in Osiecznica. The applied techniques were the standard ultrasonic and sclerometric methods, and additionally the original ultrasonic method with an instrument for analyzing the flow velocity of transverse waves.

Dimension-reduced mathematical modeling of self-shaping wooden composite bilayers

ABSTRACT Swelling and shrinkage of wood provides challenges when used as construction material. On the positive side, it allows for manufacturing curved wood elements by self-shaping upon drying. We present a two-dimensional model for simulating the moisture-induced bending of wooden bilayers and more general composite plates with multiple, periodically distributed material phases. The model is derived in a mathematically rigorous way from a fully three-dimensional nonlinear hyperelasticity model of the plate and is computationally cheap to handle. We focus specifically on the scenario of free deformations. While the derived model is capable to describe general isometric bending deformations, it has the property that free deformations in equilibrium are given by uniaxial bending deformations that can be computed without the need for solving the plate equations via finite element simulations. The hereby gained computational efficiency enables extensive parameter studies to be conducted regarding the design of wooden composite plates with complex composite geometry. We validate the model for homogeneous wooden bilayers and obtain good agreement between simulations and experimental data. Then we use the model to predict the bending behavior of periodically perforated bilayers. The comparison to other existing models and implications for practical use are discussed.

Morphology and composition of calcium oxalate monohydrate phytoliths in the bark of Betula ermanii (stone birch): Case study from Sakhalin Island.

The morphology of calcium oxalate monohydrate precipitates (COM, Ca(C2O4)·H2O, P21/c, whewellite) occurring as crystals or intergrowths, as well as distribution of crystal-bearing idioblasts, have been studied for the first time in the bark of stone birch Betula ermanii from Sakhalin Island sampled in an area affected by mud volcanism and an unaffected typical forest environment taken for reference. The study addresses several issues (i) number and size of phytoliths and their distribution in different cell types; (ii) density of calcification in specific cells; (iii) habits of single crystals, twins, and complex intergrowths, as well as frequency of different morphologies and their relations. The trends of time-dependent morphological changes in separately analyzed crystals and intergrowths record the evolution of COM morphology from nuclei to mature grains. Of special interest are the nucleation sites and features of organic and inorganic seeds and nuclei for COM phytoliths. The precipitation process and crystal habits are mainly controlled by supersaturation, and it is thus important to constrain the Ca distribution patterns in different bark tissues. The B. ermanii samples were analyzed by several methods: scanning electron microscopy (SEM) for the distribution patterns and micromorphology of COM precipitates and bulk Ca content in bark; electron probe microanalysis (EPMA) for the mineral chemistry of COM precipitates; inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) for trace elements in bulk bark and wood. RESEARCH HIGHLIGHTS: The distribution and morphology of whewellite precipitates in the analyzed B. ermanii bark samples indicate that the aqueous solution was most strongly supersaturated with respect to the Ca(C2O4)·H2O solid phase at the parenchyma-sclerenchyma boundary, where most of the COM spherulites are localized and often coexist with large single crystals and contact COM twins.

Use of threaded washers in the joints of wooden structures

Introduction. One of the promising types of joints in wooden structures is the joint using glued steel washers. However, the use of adhesive compounds is, for a number of reasons, characterized by lower manufacturability as compared to a threaded connection. Given the relevance of developing new technological types of joints in structures, it is necessary to study the threaded washer connection of wooden elements without the use of adhesives.Aim. To study the performance of a threaded washer connection by conducting a full-scale experiment of specimens exhibiting different parameters of threaded washers in order to assess the prospects for further study of the joint in question and its implementation in construction practice.Materials and methods. The procedure for studying the joint under consideration involves making a series of specimens and conducting an experiment to determine the failure loads and ultimate strains, followed by the visual inspection of these specimens after failure.Results. The experimental study of twelve specimens (four series of specimens exhibiting different parameters of threaded washers, with three specimens in each) yielded failure loads, and graphs showing their deformation were constructed. The performance of the joint in question was examined; its advantages and disadvantages in terms of bearing capacity, manufacturability, and reliability were identified.Conclusions. Threaded washer joints in wooden structures are characterized by high bearing capacity and manufacturability. In spite of such a disadvantage as the effect of wood moisture on the strength and reliability of this joint, its advantages make it promising for further study and use in construction practice.