Moisture Content Of Timber Research Articles

Preliminary Insights on Moisture Content Measurement in Square Timbers Using GPR Signals and 1D-CNN Models

Accurately measuring the moisture content (MC) of square timber is crucial for ensuring the quality and performance of wood products in wood processing. Traditional MC detection methods have certain limitations. Therefore, this study developed a one-dimensional convolutional neural network (1D-CNN) model based on the first 8 nanoseconds of ground-penetrating radar (GPR) signals to predict the MC of square timber. The study found that the mixed-species model exhibited effective predictive performance (R2 = 0.9864, RMSE = 0.0393) across the tree species red spruce, Dahurian larch, European white birch, and Manchurian ash (MC range 0%–133.1%), while single-species models showed even higher accuracy (R2 ≥ 0.9876, RMSE ≤ 0.0358). Additionally, the 1D-CNN model outperformed other algorithms in automatically capturing complex patterns in GPR full-waveform amplitude data. Moreover, the algorithms based on full-waveform amplitude data demonstrated significant advantages in detecting wood MC compared to those based on a traditional time–frequency feature parameter. These results indicate that the 1D-CNN model can be used to optimize the drying process and detect the MC of load-bearing timber in construction and bridge engineering. Future work will focus on expanding the dataset, further optimizing the algorithm, and validating the models in industrial applications to enhance their reliability and applicability.

Kiln-drying effectiveness as influenced by moisture content and density variation within a Scots pine timber batch

ABSTRACT Sorting of sawn timber batches is crucial for efficient kiln-drying. This study aimed to verify the hypothesis of different drying attributes of 25 mm thick sapwood and mixed Scots pine boards sawn from a group of butt, second, and top logs and assess the effects of kiln-drying. Three options dry-bulb temperature were taken into account. The drying results were evaluated based on the final moisture content distribution, changes in the cross-sectional dimensions of the sawn timber, drying time, and unit heat consumption. Correlations between sawn timber features, drying temperature, and drying results were analyzed using non-parametric statistical tests. The study proved the dependence of the initial moisture content and wood density variation of Scots pine sawn timber on the log type and the position on the round timber cross-section. The variation of drying attributes of the sapwood and mixed 25 mm Scots boards is insignificant in the final moisture content distribution and cross-sectional dimensions. However, green sorting may have only a beneficial effect on drying time and heat consumption.

Investigation of the behaviour of adhesively bonded joints between timber and self-compacting concrete

Composite constructions made of wood and concrete are being researched as revolutionary structural components that offer many benefits. The connection in timber-concrete-composite (TCC) is typically made via mechanical means. This study describes the TCC bonded by adhesives, particularly the mechanical behaviour of the joints between timber (GL24h) and self-compacting concrete (SCC) set by the dry or wet bonding process. For this purpose, double push-out shear tests on TCC joints bonded by epoxy resin of adhesives were performed. The role of several variables was considered for both fabrication processes. These parameters were: variation of moisture content (m.c.) of timber, adhesive type, adhesive thickness, sand addition, concrete surface treatment, and scale of bonding length. The results showed that glueing seems to be a feasible alternative instead of mechanical means for producing dry and wet TCC joints. Under dry conditions of timber elements, the shear strength can be considered highly satisfactory, with a mean value range of 6–8 MPa. The failure mode is primarily affected by concrete and timber failure. However, the findings of this study confirm the hypothesis that increasing the moisture content of timber before the gluing process significantly reduces the shear strength of adhesively bonded TCC joints by approximately 30% in certain instances. These results contribute to understanding the challenges and limitations of the bonding system, providing valuable insights for optimizing the design and manufacturing of timber-concrete composites.

Timber moisture content evaluation using spiral capacitive structures

In this work a transducer based on spiral planar inter-digital capacitive structure is designed and implemented for timber moisture content measurement. The sensor capacitance measured at frequency 100 KHz is found to depend strongly on the material dielectric properties, which is found to increase with increasing moisture contents (MC). The moisture contents in the range from 0% to 82% for 5 different varieties of timber specimens are measured and the results presented. The measured capacitances increase with moisture contents with an exponential fitting, with a correlation coefficient better than 0.98 indicating good fit for all the timber varieties. The sensitivity of the technique varies with the specimen as well as its moisture content. The best sensitivity obtained is 0.01 pF/MC%. The performance of the technique in terms of relevant sensor parameters has been analysed and compared with existing techniques for the same measurement. Although several moisture measurement methods exist for timber, the present inter-digital capacitive technique has many advantages over them in terms of sensitivity, dynamic range, cost effectiveness, non-invasiveness, non-destructiveness and measurement speed.

Airtightness of a Critical Joint in a Timber-Based Building Affected by the Seasonal Climate Change

The airtightness of buildings is an essential topic regarding energy preservation. The development of new and more sophisticated materials and technology approaches is inevitable. Uncontrolled infiltration is undesirable in buildings with lower energy demands with regulated ventilation. Envelope structure, building method, quality, and others are the main factors influencing the airtightness of the building. However, the correlation between airtightness and climatic factors is less known and researched. This paper comprises measurements of a critical timber-house corner in climatic chambers. It captures the correlation between airtightness and gradual temperature and relative humidity adjustments, simulated from the exterior side. The initial timber moisture content was 12%, and during the experiment it increased with the exterior conditions to 18%. Afterward, we simulated conditions causing a humidity decrease while measuring airtightness. The drying process caused a decrement in airtightness by 18%. In addition to this experiment, this paper also analyses two methods of an airtight membrane connection—constricting or taping the contact. The discrepancy between those two methods was more than 21% in favor of tape.

Influence of Thermo-Mechanical Densification (TMD) on the Properties of Structural Sawn Timber (Pinus sylvestris L.)

The article presents the results of thermo-mechanical densification tests conducted on Scots pine timber. The densification process was carried out in industrial conditions with a high-pressure press, which allowed flat compression of boards that were up to 2.5 m long. A phenomenon of elastic redeformations was observed in the densified boards after each pulse of compression. As a result of thermo-mechanical compression, the average timber moisture content dropped to 9%, and the average density increased by 13.5%, from the level of 547 to 621 kg/m3. As a result of thermo-mechanical densification, the strength class C of most Scots pine timber pieces improved. Most timber pieces that were subjected to thermo-mechanical densification have improved their strength class, C, by one (72.7% of the tested batch) or two C classes (3.6% of the batch under study).

Comparative Evaluation of Physical and Mechanical Properties in the Radial Positions of Coconut (Cocos nucifera) Timber

This study evaluated the variation of the physical and mechanical properties within coconut timber's radial position (dermal, sub-dermal, core). Properties were studied on the 55-year-old coconut palm from KAU coconut farm Vellanikkara, in Thrissur, district Kerala. The density of coconut timber at the radial positions was 862.3 kg m-3, 670.8 kg m-3 and 287.9 kg m-3, respectively, for the dermal, sub-dermal, and core positions. The average moisture content of coconut timber in the dermal, sub-dermal, and core positions was 15.7 %, 16.6 %, and 17.5 %, respectively. Compressive strength parallel to the grain at the three radial positions such as dermal, sub-dermal, and core is 32764.77 kg cm-2, 25591 kg cm-2, 7532.35 kg cm-2, respectively, and the compressive strength perpendicular to the grain was found as 46712.42 kg cm-2, 39233.3 kg cm-2, 22353.04 kg cm-2. Hardness measured at the side and ends of the dermal position is 1207.612 kg and 767.65 kg, respectively. In the sub-dermal position, 1035.7 kg and 750.88 kg, respectively. The core position is 252.34 kg and 359.31 kg, respectively.

Benchmarking moisture prediction in kiln-dried Pacific Coast hemlock wood

ABSTRACT The uniformity of final moisture content within a drying timber batch is crucial. Lack of such uniformity leads to producing large percentages of over-dried and under-dried timber, resulting in significant quality degradation and value downgrade. This study aims to predict kiln-dried timber moisture content using its initial moisture value, timber weight, and density. The distribution of wood properties in different drying runs was analyzed, and the difference in their means was statistically assessed. Various machine learning models were used for moisture prediction. The performance of the group method of data handling network was compared with the adaptive neuro-fuzzy inference system, support vector regression, decision tree, and random forest method. The best performance was achieved using random forest with the initial moisture content and weight of the wood as input parameters. Finally, the models’ performances were compared and practical recommendations for employing the adopted methodology in industrial settings were provided.

Timber encasement of steel structures as an alternative fire insulation

AbstractThis paper presents the results of an investigation on the thermal behaviour of fire‐exposed steel profiles embedded in timber elements.Several tests were performed on small unloaded specimens in a small furnace. The different specimens were made of bare steel profiles, timber elements or steel‐timber hybrid members. Different welded I or T steel sections and wood species were used. The specimens were set horizontally (3‐side exposure) or vertically (4‐side exposure) in the furnace and heated using a couple of burners. The temperatures of the steel profiles were measured by welded K thermocouples.The results from this experimental campaign, in terms of temperature of the furnace and of the specimens, density and moisture content of timber, were then used to calibrate a heat transfer model under Ansys finite element code. This 2D numerical model is mainly based on the behaviour laws of structural steel and timber from Eurocodes 3 and 5 respectively. Regarding the specific heat of timber, several relationships were applied. A comparative analysis of experimental and numerical results confirms the fire insulation brought to steel by timber. It also highlights the ability of the model to simulate the thermal behaviour of both steel and timber, in terms of heating and charring rates.

The Efficiency of Different Wood Coatings against Water Surface Absorption

Abstract In the market of the Latvia different wood surface coating materials suitable for use in outdoor conditions are offered, but available information on the efficiency of these against direct water exposure is insufficient. For structural timber building elements, such as glued laminated timber (GLT), the surface coating should be applied taking into account technological, visual or colour changes (ISO 7724:1984) and – last, but not least – economic aspects are considered. Wood surfaces coated with coating materials, such as varnishes, paints, etc. can stabilize some properties such as movement of moisture content, dimensional changes and attack by microorganisms and fungi. The changes in the moisture content of timber may influence such important parameters as mechanical properties and the total life time of the structural timber elements. A study has been conducted with the aim of assessing the efficiency of coating materials used for wood protection against water absorption. In this study, six different commercial coating products used for the treatment of spruce (Picea Abies L. Karst.) and pine (Pinus Sylvestris L.) samples were tested. The efficiency of different coating substances was assessed using two modified test methods according to the standards EN 382-2 (1994) and EN 927-5 (2006), determining the surface water absorption after immersion in water for 24 h and the dynamics of water absorption of the glued laminated timber for 696 h kept in water. As a result of the study, it has been ascertained that organic solvent-based commercial coating products are more efficient against short-term and long-term wood water absorption compared to oil-based coating materials.

Normal stress distribution of timber-concrete composite panels with an adhesive shear connection under thermal and humidity loadings

Humidity and temperature conditions have a substantial influence on the stresses and total deformation of timber-concrete composite panels, especially in terms of the high rigidity of the shear connection. In the present research, the normal stresses that resulted from the hygrothermal load of timber-concrete composite panels with an adhesive shear connection were analyzed. Three timber-concrete composite panel specimens were placed in controlled climate conditions. Strains in two orthogonal directions were measured. The stress distribution resulted from an approximate analytical calculation model. The results show that the highest stresses occurred near the shear connection. An increase in timber moisture content by 2.1% was predicted to result in exceeding the flexural tensile strength in the concrete perpendicular to the timber grain direction. At an outdoor temperature range, stresses influenced only by the temperature alone will possibly not cause a failure of timber or concrete. Under winter environmental conditions, the stress in timber can possibly reach 12% of the bending strength of the timber used.

Short-Term Analysis of Adhesive Types and Bonding Mistakes on Bonded-in-Rod (BiR) Connections for Timber Structures

Bonded-in rods (BiR) represent a structural connection type that is largely used for new timber structures and rehabilitation (repair or reinforcement) of existing structural members. The technology is based on steel / Fiber Reinforced Polymer (FRP) / Glass Fiber Reinforced Polymer (GFRP) rods bonded into predrilled holes in timber elements. The mechanical advantages of BiRs include high local force capacity, improved strength, a relatively high stiffness and the possibility of ductile behaviour. They also offer aesthetic benefits, given that rods are hidden in the cross sections of wooden members. As such, BiR connections are regarded as a solution with great potential, but still uncertain design formulations. Several research projects have dealt with BiRs, but a final definition of their mechanics and a universal design procedure is still missing. This research study explores the typical fracture mechanics modes for BiR connections. A special focus is given to the evaluation of the impact of adhesive bonds under various operational conditions (i.e., moisture content of timber). A total of 84 specimens are tested in pull-out setup, and investigated with the support of digital image correlation (DIC). The reliability of empirical equations and a newly developed analytical model in support of design, based on linear elastic fracture mechanics (LEFM), is also assessed.

Timber moisture detection using wavelet packet decomposition and convolutional neural network

As timber structures are vulnerable to degradation due to the tendency to trap moisture, the present study proposed a new percussion-based method to replace the existing constant contact between structures and sensors. A total of two approaches have been proposed to automated detect the moisture content (MC) of timber: (a) the random forest classifier (machine learning-based) was employed to classify the wavelet packet decomposition (WPD) features extracted from excitation-induced sound signals (WPD + RF); and (b) the 2D-CNN framework (deep learning-based) was employed to classify the Mel frequency cepstral coefficient (MFCC) features extracted from excitation-induced sound signals (MFCC + 2DCNN). The proposed automatic detection methods are covered from 1D time-domain signal classification to 2D image classification. To verify the effectiveness of both two approaches, an experimental study was conducted. The MC of two types of timber specimens (i.e. softwood and hardwood) was gradually increased from 0% to 60% with 10% increments. The change of MC of timber material caused different material properties, resulting in a measurable differential in forced vibration among the various specimens used. The results demonstrated that MFCC + 2DCC outperformed the RF + WPD in MC classification of timber material. Overall, the percussion-based method proposed in this study can provide an outstanding classification performance.

Sensor Node Network for Remote Moisture Measurement in Timber Based on Bluetooth Low Energy and Web-Based Monitoring System.

This paper proposes an IoT system based on wireless BLE connectivity to monitor the moisture content of wood, using a compact and low-cost moisture device that relies on a resistance measurement method valid for an ultra-wide range of resistance values. This device is digitally controlled with a BLE-incorporated micro-controller characterized by its small size and low power consumption, providing long-life battery. The proposed system consists of two main parts: first, the BLE moisture device including the moisture content measurement and wireless capability (BLE); second, the cloud-based monitoring platform, providing remote visualization and control for all the sensor nodes of the network. The complete infrastructure shows how multiple nodes can read and transmit moisture content of timber in buildings using small and unattended devices, with data saved in a central database and monitored by multiple commercial devices such as PC, smartphone, tablet, etc. The proposed system is innovative, scalable and low cost, and it can be deployed in wooden buildings and the wood industry, providing a practical solution that will help to avoid rot and other damaging effects caused by the moisture content.

Orchard biomass residues: Chemical composition, biological activity and wood characterization of apricot tree (Prunus armeniaca L.)

AbstractRecent EU directives have encouraged member states to follow circular economy guidelines on waste reuse, especially for waste originating from wood agro‐forest biomass. Delineating the antioxidant and chemical activity of biomass is a starting point to find new ways to utilize such materials. Here, an 8‐year‐old apricot (Prunus armeniaca L.) tree stand located in southern Italy was evaluated. First, dendrometric parameters (total volume, diameter, and height of trunk below the branches) and physical‐mechanical properties (density, total, tangential and radial shrinkage, moisture content, and compression strength) of timber collected from five experimental plots was evaluated. Bark and wood from apricot pruning were then subjected to different extraction techniques, in vitro antioxidant assays, and gas chromatographic studies to determine their antioxidant activity and their phytochemical composition. Bark had the highest antioxidant activity compared to wood. Several antioxidant compounds (e.g., scopoletin and naringenin) were detected in the samples, explaining the measured antioxidant activity. In conclusion, this study demonstrates the potential of using apricot extracts in nutraceutical, cosmeceutical, and industrial fields. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Performance of Notched Connectors for CLT-Concrete Composite Floors

CLT-concrete composite floor systems are a solution for timber buildings with a long-span floor. It yields a reduction of carbon footprint and even eco-friendly structure at the end of its service life. This study will evaluate the structural performance of notched connectors in the CLT-concrete composite floor, comprised of the serviceability stiffness, maximum load, and behavior at failure. The parameters of the test plan are the loaded edge length, the notch depth, the concrete thickness, and the screw length. Other secondary variables are also assessed, such as different loading sequences, speed of test, and timber moisture content. Experimental results prove that the performance of the connector depends significantly but not linearly on the notch depth and the length of the loaded edge. The connector with a deeper notch and a shorter heel will be stiffer and more robust, but it also tends to have a brittle rupture. The test results also help validate a solution for deconstructable connector systems. A nonlinear finite element model of the connector is built and validated versus the experimental results. It yields reasonably good predictions in terms of resistance and can capture the load-slip relationship.

Modelling the hygro-mechanical creep behaviour of FRP reinforced timber elements

A fully coupled moisture-displacement finite element model has been developed to predict the viscoelastic, mechano-sorptive and swelling/shrinkage behaviour of FRP reinforced timber elements when stressed under long-term load and simultaneously subjected to changes in relative humidity. A DFLUX subroutine, to describe the changes in relative humidity with time, and a UMAT subroutine, implemented to describe the viscoelastic, mechano-sorptive and swelling/shrinkage behaviour, are presented. Additionally, an irrecoverable mechano-sorptive component is presented. This additional irrecoverable component occurs when the timber moisture content increases to a moisture content above levels previously attained. The model is found to be in agreement with experimentally determined deflection and strain results on both unreinforced and FRP reinforced beams subjected to constant and variable climates.

Moisture content and its influence on glued timber structures

The glued timber structure is well-known worldwide engineering product nowadays. Extensive knowledge of wood structure behavior has been as important basic to create new design projects. This paper presents the issue of determining moisture content (MC) in load-bearing glued wood structures, depending on a value of indoor relative humidity and temperature. There are two ways to study timber moisture content – calculation (manual or in programs) and measurement methods. this ways complement each other. Each of methods is more or less suitable for monitoring of structural elements or not suitable at all. Graphs, tables or 3D models of timber moisture content distribution in structure are can received using these methods. Two simple equations to determine timber moisture content are given in the paper. Besides, effect of timber moisture content on durability properties of wood structure is describes there.

Experimental and analytical investigations into the time-dependent performance in post-tensioned timber beam-column joints under sustained loads and varied environment

Experiments investigating the time-dependent performance of post-tensioned timber beam-column joints were conducted in an uncontrolled environment. The aim of these experiments is to study the deterioration of joint performance, especially the prestressing force losses and the rotational stiffness degradation. Two types of post-tensioned joint specimens were monitored: one was without external loads, and the other one was subjected to external loads. Environmental temperature and relative humidity were measured in combination with timber moisture content, prestressing force, joint rotation, beam deflection and timber strain. It was shown that the maximum loss percentage of the prestressing force was 11.4% and 19.1% for the unloaded and loaded joints, respectively. The variation of prestressing forces was dominated by the stress level and the relative humidity change. Meanwhile, the joint rotation increased by a factor of 6.56 in the first four months compared to the elastic joint rotation, and the deflection at the end of the beam was 2.55 times bigger compared to the elastic deflection. The stress concentration on the beam-column interface was found as a determinant factor causing the excessive joint rotation. An analytical model was adopted to simulate the prestressing force losses and achieved good agreement with the experimental results.

Thermogravimetric Analysis and Pyrolysis Kinetics of Malaysian Wood Species

The mass loss of three wood species in Malaysia, Shorea laevis, Koompassia malaccensis, and Shorea parvifolia were measured against time and temperature at three different heating rates (5, 10 and 20 °C/min) in nitrogen environment, through thermogravimetry analysis (TGA) technique. This measurement revealed that the decomposition of these wood generally occurred in three stages, the dehydration stage, the active stage, and; the passive stage. The maximum decomposition peak in derivative thermogravimetric (DTG) analysis curve shifted towards higher temperature range with the expedition in heating rate. The kinetic decomposition parameters of the timbers were determined by adopting thermal kinetic method of Coats and Redfern. Principally, the density and moisture content of timber does not influence the kinetic parameters studied in this work. Overall, the thermal decomposition in the second-stage (active stage) was dominated by the hemicellulose and cellulose while the decomposition of lignin was apparent in the third-stage (passive stage) of pyrolysis. The higher activation energy in the second-stage indicates that more cellulose is contained in the sample. The activation energy of lignin is observed to be much lesser compared to the activation energy of the hemicellulose and cellulose for two species tested except for the Shorea parvifolia.