Timber Materials Research Articles

Finite Modelling and Analysis on the Flexural Behaviour of Reclaimed Timber Reinforced Steel Beams

Timber-steel composites are used widely for various construction such as roofs, floors, bridges and multistory buildings due to its strength, ultimate load capacity and ductility advantages. This study investigated the structural behaviour of hollow steel and reclaimed timber reinforced steel specimens under static loading. The timber reinforcement is not only to enhance flexural behaviour but encourage the recycling of old timber materials as a way of natural resource maintainability and sustainability in the developing countries, Nigeria inclusive. A total number of eight (12) specimens were prepared in which four replicates for each set of reclaimed timber, hollow steel and reclaimed timber reinforced steel specimens, respectively. Each of these specimens was loaded slowly and statically tested using a Universal Testing Machine (UTM) with displacement control, until failure occurred and the test results were computed and analysed. Thereafter, ANSYS R.19 was used for the finite modelling and numerical analysis. The experimental results showed that reclaimed timber reinforced steel (RTRS) beams have performed better than hollow steel (SH) beams under bending. That is the reinforcement has significantly improved the ultimate load capacity and strength of RTRS beams with 31.37% experimentally. In addition, the ultimate loads, deformations, equivalent stresses and failure modes of the beams under flexural bending were accurately predicted and well agreed with experimental data. It was concluded that reclaimed timbers can be used as reinforcement materials in composite construction to increase the flexural capacity of steel hollow section.

Shear performance of glued and screwed timber-steel composite connections for composite timber-steel beams

Mid- to high-rise mass timber buildings gained popularity in the last decade. Yet, engineered wood products (EWPs) used to erect these buildings have structural limitations. EWPs present brittle failure modes, particularly in bending, shear and tension, and have a low modulus of elasticity resulting in shorted spans and deeper beams relative to those in the steel and reinforced concrete counterparts. Timber-steel hybrid beams represent a potential sustainable solution to overcome these limitations by taking advantages of the high strength, stiffness and ductility of steel, and the high capacity to weight ratio of timber. However, for this solution to be structurally performant, it is essential to create effective composite action between the two materials. This study therefore compares the structural efficiency of various bonding techniques between the steel and the timber materials. Two sets of assembly solutions, representing four connection types, were proposed and experimentally investigated: (1) connecting an embedded steel plate into the timber elements by using either polyurethane (PUR) structural adhesive with two manufacturing variations or 14 G×75 mm heavy duty screws, and (2) connecting a steel plate on the surface of the timber element using either PUR structural adhesive with self-tapping M4×40 mm screws or only self-tapping screws. Softwood Laminated Veneer Lumbers (LVL) and Grade 350 steel plates were used in the experimental tests. All bonding techniques were tested in shear. The shear capacity, the slip stiffness and the failure mode were evaluated. Additionally, the efficiency of the proposed manufacturing solutions was quantified by analytically evaluate the effective bending stiffness of a timber-steel composite beam manufactured with different bonding techniques being investigated. Results indicated that the glued connections allowed a significantly more efficient composite action, with failure occurring in the timber instead of at the composite interface and near-full composite action was reached, than the screwed connections. To achieve high composite action with the screwed solutions, a large number of screws was needed which may incur high manufacturing costs.

A preliminary study on bamboo–timber composite columns under axial compression

Bamboo–timber composite columns hold significant promise as bio-based structural elements. However, research in this area remains limited, especially concerning modern buckling analysis methods that incorporate bio-based constitutive models of engineered bamboo and timber materials. This study aims to address this gap by proposing a proof-of-concept analytical framework based on component-based strategy for buckling analysis, utilising piecewise bio-based material constitutive models as the guide rail for its strain-stage-based component split-up. Preliminary experimental validation was performed to evaluate the feasibility of using component-based analysis to estimate the overall buckling resistance of both composite and non-composite bamboo and timber columns. This initial study offers an alternative analytical approach for estimating the buckling resistance of bio-composite columns and establishes a set of conceptual guidelines and indicative parameters for the experimental design of future research.

IMPACT OF HOLLOW CORE DIAMETER AND BFRP WRAPPING ON AXIAL COMPRESSIVE STATIC PERFORMANCE OF TIMBER

This paper presents an experimental study on the axial compressive static performance of the cylindrical timber-wrapped basalt fiber reinforced polymer (BFRP). Beech and black pine woods were used as cylindrical timber material, polyurethane (PUR) adhesive was used as the adhesive agent, and BFRP was used as fiber-reinforced polymers (FRP). The stress on compression tests was applied to 70 pieces of test samples prepared. The results showed that there was found out that the highest average stress value of 51.8 MPa was achieved inthe black pine cylindrical timber- BFRP wrapping- hollow core (Ø=70 mm)- the beech cylindrical timber blocks- BFRP wrapping samples under compression loading. The lowest average value stress value of 30.78 MPa was found in the black pine cylindrical timber- none hollow core samples. On average, the stress of the black pine cylindrical timber- BFRP wrapping- hollow core (Ø=70 mm)- the beech cylindrical timber blocks- BFRP wrapping samples were68% higher than the stress of the black pine cylindrical timber- none hollow core samples. The influence of the hollow core diameter and the BFRP wrapping type were found statistically significant.

The potential impact of legality requirements for China’s imported timber: a global forest product model‐based analysis

Utilizing the Global Forest Products Model (GFPM), this paper analyzes the potential impacts of China’s timber import legality requirement policies. Two alternative scenarios are compared with the baseline scenario: (1) China requires that imported timber must comply with the requirements of Verified Legal Compliance (VLC), (2) China imposes tighter requirements for imported timber, which must come from sustainably managed forests and meet Forest Certification (FC) requirements. The results show a decline in log production but an increase in processed wood exports to high‐risk countries, suggesting a move towards more valuable wood processing. Both high‐ and low‐risk countries are expected to see an increase in forest stocks. Welfare analysis indicates that high‐risk countries will benefit from industrial upgrades, while China might face welfare losses. Nevertheless, the enforcement of legal standards for timber imports into China is likely to enhance the perceived legitimacy of the sources of domestic timber materials, thereby facilitating the re‐entry of processed timber products into developed markets. This study proposes that China’s timber import regulations could offer mutual advantages, aiding in the fight against illegal logging and encouraging the legal timber trade.

Understanding hurricane effects on forestlands: Land cover changes and salvage logging

Hurricanes can cause catastrophic damage to forestlands, prompting forest owners to engage in salvage logging to mitigate losses and resulting in a sudden and pronounced impact on the timber supply. At the same time, salvaging efforts have profound ecological repercussions, reshaping forest dynamics and affecting vital ecosystem processes. Given the relevant impact of salvage logging to the timber market and its potential ecological effects, evaluating the main factors motivating or limiting its occurrence and the common spatial patterns of salvage sites could offer valuable support for post-storm management efforts following future hurricane events.This study evaluates the land cover change (LCC) of forested areas following hurricanes, recognizing that the change to land cover classification could be derived from storm damage or additional modifications, such as salvage logging activities. We used a set of predictive machine learning models to investigate the primary factors influencing these modifications and determining a possible connection to salvage operations. To serve this purpose, we selected variables that relate to both forest’s vulnerability to hurricane disturbance and salvage site selection criteria. This research was centered primarily on the category-five Hurricane Michael, using three additional hurricanes of different intensities to compare results. Random Forest was the bestperforming model for predicting LCC in all cases, having wind speed and distance to nearest wood-consuming mills as the most important features when trained on Hurricane Michael data, emphasizing the relevance of market- and operation-related variables alongside weather disturbance aspects. The findings of our study lead us to infer that the observed modifications in land cover following hurricanes likely represent an additional transformation induced by the removal of damaged timber material, potentially serving as a proxy for salvage logging activities.

Reverse-cyclic performance of United States prescriptive code connectors in a novel mass timber structural composite panel

Mass timber has been recently increasing in popularity, especially panel products such as cross-laminated timber (CLT), which has spurred innovation in creating new mass timber materials. One recent mass timber material utilizes structural composite lumber to create a PRG-320 compliant CLT, referred to as a structural composite panel (SCP). To increase the knowledge on the connection performance of the new SCP, reverse-cyclic testing was conducted on standard mass timber panel prescriptive connection systems within U.S. codes with SCP as the substrate. Three different types of tests were conducted: shear tests of a floor-to-wall connector, uplift tests of the same floor-to-wall connector, and shear tests of an inter-panel connector. Two monotonic and six reverse-cyclic tests were done per test configuration. The connections typically failed through a combination of wood failure and either nail bending and withdrawal or nail fracture. Two cyclic tests of the floor-to-wall connector in shear and all tests of the floor-to-wall connector in uplift failed through fracture of the plate connection. Results were compared to previous testing on CLT that was used to validate the connection and design methodology. Higher maximum strengths were observed when comparing the SCP to previously tested CLT, with an average increase of 20 percent. The displacement at maximum force and ultimate displacement capacity were similar between the SCP and previous CLT connections. Connections in SCP exhibited a lower stiffness than comparable CLT specimens for all tests, with an average difference in stiffness of 33 percent. This led to a comparatively lower ductility for the SCP specimens than for the CLT. ASCE 41 trilinear parameters were derived for all cyclic tests to aid in the utilization of the connections with this new material.

Robotic-based terahertz spectroscopy imaging for non-destructive monitoring of water loss-induced damage in timber materials under low temperature stress

Timber materials are widely used in various industries, from construction to furniture manufacturing. One of the critical factors affecting the structural integrity and longevity of timber is water loss-induced damage, which often occurs under low-temperature stress conditions. Monitoring and assessing this damage traditionally involve invasive and time-consuming methods. This study explores the application of robotic-based terahertz spectroscopy 3D imaging as a non-destructive and efficient system for assessing the impact of water loss on timber materials under low-temperature stress. The detection and localization of damage in a various species of timber-based structures were experimentally investigated by performing pulsed terahertz time-domain spectroscopy and using a six- DOF (degree-of-freedom) robotic arm. The thickness and damage length were monitored by designing the reflection geometry of the terahertz scanner. Additionally, the terahertz source was controlled with a six-DOF robot arm for path planning. The corresponding measured dielectric property reference value for the damage identification was computed using a captured terahertz wave at 12% of moisture content. The reflected signals were analyzed to determine the thickness, defectiveness, and locations of the defects through signal processing in the time and frequency domains. Finally, the validity of the structural health monitoring approach for 3D detection and visualization of water loss-induced defects in timber structures using terahertz waves, was discussed.

Bending performance of laminated veneer lumber timber beams strengthened in the compression side with near-surface mounted CFRP plates

This study investigated the bending behavior of timber beams that were strengthened using carbon fiber-reinforced polymer (CFRP) plates. Fourteen laminated veneer lumber (LVL) timber beams, each measuring 60 mm×200 mm x 2400 mm, were subjected to four-point bending tests. The objective was to investigate the effect of using CFRP plates as near-surface mounted (NSM) strengthening in the compression zone on the bending behavior of the LVL timber beams. In this experiment, two beams were left unstrengthened while the remaining beams were strengthened with varying lengths, depths and numbers of CFRP plates. The beams load-midspan deflection relationship, ultimate load capacity, stiffness, failure mode, and strain profile distribution were analysed based on experimental results. The use of CFRP plates in the compression zone of LVL beams has been found to improve their strength and stiffness. The test result showed timber beams strengthened with CFRP plates with a reinforcement ratio ranging from 1.67 % to 5.00 % experienced a significant increase in bending strength of 4.24–28.85 % and an increase in bending stiffness of 16.48–62.51 %. These results indicate that NSM CFRP plates can effectively strengthen timber materials, offering improved bending performance and durability.

Experimental Study to Determine the Development of Axial Stiffness of Wood Screws with Increasing Load Cycles

123 withdrawal tests were conducted to investigate the change in axial stiffness of fully threaded screws under axial loading and up to four loading cycles. The screws were initially loaded in two cycles within the elastic range, followed by two cycles up to 90% of the characteristic load-carrying capacity. Several parameters relevant to construction practice were varied. The angle between the screw axis and the grain ranged from 30° to 90°, the timber material was varied between glued laminated timber (glulam) and laminated veneer lumber (LVL) made of beech, and the screw diameter ranged from 8 mm to 12 mm. The test results indicate that axial stiffness increases upon reloading compared to the initial loading. On average, axial stiffness increases by 11% between the first and second loading and remains at this level during unloading and further load cycles. However, if the load exceeds the linear–elastic range, the axial stiffness is reduced due to plastic deformation. A comparison with tests on the composite axial stiffness of fully threaded screws in glulam shows that even with a different test setup and testing objective, there is a slight increase in axial stiffness from the first to the second load cycle in the range of 4 to 8%.

The potential use of mass timber in mid-to high-rise construction and the associated carbon benefits in the United States.

Nonresidential and mid- to high-rise multifamily residential structures in the United States currently use little wood per unit floor area installed, because earlier building codes lacked provisions for structural wood use in those types of buildings. However, revisions to the International Building Code allow for increased wood use in the form of mass timber, as structural and fire safety concerns have been addressed through new science-based design standards and through newly specified construction materials and measures. This study used multiple models to describe alternative futures for new construction, mass timber adoption rates, and the associated carbon benefits in higher than three-story buildings in the United States. The use of mass timber, in place of traditional constructions (i.e., structures dominated by concrete and steel), in projected new higher than three-story buildings was shown to provide combined carbon benefits (i.e., global warming mitigation benefits), including avoided embodied carbon emissions due to the substitution of non-wood alternatives and additional biogenic carbon storage in mass timber materials, of between 9.9 and 16.5 million t CO2e/yr spanning 50 years, 2020 to 2070. These carbon benefits equate to 12% to 20% of the total U.S. harvested wood products carbon storage for 2020. Future research is needed to understand how greater mass timber adoption leads to changes in forest product markets, land use, and total forest sector carbon.

The Opportunity Cost Analysis of using Jack Fruit Timber as a Construction Material in Sri Lanka


 
 
 
 The miracle tree in the world is thought to be the jackfruit tree. Its fruit-bearing capacity was well- documented by history academics. However, jackfruit wood is also regarded as one of Sri Lanka's more expensive wood types. Instead of considering the quality of the actual lumber material, this is only dependent on its legendary value. It was not considered how much money the timber was worth. They are carelessly used as one of the finest luxury lumber materials, disregarding the fact that they were originally planted as fruit trees. In an effort to compare the true worth of jackfruit wood to the current palette of premium timber materials, this study was initiated. Thus, it will assist legislators in passing a new law that forbids Sri Lanka from using jackfruit trees as a source of lumber. First, a life cycle model was used to determine the yield value and market value of jackfruit timber. The perceived value of the timber and the yield were then contrasted with the timber's real market worth. The study discovered that, before the age of 50 years, the jack fruit tree's yield value was significantly higher than its timber value. Only Rs. 100,000.00 is the typical timber value anticipated from a jackfruit tree. Only eight years of average yield value are required to restore the value of the timber. In order to preserve the jack fruit tree as one of the top fruit-bearing trees in the world, a new policy should be developed to change the jack fruit tree cutting age to a minimum of 50 years.
 Keywords: Jack fruit tree, Yield value, Selling price, Timber value
 
 
 

Application of Composite Bars in Wooden, Full-Scale, Innovative Engineering Products-Experimental and Numerical Study.

The commercialization of modular timber products as cost-effective and lightweight components has resulted in innovative engineering products, e.g., glued laminated timber, laminated veneer lumber, I-beams, cross-laminated timber and solid timber joined with wedge joints. With the passage of time, timber structures can deteriorate, or new structural elements are required to increase the stiffness or load-bearing capacity in newly built structures, e.g., lintels over large-scale glazing or garages, or to reduce cross-sectional dimensions or save costly timber material while still achieving low weight. It is in such cases that repair or correct reinforcement is required. In this experimental and numerical study, the static performance of flexural timber beams reinforced with prestressed basalt BFRP, glass GFRP and hybrid glass-basalt fiber bars is shown. The experimental tests resulted in an increase in the load-carrying capacity of BFRP (44%), GFRP (33%) and hybrid bars (43%) and an increase in the stiffness of BFRP (28%), GFRP (24%) and hybrid bars (25%). In addition to this, glued laminated timber beams reinforced with prestressed basalt rods subjected to biological degradation, 7 years of weathering and prolonged exposure to various environmental conditions were examined, and an increase in the load-bearing capacity of 27% and an increase in stiffness of 28% were obtained. In addition, full-size laminated timber beams reinforced with prestressed basalt bars were investigated in the field as an exploratory test under fire conditions at elevated temperatures, and the effect of the physical-mechanical properties during the fire was examined via an analysis of these properties after the fire. In addition, a satisfactory correlation of the numerical simulations with the experimental studies was obtained. The differences were between 1.1% and 5.5%. The concordance was due to the fact that, in this study, the Young, Poisson and shear moduli were determined for all quality classes of sawn timber. Only a significant difference resulted in the numerical analysis for the beams exposed to fire under fire conditions. The experimental, theoretical and numerical analyses in this research were exploratory and will be expanded as directions for future research.

Carbon intensity of mass timber materials: impacts of sourcing and transportation

Mass timber construction is widely considered a promising alternative construction method to reduce buildings’ total life-cycle carbon emissions because wood is a carbon sink. Cross-laminated timber (CLT) panels, manufactured by gluing lumber layers with grains at right angles, are potential low-carbon alternatives to carbon-intensive concrete and steel construction. However, most environmental impact assessment studies do not consider variation in transportation impacts within the CLT supply chain when calculating life-cycle impacts. This study investigates the embodied primary energy and the global warming potential (GWP) of CLT supply chain decisions regarding the type of timber species used, the U.S. region it is sourced from, and the location of the CLT mill. Longer transport distances in the supply chain for timber and CLT panels can contribute as much as 923 MJ/m2 (20%) of the embodied primary energy of a CLT building, and the use of a higher-density timber species increases this contribution to 1246 MJ/m2 (24%), with most of that energy derived from fossil energy sources. For perspective, the GWP of a building whose CLT panels and timber have been transported by truck over 6,000 km (252–270 kgCO2/m2) is greater than the GWP of an equivalent reinforced concrete (RC) building (245 kgCO2/m2). Thus, factors like the location of CLT processing facilities and the type of timber species can significantly impact the overall life-cycle assessment and, if chosen appropriately, can mitigate the environmental impacts of CLT construction.

Defect Detection in Solid Timber Panels Using Air-Coupled Ultrasonic Imaging Techniques

This paper reports on investigations of the air-coupled ultrasonic (ACU) method to detect common defects in solid timber panels made of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.). The ACU technology is a non-contact method for nondestructive timber testing with quicker scanning rates compared to contact methods. A testbed was set up consisting of commercially available piezo-ceramic ACU transducers and in-house manufactured signal processing circuits. To demonstrate the suitability of the ACU technique, through-transmission measurement results are presented for samples with defects such as knots, wormholes, and cracks. Pulse compression methods (Barker-coded method) were used to improve the power of received signals based on cross-correction algorithms. Results showed defects of timber panels made of Chinese fir can be detected with a thickness of less than 40 mm. Defects larger than 3 mm in diameter could be detected with high precision. Applying the pulse compression method showed better results than using common sine signals as excitation signals since it increased the signal-to-noise ratio, which is especially important for air-coupled measurement of high-attenuation materials like timber materials. The measurement results on reference samples demonstrated that ACU technology is a promising method for timber defect detection, especially for the quality assessment of engineered wood products.

Study of the construction techniques, materials and architectural prospectives of ancient monumental structures in Allahabad City, India

This research examines the construction methodologies, materials, and architectural principles employed in creating ancient monumental structures in Allahabad (now Prayagraj), India. Despite being erected over 600 years ago, these structures stand resiliently among the evolution of modern construction techniques and seismic safety standards. The history of Prayagraj can be traced back to ancient times. The city was initially referenced in the ancient Hindu scriptures, known as the Vedas, as a sacred destination. Further, established by the Mughal Empire under Akbar’s reign in 1583, Allahabad City witnessed the construction of numerous monumental structures using robust techniques involving stone, brick masonry, and timber materials bonded together with thin mortar and plaster. Many of these ancient edifices, erected during this period, continue to serve various functions today, reflecting the enduring craftsmanship of their builders. In this study, we have identified prestigious monuments for examination, utilizing visual inspection to gain deeper insights into the emphasized construction materials and techniques. Notably, mortar is a critical component in construction and structural connections. Furthermore, our investigation reveals the diverse range of materials utilized for binding, plastering, painting, and other decorative purposes during construction. However, it is evident that some of these monuments have endured significant wear and tear over time, resulting in major cracks and damage to their structural elements and construction materials. Through this exploration, we aim to unveil the intricate craftsmanship and architectural brilliance that characterize Allahabad’s ancient monumental structures, while also highlighting the preservation challenges posed by ageing and environmental factors.

Vibration response of a hybrid steel–timber building element with uncertain material and joint parameters

The design of building elements is usually done conservatively by considering safety factors. However, more efficient designs are gaining interest for economic and sustainability reasons. Hence, an adequate prediction tool can improve the design of building elements. Probabilistic modeling, for example, Monte Carlo simulations, represents a remedy to this by examining uncertainties in a structure through uncertain input parameters. In this work, a Monte Carlo simulation is performed to quantify the uncertainty in the modal properties of a hybrid steel–timber building element. The material properties of the timber material and the stiffness of the structural joints are considered uncertain inputs. The probabilistic properties of the timber material are evaluated utilizing Bayesian inference instead of the usually applied empirical methods. Using these inferred timber material properties leads to a good match of simulated and measured natural frequencies of the timber components. These parameters are utilized together with the joints’ uncertain inputs in the Monte Carlo simulation of the hybrid steel–timber building element. The results show a significant span for the identified eigenfrequencies, which proves the relevance of probabilistic analyses for the vibration characteristics of building elements.

Size effect on flexural and fracture behaviors of 3D printed engineered cementitious composites: Experimental and numerical studies

One of major problems in 3D concrete printing (3DCP) is the integration of steel reinforcement. Engineered cementitious composites (ECC) with superior tensile properties have the potential to remove steel reinforcement in 3DCP. Interlayer interfaces may affect the size effect and fracture behaviors of printed ECC, which are important for structural design. Nevertheless, the related study is lacking. To fill the research gap, three-point bending test and finite element modeling (FEM) were conducted on printed ECC notched beams with depths from 60 mm to 500 mm. Results reveal that the printed ECC beams exhibit multiple fine cracks and display a branched critical crack. Size effect behavior is found in flexural strength, which decreases from 16.92 MPa to 10.89 MPa with the increase of depth from 60 mm to 500 mm. The fracture toughness ranges from 3.71 MPa·m1/2 to 6.38 MPa·m1/2, comparable to natural timber materials. Parametric analysis reveals that the flexural strength and fracture toughness of FEM model with a depth of 100 mm and bond strength higher than 2.5 MPa are similar to that of mold-cast ECC. The fracture toughness indicates the possibility to construct structural components with ECC in 3DCP, and the findings on size effect can facilitate the structural design.

Risk‐based optimization of concentrically braced tall timber buildings: Derivative free optimization algorithm

AbstractMass timber materials are attractive alternatives for tall‐timber buildings (TBs), where the need for sustainability is apparent. Innovative structural systems and design methodologies are needed to fulfil performance requirements according to modern performance based approaches. This paper deals with the design and optimization of buckling restrained braces as earthquake protection system for tall‐TBs through risk‐based design procedure. This procedure controls the mean annual frequency of exceedance of several limit states evaluated through a SAC‐FEMA approach and using response spectrum linear analyses on linearized models for demand assessment. The features of the optimization procedure and the linearized models are shown through an application on a 20‐story mass‐TB located in a high seismic zone. The optimization is executed through a derivative‐free algorithm, the generalized pattern Search, adopting several solution strategies whose efficiency and effectiveness for this kind of applications are shown and discussed. Finally, the results are compared and validated through the execution of non‐linear analyses within a multiple stripe framework.

Bending Performance of Timber Beam Strengthened with Passive Prestressing

Prestressing technology and its application is common in concrete design and construction particularly in Malaysia and most parts of the world. However, prestress strengthening in timber is rare and not widely applied especially in Malaysia. Application of prestressing in timber has the potential to allow the use of longer span with reduced cross-sectional size and simultaneously exhibiting some level of ductility through the prestressing rod since timber material is susceptible to brittle tensile failure. This paper highlights exploratory research into the extent of bending performance enhancement in Malaysian Kempas species timber beam strengthened by way of passive prestressing. The research was conducted to investigate the change in bending strength and moment capacity of timber beam with passive prestressing rods installed at different lever arm positions, and the enhancement of moment capacity of timber beam with and without passive prestressing. Five Kempas timber specimen configurations with size of 40 mm (b) × 90 mm (d) × 900 mm (l) were prepared for four-point bending tests, and their bending behaviours were evaluated. The timber beam with passive prestressing steel rods applied at tension side bottom fibre of timber beam exhibited the greatest enhancement in bending performance and stiffness. The improvement of bending performance ranges from 1.1 to 1.5 times greater compared to the timber beam without prestressing steel rods. The improvement of stiffness in prestressed timber beam is up to 11% at service limit state and a reduced rate of stiffness degradation is prominent.