Wooden Beams Research Articles

Potential of moderately compressed wood as an elastic component of wooden composites

Japanese cedar wood was moderately compressed by 50 % in the radial (R) direction. The compressed wooden blocks were glued into the form of a beam with R directions aligned in the longitudinal direction of the beam. The compressed wooden beam (CR) showed excellent ductility and elasticity comparable to synthetic rubbers. The elastic deflection of the CR was further increased when the tensile side was reinforced by a thin compressed wooden plate (CL), because this ensured that the CR was always in a compressed state while tensile stress was supported by the CL. The CR + CL composite exhibited large deflections ten times greater than that of the original cedar lumber, a Charpy value corresponding to the high amount of energy absorbed in impact bending comparable to that of densified wood, and a large critical bending work exceeding that of uncompressed wood in the direction of the fiber. The soft and durable nature of the composite beam was attributed to the softness and elasticity of the moderately compressed wood, in which the folded cell walls behaved as flat springs.

Motor and Hippocampal Dependent Spatial Learning and Reference Memory Assessment in a Transgenic Rat Model of Alzheimer's Disease with Stroke.

Alzheimer's disease (AD) is a debilitating neurodegenerative disease that results in neurodegeneration and memory loss. While age is a major risk factor for AD, stroke has also been implicated as a risk factor and an exacerbating factor. The co-morbidity of stroke and AD results in worsened stroke-related motor control and AD-related cognitive deficits when compared to each condition alone. To model the combined condition of stroke and AD, a novel transgenic rat model of AD, with a mutated form of amyloid precursor protein (a key protein involved in the development of AD) incorporated into its DNA, is given a small unilateral striatal stroke. For a model with the combination of both stroke and AD, behavioral tests that assess stroke-related motor control, locomotion and AD-related cognitive function must be implemented. The cylinder task involves a cost-efficient, multipurpose apparatus that assesses spontaneous forelimb motor use. In this task, a rat is placed in a cylindrical apparatus, where the rat will spontaneously rear and contact the wall of the cylinder with its forelimbs. These contacts are considered forelimb motor use and quantified during video analysis after testing. Another cost-efficient motor task implemented is the beam-walk task, which assesses forelimb control, hindlimb control and locomotion. This task involves a rat walking across a wooden beam allowing for the assessment of limb motor control through analysis of forelimb slips, hindlimb slips and falls. Assessment of learning and memory is completed with Morris water maze for this behavioral paradigm. The protocol starts with spatial learning, whereby the rat locates a stationary hidden platform. After spatial learning, the platform is removed and both short-term and long-term spatial reference memory is assessed. All three of these tasks are sensitive to behavioral differences and completed within 28 days for this model, making this paradigm time-efficient and cost-efficient.

Flexural stiffness and strength enhancement of horizontally glued laminated wood beams with GFRP and CFRP composite sheets

Developments in the field of timber engineering have helped in the wise and economical use of timber for structural purposes. Glued laminated wood is composed of several layers of timber glued together with adhesives, forming large and strong structural members that can be used as beams and columns. This research study presents an experimental programme of strengthening laminated wood beams using carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) composite sheets. Laminated wood beams were made using rubber wood, which is a plantation grown timber. The results of the study are encouraging with percentage increase in flexural stiffness as 26.29% and 45.76% respectively for 2.5% and 5% addition of GFRP composite sheet to the tension side of the beam. For the same percentage addition of GFRP the flexural strength increase was 36.91% and 40% compared to un-strengthened beam. For 1.67% and 3.33% addition of CFRP composite sheet to the tension side of the beam the percentage increase in flexural stiffness to un-strengthened beam was 36.19% and 64.12%. The increase in flexural strength for the corresponding percentage addition of CFRP was 45.86% and 50.62%. Theoretically predicted flexural properties were conferred with the experimental findings.

Studying the mechanical behavior of notched wood beams using full-field measurements

This study focuses specifically on the mechanical behavior of notched timber beams and more generally on the existence of tensile stresses perpendicular to the grain, as well as shear in wood elements. The study presented here is based on full-field measurements to characterize the behavior of thin elements of a standardized beam. Experiments were carried out with a classic loading device and LVDT measurements as well as the grid method, which provides full-field displacement and strain measurements on the surface of the specimen. Tests were conducted for two orientations of the annual rings of the wood. Variations in the strain maps in the zone affected by shear and tensile stresses are analyzed, and the difference in response between specimens is pointed out, particularly with respect to ring orientations. Finally, the specimen is modeled using finite element software for comparison purposes. The constitutive material is linear elastic homogeneous, with elastic parameters obtained from ultrasonic experimentation. Our results exhibit the limit of this homogeneity hypothesis in notched zones.

Internal insulation applied in heritage multi-storey buildings with wooden beams embedded in solid masonry brick façades

The use of internal insulation is investigated in a heritage building block with wooden beam construction and masonry brick walls as part of an energy renovation. Measurements were carried out and compared to results from a hygrothermal simulation model. The risk of mould growth in the wooden beams and in the interface between the insulation and the brick wall was evaluated. Three different insulation strategies for applying internal insulation were investigated: 1) insulation applied on the entire interior façade; 2) 200 mm gap in the insulation above the floor; and 3) 200 mm gap in the insulation both above the floor and below the ceiling. The solution with a 200 mm gap in the insulation above and below the floor/ceiling showed that at low rain exposure coefficients (Catch Ratio, CR ≤ 0.1) and with wall orientations towards west, this solution can be moisture-safe. However, it not recommended to apply internal insulation on north-orientated walls, since the drying potential is reduced. Additionally, caution should be exercised also with west-orientated walls.

Analysis of Thermal – Moisture Problems in Massive Wooden Sandwich Structures

This article focuses on hygrothermal problems in massive wooden sandwich structures. Wood in sandwich structures is already artificially dried before processing, and therefore does not further shrink, as it does in the case of log cabins. Analysed sandwich structure is composed from three layers, and is formed of wooden beam in interior side, thermal insulation and wooden beam in the exterior side. The composition of analysed structure is considered in different thickness with respect to the required heat transfer coefficient. Massive wooden beam on the exterior side causes troubles which exhibits in the reducing capacity of diffusion of water vapor. It is therefore possible that water vapor condenses on the interface of wood and the thermal insulation under certain boundary conditions. Therefore, it is appropriate to place massive wooden beam closest to the interior side. This solution would improve the balance of the diffusion permeability to water vapor permeating from the interior side to the exterior side.

Strain Measuring 3D Printed Structure with Embedded Fibre Bragg Grating

In recent years, a lot of attention has been directed towards the fabricating of smart structures with embedded optical sensors providing in-situ, non-destructive and real time or on-demand information of the construction structural health.This paper describes manufacturing process and performance of a 3D printed sensor prototype. Fibre Bragg grating is used as the sensing element and is embedded during the 3D printing of the sensor structure. Such a structure is able to measure mechanical strain. This functionality is verified by laboratory testing, where the structure is glued onto the surface of a wooden beam specimen which is exposed to load force. The strain of the wooden beam is well known and compared with the measured values given by the embedded optical sensor.

二方向に有効な高耐力長押補強の実験的検証と耐震補強設計

The seismic strengthening method by using Nageshi, which is a traditional wooden beam, is sometimes adopted in the traditional wooden structures such as temples and shrines. Generally, the reinforcing construction method by Nageshi is effective only in one direction, however, we proposed the new seismic strengthening method with bi-directionally effective Nageshi by using joint metals (see Fig. 2) as seismic strengthening scheme of an existing temple (see Fig. 1, Photo1). In this paper, we verified the structural performance of bi-directionally effective Nageshi and revealed the structural mechanism of Nageshi joint and proposed the design method of the new strengthening method by Nageshi. In addition, the design example of the actual building was shown. We conducted the in-plane shear tests of seven specimens as shown in Fig. 3 and Fig. 5; one is unreinforced specimen for comparison, the others are reinforced specimens with various configurations of Nageshi. As the results of reinforced specimens as shown in Fig. 6, the stiffness and strength of all specimens were much greater than those of the unreinforced specimen, so the method to reinforce by Nageshi was proved to effective. Also, all specimens showed a stable load versus story drift angle response until large deformation area. The effectiveness of the new strengthening method by two-tiered Nageshi we proposed was confirmed, because the stiffness and strength of the specimen with two-tiered small Nageshi (75-150 cross-section) were comparable to those of the specimen with normal Nageshi (150-150 cross-section). However, the bending deformation of small Nageshi was shown at the end stage due to a lack of flexural rigidity compared to the rigidity of the joint (see Fig. 9). In addition, as the results of the specimen with three-tiered small Nageshi, the bending strains of the columns increased due to the high rigidity of the joint (see Fig. 8). The elastic frame analysis, which simulated the experimental specimen, was conducted in order to verify how the flexural rigidities of Nageshi and column are affected by the rigidity of joint. The characteristics of the bending rigidity of the joint were calculated from the mechanical model based on the Inayama theory of compression perpendicular to the grain in wood (see Fig. 13). As the analytical results, it was proved that the stiffness was considerably reduced if the flexural rigidity of the column is low (see Fig. 16). Therefore, if the flexural rigidity of the column is insufficient, the performance of Nageshi joint cannot be maximized. On the other hand, if the flexural rigidity of the column is sufficient, the analytical result changed with the difference of the bending rigidity of the joint; the stiffness of the frame decreased with the decreasing the flexural rigidity of Nageshi. Finally, an example of the reinforcement design of the actual temple was shown. Because Nageshi reinforcement method is used under floor, it has become possible to reinforce almost all of columns. As the result, the eccentricity ratio of the whole structure was improved.

Dating Wooden Beams From the Grancia Monastic Abbey in Southern Italy

ABSTRACT We present the results of a dendrochronological study carried out on timbers from the monastic abbey Grancia of Brindisi di Montagna in Southern Italy. Our objective was to date cross-sections of oak (Quercus spp.) taken from structural timbers to determine the felling dates, the time span covered by the series and to evaluate whether the retrieved tree-ring data could be used to extend an existing living trees chronology of oak from Southern Italy. Dendrochronological analyses were performed on samples collected from eight oak timbers in 2006 during the restoration of the abbey. Raw tree-ring series were crossdated and grouped into a floating chronology that was compared with an absolute reference chronology, specifically constructed from living Quercus pubescens (Willd.) trees, from the nearby Pollino National Park. Seven of eight samples could be absolutely dated in the early 19th, late 18th and mid late 17th Centuries, providing a chronology that reaches back to AD 1545.

Retracted Article: Remote sensing of formaldehyde fumes in indoor environments

: A sensor for remote detection of formaldehyde (FA) fumes in the atmosphere has been developed, based on the redox reaction between FA and silver nitrate. The sensor is worn as a bracelet and the data acquired are transferred via a Blue-tooth channel to a smartphone. A dedicated software transforms the signal from a grey to a colour scale. The signal response has been assessed over low (20 to 120 ppb) as well as higher (1-15 ppm range) levels. The sensor has been applied to monitor potential FA fumes of some artwork in two locations: the Tate’s gallery in London, during the display of several pieces of Damien Hirst, as well as in the Summer Palace in Beijing. In the first case, one of Hirst’s main subjects is the setting-up of giant fish tanks filled by thousands of liters of FA, in which intact biological specimens are immersed, such as zebras, cows, calves, even sharks. The parallelepiped-shaped basins are then covered with a lid and fully sealed with silicon gums. It has been found that the tanks are surrounded by FA fumes, constantly exuded in the atmosphere (likely via the sealant), reaching levels of 5 ppm, one order of magnitude higher than the 0.5 ppm limit set up by legislation. In the Summer Palace too posters in display and wooden beam works have been found to release FA vapours.

Approximate numerical model for adhesive scarf joints in wooden beams

The purpose of this paper is to formulate an approximate numerical model for adhesive scarf joints in wooden beams under the assumption that the joint is deformable. This approximate model is founded on observations resulting from the general solution of the plane linear theory of elasticity. It is assumed that wood is orthotropic. The joint can be subjected to a complex load combination including an axial force, a shear force and a bending moment. Within this framework, analytical relations for stresses in the adhesive, as well as stresses and displacements of the adherends, were derived in a form useful for engineering practice. A numerical example proves the high accuracy of the approximate model when compared to the general model based on the plane linear theory of elasticity.

Algorithm for the analysis of the geometric properties of cross-sections of timber beams with lack of material from LIDAR data

Beams, pillars or bars of solid timber structures, although having a nominal regular form, frequently have irregular sections along their length, that in many times represent an important lack of material in the structural member. All the changes in the cross section of the beam must be considered in any kind of strength calculation and the protocols for the structural health monitoring. The principal aim of this investigation is the development of an algorithm for the automatic analysis of the geometric properties of the cross-sections of timber beams, in order to detect any lack of material and irregular cross-sections. The developed algorithm is based on 2D projection techniques and Alpha-shape. Finally, the repercussions in the strength of the beam are evaluated. A series of tests on synthetic beams and on real wooden beams have been done to verify the correct function of the algorithm. The difference between the results obtained by the algorithm and the results obtained by contact instruments reached an average of error of 3 %. The results obtained demonstrate that the algorithm proposed is adequate for the automatic analysis of the geometrical properties in the section of timber beams with a lack of material or irregular section.

THE COUPLING ELEMENT CALCULATION OF COMBINED WOODEN BAR FOR TURNOUTS

Purpose. The deficit of permanent way (PW) material elements leads to a revision of the re-use of old serviceable object after their replacement or repair. As an example is the following fact, that after the wear in the under-rail area of wooden sleepers and beams, or other defects that prevent their further exploitation, there is an acute issue of their planned replacement. Usually, the required minimum margin of sleepers is always in the track service brigades. As for the wooden beams the length of which in the turnouts is up to 5 m, there is not always possible quickly replace them due to the lack of size in the short term. Therefore, the geometric dimensions of the connect elements of the two halves of the beams or sleepers in a single rigid structure were proposed and justified and its characteristics do not differ from solid beam. Methodology. The authors considered the calculation algorithm of wooden elements connection and mathematical models that describe the elastic properties of base. The most adequate technique that fully characterizes the interactions beam in the form of a beam of finite length on the ballast was determined. Findings. The qualitative and quantitative verification of the results showed a very good agreement between the values of bending moments, shear forces and deflections that were obtained by the finite difference method (FDM) and the analytical method. It gives the reason to believe that the received geometric dimensions of nag connection can be recommended to employees of track facilities to connect the wooden sleepers on the switches and crossovers. Originality. The nag connection geometrical sizes of two wooden sleepers in the beam for using on switches were substantiated. Practical value. The proposed joint design allows re-using of renovated old wooden sleepers and bars. This design can be applied not only for the connection of conventional wooden sleepers in the beam of desired length, but also to create the halves of a single sleeper designs for lightly loaded sections of the station and access routes.

Life cycle greenhouse gas emission of wooden guardrails: a study in Nagano Prefecture

Greenhouse gas (GHG: specifically CO2, CH4, and N2O) emissions over the life cycles of type no. 1 and no. 3 wooden guardrails widely used in Nagano Prefecture were evaluated. A comparison with steel (guardrail and guard pipe) types was conducted to investigate the GHG emission reduction effect of wooden guardrails. It was shown that the greatest GHG emissions for all types of guardrails occur during the raw material procurement and production process. The amount of total (life cycle) GHG emissions for pressure-injected wooden type no. 3 guardrails (92 % of steel guardrails and 72 % of steel guard pipes) shows that replacing steel with this type of wooden guardrail can reduce GHG emissions. On the other hand, comparison of the GHG emissions for pressure-injected type no. 1 guardrails with steel (175 % of guardrail; 138 % of guard pipe) shows that no reduction is achieved. When the disposed wooden beams (painted type no. 1; painted and pressure-injected type no. 3) are chipped and used for energy as a substitute for Type-A heavy oil, the volume of the GHG emission reduction significantly exceeds the GHG emission volume, and GHG emissions can be reduced by up to a maximum of 117.67 kg-CO2-eq/m.

Influence of sorption hysteresis on moisture transport in wood

The independent domain theory is used to analyze the influence of sorption hysteresis on the behavior of wood exposed to environmental conditions. Due to hysteresis, sorption history of wood has an impact on its performance under varying moisture conditions. An integrated Preisach–Mayergoyz (IPM) approach that is phenomenologically sound and insightful while mathematically and computationally straightforward to implement is applied, where the parameters of the IPM space are determined from experiments. The implementation of the IPM approach in a heat and moisture transport model is validated based on independent measurements of dynamic vapor sorption in spruce wood. The transport model, including sorption hysteresis, is further used to simulate the response of a wood beam to weekly humidity variations and hourly climatic humidity and temperature variations. The analysis shows that hysteresis of wood is strongly dependent on the magnitude of moisture changes. As moisture penetrates the material faster in longitudinal than in radial direction, due to a lower vapor resistance factor, the effect of hysteresis is more pronounced deeper into the wood in longitudinal than transversal directions. Furthermore, the simulations imply that errors in moisture content of more than 20 % (or 30 %) can be made when using the main adsorption curve (or main desorption curve) instead of the hysteresis model for wood sorption behavior. Sorption hysteresis must thus be accounted for in heat and mass transport models to assess moisture-related damage risks such as mold growth, rot or moisture-induced cracking, and the IPM approach offers such an appropriate avenue.

Improntas vegetales en arquitectura e improntas de cestería en el yacimiento ibérico del Cerro de la Cruz (Almedinilla, Córdoba)

Este trabajo presenta un amplio conjunto inédito de elementos asociados a la arquitectura doméstica y a partir de ello arroja nueva luz sobre las técnicas constructivas ibéricas en Andalucía, sobre las que apenas hay detallados publicados. Se analizan en detalle las improntas de elementos arquitectónicos vegetales sobre bloques de barro, que a su vez formaron parte de esa misma arquitectura, así como las improntas de elementos de cestería. Todo procede de las recientes excavaciones en el poblado ibérico del Cerro de la Cruz (Almedinilla, Córdoba), destruido a mediados del s. II a.C. Se relacionan estos elementos con otros similares ya conocidos.

Experimental study on behaviour of piles in berthing structure

This paper deals with an experimental investigation on laterally loaded piles of a berthing structure. A prototype berthing structure constructed at Chennai Port in India is simulated in a 1∶40 laboratory scale model. The model consists of a row of five piles connected at the top by a wooden beam for rigidity and to transfer the load laterally to the piles. A tie rod is incorporated in this frame to study its effect. A series of seven experiments was conducted with and without the anchoring tie rod, in sloping and horizontal ground under berthing and mooring forces. The experimental results were analysed to assess the effect of the tie rod anchor on the berthing structure. The distribution of load among the piles and the tie rod anchor, the lateral capacity of the pile under various cases and the reduction in deflection and bending moment due to the provision of a tie rod anchor are discussed in this paper. The provision of tie rods is found to be effective for open-type berthing structures.

Восстановление деревянной балки импрегнированием полимерной композицией на основе эпоксидной смолы

This paper proposes a method of restoration of wooden structures by impregnating polymer composition based on epoxy resin, locally weakened destruction. Objective - research and development of technology for site remediation of wooden structures with areas of locally de-graded wood. We analyzed the causes of the destruction of wooden building structures. The pa-per sets out the methodology and the engineering based on the example of a wooden beam, the destruction of locally weakened in the core zone. Engineering calculations were confirmed by numerical experiments carried out in the program complex "Lira 9.6".

Structural evaluation and design procedure for wood beams repaired and retrofitted with FRP laminates and honeycomb sandwich panels

As compared to other structural applications of polymeric composites, limited information is available on structural behavior of wood members strengthened with polymer composites. The focus of this paper is to evaluate the structural performance and practical use of wooden beams repaired and retrofitted with fiber-reinforced-polymeric (FRP) composites. The paper presents a summary results of an experimental study on the behavior of both Douglas Fir and Glulam wood beams repaired and retrofitted with different composite strengthening systems. In addition, the paper presents a simplified design procedure to predict the capacity of timber beams strengthened with FRP composites. Two types of composites; wet layup laminates and sandwich panels, and two lamination schedules; unidirectional and bidirectional, and two lamination geometries; U-laminate and flat laminates were evaluated. For “flexure/shear” wood beams repaired and retrofitted with bidirectional, carbon/epoxy U-shaped wet layup laminates, a total of eight Douglas Fir (Dug Fir) Larch # 1 wood beams were tested to failure. For “flexure-only” wood beams retrofitted with flat unidirectional laminates, both wet layup and precured sandwich honeycomb composites were evaluated. Experimental results indicated that the use of composites as external repair and rehabilitation elements resulted in an appreciable increase of both strength and stiffness. A practical case study is also presented that provides a step-by-step procedure for analyzing and designing a polymeric composite system for repair of partially damaged wood girders by fire.

Experimental and analytical study of the mechanical behavior of heterogeneous glulam–UHPFRC beams assembled by bonding: Short- and long-term investigations

In wood-based structural design, in addition to the criteria of strengthening and stiffness, the criterion of deformability due to the creep of wood, especially in horizontal members, is a factor that often limits the design. New developments have further improved the structural performance, such as the strengthening of timber (glulam) beams by bonding composite material combined with an ultra-high performance fiber reinforced concrete (UHPFRC) that is internally reinforced with or without carbon fiber reinforced polymer (CFRP) bars. Glulam, UHPFRC and CFRP may be an interesting composite mix for responding to the problem of the creep behavior of composite structures made of different materials with different rheological properties. This paper describes an experimental and analytical investigation on the short-term and long-term (creep) performances of glulam–UHPFRC–CFRP beams. The experimental investigations of creep behavior were conducted in indoor and outdoor environments under constant loading for approximately 1year. The measured results are compared to the results from an analytical model. This model was developed to predict the creep response of the glulam–UHPFRC–CFRP beams based on the creep characteristics of the individual components. The results indicate that heterogeneous glulam–UHPFRC beams improve both strength and stiffness and can also effectively reduce the creep deflection of wooden beams.