Pine Beams Research Articles

ASSESSMENT OF THE POSSIBILITY OF USING RECYCLED COARSE AGGREGATE IN A WOOD-SOIL CONCRETE SLAB

Problem statement. During the process of post-war reconstruction in Ukraine, there will be a need for a large number of affordable and ecological building materials, especially in the part of restoration and construction of low-rise buildings. Such building materials can be soil-concrete and aggregates from crushed concrete waste. The proposed constructive solution of the ribbed floor, in which the ribs are made of pine beams and OSB sheets, and the slab part is made of soil concrete on fixed formwork. The purpose of the article is to determine the optimal composition of the soil-concrete mixture using crushed stone obtained after crushing concrete scrap, taking into account the configuration of the wood-soil concrete slab, to determine the strength of soil-concrete of this composition, to determine the possibility of using recycled coarse aggregates. Conclusions. Based on the results of determining the optimal composition of soil-concrete, it was established that the maximum compressive strength is achieved when the mass content of the binder in the cement-soil mixture is at the level of 20 %. Taking into account the configuration of the slab part of the floor, a fraction of 5...7.5 mm is accepted for coarse aggregate. During the test of soil-concrete samples with recycled aggregate with a mass content of 10 %, 20 % and 30 %, the compressive strength of soil concrete decreased. Obviously, the presence of a clay component (loam) in the mixture reduces the adhesion in the contact zone between the aggregate and the soil-concrete, which increases the heterogeneity of the entire structure of the soil-concrete. Thus, the use of natural or recycled coarse aggregates in soil-concrete is impractical. Taking into account the determined strength of soil-concrete without aggregate, a scheme of combined concreting of the soil-concrete slab is proposed – heavy concrete above the rib and soil-concrete in the overhangs. In this case, there is a need for research on the possibility of using recycled coarse aggregate of the required size in heavy concrete.

Static Analysis of Wooden Beams Strengthened with FRCM-PBO Composite in Bending

The article presents an analysis of the static work of bent solid-wood beams reinforced with FRCM-PBO (fiber-reinforced cementitious matrix-p-phenylene benzobis oxazole) composite. In order to ensure better adhesion of the FRCM-PBO composite to the wooden beam, a layer of mineral resin and quartz sand was applied between the composite and the wooden beam. Ten wooden pine beams with dimensions of 80 × 80 × 1600 mm were used for the tests. Five wooden beams, unreinforced, were used as referenced elements and another five were reinforced with FRCM-PBO composite. The tested samples were subjected to a four-point bending test in which the static scheme of a simply supported beam subjected to two symmetrical concentrated forces was used. The main purpose of the experiment was to estimate the load capacity, the flexural modulus and the maximum bending stress. The time needed to destroy the element and the deflection were also measured. The tests were carried out based on the PN-EN 408: 2010 + A1 standard. The material used for the study was also characterized. The methodology and assumptions adopted in the study were presented. The tests confirmed a significant increase in destructive force by 141.46%, maximum bending stress by 118.9%, modulus of elasticity by 18.32%, time needed to destroy the sample by 106.56% and deflection by 115.58% compared to the reference beams. The unusual method of wood reinforcement presented in the article can be considered as innovative, characterized not only by a significant load capacity margin exceeding 141%, but also by simplicity of application.

Численное исследование напряженно-деформированного состояния модифицированной деревянной балки

Preservation of wooden architecture monuments requires special attention since during their operation for 100 years and more wooden structures are exposed to environmental influences resulting in weakening their bearing capacity. The use of external reinforcement systems for buildings of historical value leads to a loss of architectural look. The proposed method of restoring the bearing capacity of the destructed wooden beams in the support zones is based on modification with a polymer composition. We have considered 3 types of pine beams: destructed, modified in the support zones; wooden, weakened by destruction; “healthy”. Numerical calculation of beams with a length of 6 m and a cross-section of 100×200 mm is performed in the Lira software package. The calculation model of the beams considered was created by adapting the initial data for the working environment of the software package used. The computational model is set as a three-dimensional body obtained by triangulation and “extrusion” of beam projection section. Shear stresses in the supporting zone, as well as vertical movements of the beams have been determined according to the developed method of calculation of wooden beams. The parameters of the modified beam and the reference “healthy” structure were compared. Shear stresses in the strengthened beam are 15–17 % higher than in the “healthy” beam. It was found that the strength of the destructed beam modified on supports increased by 16–18 % compared to the destructed beam. The boundary conditions for the modification of destructed wooden beams in the support zones to restore their bearing capacity have been determined on the basis of the obtained results. If the loss of bearing capacity is more than 35 %, then this method is not recommended due to the expediency of replacing such structures.

Behavior of Glulam Beams Strengthened in bending with BFRP Fabrics

The article presents results of an experimental studies on reinforcement of pine beams made from glued laminated timber with subsurface basalt fibers (BFRP). An experimental research program was presented, in which the bending strength of glued laminated timber of middle and lower quality class was increased after using BFRP basalt fabrics. Thanks to the use of BFRP reinforcement, an average load capacity increased by 47% and stiffness by 6% in comparison to non-reinforced elements. Based on the research, it was found that the use of BFRP basalt fabrics is an effective method for strengthening damaged wooden elements. Thus, it is an environmentally friendly method of improving the static work of structural elements by combining wood with other natural materials such as basalt fiber reinforced polymers.

Acoustic Emission and Numerical Analysis of Pine Beams Retrofitted with FRP and Poplar Wood.

Acoustic emission (AE) released by pine beams retrofitted with fiber reinforced plastic (FRP) and poplar planks in bending is analyzed. Basalt fabric (FB), carbon fabric (FC), and carbon pultruded laminate (LC) have been used as FRP. Experimental results and AE behavior are discussed based on an elastoplastic finite-element numerical model. The model demonstrates a strong strain concentration at the end of poplar planks, which causes high AE activity in these areas and acts as a precursor of the delamination of the poplar plank. Based on the experimental results, some AE criteria for predicting the onset of the delamination are tentatively proposed.

Old Timber Reinforcement with FRPs.

The tests included the determination of the reinforcement effectiveness of old larch timber originating from a building built in 1860 with the use of carbon-fibre and aramid-fibre mats and strips, BFRPs and GFRPs. The test results showed that in old solid timber pieces from European larch (Larix decidua Mill.), the highest mean flexural bending capacity occurred in samples reinforced with carbon-fibre mats (increase in flexural bending capacity was 60.66% in relation to non-reinforced elements), while the lowest flexural bending capacity of the tested components occurred with reinforcement with GFRP (10 mm in diameter) (increase by only 19.04% in relation to non-reinforced elements). Additionally, bending tests of repaired 130-year-old pine (Pinus sylvestris L.) beams were shown (real-size scale) using CFRP strips and mats. The problems associated with the delamination of the CFRP strip due to uneven deformation of the damaged timber surface and the effectiveness of these repairs are also shown.

Pine Beams Retrofitted with FRP and Poplar Planks: Mechanical Behavior.

The paper presents an experimental analysis of the bending behavior of pine beams (Pinus Sylvester) retrofitted with fiber reinforced plastic (FRP) and poplar planks used as external covering. Poplar wood was chosen because of its rapid growth in planted forests, its homogeneity and attributes for sustainable local development, and high CO2 absorption rate. Vibration tests were also conducted in order to evaluate the stiffness in a non-destructive way and compare it with that obtained by means of the destructive tests. Three types of reinforcement were compared, namely: basalt fabric (FB), carbon fabric (FC) and carbon laminate (LC). In addition, some pine beams were reinforced only with poplar planks and used as control specimens in order to evaluate the improvement provided by the FRP. It was observed that a strong delamination preceded the final breakage of beam. Moreover, the results indicated that stiffness is provided mainly by the poplar plank and not by the FRP, as was expected.

A probabilistic approach to the evaluation of the bending strength of timber beams with integration of data from on-site tests

A probabilistic method to evaluate the bending strength of maritime pine beams (Pinus pinaster Aiton) was explored. The beams were subjected to an experimental campaign that started by allocating them to a visual strength grade and segmenting them lengthwise into clear wood and weak zones. The weak zones are associated with a reduced bending strength that is caused by the presence of knots or grain deviation. Non-and semi-destructive techniques were used to gather information regarding the physical and mechanical properties of the clear wood. Bending tests were carried out until failure to determine the strength of the beams. The method to predict the structural behaviour of the elements was developed under a probabilistic framework based on Monte Carlo simulations in which the reference properties of the beams were assigned randomly based on their probability distributions. The results show that the characteristic strength values assigned to the timber pieces after strength grading only frequently underestimate their strength and that the probabilistic method applied could be used to safely explore the capacity reserve of the timber elements.

Experimental and analytical investigation into the stiffness of composite steel-reinforced timber beams with flexible shear connectors

Most of the current research on the design of timber composite beams involves either complex mathematical models which are not checked with experimental testing, or is purely based on experimental work with no attempt to model the behaviour. In a literature review the authors failed to find a practical way of designing composite timber beams, other than in the Eurocode 5. The equations in Eurocode 5 are unfortunately limited in their application. This paper looks at stiffening timber beams, with a known stiffness distribution, by screwing or nailing a steel strip to the underside of the beam. The modelled behaviour is compared with experimental test results and recommendations for the analysis and design of such members are given. The experimental work involved determining the stiffness of twenty-four South African pine beams reinforced with metal strips. The spacing of the connectors was varied to ascertain the increase in stiffness of the composite with a reduction in the connector spacing. The analytical methods used were the Eurocode 5 method, as well as two finite element modelling methods, which may be used to determine the composite stiffness. The results of the three methods used show a remarkably good fit with the lower-bound experimental results.

Bending and shear reinforcements for timber beams using GFRP plates

The aim of this paper is to present the results from a procedure developed for the repair or reinforcement of timber beams. This procedure uses fiberglass and cork plates bonded with epoxy resin. The proposed experimental technique was tested in two situations: repairing beam ends that had rotted (Reinforcement system 1), and repairing and/or reinforcement of the center of the beam damaged because of a fault or the need to increase the resistance capacity of the timber (Reinforcement system 2). Tests were carried out using Scots pine beams with a size of 50×50×725mm3 for the reinforcement system 1, and 50×50×1000mm3 for the reinforcement system 2. In both systems, the reinforcements were tested in various situations, and provided effectiveness similar to that of a healthy beam, and an increased load-carrying capacity of up to 50%.

Local Reinforcement of Timber with Composite and Lignocellulosic Materials

This work compares the effectiveness of local reinforcements of pine beams. Test beams were reinforced with carbon fiber reinforced polymer (CFRP) tape and layered laminate bamboo composite (LLBC) plates. The effective length of local reinforcement reached 5% of the entire beam length. Beams were tested to determine static bending strength in accordance with the EN-408 (2012) standard. On the basis of testing and calculations, it was concluded that local reinforcement with both reinforcing materials caused a significant (p < 0.05) gain in load capacity and modulus of elasticity. The LLBC, which has a tensile strength 25 times lower and a modulus of elasticity 17 times lower than CFRP, resulted in the highest load capacity. This phenomenon is related to the more uniform stress distribution on the composite with LLBC plate - glue bond - wood layers and lower strain within the bond in comparison to the CFRP reinforcement. Therefore, critical stresses within the bond were not exceeded, which often happens in reinforcement with materials of high modulus of elasticity (such as CFRP tape).

Flexural Behavior of Typical Chinese Traditional Timber Stitching Beams

In Chinese traditional timber buildings, stitching is very common. When the bearing capacity or the rigidity is inadequate, a timber beam is often strengthened with another beam using the stitching method. The timber stitching beams are mainly of two types—the small-top/big-bottom type and the big-top/small-bottom type. To study the bending behavior of these two types of timber stitching beams, including the failure mode, the flexural capacity, the strain distribution at mid-span section, and the maximum deflection, bending tests are carried out on 14 timber stitching beams with Chinese traditional conformation for seven pine beams and seven fir beams. The results show that the failure modes of the small-top/big-bottom type of stitching beams all show brittle fractures at the bottoms of the bottom beams. The failure modes of the big-top/small-bottom type of stitching beams all show brittle fractures at the bottoms of the top beams. The distribution of section strain along the height of each part of the beam basically obeys plane hypothesis. Based on the theoretical and experimental analysis, the calculation formulas of flexural capacity and maximum deflection of these two types of timber stitching beams made of pine and fir are presented.

Los materiales utilizados en la ejecución de la bóveda encamonada del Salón de Plenos del Senado de España

The constituent materials used to build the wooden vault over the Plenary Hall in the Spain’s Senate Building (ca 1814-1820) are analyzed in this paper. Characteristics of gypsum mortar applied on pine beams, boards and blockboard, have been determined. The esparto (=needlegrass) fibre provides a framework for the gypsum mortar to ensure adhesion and forming the surface of the dome. Physical-mechanical properties of the burnt clay-lightened gypsum mortars were determined with laboratory tests, while the composition of these materials was found with XRD,SEM and IR.

Determinación de la curva tensión-deformación en madera de ‘Pinus sylvestris’ L. para la simulación numérica de vigas de madera libre de defectos

The objective of this paper is to develop a twodimensional numerical model to simulate the response of Scots pine (Pinus sylvestris L.) defect free timber members in order to predict the behaviour of these members when subjected to external forces. For this purpose, data of the mechanical properties of Scots pine were obtained by performing experimental tests on specimens. We determined the stresses and deformations of timber beams in the elastic-plastic and plastic phases. In addition, we developed a finite element software that considered the orthotropic nature of timber, the non-linearity of the compression-reduction branch and the differing moduli of elasticity in tension and compression for Scots pine beams free from defects. The software developed simulates an experimental four point bending test according to UNE-EN 408 Standard.

The effect of wanes on the bending strength of solid timber beams

A theoretical analysis is conducted to determine the effect of wanes on the bearing capacity of timber in light of the reduction they entail in cross-sectional area compared to fully rectangular sections. The concomitant loss of bending strength is likewise evaluated. Parallel tests are run on 84 samples —51 with wanes— of large section, Scotch ( Pinus sylvestris L.) and Corsican ( Pinus pinaster Ait.) pine beams taken from old buildings. The bending strength, modulus of elasticity and density are found in accordance with European standard EN 408. The mechanical properties of the specimens with and without wanes are found to be very similar, and no statistically significant differences are recorded. The effect of the decline in section may be offset by greater continuity of surface fibers and the section shape effect. One practical consequence of this finding is that (within certain limits) wanes may be disregarded when grading large section timber beams in existing structures, where this flaw is very common; this in turn would reduce the high percentage of rejected beams imposed by the present visual grading standards.

Improving the prediction of strength and rigidity of structural timber by combining ultrasound techniques with visual grading parameters

The present study explores the possibility of using longitudinal ultrasound transmission to evaluate the bending strength and modulus of elasticity in structural timber made from the two species most commonly found in Spanish construction and rehabilitation works: Scots pine ( Pinus sylvestris L.) and Laricio pine ( Pinus nigra Arn.). An analysis of 1305 Scots pine and 852 Laricio pine beams shows that ultrasound transmission velocity alone can predict neither the bending strength nor the modulus of elasticity and that other predictive variables are required. A series of models are proposed based on ultrasound transmission velocity measurements, the relative size of the largest face and edge knots, length and density. After running models for each species individually and for the two jointly, a single model is found to be suitable for both. The models proposed explain from 63 to 73 per cent of bending strength and modulus of elasticity variability.

Mechanical Grading of Round Timber Beams

Current procedures used to sort round timber beams into structural grades rely on visual grading methods and property assignments based on modification of clear wood properties. This study provides the technical basis for mechanical grading of 228 mm (9 in.) diameter round timbers. Test results on 225 round Engelmann spruce–alpine fir–lodgepole pine beams demonstrate the conservative nature of current timber strength assignments. A good correlation was obtained between static bending strength and static modulus of elasticity (MOE), and between bending properties and dynamic MOE determined in transverse vibration. Relationships were also developed between compressive strength parallel to grain, bending strength, and MOE by transverse vibration. The property relationships developed in this study were used to propose grading criteria consistent with procedures used with mechanically graded softwood dimension lumber. Estimated grade yields obtained using the proposed criteria show that significant increases i...

The use of dendrochronological material from buildings to get information about past spruce budworm outbreaks

The history of the spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks during the last three centuries has been reconstructed by analyzing material from churches. Wood samples were taken from eight churches within a 25-km radius of Chicoutimi, Quebec, Canada. The buildings were constructed between 1864 and 1924. Sampling was realized in the basement, under the roof (loft), and in the bell tower whenever possible. All the material from the basement has been identified as Thuja occidentalis L. (white cedar), with exception of Notre-Dame Church in Laterrire, where pine beams (Pinus sp.) were found. Pine and spruce species (Picea sp.) were found in the bell tower and under the roof in all churches. Chronologies were established for the three tree species: spruce covered the period from 1672 to 1954; white cedar, from 1616 to 1924; and pine, from 1771 to 1925. White cedar was used for a nonhost chronology. To demonstrate information about past spruce budworm outbreaks, only the results for the spruce samples have been presented. Spruce chronologies for the eight churches showed an average correlation of 0.54, with the highest correlation value (0.88) registered between Sainte-Anne and SacrO-Coeur churches. All these chronologies showed clear growth reduction periods caused by defoliation of the spruce budworm. The oldest spruce chronology (1672 to 1920) from the Chicoutimi Cathedral showed two clear defoliation periods during the 18th century, one from 1710 to 1716 and the other from 1754 to 1759. The 19th century was also marked by two defoliation periods: the first from 1811 to 1813 and the second from 1835 to 1841. These periods of spruce budworm outbreaks have also been observed in the wooden structures of the other churches. A third outbreak probably occurred in the 19th century from 1868 to 1878. It is visible in the samples taken from the Chicoutimi Cathedral and Saint-Cyriac.

Transverse Isotropy Modeling of 3‐D Glulam Timber Beams

The mathematical modeling of glued‐laminated (glulam) timber beams is greatly simplified by considering the material to be isotropic in the plane of the cross section. In this paper, the hypothesis of transverse isotropy for southern pine glulam beams is verified through an experimental torsion program. Solid‐sawn samples of rectangular cross sections that exhibit rhombic symmetry were tested in torsion about their longitudinal axes (L) to compute the principal shear moduli in the radial (GLR) and tangential (GLT) directions. The small difference between GLR and GLT was indicative of the transversely isotropic behavior of southern pine beams. Based on this behavior, the shear moduli (G) of rectangular and circular glulam samples were computed from torsion tests and Saint‐Venant's isotropic torsion solution. The experimental results show that the depth‐to‐width ratios of the cross sections have no significant influence on the computed shear moduli of the glulam samples; thus, Saint‐Venant's torsion solution can accurately represent the linear torsional response of southern pine glulam beams.

Creep Behaviour of Laminated Pine Beams under Sustained Loading

SYNOPSIS Studies on the creep behaviour of four groups of small defect-free laminated S.A. pine beams kept under varying bending stresses for 45 days at constant environmental conditions were carried out to establish the creep limit in bending. In addition, a computer program based on the equation was employed to calculate the values of d (creep factor), k (rate of creep) for each beam and to fit a theoretical creep deflection curve to the measured data. It was found that a creep limit exists at approximately 50% of the ultimate static bending stress. Contrary to expectations, long duration loading for 45 days did not seem to have a decreasing effect on the strength and stiffness of the defect-free laminated beams.