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ISSN 1995-4212, Polymer Science, Series D, 2018, Vol. 11, No. 4, pp. 378–381. © Pleiades Publishing, Ltd., 2018.Original Russian Text © S.A. Ugryumov, S.V. Kuklin, E.A. Minina, N.S. Paklyuseva, 2018, published in Klei, Germetiki, Tekhnologii, 2018, No. 6, pp. 29–32.

A Study of the Performance Properties of Glued BeamsS. A. Ugryumova, *, S. V. Kuklina, E. A. Mininaa, and N. S. Paklyusevaa

aVolga State University of Technology, Ioshkar-Ola, 424000 Russia*e-mail: ugr-s@yandex.ru

Received July 3, 2017

Abstract—The strength and physical characteristics of glued H-beams based on whole timber and plywoodwere evaluated experimentally. The type of fracture was determined. The strength of structures under bendingand shear along a glue line and the swelling and water absorption parameters were calculated.

Keywords: glued H-beam, plywood, wood, gluing, strength, water absorptionDOI: 10.1134/S1995421218040263

The manufacture of timber structural systems andglued wooden structures in construction is anadvanced woodworking industry, which is now under-going dynamic and sustainable development [1, 2].Glued wooden structures are characterized by rela-tively high strength and low weight: glued structuresare five times lighter than reinforced concrete ones,which makes it possible to construct structures of largesizes, complex curvilinear shapes, and architecturalsolutions [3, 4]. Wood raw materials treated with pro-tective compositions can be used in structures exposedto alternating temperature and moisture conditionsand in contact with aggressive media [5]. The signifi-cant aesthetic and environmental advantages of tim-ber, combined with the reliability of glued structures,make them efficient in an open interior [6, 7].

One type of glued wooden structure that decreasesthe material (whole timber) consumption and thestructure weight without affecting significantly theperformance characteristics is H-beams [8]. Awooden glued H-beam is a building material used as aload-carrying element of f loors and roofs in buildingsof different uses, f loors, parts of wooden roofs (rafters,spans, stands, struts, etc.), and frame elements forindustrial and civil buildings [9]. According to the cal-culation techniques used in the strength of materialstheory, the H-shape is optimal for a load-carryingbeam. The bending load distribution in this case cor-responds to the material distribution; thus, an H-beam complies with the building requirements forload-carrying structures [10].

The raw material for the manufacture of H-beamsmay be not only whole timber, but also glued woodmaterials characterized by the necessary strength, e.g.,general-purpose glued plywood [1, 6]. In this work,the performance characteristics of H-beams based on

timber and plywood with phenol formaldehyde andurea formaldehyde resins as binders were evaluated.

Model timber and plywood H-beams with a crosssection of 40 × 60 mm and a length of 400 mm weremanufactured in laboratory conditions in accordancewith the scheme shown in Fig. 1.

In a beam based on timber, fir lumber was used, theouter layers made of tangentially sawed materials andthe inner ones made of radially sawed materials. In abeam based on plywood, laths left after sawing birchplywood were used.

The experimental assemblies were created usingSFZh-3013 phenol formaldehyde resin (GOST (StateStandard) 14231–88) and KF-Zh urea formaldehyderesin (GOST (State Standard) 20907–75), which wereapplied on the contact surfaces with the standard con-sumption of 140 g/m2. Curing was performed in a

Fig. 1. Design of an H-beam based on (a) timber and(b) plywood.

(a) (b)

POLYMER SCIENCE, SERIES D Vol. 11 No. 4 2018

A STUDY OF THE PERFORMANCE PROPERTIES OF GLUED BEAMS 379

hydraulic press at 130°C under a specific pressure of1.2 MPa, which provided the full contact. In Fig. 2,the appearance of the resulting beams is shown.

Ready H-beam specimens were conditioned for1 day, after which the bending strength was deter-mined in accordance with GOST (State Standard)21554.2–81, the shear strength along a glue layer wasdetermined in accordance with GOST (State Stan-dard) 25884–83, and swelling and the water absorp-tion were determined in accordance with GOST (StateStandard) 16483.20–72 (Table 1).

As can be seen from the data presented in Table 1,the bending strength of H-beams is somewhatdecreased compared to that of a whole bar. However,it remains at a high level and the plywood structurespossess higher strength owing to enhancing glue inter-layers in the source material.

Under the bending force acting on a whole barspecimen, fracture occurs, which is caused by thedominating normal stresses. In glued beams based ontimber and plywood, fracture is caused by the action ofboth normal and tangential stresses (Fig. 3).

In all specimens, under shear strength testing, cohe-sive fracture with tearing of wood fibers is observed(Fig. 4), which indicates high gluing strength.

Owing to glue interlayers, glued beams based onboth timber and plywood are characterized by lowerswelling and water absorption values.

The comparative graphical dependences in Figs. 5and 6 demonstrate the effect of the beam design on thedestructive bending load in time. As can be seen fromthe graphs, the destructive load and the duration of itsimpact are the highest in a whole timber bar, while, forthe fracture of glued timber and plywood beam speci-mens, a shorter time and a lower load are neededowing to a smaller cross section.

In the cross section design of an H-beam based ontimber or plywood, its cross section should be calcu-lated as applied to the specific operating conditionswith consideration of actual loads [11, 12].

In terms of material consumption, the consideredH-beam structure not only saves wood material, butalso makes it possible to use lumber materials of rela-tively small cross section to form the structure of therequired cross section, which can effectively resistloads.Fig. 2. Glued beam specimens.

Table 1. Consolidated results of physicomechanical tests of glued beams

Beam material Glue Bendingstrength, MPa

Shearstrength, MPa

Swelling along thickness, %

Water absorption, %

Timber KF-Zh 55.1 4.3 6.6 46SFZh-3013 54.6 4.4 5.5 43

Plywood KF-Zh 65.8 4.6 4.0 46SFZh-3013 67.6 4.8 3.8 42

Whole bar specimen – 75.2 5.2 8.2 52

Fig. 3. Bending fracture of specimens: (a) whole bar and (b) beam based on plywood.

(a) (b)

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Fig. 4. Shear fracture of beams based on (a) timber and (b) plywood.

(a) (b)

Fig. 5. Effect of the structure design on the destructive bending load in time: (1) whole bar, (2) beam based on timber andKF-Zh resin, and (3) beam based on timber and SFZh-3013 resin.

Loa

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Fig. 6. Effect of the structure design on the destructive bending load in time: (1) beam based on plywood and KF-Zh resin and(2) beam based on plywood and SFZh-3013 resin.

Loa

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8. Yu. B. Levinskii and R. I. Agafonova, “Features offorming the composition of glued beams on the basis ofthe structural model of wood,” Izv. S-Peterb. Lesotekh.Akad., No. 185, 213–224 (2008).

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Translated by E. Petrova

SPELL: 1. ok