Eksperimentalnyie researches of durability wooden kleenyih beams

In domestic and foreign practice of industrial and civil building the wooden designs received by pasting of boards and bruskov are known. Advantage of such designs is possibility of manufacturing of elements of the big sections from separate malomernyih half-finished products that allows to save material resources.

Among constructive elements of buildings the special place is taken by beams of overlappings and covers. Durability and stability of all building depends on their durability. And durability of beams, in turn, isdefined by the sizes of its cross-section section and quality of a material from which it is produced. It is obvious, that the the big load the beam should maintain, the there should be sizes of its section more. At the same time it is known, that if at action of bending efforts the top layers of a beam work on compression, and bottom on a stretching the middle class of section does not test any efforts. It has served in due course as the precondition of creation of thin-walled metal, ferro-concrete and wooden building designs. In the given work the beam which has been stuck together from four segments, logs received at longitudinal sawing up is considered. Such beams, in particular under mark SKV, are manufactured at the Swiss enterprise Schilliger HolzAG possessed near to a city of Lucerne.

Significance of strength on a bend

# experience

Design type

Average significance by results of duplication of experiences, MPa

Deviation from durability of integral wood, %

1

The five-layer

155.11

46.6

2

The four-layer

135.01

27.6

3

The three-layer

116.51

10.1

4

The two-layer

113.97

7.7

5

The integral

105.81

0

Considering a question of economy of wood at manufacturing of wooden beams, the clear advantage of beams of type SKV before beams of continuous section, as from integral wood, and stuck together of boards has been proved. Simple accounts show, that for manufacturing, for example, beams of continuous section in the size 200h200 mm it is necessary to use pilovochnoe raw materials in diameter of an order 32-34 see For reception of beams of type SKV of the same sizes it is possible to use logs in diameter 24 see At test for durability of scale models of considered beams has been established, that durability of beams not continuous section does not concede durability of a beam from integral wood.

As recently the increasing attention is given to the building bar received by pasting of boards, in laboratory of chair of mechanical technology of wood Kostroma GTU influence experimental researches sloynosti kleenogo a bar on its durability have been conducted. Durability researches on a bend were conducted by a standard technique. Results of experiences are presented in the table.

The analysis of the received data allows to draw a conclusion that durability kleenyih items above, than at samples from integral wood. And, the more layers, the above durability. This results from the fact that as a result of pasting of separate details under pressure has occurred, first, wood consolidation (density of the sample of a five-layer design on 22,1 % of more density of the sample from integral wood), secondly, durability increases at the expense of properties of glue.

Thus, production of beams not continuous section in the conditions of deficiency krupnomernogo pilovochnogo raw materials will allow to reach economy of a source of raw materials and is actual.
A.A. TITUNIN, Kostroma the state technological university Source: «the Building expert» #18 (2003)

It is introduced: on January, 20th, 2003

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