Pecularities of Calculation and Strengthening of Glulam Timber Beams

This paper deals with analysis of pecularities of design and strengthening of tapered, curved and pitched cambered glulam beams under action of lateral tension. The formulas and drawings presented give the possibility for addition and clarification of existed design methods of such beams in our country. For strengthening the apex zone of pitched cambered beams the author offers the way of precompression of the member according to the patent of Lithuanian Republic No 2045. By the use of this method it is possible to increase bearing capacity, fire resistance and durability of glulam bearing elements. The given method allows to simplify manufacturing of alike elements and to improve their technology. Another method (according to the patent of Lithuanian Republic No 2046) also gives the solution of the problem of setting inserts of any size and shape made of different materials. The inserts are used for joint constructions as well as for strengthening dangerous places. The method is carried out in the following way. The most strained parts of wooden bearing element are set and inserts are installed where needed. Corresponding grooves, usually longitudinal, are made before glueing separate planks. The planks having been glued into one piece, grooves of wanted size and shape are made. Inserts of different shape are set into package during its assemblage. In such cases inserts serve as additional plank package fixers. After that by means of pneumatic or hydraulic presses pressurization and final element treatment follows. Alongside of flat inserts another method of insert setting may be used: planks after corresponding grooves have been made are stowed into package and by means of diaphragm made of steel or any other like material are fixed into a position. Then pressurization by pneumatic or hydraulic presses, extraction of diaphragms out of grooves, setting of flat glued inserts into grooves follows. The given method may be applied at any glulam bearing elements plant. The usage of this glulam bearing element strengthening method assures the following advantages: the possibility of making grooves of any size and shape, as well as setting corresponding inserts into grooves which help to strengthen and connect the elements. It allows not only to increase the bearing capacity and durability, but also the fire resistance of the given element. The usage of nonmetallic inserts increase dielectricity or “ratio transparency” of structures.

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