Abstract
The results of long-term experiments are presented in the paper. As a result of the experiments, invention SU 1025831 was developed under the name “The method of manufacture of a timber load-bearing element” (E 04 C 3/12, priority since July 11, 1981). The objective of the experiments performed was to check the method of increase of load bearing capacity of glulam beams under the influence of long-term shear. 14 beams were tested: nine of them were multilayered and 5 made of board-package and square-sawn timber. All the beams failed because of the action of shear forces. Two beams were tested by static short loading, the rest twelve by long-term loading. Three beams, that have not failed because of the action of long-term loading, then were tested by short-term loading. From the tests of multilayered, glulam and solid square-sawn timber beams the decrease of the relative strength wood split alongside fibres under the action of long-term shear is bigger than that given in literature in case of standard experiments. Relationship of the level of decrease of this strength with the duration of long-term loading may be calculated according to the equation (2). The influence of long-term loading on the load-bearing capacity of these beams depends on the intensity of actions: if such a load does not cause the plastic deformations in the beam, their load-bearing capacity does not decrease and vice versa—the appearance of plastic deformations and micro-cracks means the decrease of load bearing capacity of the beam under a short-term shear. A short description of invention SU 1025831 is also presented in the paper. The invention is devoted to the perfection of the former invention No 954237. The latter one suggested an increase of load-bearing capacity of glulam elements under a short-term shear. Under a long-term load, or in case of fire, when the temperature and moisture around is changing, the strength of prestressed joint of these beams may not be fully guaranteed because of the influence of inner stresses and possible micro-cracking. With the purpose to increase the strength of beams under a long-term shear the author offers additionally to install pivots (Fig 6, 3) after giving prestress and full polymerisation. This method does not only increase the load-bearing capacity of multilayered elements under a long-term shear, but also ensures a higher reliability and fire resistance of such structures.
Highlights
The results of long-term experiments are presented in the paper
invention SU 1025831 was developed under the name
solid square-sawn timber beams the decrease of the relative strength wood split alongside fibres under the action
Summary
Medines sijas buva pagamintas Jiires SKMK bei VISI Statybinil! kanstrukcijl! labaratarijaje. Dvi sijos buva isbandytas statine trumpalaike, likusias - ilgalaike apkrava. Nesuirusias per si laikatarpj, buva papildamai isbandytos statine trumpalaike apkrova, siekiant issiaiskinti ilgalaikil! Vaizdai ilgalaikia bandyma metu pateikti 2 ir 3 pav. Daugiasluoksniq sijq konstrukcija: 1, 4 - 4010 A III armati:iros strypai, jklijuoti visu sijos ilgiu; 2 - pusines lentos; 3 - fanerinis jdeklas Fig 1. Sijos ilgalaikio bandymo metu: a - bendras vaizdas; b - prietaisq isdestymas. Per ilgalaikius bandymus deformacijos buvo matuojamos tik mechaniniais prietaisais (indikatoriais), per trumpalaikius - indikatoriais ir tenzojutikliais (3 pav.). Atliekant bandymus buvo laikomasi spccialiqj[4] darb[4] saugos taisykliq: Jaisvasis sverto galas ga!ejo Jaisvai jlinkti tik 3-4 em, - tai atitiko ""0,5 em sijos jlinkj. Sij[4] deformacijos pirm'l savait~:t po apkrovimo buvo fiksuojamos kas 12 dienos, ve!iau 1-2 kartus per savait((. llgalaiki[4] bandymq stcndo metalinio rygelio savitasis svoris, kai jegos petys 1:4, nustatytas ziediniu dinamometru, buVO Jygus 5,7 kN, o kai petys 1:2 - 2,85 kN
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.