Profiilpleki PP-45B paigutiste uurimine

Käesolevas töös on uuritud profiilpleki Rannila PP-45B paksusega 0,7 mm käitumist erinevate kinnitustega (joonis 2 ja 5). Arvutuslikult on leitud profiilplekki tunnussuurused, kriitilised koormused ja katselised tulemused. Katsetused viidi läbi Tallinna Tehnikakõrgkooli mehaaniliste katsetuste laboris. Katse1 puhul jäid katsetatud koormused väikseks, sest andurite liikumise vahemaa oli väike ja esialgu ei hakanud andureid liigutama. Katse 2 puhul sai võtta appi vastavad abinõud, et andurid saaks näidata suuremaid erinevusi. Kahjuks ei saavutanud oodatud tulemust vaid katsekeha vajus enne läbi, mis pani punkti ka Katse 1- e juurde tagasi tulekul. Katsetulemuste analüüsides on tehtud järgnevad tähelepanekud: Katse 1 1. Kuna katse viidi läbi asendis „kitsam vöö üleval“, siis vastavalt arvutustele oleks välja mõlkuv osa kõigest 6,93 mm, millest võib järeldada, et profiilplekk paindub läbi enne kui nii väike mõlkumine tekib. 2. Katselised paigutised üldiselt suurenesid lineaarses seoses, kuid paigutised olid väiksemad, kui arvutuslikult leitud tulemused. Tõenäoliselt oleks suuremate koormuste juures paigutis liikunud arvutuslikku vahemaasse. Kuigi koormused jäid väikesteks oli näha sümmeetrilist paigutist, kus maksimaalne paigutis tekkis silde keskel (joonis 15-17). Katse 2 1. Katsetuse käigus saadud tulemused erinesid arvutuslikest tulemustest. Oodatud mõlkumine pidanuks juhtuma alumises tsoonis, kuid katsekeha kaotas kandevõime enne mõlkumise toimumist. 2. Katselised paigutised üldiselt suurenesid lineaarses seoses, kuid paigutised olid suuremad, kui arvutuslikult leitud tulemused. Kuna tekkis pöördenurk jäiga kinnituse juures, siis eeldatav järeleandmise koht on toodud joonisel 25. Võrreldes paigutisjooni (joonis 15-20) on näha, et kinnitus oli jäigem kui liigend toel, sest paigutisjoonte maksimum koht oli nihkunud ja paigutisjoone kuju ei olnud enam sümmeetriline. Kuna kinnitus ei olnud täiesti jäik, põhjendab see miks paigutis oli suurem kui arvutatud tulemus.

Classical structural mechanics features linear dependence between displacement and load. The same is also relevant for shape steel that works under the simple scheme of beams supported by consoles at both ends and with even longitudinal force applied. However, if loss of stability occurs this dependence changes. In case of exceeding critical load of tiles and coating, it usually leads to in-surface buckling only. Structural load capacity will not decrease, but non-linear increase in displacement occurs. The characteristic example is loading of shape steel with longitudinal load. Research into the Displacement of Corrugated Steel PP-45B - researches performance of shape steel Rannila PP-45B 0.7 mm thick depending on different support attachments (drawing 2 and 5). Shape steel performance characteristics, critical loads and test results were found by method of calculation. Tests were carried out on the Test Rig for Building Structures of Tallinn University of Applied Sciences. In Test 1 the tested loads were small as the indicating range of measuring devices remained narrow and, firstly, no motion was detected. In Test 2 some measures were applied so that detectors would show more differences. However, no desired result was achieved as the examined object sagged earlier, which meant there was no way to go back to Test 1 anymore. On the basis of the results analysis the following was found: Test 1 1. Since the test was done in a position „the narrower framework up“, according to the calculation, the in-surface buckling should only be 6.93 mm, the conclusion can be made that shape sheet sags before minor buckling occurs. 2. Test displacements generally increased in the linear dependence though the displacement values were smaller than the calculated ones. Evidently, in case of larger loads displacement would have shifted into the calculated range. Although loads remained small, a symmetrical displacement was noticed, with maximal displacement in the centre of the bay (drawing 15-17). Test 2 1. The test results differed from the calculated values. The expected buckling should have occurred in the bottom part, however, the test object lost the bearing capacity before buckling occurred. 2. Test displacements generally increased in the linear dependence, though the displacement values were bigger than the calculated ones. Since angular displacement occurred at the rigid frame support, the presumed place of yielding is given on drawing 25. Comparison of displacement lines (drawing 15-20) shows that the rigid frame support has stronger performance characteristics than with pinned support as the spot with lines of maximum displacement shifted and the shape of displacement lines is not symmetrical anymore. Since the rigid frame was not totally rigid it explains why the actual displacement was bigger than the calculated result.