The Effect of Arrangement of Old Rubber- Wood Laminae on StrengthProperties of the Resulting Laminated I-Joist Beam

The assembling of I-joist laminated beam was carried out using old-rubberwood (Hevea brasiliensisM.A.) taken from rubber plantation regarded no longer prodnctive for latex-exudate removal (about25-30years old). Initially,old rubber-woodlogs (diameterabout 10-25 cm)were sawn into laminae. It revealedthat the laminaeyield (36-39%) was lower than that commonly obtained.from the sawing of large-diameter logs. The resulting laminae were recon stituted into I- joist laminated beam using phenol-recorcinol formal defly deadhesiveat room temperature. & suitsof reconsitution (assembling) showed that strength properties of laminatedly oist beam with horizontal- giuing profiles between laminae in the webportion (FSPL = 132.97 kg/ m/, MOR= 184.13 kg/en/, MOE= 54425.196 kg/ en/, and Sh = 2.9 397 kg/ C1n2) werelower than those of small-sizedclear solid (defectfree) kayumanis wood, but higher than those of I-joistwith vertical gluingpro.ftlesbetween laminae in the web as well as than those of thehorizontally laminated beam made-up of old rubber-woodlaminaes as well. Besides, the angle between wood rqy and glue Jines (planes) correlated negatively with the strengths of I- joist beam. This suggests the positive prospect of manufacturing laminated I-joistbeamfrom old rubber-tuood with vertical giuing patterns(in the webportion) between the laminaefar construaion, due to thesaving-enhancementon raw-materialusage.