Perilaku mekanika balok laminasi kayu keruing-Bambu Petung terhadap pembebanan lentur

WIJAYA, I Putu Eddy Purna, Ir. Morisco, PhD

2003 | Tesis | S2 Teknik Sipil

Penggunaan kayu dalam bangunan sipil terus mengalami peningkatan baik untuk pemakaian struktural maupun non struktural. Permintaan akan kayu tersebut tidak dapat terpenuhi akibat kurangnya kayu dalam diameter yang besar. Di sisi lain pemanfaatan bambu selama ini belum optimal walaupun hasil penelitian telah menunjukkan bahwa bambu memiliki kekuatan dan keunggulan dibandingkan dengan material bangunan lainnya. Selain itu bambu dapat dibuat dalam bentuk balok laminasi untuk meningkatkan perilaku mekanikanya. Penelitian ini bertujuan untuk mengetahui besarnya kekuatan dan kekakuan dari balok tersebut dalam kondisi pembebanan lentur murni. Dalam penelitian ini dibuat balok laminasi yang tersusun atas kayu keruing (Dipterocarpus spp.) dan bambu petung (Dendrocalamus asper) dengan variasi jumlah lamina bambu terhadap balok sebesar 0%, 25%, 50%, 75% dan 100%. Jumlah perekat terlabur dihitung sehingga diperoleh keteguhan geser yang optimal dan masing–masing variasi balok laminasi dibuat dalam 3 (tiga) ulangan, dengan ukuran penampang dan panjang yang sama. Hasil penelitian menunjukkan bahwa jumlah perekat terlabur yang optimal adalah sebanyak 40/MDGL untuk perekatan antar kayu keruing dan antara kayu keruing dengan lamina bambu, serta 50/MDGL untuk perekatan antar lamina bambu. Kekuatan balok laminasi tertinggi diperoleh pada rasio bambu terhadap balok 100% (RBB-100) yaitu sebesar 3.484 kg dan terendah pada rasio bambu terhadap balok 50% (RBB-50), sebesar 2.564 kg. Kekakuan balok mengalami peningkatan bersamaan dengan bertambahnya rasio bambu terhadap balok dimana balok RBB-100 memiliki kekakuan yang besarnya 112,38% lebih tinggi daripada balok RBB-0 (kayu keruing murni). Selama pengujian, balok laminasi mengalami kerusakan lentur, namun dijumpai pula kerusakan geser dan puntir pada beberapa benda uji akibat ketidaksempurnaan balok.

Wood usage in civil buildings has shown increasing demand whether for structural or non-structural means. The demand itself can not be fulfilled because of the lack of lumber woods in large diameter. On the other hand, bamboo has not been optimally exploited although research results have shown that bamboo has strength and better performance compared to other building materials. Bamboo can also be made as beam to improve its mechanical behaviour. This research was aimed to reveal the strength and the stiffness of that beam under pure bending loading. In this research, glue-laminated beams were made from keruing wood (Dipterocarpus spp) and bamboo petung (Dendrocalamus asper) with variations in numbers of bamboo laminae to the beam as much as 0%, 25%, 50%, 75%, and 100%. The amount of glue-spreads was calculated so that optimum shears strength were achieved and every variation were made in 3 (three) replication, with constant dimension and length. Research results showed that optimum glue-spreads were 40/MDGL for adhesion between keruing woods, and also for keruing wood and bamboo laminae, and 50/MDGL for adhesion between bamboo laminaes. Highest gluelaminated beam strength was achieved at bamboo with beam ratio of 100% (RBB- 100), which was 3.484 kgs and the lowest at bamboo with beam ratio of 50% (RBB-50), as much as 2.564 kgs. Beam stiffness increased as the bamboo with beam ratio were increased in which specimen RBB-100 stiffness were 112,38% higher than RBB-0 (pure keruing wood). During the experiment, the beam experienced bending failures, yet both shear and torsion failures were also found at several testing specimen because of their imperfections.

Kata Kunci : Balok Laminasi, Perekatan Kayu, Keruing dan Bambu Petung, glue-laminated beam, wood adhesion.