Pengaruh posisi sambungan terhadap kapasitas geser balok bambu laminasi horisontal

IRAWATI, Inggar Septhia, Ir. H. Morisco, Ph.D

2004 | Tesis | S2 Teknik Sipil

Bambu merupakan hasil alam potensial pengganti kayu. Salah satu usaha untuk memperluas pemakaian bambu dalam bidang konstruksi adalah dengan mengembangkan teknik laminasi. Balok dalam berbagai ukuran (panjang, lebar, tinggi) dan bentuk (lurus, lengkung) dapat diperoleh dengan teknik laminasi. Walaupun demikian, pemakaian sambungan sulit dihindarkan pada struktur bentang panjang sehingga perlu diketahui pengaruh sambungan terhadap kapasitas balok laminasi. Penelitian ini bertujuan untuk mengetahui pengaruh posisi sambungan terhadap kapasitas geser balok bambu laminasi horisontal. Bambu yang digunakan dalam penelitian ini adalah bambu petung. Penelitian pendahuluan dilakukan untuk mengetahui sifat fisika dan mekanika bambu serta keteguhan rekat menurut ISO 3129-1975. Sifat mekanik bambu yang diperoleh digunakan untuk menentukan dimensi balok laminasi. Benda uji balok laminasi terdiri dari 4 variasi sambungan butt joint (BLP-1, BLP-2, BLP-3 dan BLP-4) dan balok utuh tanpa sambungan. Pembebanan lateral statik diberikan secara bertahap sampai balok runtuh. Hasil penelitian menunjukkan bahwa kuat tekan sejajar dan tegak lurus serat, kuat tarik sejajar serat, kuat geser, MOR dan MOE bambu bahan penelitian adalah 50,29 MPa, 51,06 MPa, 402,18 MPa, 7,62 MPa, 128,80 MPa and 13746,33 MPa. Keteguhan rekat optimal tercapai pada jumlah perekat terlabur 50#/MDGL dengan kuat geser rata-rata 11,304 MPa. Pengaplikasian butt joint memberikan pengaruh reduksi kuat geser balok laminasi sebesar 23,21% (BLP-1) sampai 28,27% (BLP-4) rata-rata 25,41%. Variasi posisi sambungan tidak memberikan pengaruh yang signifikan terhadap kapasitas gesesr balok bambu laminasi horisontal karena pada balok bambu laminasi horisontal bagian lamina terlemah akan menjadi kontrol keseluruhan kekuatan geser balok. Retak geser terjadi pada sambungan yang terletak paling dekat dengan tumpuan.

Bamboo is a natural resource that can substitute the use of wood in building stucture. One method to develop bamboo usage in structural building is lamination technique. Beams in various dimension (length, width, height) and shapes (straight, curve) can be produced by means of this method. Nevertheless, the occurrence of joints can not be avoided in such long span structure. As the consequence, it is necessary to determine its effect to the capacity of laminated beam, which is also taking place as the main aim of this research. The type of bamboo that was in the research was “petung” (Dendrocalamus Sp). Preliminary research was previously conducted to obtain physical and mechanical behavior of the bamboo and block shear strength based on ISO 3129- 1975. The obtained bamboo mechanical properties afterwards were used to define the laminated beam dimension. The laminated beam specimen consisted of four variation of butt joint pattern (BLP-1, BLP-2, BLP-3, BLP-4). Lateral static loading was applied gradually until failure. The result showed that density of the bamboo was 0.653g/cm3.The compression parallel and perpendicular, tensile, shear strength, modulus of rupture and modulus of elasticity were 50.29 MPa, 51.06 MPa, 402.18 MPa, 7.62 MPa, 128.80 MPa and 13746.33 MPa. The shear laminated block test showed that the optimal glue spread was 50# /MDGL with 11.304 MPa of shear strength. The application of butt joint introduced the decrease of shear strength of the laminated beam varying from 23.21% (BLP-1) up to 28.27% (BLP-2) with average 25.41%. Join pattern variation made no significant effect to the shear capacity of horizontally laminated bamboo beam due to the weakest part of lamina would control the over all shear strength of the beam. Shear crack that occurred at the joint that take the closest place to the bearing.

Kata Kunci : Balok Laminasi,Bambu,Kapasitas Geser,Posisi Sambungan, shear capacity, horizontally laminated beam, butt joint.