Judul: Modulus Elastisitas dan Kekuatan Tekan Glued Laminated Timber (Glulam)
Abstrak: Latar Belakang Diversifikasi pemanfaatan jenis kayu, termasuk yang berasal dari hutan rakyat, merupakan salah satu upaya memenuhi kebutuhan atas kayu yang terus bertambah sembari tetap menjaga kelestarian hutan alam. Jenis kayu dari hutan rakyat pada umumnya berdiameter kecil dan berumur muda. Dalam penggunaannya diperlukan penanganan khusus guna meningkatkan sifat kekuatan dan kekakuannya. Salah satu cara yang dapat dilakukan adalah dengan merekayasa glue laminated timber (glulam) dari kayu yang tersedia. Glulam bisa menerima beban aksial ataupun lentur/bending. Struktur yang menerima beban aksial tekan atau tarik adalah tiang dan komponen kuda-kuda. Material yang menerima beban aksial akan mengalami perubahan bentuk berupa perpendekan atau perpanjangan. Besarnya perubahan bentuk ini berhubungan erat dengan modulus elastisitas material. Metode. Ukuran papan yang digunakan dalam penelitian ini adalah 2x5x176 cm yang terdiri dari 4 jenis kayu, yaitu kayu Nangka, kayu Afrika, kayu Sengon kayu Randu dan perekat isosianat merk koyobond. Untuk Face dan Back digunakan kayu Nangka dan untuk Core digunakan kayu Sengon, Afrika dan Kayu Randu. Contoh uji kecil bebas cacat berukuran 2x2x8 cm, yang digunakan untuk pengujian Kadar air, BJ, MOE tekan sejajar serat dan tekan tegak lurus serat, kekuatan tekan (Fc) sejajar serat dan kekuatan tekan tegak lurus serat. Untuk glulam tekan sejajar muka lamina berukuran 6x5x5 cm dan glulam tekan tegak lurus muka lamina berukuran 6x5x20 cm. Penghitungan MOE dihitung dengan dua metode yaitu metode pertama dan metode kedua (Bahtiar 2008). Nilai MOE lamina penyusun glulam metode pertama tekan tegak lurus serat kayu Nangka 5,3x103 kg/cm², kayu Afrika 4,1x103 kg/cm², kayu Sengon 3,4x103kg/cm² dan kayu Randu 1,7x103 kg/cm², sedangkan untuk tekan sejajar serat kayu Nangka adalah 2,2x104 kg/cm², kayu Afrika 1,5x104 kg/cm², kayu Sengon 1,3 x104 kg/cm² dan kayu Randu 7,2x103 kg/cm². Rata-rata MOE untuk metode kedua tekan tegak lurus adalah untuk kayu Nangka 4,7x103 kg/cm², kayu Afrika 3,3x103 kg/cm², kayu Sengon 3,8x103 kg/cm² dan untuk kayu Randu 1,7x103 kg/cm², sedangkan untuk nilai MOE tekan sejajar serat kayu Nangka 2,1x104 kg/cm², kayu Afrika 1,4 x104 kg/cm², kayu Sengon 1,2 x104 kg/cm² dan untuk kayu Randu 6,8 x103 kg/cm². Nilai kekuatan tekan sejajar serat kayu penyusun glulam untuk kayu Nangka sebesar 383,16 kg/cm2, kayu Sengon 302,91 kg/cm2, kayu Afrika 279,40 kg/cm2, dan kayu Randu 125,82 kg/cm2. Sedangkan nilai kekuatan tekan tekan tegak lurus serat kayu Nangka sebesar 66,70 kg/cm2, kayu Afrika 42,60 kg/cm2, kayu Sengon 34,50 kg/cm2, dan kayu Randu 20,20 kg/cm2. Nilai rata-rata modulus elastis untuk glulam sejajar muka lamina dengan core kayu Afrika 9,103 kg/cm2, dengan core kayu Sengon 7,3x103 kg/cm2 dan glulam dengan core randu adalah 6,0x103 kg/mm2 , Sedangkan untuk glulam tekan tegak lurus muka lamina, untuk core kayu Afrika 4,1x103 kg/cm2 core kayu Sengon 3,7x103 kg/cm2 dan untuk glulam dengan core kayu Randu adalah sebesar 2,9x103 kg/cm2. Nilai kekuatan tekan untuk glulam sejajar muka lamina dengan core kayu Afrika 61,42 kg/cm2, dengan core kayu Sengon 56,35 kg/cm2 dan glulam dengan core randu adalah 37,09 kg/cm2 Sedangkan untuk glulam tekan tegak lurus muka lamina, untuk core kayu Afrika 5,63 kg/cm2 core kayu Sengon 4,51 kg/cm2 dan untuk glulam dengan core kayu Randu adalah sebesar 4,11 kg/cm2. Bila dibandingkan antara metode pertama dan
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Judul: Verifikasi Empiris Persamaan Lentur Statis Glued Laminated Timber (Glulam)
Abstrak: INTRODUCTION. Wood in construction is often loaded by bending moment. Since the development of wood engineering increasing, the solid wood tends to be substituted by wood’s engineering such as glulam. Glulam is usually made from some laminas. A Transformed Cross Section method has widely used to calculate the mechanical properties of glulam if each lamina’s properties are known. The method transforms each lamina based on its MOE. The longitudinal width is decreased if the MOE is lower, and increased if the MOE is higher. However MOE is a material property which is independent from the geometric property, calculated MOE based on geometric properties is not accurate. Bahtiar (2008) was developed a new methods to calculate the bending properties of glulam. The method is mathematically proven. However it would be better if empirical experiment is conducted to prove it. METHOD. Materials used in this research are 2x10x170 cm3 boards from 4 wood species, namely : Nangka (Artocarpus heterophyllus), Kapuk (Ceiba pentandra), Afrika (Maesopsis eminii), and Sengon (Paraserianthes falcataria), noted by N, R, A, and S respectively, and isosyanate adhesive to bond three layers glulam. Face and back of glulam are N and core is R, A, or S. Test of wood small clear specimen and glulam bending properties is conducted with center point loading configuration based on ASTM D143. Then the equation of load-deformation curve is built on two ways. The first way is only linier regression for data below proportional (elastic) limit; the second way is dummy variable regression which allows both linier regression for data bellow proportional limit and continued by quadratic regression for data upper proportional limit until maximum load. The empirical MOE and MOR are calculated by and equation respectively. The theoretical MOE and MOR are calculated by Bahtiar’s methods (2008). RESULTS AND DISCUSSION. The results of this research show that the average value of MOE calculated by first method for Nangka is 6,3x104 Kg/cm2, Afrika 5,9x104 Kg/cm2, Sengon 5,3x104 Kg/cm2, and Kapuk 2,7x104 Kg/cm2. Average value of MOE calculated by second method for Nangka 6,0x104 Kg/cm2, Afrika 5,6x104 Kg/cm2, Sengon 5,0x104 Kg/cm2, Kapuk 2,6x104 Kg/cm2. The MOE calculated by second method is similar with the first methods for Kapuk but lower for three other species. Average value of MOR of Nangka is 680 Kg/cm2, Afrika 490 Kg/cm2, Sengon 460 Kg/cm2, Kapuk 273 Kg/cm2. The average value of theoretical MOE for glulam N-A-N formation is 6,2x104 Kg/cm2, N-S-N is 5,8x104 Kg/cm2, and N-R-N is 5,9x104 Kg/cm2. The average value of theoretical MOR for glulam N-A-N is 617 Kg/cm2, N-S-N is 584 Kg/cm2, and N-R-N is 675 Kg /cm2. The average value of empirical MOE for glulam N-A-N is 4,6x104 Kg/cm2, N-S-N is 4,9x104 Kg/cm2, and N-R-N is 4,5x104 Kg/cm2. Meanwhile the average value of empiric MOR for glulam N-A-N is 256 Kg/cm2, N-S-N 261 Kg/cm2, N-R-N is 223 Kg/cm2. Theoretical calculation of MOE and MOR of glulam are significantly different with empiric testing result of glulam. Empirical testing shows that the average value of MOE and MOR lower than theoretic calculation. The adhesion of glulam is weaker than the
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Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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