Judul: Shear Strength Parallel to Fibers and Bending Strength and Stiffness Perpendicular to Fibers of Betung Bamboo (Dendrocalamus asper)
Abstrak: Dendrocalamus asper (betung) merupakan bambu berdiameter besar dan sering digunakan untuk konstruksi. Penelitian ini bertujuan untuk menentukan nilai kapasitas dan kuat geser sejajar serat dan lentur tegak lurus serat bambu betung serta nilai estimasi 5% batas bawahnya. Ukuran contoh uji dan pengujian sifat mekanis mengacu pada BS ISO 22157:2019. Kadar air rata-rata bambu betung 14.50% untuk contoh uji geser sejajar serat dan 11.97% untuk contoh uji lentur tegak lurus serat. Kapasitas geser maksimum (Fult) berkisar 15518−66827 N. Kuat geser sejajar serat (fv) sebesar 5.38-14.01 N/mm². MOR (Modulus of rupture) dibedakan menjadi dua sesuai posisi kerusakannya yaitu Utara (U) atau Selatan (S) (fm,90 US) dan Timur (T) atau Barat (B)(fm,90 TB) . Rata-rata fm,90 US yang diperoleh sebesar 13.68 N/mm² sedangkan nilai rata-rata fm,90 TB yang diperoleh sebesar 7.95 N/mm². Nilai fm,90 US lebih tinggi karena kerusakan terjadi pada bagian dalam buluh bambu. Rata-rata modulus elastisitas lentur tegak lurus serat (Em,90) diperoleh sebesar 1798.35 N/mm². Nilai estimasi 5% batas bawah geser sejajar serat sebesar 5.53 N/mm² sedangkan untuk MOE dan MOR sebesar 305.53 dan 4.39 N/mm²., Dendrocalamus asper (betung) is large diameter bamboo, and commonly used for construction. This research aims to determine the values of shear strength parallel to fiber and bending strength and stiffness perpendicular to fiber of betung bamboo and its 5% exclusion limit value. The sample size and mechanical properties testing refers to BS ISO 22157:2019. The average moisture content of bamboo betung was 14.50% for shear parallel to grain samples and 11.97% for bending strength and stiffness perpendicular to the fiber. The maximum shear capacity (Fult) has a range between 15518-66827 N. The shear strength parallel to grain (fv ) has a range between 5.38-14.01 N/mm². The MOR (Modulus of Rupture) value obtained was categorized into two groups based on the failure position, which are North (U) or South (S) (fm,90 US ) and East (T) or West (B) (fm,90 TB). The maximum fm,90 US and fm,90 TB values obtained were 13.68 and 7.95 N/mm². fm,90 US was higher than fm,90 TB because fissure occured in bamboo internal surface. The average MOE (Modulus of Elasticity) (Em,90 ) was 1798.35 N/mm². Estimated value of 5% exclusion limit value of fv was 5.53 N/mm², while that of MOE and MOR were 305.53 and 4.39 N/mm².
Keyword: Dendocalamus asper, Moisture content, Shear strength, Estimated value, Flexural properties

Judul: Buckling Properties of Betung Bamboo (Dendrocalamus asper)
Abstrak: Bambu betung potensial digunakan sebagai konstruksi struktural. Tidak seperti bambu kolom pendek, kolom panjang dipengaruhi oleh peristiwa tekuk. Penelitian ini bertujuan untuk membuat rumus eksperimental hubungan antara angka kelangsingan dan faktor tekuk serta menentukan nilai faktor tekuk bambu betung pada berbagai angka kelangsingan. Bambu betung ditebang dari Jalan Huni Fakultas Kehutanan dan Lingkungan, Institut Pertanian Bogor dengan panjang 13-14 m yang dipotong menjadi dua bagian. Pengukuran kadar air, kerapatan, kerapatan linear, bentuk geometri dan kandungan cacat (dimensi, keruncingan, eccentricity, kelengkungan, ovality) mengacu pada BS ISO 19624:2018 tentang pemilahan buluh bambu. Uji t-test digunakan untuk membandingkan sifat fisis dan mekanis contoh uji berukuran pendek dan contoh uji berukuran panjang. Ukuran contoh uji pendek dan contoh uji panjang yaitu 6.05-15.81 cm dan 40-410.7 cm. Pengujian tekan contoh uji pendek dilakukan menggunakan alat UTM Shimadzu tipe UMH-30, sedangkan pengujian contoh uji panjang menggunakan alat UTM Baldwin dan alat uji tekuk ukuran panjang. Kedua pengujian dilakukan pembebanan secara vertical (sejajar serat). Pengolahan data menggunakan formula Rankin Gordon, Ylinen’s, Euler, Newlin Gahagan’s, dan Euler Johnson. Tekuk merupakan suatu jenis kegagalan yang disebabkan oleh ketidakstabilan suatu elemen struktur yang dipengaruhi oleh aksi (beban tekuk). Angka kelangsingan merupakan panjang tekuk dibagi dengan jari-jari inersia. Kerapatan dan kerapatan linear berhubungan erat dengan kuat tekan dan kapasitas tekan. Semakin tinggi nilai kerapatan dan kerapatan linear, maka nilai kuat tekan dan kapasitas tekan semakin tinggi. Korelasi antara kerapatan dengan kuat tekan dan kerapatan linear dengan kapasitas tekan dapat dibuktikan menggunakan analisis linear sederhana. Hasil penelitian menunjukkan kerapatan linear kondisi 12% dapat digunakan untuk menduga kapasitas tekan lebih baik daripada kerapatan kondisi 12%. Angka kelangsingan semakin tinggi berdampak pada nilai tekuk semakin rendah. Formula Ylinen’s cocok digunakan untuk menduga nilai tekuk pada berbagai angka kelangsingan., Betung bamboo is a potential material for structural construction. Unlike short bamboo columns, long columns are affected by buckling effect. This study aims to create an experimental formula of the relationship between the number of slenderness ratio and buckling factors and determine the value of the buckling factor of betung bamboo in various numbers of slenderness ratio. Betung bamboo is taken from Huni street, Faculty of Forestry and Environment, IPB University with 13-14 m length which is cut into two parts. Measurement of moisture content, density, linear mass, geometric shapes and defects (dimensions, taper, eccentricity, curvature, ovality) referred to BS ISO 19624:2018 about grading of bamboo culms. T-tests are used to compare the physical and mechanical properties of short test samples and long test samples. The short test sample and long test sample size are 6.05-15.81 cm and 40-410.7 cm length. The short test sample used UTM Shimadzu UMH-30 for compressive test, while the long test sample used UTM Baldwin and a long-size buckling test tool. Both tests were carried out vertically (parallel to grain). Data analysis used Rankin Gordon, Ylinen's, Euler's, Newlin Gahagan's, and Euler Johnson's formula. Buckling is a type of failure caused by the instability of a structural element affected by action (buckling load). Slenderness ratio is the length of bamboo culm divided by the radius of gyration. Linear mass and density are closely related
Keyword: slenderness ratio, betung, column, compressive, buckling

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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