Judul: Kekuatan sambungan batang kayu-pelat baja dengan beberapa jenis alat sambung tipe dowel dan ketebalan batang kayu Acacia mangium Wild.
Abstrak: Wood joint is a joint that fasten two or more lumber together by using the mechanical joint such as nails, bolts, connectors or using grafting in the form of structural adhesive. The purpose of this study is to know the influence of the type of fasteners and the thickness of the beam to the strength of beams with steel plate joint on Acacia mangium wood. This study uses three types of dowel type fasteners, ie nails, bamboo pegs and wooden pegs. Wood that used in this study is Acacia mangium wood with variations in thickness from 3 cm, 3.5 cm, 4 cm, 4.5 cm, 5 cm and 5.5 cm, while the wood used to be a wooden pegs is bangkirai wood. This joint technique use a steel plate as connection plate. Testing is done by putting pressure tap on the joint. The direction of loading is an axial direction of the long wooden beams and perpendicular to the length of the fasteners. The results showed that the type of fasteners and thickness of the beam give effect to the strength of the beam-steel plate joint. Joint with nails has the highest allowable load on mangium wood-steel plates joint, followed by a bamboo pegs, and the lowest is the wooden pegs. There is a general tendency that the allowable load of mangium wood-steel plate joint will increase with increasing the beam thickness. Thus, under the provisions of limit displacement set by the the United States, Australia and Indonesia, respectively in displacement of 0.38 mm, 0.80 mm and 1.50 mm, the allowable load of mangium wood-steel plate joint in the same diameters of nails, bamboo pegs and wood pegs (5.2 mm) differ according to the thickness of the beam.
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Judul: Behaviour of double shear connections strength wood beam with nails of steel side plates under uni-axial compression loading
Abstrak: Connection is the weakest point of the structural building. Structural construction building system must try to ensure that there is only a tensile force or just axial compression that is working on the connection. This research objective is to analysis the behaviour of the strength or the lateral design values (Z) double shear connections wood beam with nails of steel side plates under uni-axial compression loading of ten Indonesian wood species. The research results showed that average moisture content (MC) for the main member varies from 13.3 to 22.5% while average specific gravity (SG) from 0.27 to 0.76 and then wood density from 0.31 to 0.89 g/cm3. From this average value of MC, SG and wood density the lowest was sengon and the highest was rasamala wood. Average allowable load of compression parallel to grain (Fc//) and parallel tensile to grain (Ft//) was sengon, but the highest was bangkirai. There was a general tendency that Fc// and Ft// was linier to SG or ρ of those wood. Ft// was approximately 2 times greater than its Fc//. The number of nail (4-10 pieces) did not give effect of average Z value, but with the nail diameter 4.1 to 5.2 mm Z value increased significantly and this value decreased on 5.5 mm diameter nail. Average Z value were also increases with increasing of SG of wood for several displacement such as 0.38 mm displacement (American Standard), 0.80 mm (Australian Standard), 1.50 mm (Indonesian Standard) and 5.0 mm (breaking load), respectively. The increasing of Z happens because SG effect. At 5.0 mm displacement the increase of Z is not as sharp as 0.38 mm, 0.80 mm and 1.5 mm displacement. On the contrary wood species, amount and diameter size of nails didn’t effect to proportional limit of double shear connections. Power regression type was the best equation to predict Z of wood density for several diameters of nails.
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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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