Naresworo Nugroho

A New Method To Estimate Modulus Of Elasticity And Modulus Of Rupture Of Glulam I‐Joist

Glulam consists of laminaes and each laminae influences glulam’s strength. Transformed cross section (TCS) method is a well known method to calculate the modulus of elasticity (E) and modulus of rupture (SR) of glulam. However, the TCS does not follow the principles due to its assumption that the material properties depend on its shape and size. Therefore, a new calculation method is required. This paper discusses the formulation of a new method to determine E and SR of glulam. It was found that E and SR calculated by the TCS and new methods are the same. The new method confirms the independencies of E and SR which could not be fulfilled by the TCS one. Therefore, the TCS method could be replaced by the new method.

Bolt-bearing strength and its relationship to mechanical properties of wood, evaluated in six Indonesian tropical hardwoods

ABSTRACT Bearing strength largely affects the performance of wood connections. This study, determines the bearing strengths of six Indonesian tropical hardwoods with different specific gravities (ranging from 0.43 to 0.84) by half-hole testing. The results for three bolt diameters were compared to the bearing strengths in the Indonesian National Standard (SNI) and the National Design Specification (NDS) for Wood Construction. Next, the bolt-bearing strengths were related to the specific gravities and mechanical properties of the woods. With increasing specific gravity, the bearing strength increased from 26 to 70 MPa. The experimentally obtained bearing strengths of light and heavy red meranti, mersawa, kapur and bangkirai woods were 3–15% and 11–23% lower than the SNI and NDS values, respectively. In contrast, the experimental result for merbau was 23 and 11% higher than the SNI and NDS values, respectively. The bearing strength most closely approached the compression strength parallel to the grain.

Erratum to: The effect of juvenility and veneer thickness on bending strength of Douglas-fir laminated veneer lumber

Most of wood industry requires well conformed logs and middle diameter trees to optimize primary processing yields. The raw material, mostly coming from monoculture plantations, contains a considerable proportion of juvenile wood. The objectives of present study were to identify the transition ring between juvenile and mature wood in Douglas-fir and to analyze the effect of juvenility and veneer thickness on bending strength of Douglas-fir laminated veneer lumber (LVL). Microfibril angle (MFA) and tracheid length from five Douglas-fir logs were measured from pith to bark. Veneers peeled with an instrumented lathe to produce LVL. Total of 140 LVL samples were mechanically characterized by measuring modulus of elasticity (MOE) and modulus of rupture (MOR). The results showed that transition rings from juvenile to mature wood at breast height, according to MFA and tracheid length, were at twentieth and twenty-first, respectively. According to analysis of variance, there was a significant effect of juvenility on LVL bending strength. The advantage of using veneers of mature compare to juvenile wood for LVL was due to an improvement of bending strength in the range of 7–22 %. LVL made of 3 mm veneers has lower stiffness (2.2 %) compare to LVL made of 5.25 mm veneers. High correlation between static and dynamic MOE was noted.

Utilization of Coir and Recycled Polypropylene for Bamboo Matting Layer Composite

Utilization of non wood material as raw material in wood industry would be increase in the future because environmentally issues. The objective of this research were to evaluate characteristic of coir, recycled polypropylene (RPP), and tali bamboo (Gigantochloa apus) as raw material in composite board and find out the optimum quality of composite board made from its material. The board samples target density was 0.7 g/cm3. The board construction type was core type composite board (three layers). The bamboo sheet wide was 1 cm and 2 cm with and without bark. The bamboo matting was used in angle and perpendicular orientation to length of the board. The results showed that coir, RPP, and tali bamboo suitable for composite board material. Utilization of bamboo matting layers increases the mechanical properties of board, except internal bond. All of composite board made from coir and RPP with bamboo matting layers fulfill the JIS A 5908 standard in density and thickness swelling after 2 and 24 hours of water immersions. However, only composites with bamboo matting layers with bark and sheet wide 1 cm fulfill JIS A 5908 standard for veneered particleboard in MOE.