Jung-Hwan Park

A study on log diameter classes of Korean softwood log

Log grading rules are essential tools to ensure the quality of logs in distribution structure. The rules should reflect the long experience and accepted usage practice in the market. A gap between the rules and market should be improved based on analysis of log qualities that produced and market demand. In this study more than ten millions logs which were produced by 5 Regional Forest Services in 2010~2011 period, were analyzed in their qualities including diameters and lengths by species. A proposal was driven to improve the current log grading rules in terms of log diameter classes and length. The followings are the summary of this study. Most of domestic softwood logs are belong to small diameter class of 100~160 mm, which imply the diameter classes of current log grading rules are immoderate. Distributions of log diameter shows distinctive patterns by species, which indicate a necessity of differentiated diameter classes by species in an improved rules. Lengths of logs in productions do not corresponding to the demands and preferences in sawmills. Therefore it is highly recommended to include log length term in an improved log grading system. Based on these findings, 6 log grading systems for 3 species groups of softwood are newly proposed to improve current log grading rules. Limits of log diameter and log length are also proposed for each log grading system.

Characteristics of the Radio-Frequency/Vacuum Drying of Heavy Timbers for Post and Beam of Korean Style Housings Part I : For Japanese larch round logs with 150 mm and 210 mm in diameter and 2,500 mm in length

ABSTRACT The characteristics of radio-frequency/vacuum drying Japanese larch boxed heart round logs with 150 mm and 210 mm in diameter and 2,500 mm in length, subjected to compressive loading, after the pretreat-ment of kerf were investigated. The results of this study were as the follows: The drying time of about 120 hours∼130 hours was needed from green to about 15 percent of moisture content. The gradient of final moisture content for all specimens was very gentle in both longitudinal and transverse directions ow-ing to dielectric heating. The surface checks seriously occurred although the occurrence extent of surface check for the kerfed specimens was slight compared with that for the control specimens because drying stress was relieved by kerf. The occurrence of surface checks for the L-specimen was more serious than that for the S-specimen. Keywords : Boxed heart round logs, Kerf treatment, Radio-frequency/vacuum drying, Surface check 1. INTRODUCTION The importance of wood as a building mate-rial and a renewable resource was increasing due to the growing concern of human health and well-being housing environment. Consequently, the gross wooden building area in Korea had largely increased in years past. The result of a recent investigation showed that both suppliers and users of wooden houses preferred the wooden house constructed traditionally with the post-beams with very large cross section, which