Deterioration of Dowel Bearing Properties of Timber due to Fungal Attacks Ali Awaludin, J.P. Gentur Sutapa – Universitas Gadjah Mada Kei Sawata, Tomonori Azuma, Mitsunori Mori – Hokkaido University SABH 2012 The 214 th Symposium on Sustainable Humanosphere International Symposium on Sustainable Development and Human Security in Southeast Asia through Biorefinery and Low Cost House Kyoto University, December

 Timber structures would experience deterioration during their service life.  Deterioration leads to a reduction of Strength, Stiffness, Structural integrity, and Service life of timber structures.  Deterioration of timber structures Mechanical loadings: creep (mechanosorptive-creep), overload at such extreme loads (earthquakes or winds) Environmental loadings: weathering, fungal attacks, termite attacks and aggressive marine environment. Introduction 2

Termite attacks Wood-decaying organism, Termite 3

4 Exposed wooden house

Exposed timber bridge structure 5

Fungal attacks  Condition for development of fungal attacks: nutrient (wood), air (oxygen), moisture, and temperature.  Deteriorated timber becomes soft – significant decrease of mechanical properties.  Previous studies used mass loss or decrease of specific gravity to predict strength loss of deteriorated timber. (Machek et al. 2001, Tsuomis 2003, Kent et al. 2005, and Sawata et al. 2008)  This study focused on dowel bearing properties of timber due to fungal attacks, Schizophyllum commune Fr. 6

Test methods  Deterioration here was assumed only at contact area between steel dowel and wood specimen – other wood surfaces were sealed.  Dowel bearing specimen followed ASTM D5764.  Steel dowel diameter – 12 mm.  Incubation period – six and twelve months  Wood species – Melia azedarach (SG – 0.52), Swietenia mahagoni (SG – 0.51), and Pterospermum javanicum (SG – 0.61). 7

Test photos – Clear specimens Melia azedarach Swietenia mahagoni Pterospermum javanicum 8

Test photos – Inoculated specimens 9

Results and discussions  Wood exposed to wood-decaying fungus had a significant increase of moisture content. Therefore, all dowel bearing strength test data was normalized to 12% moisture content as following equation. MC<= 28% MC> 28% 10

Results and discussions  Mass loss measurement Mass loss increases as incubation period is prolonged. Mass loss of Pterospermum javanicum samples is the lowest among the three species. (a) Melia azedarach (b) Swietenia mahagoni(c) Pterospermum javanicum 2.25% 1.45% 5.90% 1.73% 7.86% 4.28% 11

Results and discussions  Dowel bearing strength parallel-to-grain evaluation Decrease of bearing strength was observed as incubation period is extended. Average reduction of dowel bearing strength is indicated below where Melia azedarach samples had the greatest reduction among the three species. (a) Melia azedarach (b) Swietenia mahagoni(c) Pterospermum javanicum 29% 10% 33% 18% 40%24% 12

Results and discussions  Dowel bearing stiffness evaluation The stiffness is defined as the slope of a line passes through on the bearing curve corresponding to 10% and 40% of the maximum load. Decrease of bearing stiffness is well observed in Swietenia mahagoni samples. However, this decrease is fairly observed in the other wood species. (a) Melia azedarach (b) Swietenia mahagoni(c) Pterospermum javanicum 13

Conclusions  Dowel bearing strength tests was conducted on three wood species (Melia azedarach, Swietenia mahagoni and Pterospermum javanicum) exposed to wood-decaying fungus, Schizophyllum commune Fr, for six and twelve months incubation period.  Reduction of dowel bearing strength caused by the fungus differed according to wood species and incubation period.  Among the three wood species considered here, the least bearing strength reduction was observed in Pterospermum javanicum specimens.  A remarkable strength reduction was found in Melia azedarach samples.  As this significant bearing strength reduction was potentially related to a small percentage of mass loss, detection and monitoring activities at early stage of fungal attacks is most important. 14

Thank you for listening 15