木質構造建築構件火災災後調查與抗彎性質評估－－以溪頭青年活動中心為例

Investigation on the Wooden Structure Member and Bending Properties Evaluation after Fire Damaged-A case study for Xitou youth activity center

本研究以救國團溪頭青年活動中心之木結構建築為例，探討火災被害材之強度性質，以及利用非破壞檢測技術評估受害材之抗彎性質之可行性。結果指出，火災被害材經鑑定結果發現，該木質結構體之樑體為柳桉木（Lauan, Shorea spp.）與冰片木（Kapur, Dryobalanops spp.），而柱體則為柳杉（Japanese cedar, Cryptomeria japonica）。經強度試驗及與文獻資料比較後指出，柳桉木火災被害材之抗彎強度保留率與抗彎彈性模數保留率各為65.4%與91.5%；冰片木火災被害材之抗彎強度保留率為50.5%，而抗彎彈性模數保留率為67.6%；柳杉火災被害材之抗彎強度保留率約為59.9%，抗彎彈性模數保留率則約為44.6%，至於抗壓強度則較無顯著影響。另利用超音波法與打音法兩種非破壞檢測技術評估火災被害材之抗彎性質指出，以超音波動彈性模數與打音動彈性模數評估抗彎彈性模數與抗彎強度，其R2 值分別為0.95與0.71-0.72，顯示良好之正相關性，因此可利用此法評估火災被害材之強度性質，以作為將來評估其再利用之可行性參考。 This study was to investigate the strength properties of the fire-damaged wooden structural members and evaluate those bending properties using nondestructive testing. The fire-damaged wooden construction materials were selected from Xitou youth activity center, Nantou County, Taiwan. Three species, Lauan (Shorea spp.), Kapur (Dryobalanops spp.) and Japanese cedar (Cryptomeria japonica) could be identified form beam and column structure, respectively. Results indicated that modulus of rupture (MOR) retention for fire-damaged Lauan, Kapur and Japanese cedar lumber were 65.4%, 50.5% and 59.9%. Additionally, the modulus of elasticity (MOE) retention for those were 91.5%, 67.6% and 44.6%, respectively, and it seemed that there was no significant effect on compression strength between normal wood and fire-damaged wood. Furthermore, it was found that there were well correlations between static bending properties and dynamic modulus of elasticity (DMOEu and DMOEt, which were calculated from ultrasonic wave and tap tone method, respectively). R2 value was 0.95 and 0.71-0.72 for MOE to DMOEu and DMOEt, and MOR to DMOEu and DMOEt, respectively. Therefore, these types of nondestructive techniques could be used to evaluate the bending properties of fire-damaged wood.