JZUS - Journal of Zhejiang University SCIENCE

Journal of Zhejiang University SCIENCE A 2015 Vol.16 No.7 P.541-550

Research on residual bending capacities of used wood members based on the correlation between non-destructive testing results and the mechanical properties of wood

Author(s): Jin Zhang, Qing-feng Xu, Yi-xiang Xu, Ming Zhang
Affiliation(s): Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast University, Nanjing 210096, China; more
Corresponding email(s): zhangjin0622@139.com
Key Words: Used wood members, Non-destructive testing (NDT), Mechanical test, Residual bending capacity

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Abstract: To quantitatively assess the residual strength of wood members after rot and infestation using non-destructive testing (NDT), the multi-point Resistograph method was applied to test six used wood beams with initial imperfections. Each wood beam was then divided into a shorter segment for mechanical tests and a longer one for bending capacity tests. With the help of finite element analysis using ANSYS, bending capacity is predicted by taking account of the initial imperfections. Results show that there is a significant correlation between drill resistance values and strengths for small specimens. Therefore, the strengths of wood at other measurement points may be obtained through drill resistance values. The beams showed a near linear behaviour up to the maximum load with poor ductility performance in bending capacity tests. It can also be found that the effects of initial imperfections on failure modes and ultimate loads are significant. The lateral side of specimen BA1 has serious infestation and the bottom of BA2 has a long longitudinal crack, the ultimate bearing capacities of these specimens are respectively only 67.6% and 64.8% of BA3, which has fewer cracks. BB1 and BB3 have knots at the bottom and their ultimate bearing capacities are respectively 83.9% and 81.0% of BB2, which has fewer cracks as well. Furthermore, there is quite good agreement between test results and numerical prediction using strength values obtained by NDT results. Therefore, the bending capacity of used wood beams can be obtained using NDT, which can provide the basis for the protection and retrofitting of wood structures.

The paper deals with the correlation between mechanical testing and results obtained through drilling resistance measurements. Further, a finite element model is considered with information obtained from those correlations, obtaining reasonable results for the field of timber engineering analysis. The methodology is based on common practices and the results are consistent with what could be expected. Although the methodology's concept is well known in the field of timber engineering, the increased value of the paper resides in the use of the drilling resistance test correlations in defining different strength sections along the timber element, as well as the introductions of initial imperfections in the model.

基于无损检测与木材力学性能相关性的既有木构件剩余抗弯承载力研究

目的：利用无损检测的方法，定量评估经腐朽和虫蛀后的既有木构件的剩余抗弯承载力。
方法：1.通过对木材小试件进行阻抗仪检测试验和材性试验，建立木材阻力值与抗压/抗拉强度之间的线性回归方程；2.对大段木梁试件进行阻抗仪检测试验，基于木材阻力值与抗压/抗拉强度之间的关系，计算得到大段木梁各部分的强度值；3.在Abaqus中对既有木梁的初始缺陷进行模拟并将木梁的计算强度值赋予木梁的各个部分，综合分析木梁的剩余抗弯承载力。
结论：1.木材小试件的阻力值与抗压/抗拉强度值之间呈现出显著的相关性，各测点处的木材强度值可通过阻力值计算得到；2.虫蛀、木节和裂缝等初始缺陷对试件的破坏形式和极限荷载影响显著；3.非线性仿真分析所得的结果与试验结果基本吻合。

关键词：既有木构件；无损检测；力学试验；剩余抗弯承载力

Reference

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