Abstract
In China, preserving historic trees and ancient timber structures has attracted more attention from researchers and institutions. Nondestructive testing (NDT) technology has gained momentum in the application and research in recent years. This paper presents some examples of the application of NDT techniques in the protection of historic trees and ancient timber structures in China. A total of nine NDT techniques were applied, including five techniques of visual inspection, sounding, Resistograph, stress wave transmission velocity, stress wave tomography for both historic trees and ancient timber structures, two techniques of the pulling-test and ground-penetrating radar (GPR) for historic trees alone, and two techniques of acoustic emission (AE) and digital imaging for ancient timber structures. Based on field testing, there is a very good detecting effect for visual inspection and Resistograph, but sounding works unsatisfactorily. The stress wave transmission velocity is found to be excellent in screening for the internal defects of historic tree trunks, but performs badly in screening for the internal defects within the wood members of ancient timber structures. AE is less successful but digital imaging performs well in long-term monitoring and damage warning of wood structures. The stress wave tomography successfully obtains images of internal defects inside tree trunks. The anchorage of some historic trees cannot be quantitatively evaluated with the pulling test if the tree is too large. GPR’s resolution and accuracy are very low, which limit its application. Theoretical research on NDT and promotion of NDT technology are still an essential part of the work in the future.
Highlights
It is well known that China has countless historic trees and ancient timber structures, which leads to a great research value and application potential for nondestructive testing (NDT) technologies in preserving the historic trees and ancient timber structures in China
Some NDT techniques are available for the inspection of both trees and timber structures
There is an excellent effect of detection in the inspection of historic trees and ancient timber structures using visual inspection
Summary
It is well known that China has countless historic trees and ancient timber structures, which leads to a great research value and application potential for nondestructive testing (NDT) technologies in preserving the historic trees and ancient timber structures in China. The methods for testing the performance of components of ancient timber structures involve the probe detection method and wave detection method, and testing contents include internal defects and residual mechanical properties of the wooden components. In 2001, American scholars conducted a detailed inspection of a nearly 40-year-old wooden bridge on the Peshtigo River in Wisconsin, which included visual inspection, a stress wave transmission velocity method, and moisture content testing. Combining the results of visual inspection, Pilodyn, pullout resistance, and a stress wave transmission velocity method, the density and strength grading of each wooden member was determined. In 2015, Ross et al conducted a nondestructive evaluation of a scenic tower ( known as Eagle Tower) located in Peninsula State Park, Wisconsin, USA [43] This evaluation adopted a combination method of visual inspection, a stress wave transmission velocity method, and Resistograph, which revealed that the tower’s. By focusing on recent implementation cases of NDT methods for historic trees and ancient timber structures, this paper provides a brief overview of the utilization, development, and challenges of NDT methods for historic trees and ancient timber structures in China
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