Method for testing wind-induced torque and shearing elastic modulus of tree

Abstract

Disclosed is a method for determining a wind-induced tree torque and a trunk shearing elastic modulus. Crown deflecting trees will generate torsional cracks and damage under the action of a strong wind. In order to prevent tourists and pedestrians from injury caused by urban street trees or ancient garden trees, people need to know anti-torsional stiffness of the trunk and the relationship betweena wind-induced torque and a wind speed so as to take preventive measures in time. The determination of the wind-induced tree torque is achieved by the steps of: arranging a pair of cross-stacked displacement sensors on the trunk of a standing tree at an angle of + / -45 degrees with respect to an axial direction of the trunk as shown in the figure; establishing a relationship between maximum tangential strain and a wind speed under the condition of a strong wind; establishing a relationship between a torque and the maximum tangential strain that Mn = F.e = g (gamma LT) by applying an eccentricpulling force under a windless condition; and obtaining an equation for wind-induced tree torque characteristics by combining the two equations above. The determination of the standing tree shearing elastic modulus is achieved by the steps of: arranging the displacement sensors as shown in the figure as well; applying an eccentric pulling force F and reading the shearing strain values gamma LT, 1and gamma LT, 2 when the pulling force is F1 and F2; and calculating the shearing elastic modulus.

Description

technical field [0001] The invention belongs to the field of forest safety protection and relates to an experimental method for measuring wind-induced tree torque and shear elastic modulus of standing trees. Background technique [0002] Wind disasters often cause serious damage to forest resources and forestry production, and urban street trees and ancient garden trees will also break due to this, endangering the lives of pedestrians and tourists. [0003] Partial-crown trees are often twisted and cracked before losing their overall rigidity under the action of strong winds, and then broken. In order to evaluate the damage of trees against wind torsional fracture, it is necessary to quantify the torque formed by wind pressure on the canopy, that is, to build the relationship between tree torque and wind speed. [0004] The wind torque formed by the wind pressure on the tree will be affected by many factors such as the shape and size of the canopy, the characteristics of th...

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Problems solved by technology

Before this, there was no research report on how to measure the torsional shear strain of tree trunks.

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