Determining parameters related to the likelihood of failure of red oak (Quercus rubra L.) from winching tests

Abstract

Key message This study provides data necessary to develop mechanistic models of the failure of opengrown trees. The literature contains few such data. Some results contrast previous studies on conifers. Abstract In cities and towns, tree failure can cause damage and injury. Few studies have considered large, open-grown trees when measuring parameters related to tree failure. To measure elastic modulus and maximum bending moment and stress, we winched red oaks (Quercus rubra L.), including some with co-dominant stems and others with extant decay. To simulate decay in a subsample of trees, we cut voids in the trunk before pulling trees to failure. Maximum bending moment was greatest for uprooted trees, but maximum bending and shear stresses were greatest for trees that failed in the crown in the vicinity of branches. The likelihood of failure at a void or area of extant decay increased as the loss in area moment of inertia increased. The moduli of elasticity and rupture of specimens taken from trees were greater than values measured on the trees themselves. Failure at the union of co-dominant stems only occurred when we pulled them apart, loading them perpendicular to the plane bifurcating the union. Some of the results are inconsistent with previous work on conifers; more data on open-grown trees are necessary to develop mechanistic models to predict tree failure.

Factors affecting branch failures in open-grown trees during a snowstorm in Massachusetts, USA

“…By convention (Smiley et al 2011 ), we considered weakly attached branches as those with a narrow attachment, included bark, visually similar diameters of branch and trunk, or a combination of these. Secondly, for most structural defects of trees, thresholds at which failure is more likely have not been established [see, for example, Kane ( 2014 )]. Regarding the most common defect we observed (weakly attached branches), previous studies have suggested that the strength of a branch attachment decreases (i) as the ratio of the branch and trunk diameters increases (Kane et al 2008 ) and (ii) with the presence of included bark (Smiley 2003 ), and these findings have been consistent among several species (Kane et al 2008 ).…”

“…Evaluating the severity of some defects, however, is still based largely on experience rather than empirical data. For example, there are very few studies that have quantified the breaking strength of stems of large, open-grown trees with and without defects (Kane and Clouston 2008 ; Kane 2014 ). In urbanized settings, tree failure can damage property and injure persons, which, in the United States, are sometimes associated with costly litigation (Mortimer and Kane 2004 ).…”

Determination of Strain Patterns Across the Root-Stem Transition Zone in Trees

“…While this work was on thin bark samples of 2-4 year old Quercus rubra (L.) stump sprouts, Dahle et al (In Review) believes that with the minimal loading taking place during our sampling, strain measurement with bark intact will be sufficient. Kane (2014) found in pulling tests that bark thickness may not be accounted for. However, Coutts (1983) reports that bark contributed little strength in roots.…”

“…However, to ensure that the likelihood of tree failure and tissue deformation is minimized, a specific bending moment is needed that will be compatible with the wood materials' Y (proportional limit) and within elastic domain for the tree species. Since there are few published values available for Y for large, open grown trees, (Kane et al 2014), bending moment and Y could be used in conjunction with root-plate tilt data to better quantify the movement of strain across the RSTZ. Brudi and van Wassenaer (2002) have proposed the following stress equation for nondestructive pulling trials, using a bending moment calculation to account for the height of the attachment and the circumference of the cross section of attachment.…”

Assessment of Unmanned Aerial Systems and lidar for the Utility Vegetation Management of Electrical Distribution Rights-of-Ways

“…In summary, although static pull tests and static biomechanics have aided our understanding of how trees handle loads, they use simplifying assumptions which may or may not accurately represent real world loading schemes (Niklas 1992, Hale et al 2010, Dahle et al 2017. For examples of static pull test studies, see: Kane 2014or Peterson & Claassen 2013.…”