68 tion compare to other fasteners, and what is the impact on the tree of having a flexible cable running through the branch? This study had two components: a field evaluation of dead-end stop terminated cables in large trees and a strength evaluation of small diameter cable systems using static pull testing. The overall goal of the project was to evaluate dead-end stop terminated cables for use in landscape trees. MATERIALS AND METHODS Field Study In July 2005, 20 supplemental support cables were installed in six species of trees on a hillside garden at the Bartlett Tree Research Laboratories in Charlotte, NC, U.S. Trees in the trial had two or three codominant stems with junctions within 1 m of the ground. One or two cables were installed in each tree. Cable used was a seven strand EHS cable, 0.48 cm (3/16 inch) diameter with a listed breaking strength of 17.8 kN. EHS cable of this diameter is recommended for branches up to 20 cm in diameter (Smiley and Lilly 2007). The cable was either terminated with a manu- factured grip (Preformed Line Products, Mayfield Village, OH, U.S.) and a heavy duty thimble that was anchored to the tree us- ing a 1.2 cm (1/2 inch) diameter eyebolt, or the cable was inserted through the tree and fastened with a Wire Stop 301 dead-end, wedge and ferrule, stop type fastener (RigGuy Inc., Athens, GA, U.S.). Ten trees with codominant stems in the same area were retained as control trees without cables. Tree species and treat- ments were willow oak (Quercus phellos) 1 eyebolt, 1 no cable; red oak (Q. rubra) 2 Wire Stop, 3 eyebolt, 4 no cable; white oak (Q. alba) 4 Wire Stop, 4 eyebolt, 3 no cable; blackgum (Nyssa sylvatica) 1 Wire Stop, 1 eyebolt, 3 no cable; hickory (Carya spp.) 1 eyebolt; and red maple (Acer rubrum) 2 Wire Stop, 1 no cable: Tree heights ranged from 19 to 26.5 m. Mean branch di- ameter at the point of cable attachment was 16.1 cm (SD = 1.06). Trees, cable, and cable terminations were visually inspect- ed and measured on March 5, 2010. Factors evaluated includ- ed cable or branch failure, presence of visually apparent rust or other damage to the cable, degree of cable or anchor over- growth by the tree, and evaluation of the hole that was drilled for the eyebolt or cable insertion. If there was an enlargement of the drilled hole, the hole was measured across the largest axis, from edge to edge. Initial hole diameter was subtracted from the measurement to provide a hole enlargement size. That number was averaged for all of the holes that were enlarged. Static Breaking Tests The static breaking strength of seven different cable attachments were compared when fastened to branch sections of two tree spe- cies. Detached, 2.5 to 9.0 cm diameter branch or trunk sections were harvested one to three days prior to testing and were in “green condition” at the time of the test. Test species were willow oak (Quercus phellos) and Virginia pine (Pinus virginiana). Oak samples were from five different trees and pine samples were from 15 trees, data was blended for analysis. Branch diameter was measured in-line with the hole drilled for the anchor or cable. Cable attachments tested were (Figure 2): 1) Screw eye: A 5.8 mm (nominal 1/4 inch) diameter bent eye lag (number 4, 5.5 cm, 2 3/16 inch long), installed in a 0.48 cm ©2011 International Society of Arboriculture Figure 1. Wire Stop 301 dead-end, wedge and ferrule, stop type fastener (RigGuy Inc, Athens, GA, U.S.) installed in a small branch. Smiley: Dead-end Stop Terminated Tree Support Cable Systems Figure 2. Cable systems that were evaluated using a static pull test. From left to right: double swage stop with washer, single swage stop with fender washer, single swage stop with washer, single swage stop without washer, eyebolt, welded eye lag, eye lag (not inserted in branch). diameter hole that was drilled to a depth of approximately 19 mm. The full depth of the threaded portion of the lag was screwed into the branch. The cable was attached through the eye with a 5 cm loop of cable secured with an oval swage connector. 2) Welded screw eye: A 5.8 mm (nominal 1/4 inch) diame- ter bent eye lag (number 4, 3.5 cm, 2 3/16 inch long) that had the eye welded closed, installed in a 0.48 cm diameter hole that was drilled to a depth of approximately 1.9 cm. The full depth of the threaded portion of the lag was screwed into the branch. 3) Eyebolt: A 5.8 mm (nominal 1/4 inch) diam- eter drop forged galvanized steel eyebolt was installed through a 6.3 mm diameter hole that was drilled entire- ly through the branch. An 18.7 mm O.D., 7.7 mm I.D., 1.6 mm thick washer and nut was used to secure the bolt. 4) Single swage stop, no washer: A copper or alu- minum swage stop was fastened to the dead end of a stainless or galvanized steel cable after it was insert- ed through a 0.40 cm diameter hole. A swaging tool (HIT 350-3, Japan) was used to crimp the swage stop. 5) Single swage stop with washer (Figure 3): A cop- per or aluminum swage stop was fastened to the dead end of a stainless or galvanized steel cable after it was insert- ed through a 0.40 cm diameter hole and a 1.12 cm O.D., 0.45 cm I.D., 0.9 mm thick (number 8) round, flat, stain- less steel washer. The swage stop was securely crimped.
March 2011
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
