Bureau of Reclamation Banner

Technical Service Center
Materials Engineering and Research Lab

Where anchor bolts are used

Reclamation has built a number of dams that use large anchor bolts to support spillway gates. These bolts measure up to three inches in diameter and are over 10 feet long. Many of them were installed over 50 years ago. Having been in place for half a century or longer, it is imperative to find a non-destructive method to determine the load-carrying capacity of these bolts. No methods currently exist.

Large anchor bolts are also used on a wide variety of infrastructures besides dams including highway structures, electrical towers, large tanks, nuclear power-plants, foundations and in mining.

Large anchor bolts are used on a wide variety of infrastructures including dams, highway structures, electrical towers, large tanks, nuclear power-plants, foundations and in mining.

Highway projects

On highway projects, large anchor bolts are used to support steel beams, girders, trusses, and large road signs. These anchor bolts primarily provide support for wind loads. A significant issue is failure due to fatigue loading, ( Texas DOT Bridge Design Manual, December 2001). Fatigue strength is significantly lower than manufacture specified strength. In response to this problem, Florida DOT requires six to eight bolts to provide redundancy in case one of the bolts fails.

Towers

Large anchor bolts are also used to hold down power transmission towers and in radio tower reaction blocks. Two failures of note are a radio tower in Cedar Rapids and a parachute tower in Oklahoma.

Nuclear Power

The nuclear power industry uses large anchor bolts in a number of ways. With their higher quality control inspections, they have found anchor bolt problems including anodic corrosion occurring between zinc and steel in presence of water, known as hydrogen embrittlement (http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0933/sec3/029r2.html). They also found anchor bolts that had a significantly lower tensile strength than was specified by the manufacture (http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1986/in86094.html).

Storage Tanks

When holding down large tanks, large anchor bolts are also known as “tie-downs.” They are used to handle wind loads (Wind Loads and Anchor Bolt Design for Petrochemical Facilities, ASCE).

Mining and Foundations

Large anchor bolts used in mining and foundations as also known as rock anchors. Part of the anchor bonded to rock or concrete by cement grout, resin, or fixed by a mechanical anchor. The upper portion, or free length, is left un-grouted, but is grouted afterwards to provide protection against corrosion. They are used in retaining walls, tunnels, mines, slope stabilization, and rock fall protection.

Recorded failures

Reclamation has not found many references to structural failures directly attributed to large anchor bolts. We would appreciate your input to record structural failures from large anchor bolts.

Most of the recorded failures of rock have occurred in mining applications, primarily because failures in other locations are not visible.