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Repair or Replacement of Damaged Anchor Bolts

Description:

Anchor bolts are vital components that provide stability for structures when properly connected to their foundations. Anchor bolts for light poles and signal structures are frequently damaged due to vehicular collision or due to forces induced by storms when wind speeds are in excess of 90 mph. They may also sustain corrosion damage above the foundation concrete, although the steel within the concrete may be still intact or only sustain minor section loss. Rather than completely abandon the damaged anchor bolt and install replacements that may require relocation to a new foundation, repair of the damaged anchor bolts may prove more cost effective and decrease the time the structure is placed back in service or refurbished. However, no actual study of equivalency of the various anchor bolt repair methods has actually been conducted. This includes their equivalent load-carrying capacity, their fatigue properties if subject to varying load cycles, or their ease of repair.

Objective:

The objective of this research is to compare various anchor bolt repair methods and their structural integrity. This comparison must include actual differences in repaired F1554 steel anchor bolts in terms of their yield and tensile strength, strain capacity, and their fatigue strengths in tension and rotating bending. Impact toughness properties at different temperatures for the various anchor bolt repair methods would also be determined. This research would provide transportation engineers which are the most effective repair methods for damaged or corroded bolts used to anchor light poles, bridge bearings or various roadside hardware.

Benefits:

* SCOBS global focus : *Enhance maintenance or repair efforts; minimization of traffic disruption.


SCOBS prioritized objectives:

  1. Determine the properties of anchor bolt repair methods.

  2. Provide for rapid repair of existing damaged anchor bolts in comparison to a new foundation and relocation of anchor bolts that would require greater costs and delay, minimizing safety hazards and traffic disruption.

Related Research:

Internet searches indicate that only a limited number of methods are used to repair damaged anchor bolts. These include (a) welding methods, (b) the use of various types of mechanical couplings, and (c) heating. Welding methods are recommended by AISC. The first method describes the use of a full penetration weld whereby the damaged section is cut off flush and the replacement bolt end is cut to a near point and then welded with shielded metal arc electrodes. A second welding method attaches two side plates to the damaged bolt and the new bolt is then fillet-welded on each side. AISC does not recommend welding F1554 Grade 105 quenched & tempered anchor bolts; however, Grade 36 and Grade 55 bolts are weldable. Mechanical couplings are used when threads are available or threads are cut onto the damaged anchor bolt with dies. US Patent 5,163,775 describes a special coupling which employs both threads and wedges for the unthreaded shanks of anchor bolts. Couplings which have “sight holes” are purported to be most beneficial because they disclose sufficient thread engagement. Other couplings, such as those used for joining of rebars, can be used. If the couplings are not threaded (called “sleeves”) but each end is fillet-welded, there must be sufficient weld throat sectional area to carry the intended anchor bolt loadings. Heating to re-bend the anchor bolt is the least desirable because of metallurgical changes, especially for quenched & tempered anchor bolts made of either SAE 4140 or 4340, the most commonly used alloys. If excessive heat and temperatures are applied, the yield strength can be altered and excessive grain growth can decrease impact and fracture toughness.

Sponsoring Committee:AKC70, Fabrication and Inspection of Metal Structures
Research Period:24 - 36 months
Research Priority:Medium
RNS Developer:Christopher Hahin, MetE, CorrE, PE, Illinois DOT, Bureau of Materials
Date Posted:06/09/2020
Date Modified:06/15/2020
Index Terms:Anchor bolts, Repairing, Bearing capacity, Fatigue (Mechanics),
Cosponsoring Committees: 
Subjects    
Highways
Maintenance and Preservation
Materials
Bridges and other structures

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