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RE: OSHA 4-bolt column anchorage

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* Standard Number: 1926.755(a)(1); 1926.755(a)(2); 1926.752(b) 

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OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at http://www.osha.gov. 


May 27, 2004 

Mr. L. Carlos Garcia
Project Manager
Urban Associates LP
1400 Geronimo
San Antonio, TX 79925 

Re: Under Part 1926 Subpart R, is it permissible to field-weld a column to a base plate that has four anchor rods welded to its bottom side and is already embedded in the footing? 

Dear Mr. Garcia: 

This is in response to your telephone call of March 24, 2004, to the Occupational Safety and Health Administration (OSHA) in which you ask about the requirements for securing a column to a foundation under 29 CFR Part 1926 Subpart R (Steel Erection). Wehave paraphrased your questions below: 

Question (1): This question has to do with a procedure for erecting steel columns on concrete footings. The scenario is as follows: A steel base plate with four ½" diameter headed studs welded to its bottom side is embedded in a concrete footing. Once the concrete meets the strength specified in Part 1926 Subpart R, the steel column is lowered by crane onto the base plate. While still attached to the crane, the column is braced in two directions (i.e., east-west and north-south). The column is then attached to the plate with a continuous ¼" weld. After the column is field welded, employees in aerial lifts will remove the crane hook and guy wires. 

 
Section 1926.755(a)(1) requires four anchor rods. Is it permissible under §1926.755 to use this installation procedure? 

Answer: 

Section 1926.755 "Column Anchorage" states: 
(a) General requirements for erection stability. (1) All columns shall be anchored by a minimum of 4 anchor rods (anchor bolts). 

(2) Each column anchor rod (anchor bolt) assembly, including the column-to-base plate weld and the column foundation, shall be designed to resist a minimum eccentric gravity load of 300 pounds (136.2 kg) located 18 inches (.46 m) from the extreme outer face of the column in each direction at the top of the column shaft. * * * 
The intent of §1926.755(a)(1) and (2) is to ensure the stability of a column during the erection process. These hazards are addressed in part by the requirement that the column be "anchored by a minimum of 4 anchor rods." 

However, §1926.755(a)(1) does not specify the manner in which the four anchor rods must be attached to the column. So long as the column anchoring system meets the strength criteria in (a)(2) and has four anchor rods, the assembly meets the requirements of §1926.755(a)(1). 

In your scenario, the four anchor rods are pre-attached to the base plate, and that assembly is embedded in the concrete footing. Once the concrete has reached the strength required under §1926.752, the column is placed on the steel plate, and pre-attached guy wires are used to brace it. The column is then field welded with continuous weld to the embedded base plate. At that point the column is anchored to the footing with four anchor rods. The requirement in §1926.755(a)(1) is thus met once the column is welded to the base plate. So long as the column in your scenario, after the anchorage assembly is completed, can resist a 300-lb. eccentric gravity load in all directions, the column anchorage will satisfy the stability requirements of §1926.755(a)(1) and (2). 

If you need additional information, please do not hesitate to contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax # 202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail. 

Sincerely, 


Russell B. Swanson, Director
Directorate of Construction




-----Original Message-----
From: Charley Hamilton [mailto:chamilto(--nospam--at)uci.edu] 
Sent: Monday, February 06, 2006 12:43 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: OSHA 4-bolt column anchorage

Dave -

Bill is right:  it's a federal OSHA ruling.  As far as I
understand, there are no exceptions in 29 CFR 1926.755.
The rule can be found here:

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=12746

Take a look at osha.gov and search for "base plate anchorage".
It brings up quite a bit of info about the why's and wherefore's
of the 4-bolt rule.  For example:

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=FEDERAL_REGISTER&p_id=16290

Scroll down to "Section 1926.755 Column Anchorage" and you can see some of the 
testimony that was offered.

Personally, I suspect it would be greater total cost to go to
(e.g.) two bolts and guying to provide stability than to simply
design in the four bolts from the get-go.  Adding a process (guying
and un-guying each column) to the erection seems like it would add
cost, mostly through labor.  You might save a bit on the labor of
installing half the anchor bolts, but that seems like less labor to
me than installing and removing the guys.  Also, it seems that the
guys could potentially be in the way during erection of the girders.

Just my $0.02,

Charley

-- 
Charles Hamilton, PhD EIT               PGR
Department of Civil and                 Phone: 949.824.3752
     Environmental Engineering           FAX:   949.824.2117
University of California, Irvine        Email: chamilto(--nospam--at)uci.edu




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