I know why people look upon the crane runway as part of the Building and not part of the crane. Runways look like building steel, they're made with building steel, they're fabricated by building steel fabricators, and more often than not, they're installed by building steel erectors. But I caution this attitude will put you "at-risk" on anything but the most vanilla of projects. In other words, you will only be safe on crane projects in which all of the following conditions are met, including;

1. CMAA Class A, B or C

2. Fifty-foot span or less

3. Thirty-foot or less to top of runway rail

4. Twenty-ton or less capacity crane

I recently had a project in which I had to sit down and re-read the AISC Design Guide 7 section on crane runways. I must have read this a couple dozen times over the years, but for some reason, the first paragraph of Section 19 hit me like a ton of bricks;

Section 19: CRANE RUNWAY FABRICATION AND ERECTION TOLERANCES

Crane runway fabrication and erection tolerances should be addressed in the project specifications because standard tolerances used in steel frameworks for buildings are not tight enough for buildings with cranes. Also, some of the required tolerances are not addressed in standard specifications.

It's not that this position is new to me; I've been clumsily attempting to make this exact point for years, and for some reason, I've skimmed over this paragraph by Jim Fisher in Design Guide 7.

It's worth noting that this statement is not only published under the auspices of the AISC (American Institute of Steel Construction), but the author is Jim Fisher, the former Chairman of the AISC Specification Committee from 2003 until 2010, and the 2000 recipient of the AISC's Lifetime Achievement Award. In other words, Jim is a man worth listening to.

The following are the tolerances as set down by Jim Fisher in the AISC Design Guide 7, 2nd edition;

A) STEEL TOLERANCES FOR OVERHEAD CRANES AND CRANE RUNWAYS

1. Sweep: not to exceed ¼ inch in a 50-foot beam length.

2. Camber: not to vary from the camber given on the drawing by plus or minus ¼ inch in a 50-foot beam length.

3. Squareness: within 18 inches of each girder end the flange shall be free of curvature and normal to the girder web.

B) COLUMNS, BASE PLATES, AND FOUNDATIONS

1. Column anchor bolts shall not deviate from their theoretical location by 0.4 times the difference between bolt diameter and hole diameter through which the bolt passes.

2. Column base plates: Individual column base plates shall be within ±1 /16 inch of theoretical elevation and be level within ± 0.01 inch across the plate length or width. Paired base plates serving as a base for double columns shall be at the same level and not vary in height from one to another by 1 /16 inch.

C) CRANE RUNWAY GIRDERS AND CRANE RAILS SHALL BE FABRICATED AND ERECTED WITH THE FOLLOWING TOLERANCES

1. Crane rails shall be centered on the centerline of the runway girders. The maximum eccentricity of the center of the rail to the centerline of the girder shall be three-quarters of the girder web thickness. See illustration to the right side.

2. Crane rails and runway girders shall be installed to maintain the following tolerances. See the table below.

NOTES;

1. The horizontal distance between crane rails shall not exceed the theoretical dimension by ± 1⁄4 inch measured at 68 °F.

2. The longitudinal horizontal misalignment from straight of rails shall not exceed ± 1⁄4 inch in 50 ft with a maximum of ± 1⁄2 inch total deviation in the length of the runway.

3. The vertical longitudinal misalignment of crane rails from straight shall not exceed ± 1⁄4 inch in 50 measured at the column centerlines with a maximum of ± 1⁄2 inch total deviation in the length of the runway.

SUMMARY

In paragraph “C” above, it is essential to note that Fisher’s headline specifically calls out BOTH the "runway girders" as well as the "crane rails." In my forty-plus years' experience, this is the most frequent point of trouble. Because the runway girders usually are part of the building contract, they are fabricated and installed by the building contractor of standard building steel. As Jim Fisher states at the beginning of this article, "standard tolerances used in steel frameworks for buildings are not tight enough for buildings with cranes." This lack of sufficiently tight requirements for the crane runway girders spells trouble for the runway rail installer as well as for the useful life of the crane.

As J.C. Rowswell of the University of Toronto's Department of Civil Engineering determined;

Alignment of a runway is an exacting process; the proper alignment can add from 5 to 15 years of life to a runway.

By the same token, it can safely be said that bad runway design and alignment can chew up runway rail and crane wheels in less than a year. Further, if your runways are out of alignment your crane builder will refuse to honor their warranty, and justifiable so.