Frequently Asked Questions

General

The route one takes through the Code [National Building Code of Canada] and Standard [CAN/CSA-S16-01] to arrive at the crane loading is confusing. Taking into account that CSA is a Standards Development Organization (SDO) and the NRC/IRC is a government agency (NBCC 2005 becoming the law once it is adopted by provincial statute), does the Guide supersede the NBCC and CSA-S16? - A.L.
7/1/2007

Here is a historical answer. You know, the kind of answer engineers like to hear! We'll call it a “work in progress”. Indeed, your question generated a long thread of discussion between Alfred Wong, Bob MacCrimmon, Richard Vincent, Mike Gilmor and myself. I have tried to provide an answer that reflects the situation at publication time! Basically, the winding route starts at Paragraph 24 (Part 4 Commentary A) of NBCC 2005 which refers to CSA-S16-01 for certain crane loading conditions. CSA S16-01 refers to Appendix C which is mandatory. Paragraph C2 of Appendix C refers to the “Guide“ - CISC Guide for the Design of Crane-Supporting Steel Structures by Robert MacCrimmon – available as a downloadable PDF from our web site: www.cisc-icca.ca/publications/technical/design/craneguide/

Normally, one would expect all loads to be treated in the NBCC rather than in a material design standard, but crane-supporting structures require supplementary rules and that is one reason why they cannot be treated like other structures. Thus, S16 is probably the most appropriate place to address the issue, as almost all crane runways are designed using S16. In fact, much of the minimum requirements found in NBCC 2005 date back to NBCC 1953. Incidentally, these minimum requirements are those stipulated for impact factors and for the horizontal forces as a function of the lifted load and the crane trolley. Other important considerations outlined in Appendix C of S16 and the Guide are not addressed.

Alfred Wong recalls that in the last code development cycle, the CSA-S16 Committee recommended NBCC 2005 drop these requirements and reference S16 that would mandate the CISC Crane Guide that was in development. At the end, the dated requirements remained in NBCC 2005 as published. Because the NBCC’s Part 4 Committee recognizes that this area needs attention, a task group, chaired by Richard Vincent, is looking into issues related to live loads, including crane loads. The Part 4 task group on Live Loads Due to Use and Occupancy has agreed in principle to refer to S16 for the load combinations involving cranes.

S16 has formed a subcommittee to study the load combinations including crane loads, and this subcommittee has  prepared the following draft for Appendix C, Clause C2.
 
C.2 Factored Loads for the Ultimate and Fatigue Limit States
The factored load combinations shall be taken as follows
 
CASE   PRINCIPAL LOADS  COMPANION LOADS
 1  1.4D  
 2  1.25D + 1.5C +1.0L  1.0S or 0.4W
 3  1.25D+ 1.5L=1.0C  0.5S or 0.4W
 4  1.25D + 1.5S  (1.0C + 0.5L) or 0.4W
 5  1.25D + 1.4W  (1.0C + 0.5L) or 0.5S
 6  1.25D + 1.0C7  
 7  0.9D + 1.4W   (0.5L + 1.0C) or 0.5S
 8  1.0D + 1.0E   1.0 Cd + 0.5L + 0.25S
 9   1.0D + C1  

where C is any one of the crane load combinations defined in the “Crane-Supporting Steel Structures Design Guide”, Second Edition, to be published by the Canadian Institute of Steel Construction, Cd is the dead load of all cranes positioned for maximum effect, C1 is the fatigue load, and C7 is the bumper impact load.

And since I often have something to add, those who use both French and English versions of CSA S16-01 should note that the French version states that Appendix C is not mandatory, which is a mistake. Appendix C is mandatory.