Testing to 100 percent of the minimum required strength
If load-testing is performed to 100 percent of the minimum required strength and the equipment successfully holds the minimum required loads, the tester (and users) can be confident the equipment has the minimum required strength. Successfully passing the test load includes confirming the tested element did not suffer damage during the test (e.g. significant yielding, cracking, or fracture).
Unfortunately, not all equipment can be load-tested; some equipment is designed such that it must develop significant inelastic deformations in order to resist the minimum required loads. In these instances, load-testing may not be an option, and other methods may need to be employed if the capacity of the equipment is
to be verified—however, even in this situation, load testing to only half the required capacity is clearly not an acceptable means of verifying the capacity of the element.
IBC load test requirements
Where the 2015 IBC has been adopted, Section 1708 governs in-situ load tests. Where load-testing requirements are not specified by the appropriate materials standard (e.g. components constructed of wood, which employ a design standard that does not include provisions for in-situ testing), Section 1708.3.2 requires the minimum load applied during the test to be the factored design load. For davits, outriggers, and their supports, the factored design loads—and therefore the minimum test loads—are the greater of the two loads shown below:
- 4.0 times the rated load of the supported
hoist; and - 1.6 times the stall load of the supported hoist (which equates to 4.8 times the rated load of the hoist if the stall load is 3.0 times the rated load or is unknown).
For fall-arrest anchorages, the factored design load—and therefore the minimum test load—is 1.6 x 13.8 kN (3100 lb), or 22.1 kN (4960 lb).
Where load tests are specified by an IBC-referenced material standard (e.g. components constructed of steel or concrete), Section 1708.3.1 requires load testing be conducted according to the provisions of that standard, as described below.
AISC load test requirements
Load-test requirements for steel structures are provided in Section 5.4 of Appendix 5 of American Institute of Steel Construction (AISC) 360-10, Specification for Structural Steel Buildings. Like IBC, the load test provisions require the factored load be applied. As the load factor for live loads is 1.6, the net result is identical to IBC.
ACI load test requirements
Load-test requirements for concrete structures are provided in Chapter 27 of American Concrete Institute (ACI) 318-14, Building Code Requirements for Structural Concrete. ACI requires the magnitude of the load test be determined using a live load factor of 1.5. In the case of davits, outriggers, and their supports, the minimum test load can be calculated as the greater of the following:
- 1.5 x 2.5 times the rated load of the supported hoist = 3.75 times the hoist’s rated load hoist; and
- 1.5 times the stall load of the supported hoist (which equates to 4.5 times the rated load of the hoist if the stall load is 3.0 times the rated load or is unknown).
For reinforced concrete components of fall-arrest anchorages and their supports, the minimum test load can be computed by multiplying the live load factor of 1.5 times 13.8 kN (3100 lb), which equals 20.7 kN (4650 lb).
These values are within six percent of the test loads required by AISC and IBC, which is a negligible difference.
Voluntary standards
International Window Cleaning Association (IWCA) I14.1, Window Cleaning Safety, and American Society of Mechanical Engineers (ASME) A120.1, Safety Requirements for Powered Platforms and Traveling Ladders and Gantries for Building Maintenance, are two voluntary standards often cited by engineers justifying testing to only 50 percent of the minimum required strength. However, neither of these two voluntary standards can supersede the requirements of mandatory standards. More importantly, both documents have significant technical flaws.
The IWCA I14.1 standard was published only once, in 2001. Concerns about technical issues in the standard were pointed out numerous times by this article’s authors, as well as other engineers and the National Council of Structural Engineering Associations (NCSEA), but the committee never addressed and incorporated the comments into an updated standard.
As the standard had not been maintained or updated for more than a decade, the American National Standards Institute (ANSI) administratively withdrew it in 2011. Further, ANSI suspended IWCA’s accreditation for cause in 2012, then took the unusual step of permanently withdrawing IWCA’s accreditation in 2016, citing “repeated serious procedural and administrative concerns… including but not limited to unreasonable restrictions on consensus body membership and failure to properly process public review comments, substantive changes, and appeals.” For these reasons, this document should not be relied on for technical information.
Many of the members of the de-accredited IWCA committee are also members of the ASME A120 committee. In 2010, that committee proposed restrictions on load testing of façade access support elements to no more than 50 percent of the minimum required capacity—restrictions essentially identical to those in IWCA I14.1. Like the IWCA committee, the A120 committee is dominated by individuals without engineering degrees or licenses. Although a large number of public comments were provided objecting to the proposed changes, the test limits were adopted into the 2014 edition. Fortunately, A120.1 is only a voluntary, advisory standard. Unfortunately, some engineers do not appreciate or understand its various shortcomings, including contradicting codes and standards that are legally required to be used.
