Examples of proper testing
Often, load tests can only approximate the actual loads a structure may experience. Still, with comprehensive planning along with careful implementation, proper load-testing of façade access equipment can often be performed.
Figure 2 shows a davit base being load tested by a hydraulic ram pushing upward off the roof structure against a long inward-pointing beam provided for this purpose. By creating a moment toward the side of the building, it mimics the overturning demand that would be caused by a work platform suspended over the side of the building. Deflections of the equipment were carefully monitored during the load test, and the load test ensured the results were repeatable.
Figure 3 shows the load-testing of a fall-arrest/tie-down anchorage. In this case, the load is being applied toward the edge of the roof to match one of the potential directions for a fall-arrest load. Since fall-arrest loads could come from a number of directions, this anchorage was also pulled toward the adjacent edge of the building just out of view on the left side of the photo. Loads were applied several times to verify the results were repeatable.
Figure 4 shows a davit being load-tested. The load is applied downward at the tip of the davit, simulating the demand from a suspended work platform. Load-testing of the carriage and the rails supporting the davit was accomplished separately via a cantilever loading beam similar to that shown in Figure 2.
Conclusion
Although the aforementioned September 2016 article from The Construction Specifier may have been intended to highlight the importance of properly load-testing façade access equipment, these authors feel a number of technical inaccuracies and other misinformation undermined its stated purpose. Engineers conducting or specifying load tests of this type of equipment must fully understand both fundamental engineering principles and the requirements governing such testing. Failing to understand the requirements, or basing certifications on inappropriate testing, may result in equipment users experiencing excessive risks.
OSHA regulations form the basis for numerous code requirements related to the design of this type of equipment contained in the 2015 IBC and ASCE 7-16. In addition, AISC 360 and ACI 318 govern key issues related to design and testing of elements constructed of steel and concrete. By the IBC and ASCE 7-16 restating some design requirements in more familiar form, they can bring clarity to engineers who may struggle with the unorthodox wording of the various OSHA regulations.
For design professionals specifying new or replacement equipment, this article’s authors recommend the following:
- Require hoist-supporting elements (e.g. davits, outriggers, rooftop carriages, and tiebacks and their structural supports) be designed elastically or essentially elastically to support the loads provided in Section 1607.9.3 of the 2015 IBC when multiplied by the required live load factor of 1.6.
- Require fall-arrest/lifeline anchorages and their supports be designed elastically or essentially elastically to support the loads provided in Section 1607.9.4 of the 2015 IBC when multiplied by the required live load factor of 1.6.
- Require all façade access equipment be load-tested to satisfy OSHA requirements prior to initial use. Testing should be performed according to Section 1708 of the 2015 IBC, Section 5.4 of Appendix 5 of AISC 360-10, and Section 27.4 of ACI 318-2014, using the full factored loads required by the 2015 IBC and ASCE 7-16. Equipment should be required to show no evidence of significant deformation or failure during the test or upon removal of the test load.
Although the recommendation that façade access equipment remain elastic (or essentially elastic) may exceed the minimum requirements of IBC and OSHA, it should result in a design that facilitates any load-testing that may be required, particularly in the event that the equipment’s ability to sustain the required loads is ever in question.
While this article highlights key aspects of façade access design and testing, the topic is too complicated to fully cover here. Interested readers can find a comprehensive discussion of this topic in ASCE’s Façade Access Equipment: Structural Design, Evaluation, and Testing.
Richard A. Dethlefs, PE, SE, is a principal at Wiss, Janney, Elstner Associates (WJE), with 22 years of experience. Dethlefs has designed, tested, and certified façade access systems for over 100 buildings. He can be reached at rdethlefs@wje.com.
Howard J. Hill, PhD, PE, SE, is a senior principal and director of project operations at WJE, with more than 34 years of experience in the evaluation and design of structural elements and systems. He can be contacted via e-mail at
hhill@wje.com.
Leonard M. Joseph, PE, SE, is a principal at Thornton Tomasetti Inc., with 42 years of experience designing structures for varied buildings around the world, from sports facilities to skyscrapers, using steel, concrete, masonry, and timber. He can be reached at ljoseph@thorntontomasetti.com.
Jonathan E. Lewis, SE, is an associate principal at WJE. He has evaluated fall protection issues and façade access equipment at dozens of buildings in multiple states. Lewis can be e-mailed at jlewis@wje.com.
Karl J. Rubenacker, PE, SE, is a partner at Gilsanz Murray Steficek LLP. Having designed structures on both the East and West Coast, he is the lead engineer for a diverse portfolio including new construction and restoration projects. Rubenacker can be reached at karl.rubenacker@gmsllp.com.
Gwenyth R, Searer, PE, SE, is an associate principal at WJE. She has 23 years of experience, and has evaluated, designed, and tested numerous façade access installations. Searer can be e-mailed at gsearer@wje.com.
