Nonstructural Product Line Certification: the Evolution of Shake-Table Testing To Satisfy International Building Code Requirements

Abstract eng:
This paper highlights the evolution of shake-table testing methods to satisfy IBC (International Building Code) compliance requirements for seismic certification of essential building equipment. The IBC is the model building code used in the United States, and elsewhere, that is linked to the ASCE/SEI 7 design standard (Minimum Design Loads for Buildings and Other Structures). In 2000 an International Code Council Acceptance Criteria AC156 (Acceptance Criteria for Seismic Certification by Shake-Table Testing of Nonstructural Components) was developed to correlate nonstructural lateral force demands with response spectra test requirements. For the last eighteen years, AC156 has been used across industry as an accepted test protocol to certify essential equipment to IBC nonstructural requirements. AC156 has been an enormous success in establishing a uniform compliance rating for equipment seismic capacity. However, seismic certification in the United States has reached a regulatory maturity level that has outpaced industry’s ability to maintain compliance when testing is conducted at the top-level of product assembly. Modern day mechanical and electrical equipment product lines will add and/or modify active subcomponents on a frequent basis. Retesting equipment to certify new or modified sub-components is simply cost prohibitive. The next logical step in equipment seismic certification is to evolve an ability to establish product capacity ratings at lower levels of product assembly. What is needed is a generic methodology where the nonstructural test unit can be either a toplevel building component / system, or can be lower-level product subsystems and subcomponents. The top-level products are referred to as “parent” product lines and the lower-level products are referred to as “child” product lines. The evolution of shake-table testing standards will need to include provisions to support testing of child products independent of the equipment parent they are contained. This would be a fundamental paradigm shift in nonstructural seismic certification. It is envisioned the long term ramification of this approach to equipment certification would be: increased number of products being tested, increased number of viable test labs to conduct testing, product testing performed upstream of the top-level equipment development activity, increased product resistance to earthquake loading, and a more cost effective certification strategy for industry implementation. Nonstructural seismic certification is a validation process to ensure that the nonstructural product’s capacity to resist motion and loading exceeds the motion and loading demand placed on it by the earthquake event. The nonstructural product represents a manufactured product line that encompasses a wide range of design variants within the product line family. Thus, the validation needs to be based on combining shake-table test results, from a subset of product samples (i.e., parent and child test units), with comparative assessment to the overall design variation. The introduction of a shake-table test standard which provides guidelines for establishing this certification process would be a major evolutionary step forward in increasing the confidence of compliance while reducing the single most significant barrier to code adoption and enforcement, the cost of implementation.

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