Seismic Demand on Sprinkler Piping Systems: Findings from a Shake Table Testing Program and Relevance to NZ Standards

Abstract

Fire sprinkler piping systems have intricate layouts on building floors that lead to complex distribution of demands in various segments of the system during an earthquake. The New Zealand Standard (NZS) 4541: Automatic Fire Sprinkler Systems [2020] requires sprinkler systems to remain operational at the design limit state and provides a set of empirical analysis and design rules.

One vital requirement to achieve a certain seismic performance is a reliable estimation of seismic demands. This paper aims to advance the understanding in the estimation of seismic demands on sprinkler systems to improve the reliability of designs. This objective has been achieved by conducting shake table testing on sprinkler systems typical of New Zealand practices. The investigations demonstrate that seismic demands on piping systems are significantly affected by the dynamic characteristics (period & damping) of the system as well as the frequency content of the floor excitation in addition to its intensity.

Scrutiny of the test data reveals the inadequacy of design provisions in NZS 4541 [2020], such as requirements for brace forces and clearance, due to a lack of consideration for dynamic characteristics, frequency content of the floor excitation and the shaking intensity. The tests also provided valuable information on the influence of gravity supports on the dynamic response of the system and their vulnerability to failure under horizontal seismic excitation. Based on the reported findings, recommendations are provided for essential improvements to NZS 4541 [2020] to enhance the reliability of designs conducted in accordance with it.