Experimental and Numerical Investigations on Nozzle Reinforcements Available to Purchase

Pipes and nozzles attached to large liquid storage tanks can be susceptible to earthquake induced damages. Adequate design and detailing of shell nozzle reinforcements significantly improves their seismic performance. Damages to nozzles, often combined with elephant-foot-buckling, belong to the most frequent failure modes of large liquid storage tanks caused by earthquakes. The failure consequences depend very much on the liquid contents which may be hazardous; prevention of leakage is a crucial design and verification criteria. European and American standards provide detailed recommendations for structural dimensioning and detailing of shell nozzle reinforcements, however no reliable statements can be made to their seismic behaviour. This paper describes the results of six experimental tests on three typical types of shell nozzle reinforcements. These full scale tests were carried out in the range of ultra-low cycle fatigue for longitudinal and transverse load directions as they can be expected under seismic actions. Based on the evaluation of the test results appropriate FE-models were derived by which parametrical numerical investigations were conducted. Through these studies the influence of different parameters (e.g. thickness of shell plate, reinforcing plate, bottom plate etc.) on the seismic behaviour has been investigated. Finally recommendations for the dimensioning of nozzles reinforcements with particular attention to seismic resistance were developed.