Structural safety of industrial steel tanks, pressure vessels and piping systems under seismic loading (INDUSE)
Liquid storage tanks, pressure vessels and industrial piping are steel structural systems, present in all industrial facilities (chemical and petrochemical industries, and power plants). Safeguarding their structural integrity against earthquakes constitutes a key issue towards increased safety and unhindered operation of the industrial facility. Their structural behaviour, and in particular seismic design, is quite different than steel buildings and has several particularities, requiring a combined civil and mechanical engineering expertise. The particularities stem from their shape and... geometry, the presence of high internal pressure, and the dynamic behaviour of the enclosed liquid, which may affect significantly their load and deformation capacity. The design of those structures has been dominated by the use of American standards (API 650, ASME VIII and B31.3). Nevertheless, for the case of seismic design, those standards (especially ASME standards for pressure vessels and piping) contain very limited provisions, referring mainly to structural design codes and specifications. European specifications (EN 14015, 13445, 13480) also contain limited provisions for the earthquake-resistant design of industrial equipment. An effort has been made in Eurocode 8 (EN 1998-4), which concerns almost exclusively vertical-cylindrical liquid storage tanks. Nevertheless, those rules do not cover all possible limit states and, furthermore, they need significant improvement to reach a level of applicability for design practice. The program consists of an interdisciplinary research effort INDUSE that combines civil and mechanical engineering expertise, for the purpose of developing guidelines, which can be used for the seismic design of liquid storage tanks, pressure vessels and piping, within the Eurocode design framework. Towards this purpose, extensive experimental, analytical, and numerical work has been conducted within the INDUSE project with the synergy of academic units, research centres and industrial partners. The guidelines are novel and unique, incorporating modern aspects of earthquakeresistant design, and are aimed at: expanding EN 1998-4 provisions towards an integrated seismic design of liquid storage tanks and attached equipment, incorporating some special features and all possible failure modes (WP5) and extending the applicability of Eurocode 8 (EN 1998) concepts for the cases of industrial pressure vessels (WP6), and piping systems (WP7). The following intermediate goals have been achieved within the INDUSE project: A basic comparison has been performed between current seismic design provisions in European and American standards together with an assessment of seismic damages in industrial facilities (WP1). Taking into account the particularities of each structural system, seismic actions have been determined (WP2). Extensive experimental testing has been conducted on key piping components (e.g. nozzles, pipe connections/branches and elbows) under strong cyclic loading; furthermore a piping system has been tested under pseudo-dynamic loading (WP3). Finite element analyses on these components have been performed, simulating the experiments and covering a wide range of geometric, material and loading parameters (WP4). The results of the above investigations are summarised below, demonstrating the achievements of INDUSE project objectives, work package per work package.