Matthias Wieschollek

Guidelines for Seismic Design and Analysis of Pressure Vessels

An adequate design of pressure vessels, also for seismic actions, is crucial in particular if due to hazardous content the consequences of failure may become very severe. While very detailed and specific seismic design rules for structural buildings are provided by several codes, such rules are missing for pressure vessels. This paper describes the results of a study on seismic performance and applicability of existing European and American codes to pressure vessels with cylindrical and spherical shapes and provides a comparison of design outcomes according to these codes. The investigations were performed for different case studies of existing pressure vessels which were selected to be representative for the current practice. The studies comprised numerical investigations as well as simplified models for the estimation of the dynamic properties of the vessel structures. The applicability of behaviour factors was discussed based on proposals made by European and American codes, so that finally recommendations for the behaviour factor of pressure vessels with different shapes and types of supports have been developed based on pushover analyses and non-linear incremental dynamic analyses.Copyright

SLENDER PROFILES FOR MOMENT RESISTING FRAMES IN MODERATE SEISMICITY REGIONS - NUMERICAL AND EXPERIMENTAL INVESTIGATIONS

Abstract. Moment resisting steel frames offer an excellent ductility and energy dissipation and can be designed using high behaviour factors. The condition however is, that compact cross-sections are used allowing for large rotations in the plastic hinges. Portal frames, as commonly designed and built for storage or industrial applications, are usually aiming at light weight solutions in order to be competitive to prefabricated concrete halls. Class 3 or 4 profiles are preferably used, this prevents however the application of any significant behavior factor. In particular in low and moderate seismicity regions a behaviour factor in the range of 2-3 would be fully sufficient in order to achieve an economically optimum design.

Seismic Design of Spherical Pressure Vessels

Spherical pressure vessels are globally used for storage of pressurized liquids or gases of different hazard classes. An adequate seismic design of these structures must consider their particular structural behaviour and consequences of possible damage or failure. A study of the current standard situation for seismic design of pressure vessels revealed significant gaps and missing design rules, in particular for spherical pressure vessels. Within the European Research Project INDUSE the seismic performance and applicability of existing European and American codes to pressure vessels with cylindrical and spherical shape were investigated. This paper describes the results of a study on different examples of spherical pressure vessels which were selected to be representative for the current practice. The study comprised numerical investigations as well as simplified models for the estimation of the dynamic properties of the vessel structures. It is shown, which failure modes and stress concentrations areas are crucial in the event of an earthquake. In addition engineering calculation methods to determine fundamental periods and internal forces for braced and non-braced spherical pressure vessels were developed and compared to results of numerical simulations. The applicability of behaviour factors is discussed based on proposals made by European and American codes in comparison to own results. Recommendations for the behaviour factor of spherical pressure vessels with different dimensions were developed based on push over analyses and non-linear incremental dynamic analyses. Furthermore the influence of sloshing effects in spherical vessels, for which no specific rules are given in the codes, was investigated according to the current state of the art.

Experimental and Numerical Investigations on Nozzle Reinforcements

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.Copyright