Search

The paper presents the studies carried out on a big storage gas tank for the seismic vulnerability assessment and the retrofit through isolation system. This Gasometer, constructed in the early eighties, consists in a steel cylinder of 70 m height and 44 m diameter. The tank bearing structure is composed by a classical steel frame closed with curved steel plates. Inside the tank, a piston-fender and rubber sealing system allow the variation of the container volume and control the gas pressure. The latter represents half of the seismic mass and its position can vary along the tank height. The seismic vulnerability of the steel structure of the Gasometer on its as-it-is state is assessed through the execution of Incremental Dynamic Analyses, placing particular attention on the definition of possible limit states. Subsequently, the seismic retrofit through base isolation system, adopting Double Curved Surface Sliders, is proposed and numerically assessed. The results and comparison between the as-it-is state and the retrofitted state supplies important information about the effectiveness of base isolation for the risk mitigation of gas tanks. The research was supported by the European Union's Research Fund for Coal and Steel (RFCS) research programme under grant agreement n° RFSR-CT-2013-00019.

In concentrically braced frames, the use of dissipative connections allows to efficiently dissipate the seismic energy in earthquake scenarios and subsequently, to reduce the costs in the rehabilitation of the structure. To this end, U-shaped steel plates are simple and efficient connection components where significant dissipation of seismic energy can take place through the inelastic flexural deformation of the plate. This paper presents experimental results on the isolated U-shaped steel plate connections and on single-story concentrically braced frame (real scale) including the U-shaped steel plate to connect braces to adjacent members. The executed tests considered both monotonic and cyclic loading. The results highlight the efficiency of the U-shape steel plate to dissipate the energy input through inelastic deformations. On the other hand, the cyclic tests show potential fatigue behavior, as the deformation capacity is significantly reduced with repeated loading and increasing stress amplitude, requiring thus specific attention in practical design situations.

This paper presents a comparison of experimental tests results on unreinforced load-bearing masonry structures subjected to earthquake loading with numerical predictions. First, simple walls are submitted to cyclic and shaking table tests. Some of them include soundproofing devices in order to investigate their influence on the general behaviour in static and dynamic conditions. Additional walls with an opening and T-shaped walls are then tested under cyclic loading. The study is focused on the frame effect, the contribution of the perpendicular wall to the global strength and the efficiency of the connection. These aspects are also studied through shaking table tests on two masonry frames with T- or L-shaped piers. The main information is expressed in terms of force-displacement curves, mechanical properties and energy dissipation for the cyclic tests. The shaking table tests provide results in terms of dynamic and mechanical properties. Comparison of the results with numerical predictions is finally performed thanks to the software TREMURI. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 227887, SERIES. C. Mordant also acknowledges the F.R.S - FNRS (Belgian fund for research) for the support of his PhD and Davide Seni (S.T.A. DATA S.r.l.) for the technical support.

Prediction of the structural behaviour of pallet racks is known as a difficult task because affected by the particular geometry of their structural components, often exhibiting a highly non-linear behaviour. Due to these peculiarities, specific modelling and design rules are required for such nontraditional steel structures that cannot be considered as classical buildings. This is particularly the case for their seismic design. The most recent design standards propose therefore a combined numerical-experimental approach in which the design structural analysis is supported by specific tests to evaluate the performance of the key components (members and joints). Results presented in this paper are part of a wide research program “Seisracks2 – Storage Racks in Seismic Areas” funded by the European Union (RFCS research program). This research program aims at constituting a scientific background document for the conversion of the Code of practice FEM 10.2.08 to a European Standard. The present paper intends to summarize the current situation of two main aspects of this research: (i) the investigations carried out on the cross-aisle behaviour, with the objective of covering a wide range of configurations (D/Z/X type of cross bracing including different types of connection) and to investigate their consequences on the transverse stiffness, resistance and deformation capacity; (ii) the behaviour in down-aisle direction in presence of eccentric vertical bracings (hybrid frame/braced structural behaviour) with a significant torsional component due to the eccentricity of the bracing system with respect to the centre of mass of the stored goods. The objectives of the study are to provide an experimental corpus available for proper calibration of numerical models and to define testing procedures suitable for the identification of the main structural parameters easily transferrable into numerical models. These various issues are investigated by means of full scale push-over and cyclic testing. In the present study, a more realistic configuration has been chosen consisting in 8 meter high cross-frames tested transversally with 4 load levels equally distributed over the height which correspond to the beam levels of the case-studies, i.e. to levels where the masses are actually present. Vertical side guides prevent the out-of-plane instabilities. Displacement transducers are located at each beam level and at the bottom. The objective is clearly to test the frame in a real loading configuration in terms of shear and overall bending moment distribution. Down-aisle tests consist in 1 span – 1 level frames. The system of the longitudinal bracings is composed of vertical bracings - X bracings with extra uprights and extra horizontal element acting as a rigid frame - and horizontal bracings. The load is applied horizontally by means of an additional beam pushing against steel-stops welded at mid-length of the pallet-beams. The displacements are measured at 10 different positions: longitudinal displacements of the 6 uprights and transversal displacements of the 4 external uprights, all at the pallet-beam’s height.

This document is a Technical Report with worked examples for seismic design of buildings following the Eurocodes. It summarizes important points of the Eurocode 8 for the seismic design of concrete and steel buildings including foundations utilizing a common generic building as a basis. An overview of EN 1998 with focus on the performance requirements and compliance criteria for structures, ground conditions and seismic actions is presented at the first section. An introduction to the example reinforced concrete building with its geometrical and material properties as well as the main assumptions for analysis and the detailed structural analysis calculations are presented in the second chapter of the report. Specific rules for design of the building for ductility and the design of concrete foundation elements are presented in the following chapters. For the sake of completeness, the details of design and detailing of the same example as a steel building with three different configurations, namely; with (i) steel moment resisting frames, (ii) composite steel concrete moment resisting frames, and (iii) composite steel concrete frames with eccentric and concentric bracings is also presented afterwards. Key concepts of base isolation is summarized by utilizing the example building. Seismic performance assessment and retrofitting according to EN 1998-Part 3 is explained as the last past of the report. The reinforced concrete/steel building as worked example analyzed in this report was prepared and presented at the workshop “Eurocode 8: Seismic Design of Buildings” that was held on 10-11 February 2011 in Lisbon, Portugal. The workshop was organized by JRC with the support of DG ENTR and CEN and in collaboration with CEN/TC250/Sub-Committee 8 and the National Laboratory for Structural Design (Laboratorio Nacional de Engenharia Civil - LNEC, Lisbon). The document is part of the Report Series ‘Support to the implementation, harmonization and further development of the Eurocodes’ prepared by JRC in collaboration with DG ENTR and CEN/TC250 “Structural Eurocodes”., JRC.G.5-European laboratory for structural assessment