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Gustav Suvorov
Gustav Suvorov

Eurocode 8: Design Of Structures For Earthquake...

In the Eurocode series of European standards (EN) related to construction, Eurocode 8: Design of structures for earthquake resistance (abbreviated EN 1998 or, informally, EC 8) describes how to design structures in seismic zone, using the limit state design philosophy. It was approved by the European Committee for Standardization (CEN) on 23 April 2004. Its purpose is to ensure that in the event of earthquakes:

Eurocode 8: Design of structures for earthquake...

Special structures, such as nuclear power plants, offshore structures and large dams, are beyond the scope of EN 1998. EN 1998 contains only those provisions that, in addition to the provisions of the other relevant Eurocodes, must be observed for the design of structures in seismic regions. It complements in this respect the other EN Eurocodes.

EN 1998-5 establishes the requirements, criteria, and rules for the siting and foundation soil of structures for earthquake resistance. It covers the design of different foundation systems, the design of earth retaining structures and soil-structure interaction under seismic actions.

EN 1998-6 establishes requirements, criteria, and rules for the design of tall slender structures: towers, including bell-towers, intake towers, radio and TV-towers, masts, chimneys (including free-standing industrial chimneys) and lighthouses.

Special structures, such as nuclear power plants, offshore structures and large dams, are beyond the scope of EN 1998. EN 1998 contains only those provisions that, in addition to the provisions of the other relevant EN Eurocodes, must be observed for the design of structures in seismic regions. It complements in this respect the other EN Eurocodes.

(3)P EN 1998 contains only those provisions that, in addition to the provisions of the other relevant Eurocodes, must be observed for the design of structures in seismic regions. It complements in this respect the other Eurocodes.

This paper is intended to give the non-specialist engineer a flavour of how Eurocode 8 works, how it should be used and the principal issues for design. The paper is principally based on the draft for development that was issued for public comment in several parts between 1994 and 1996, and some more recent revisions. It is not a detailed account of the code and the reader is referred to the code for detailed information. The paper describes the design principles for various classes of structures and makes comment and provides insight into a number of particular issues of particular interest to the authors.

The chapter initially provides a summary of the contents of Eurocode 8, its aim being to offer both to the students and to practising engineers an easy introduction into the calculation and dimensioning procedures of this earthquake code. Specifically, the general rules for earthquake-resistant structures, the definition of design response spectra taking behaviour and importance factors into account, the application of linear and non-linear calculation methods and the structural safety verifications at the serviceability and ultimate limit state are presented. The application of linear and non-linear calculation methods and corresponding seismic design rules is demonstrated on practical examples for reinforced concrete, steel and masonry buildings. Furthermore, the seismic assessment of existing buildings is discussed and illustrated on the example of a typical historical masonry building in Italy. The examples are worked out in detail and each step of the design process, from the preliminary analysis to the final design, is explained in detail.

This book focuses on the seismic design of building structures and their foundations to Eurocode 8. It covers the principles of seismic design in a clear but brief manner and then links these concepts to the provisions of Eurocode 8. It addresses the fundamental concepts related to seismic hazard, ground motion models, basic dynamics, seismic analysis, siting considerations, structural layout, and design philosophies, then leads to the specifics of Eurocode 8. Code procedures are applied with the aid of walk-through design examples which, where possible, deal with a common case study in most chapters.

As well as an update throughout, this second edition incorporates three new and topical chapters dedicated to specific seismic design aspects of timber buildings and masonry structures, as well as base-isolation and supplemental damping. There is renewed interest in the use of sustainable timber buildings, and masonry structures still represent a popular choice in many areas. Moreover, seismic isolation and supplemental damping can offer low-damage solutions which are being increasingly considered in practice.

"The main strength of this book is its intermediate positioning between a classical text book on earthquake engineering and an illustrated commentary of the European standard Eurocode 8. It is therefore perfectly fitted for practicing engineers as well as advanced post-graduate students in search of relevant and well-structured information on how to perform the seismic design of building structures and their foundation."

"The new chapters on seismic design of masonry and in particular the one on timber structures cover fields which are little familiar to designers, though these types of construction are either very common, like masonry, or quite new but growingly used, like timber or base isolation."

independence of Pakistan from the British steel Moment Resisting Frames achieve good performance under seismic events. After the 1931 Mach earthquake some structures (see Figure 2) were designed according to the recommendation provided by Eng. Kumar which were tested by the 1935 Quetta earthquake and evidenced that even a modest design of steel structures saved lives in such earthquakes. These frames resisted the 1935 Quetta earthquake without significant damages [5] [6] .

Redundancy factor: It is the over-strength given by the redistribution of the plastic hinges and termed as redundancy factor; it is the ratio of Vu obtained from pushover analysis to Vy defined by Equation (2). Redundancy exists when multiple elements must yield or fail before a complete collapse mechanism forms. Structures possessing low inherent redundancy are required to be stronger and more resistant to damage and therefore seismic design forces are amplified. Therefore, normally it is assumed that structures having larger global ductility exhibits high redundancy and vice versa.

Seismic design necessitates the combinations of deformability, strength and most importantly the ductility characteristics of a structural system. Although steel structures have the capability to resist the lateral actions by means of different Lateral Load Resisting Systems (LLRS). Nevertheless the impairing of strength with the ductility and deformability is a big challenge for the designer. Several types of earthquake resistant steel structures (some LLRS can be combined with the others) which depend on the selected load carrying mechanism can be conceived. These LLRSs have pros and cons on each other due to their characteristics such as high deformability (like MRFs), architectural constraints (like cross bracing that may restrict the opening) and geotechnical issues (for example concentration of forces on the footings). The most conventional types of earthquake resistant steel structures are: a) Rigid Frames, b) Concentric Braced Frames and c) Eccentric Braced Frames.

The paper has dealt initially with the importance of seismic codes in general and particularly in Pakistan. From past earthquakes for example Quetta 1935, it is revealed that steel structures performed well within the limited use of steel frame structures; nevertheless their trend is still not so common in Pakistan. Useful and important steel structures have been constructed before the independence of Pakistan as mentioned in this paper. Furthermore, the use of most advance code such as Eurocode 8 is convenient to be used in the country as the defined spectrum of the code is based on the seismic zonation which is presently available for all the regions of the country. Common parameters that are normally adopted by seismic codes are given and the importance of over-strength factor especially the elastic one that was highlighted gives a clear understanding for the designer involved in the seismic design of structures. In addition, conventional seismic load resisting systems were illustrated and their design criteria according to Eurocode 8 were provided with synoptic tables for the counterpart US code. The procedure of Eurocode 8 is explained through the use of capacity design approach in which it is evident that the calculation of overstrength required some steps and iterations whereas in the US codes this factor is generally fixed for all the lateral load resisting systems. In addition, the behavior factor in Eurocode is less compared to the suggested value of response modification factor in the US codes. Furthermore, it is to be underline that the capacity design rule of Eurocode 8 requires some iteration as calculation of overstrength factor is involved and this becomes more complex when the deformability needs to be satisfied. It is believed and concluded that the lateral load resisting systems that dissipate more seismic energy are of prime importance and therefore need attention to be incorporated in the plastic design.

Nonlinear dynamic analysis of existing or planned structures often requires the use of accelerograms that match a target design spectrum. Here, our main concern is to generate a set of motions with a good level of fit to the Eurocode 8 design spectra for France. Synthetic time series are generated by means of a non-stationary stochastic method. To calibrate the input parameters in the stochastic approach, we select a reference set of accelerograms for a Eurocode 8 type B site category from the PEER Ground-Motion Database, which are then adjusted to the target spectrum through wavelet addition. Then, we compute nonlinear seismic responses of a soil column, including pore pressure effects, and brittle and ductile structures to the stochastic time-series, the natural accelerograms and time-series generated using stationary stochastic approaches. The results of these calculations reveal considerable variability in response despite the similarities in terms of spectral acceleration. 041b061a72


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