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Chevron concentrically braced frames are one of the most cost-effective solutions for seismic resistant steel buildings. Therefore, this system is widely used in Europe and North America. Both European and North American codes adopt capacity design rules aiming at enforcing the dissipative behaviour into the braces and at preventing the damage in the remaining structural members. However, in order to achieve this purpose, European and North American codes recommend some different requirements and detailing rules, which substantially influence the overall performance and energy dissipation capacity. The research presented in this paper is addressed (i) to verify the effectiveness of the design requirements prescribed by Eurocode 8 (EC8) compared to North American codes (i.e. both AISC 341 and CSA-S16), (ii) to identify the criticisms of EC8 needing revision and upgrading. In order to achieve these objectives, a comprehensive parametric numerical study based on nonlinear dynamic analyses is carried out. 2D frames extracted from low, medium and high-rise buildings are analysed and the main structural parameters affecting the performance against lateral loads are described and discussed. The critical review of the examined standards and the discussion of numerical results highlight that the design rules given by North American codes are more effective than those recommended by the current version of EC8. In particular, EC8-compliant frames show the poorest energy dissipation capacity with tension bracing members almost in elastic range and severe demand on those in compression. On the contrary, both CSA- and AISC-compliant cases exhibit satisfactory energy dissipation capacity. [ABSTRACT FROM AUTHOR]

The paper validates Ω* method proposed by some of the authors in previous papers for design of X-Concentric Braced Frames (X-CBFs). This method was obtained relaxing some of the requirements of the method provided by the European seismic code (Eurocode 8, EC8). Therefore, Ω* method is conceptually similar to that of EC8, which makes it easy to be incorporated into EC8 and to be embraced by the European structural designers. The paper analyses the seismic performance of a set of X-CBFs designed both according to EC8 and Ω* methods. Several buildings characterised by different numbers of storeys, numbers of bracings in plan and by different bay spans are considered. Non-linear dynamic analyses have been carried out by the computer code CLAP to evaluate the seismic performance of the analysed buildings. The results of the numerical analyses show that the Ω* method: (i) reduces the unnecessary global overstrength which typically is found in structures designed in accordance to EC8 design rules; (ii) leads to an optimized structural design; (iii) ensures a local and global ductility of braces under cyclic actions comparable to EC8 design solutions; (iv) has a greater “flexibility” in the design process. [ABSTRACT FROM AUTHOR]

Traditional seismic design, like the one adopted in Eurocode 8 (EC8), is force-based and examining a single level of seismic action. In order to provide improved control of structural damage for different levels of seismic action, the new fib Model Code 2010 (MC2010) includes a fully fledged displacement-based and performance-based seismic design methodology. However, the level of complexity and computational effort of the MC2010 methodology is significantly increased. Hence, the use of automated optimization techniques for obtaining cost-effective design solutions becomes appealing if not necessary. This study employs genetic algorithms to derive and compare optimum seismic design solutions of reinforced concrete frames according to EC8 and MC2010. This is important because MC2010 is meant to serve as a basis for future seismic design codes. It is found that MC2010 drives to more cost-effective solutions than EC8 for regions of low seismicity and better or similar costs for regions of moderate seismicity. For high-seismicity regions, MC2010 may yield similar or increased structural costs. This depends strongly on the provisions adopted for selecting the set of ground motions. In all cases, MC2010 provides enhanced control of structural damage. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Several research studies have proved the beneficial effects resulting from the presence of moment resisting frames and braced frames in dual structural systems. Nonetheless, Eurocode 8 provides design rules only for dual systems with moment resisting frames and concentrically braced frames and thus ignores that moment resisting frames may beneficially combine with other types of braced frames. In this paper, a design procedure for dual systems with moment resisting frames and eccentrically braced frames is proposed based on the current design provisions of Eurocode 8 for dual structures with moment resisting frames and concentrically braced frames. To evaluate the effectiveness of the proposed procedure, the seismic response of the designed systems is evaluated through incremental nonlinear dynamic analysis. The buildings considered are founded on hard or soft soil and are characterised by different values of the link length and number of storeys. [ABSTRACT FROM AUTHOR]

This article focuses on the likelihood of the weak storey behaviour and the weak storey collapse of diagonally concentrically braced frames designed according to Eurocode 8 provisions. The emphasis is primarily put on the nature and development of the weak storey behaviour in order to designate the effects that shall be taken into account in an effective design procedure. In a second stage, the focus is on developing supplementary conditions to Eurocode 8 based on plastic analysis that can enhance the designs by preventing the occurrence of weak storeys. [ABSTRACT FROM AUTHOR]

This paper evaluates the effectiveness of three nonlinear static methods for the prediction of the dynamic response of in-plan irregular buildings. The methods considered are the method suggested in Eurocode 8, a method previously proposed by some of the authors and based on corrective eccentricities and a new method in which two pushover analyses are considered, one with lateral forces applied to the centres of mass of the floors and the other with only translational response. The numerical analyses are carried out on a set of refined models of reinforced concrete framed buildings. The response predicted by the nonlinear static analyses is compared to that provided by nonlinear dynamic analyses. The effectiveness of the nonlinear static methods is evaluated in terms of absolute and interstorey displacements. [ABSTRACT FROM AUTHOR]

The present paper describes the effectiveness of design provisions of Eurocode 8, 2004 and IS 456 regarding the regular and irregular structures. To achieve this purpose, fifteen storey two-dimensional plane frames, three in number, were designed as per EC 8 provisions (medium and high ductility class) and IS 456 provisions for 27 different ground motions normalized to EC 8 design spectrum intensity for PGA = 0.35 g (design earthquake) and for PGA = 0.70 g (collapse prevention earthquake). The first frame (A) is a regular frame without setbacks and the other two frames (B and C) contain different configurations of setbacks in the upper storey. Firstly, these frames were designed in accordance with EC 8 and IS 456 to obtain optimum cross-sections of the structural members. Secondly, the seismic performance of the designed frames was evaluated based on both local and global criteria by inelastic static pushover and inelastic time-history analysis. Finally, EC 8 and IS 456 designed frames were compared regarding the seismic response, analysis methods and economy. Based on the observations, some important conclusions were drawn. [ABSTRACT FROM AUTHOR]