SUMMARY An improvement is suggested to the direct displacement‐based design (DDBD) procedure for bridges to account for higher mode effects, the key idea being not only the proper prediction of a target‐displacement profile through the effective mode shape method (wherein all significant modes are considered), but also the proper definition of the corresponding peak structural response. The proposed methodology is then applied to an actual concrete bridge wherein the different pier heights and the unrestrained transverse displacement at the abutments result in an increased contribution of the second mode. A comparison between the extended and the ‘standard’ DDBD is conducted, while further issues such as the proper consideration of the degree of fixity at the pier's top and the effect of the deck's torsional stiffness are also investigated. The proposed methodology and resulting designs are evaluated using nonlinear response‐history analysis for a number of spectrum‐compatible motions. Unlike the ‘standard’ DDBD, the extended procedure adequately reproduced the target‐displacement profile providing at the same time a good estimate of results regarding additional design quantities such as yield displacements, displacement ductilities, etc., closely matching the results of the more rigorous nonlinear response‐history analysis. However, the need for additional iterations clearly indicates that practical application of the proposed procedure is feasible only if it is fully ‘automated’, that is, implemented in a software package. Copyright © 2012 John Wiley & Sons, Ltd.

Summary A methodology for the development of design tools for direct estimation of peak inelastic response in reduced‐degree‐of‐freedom (RDOF) isolation and energy dissipation systems is presented. The suggested procedure is an extension of an earlier method addressing purely hysteretic isolation systems. Herein, the dynamic equation of motion is first normalised to reduce the number of design parameters that significantly affect the response. The sensitivity of normalised response quantities to the amplitude of the ground motion is then investigated through extensive parametric nonlinear dynamic analyses of isolated single‐degree‐of‐freedom (SDOF) systems with linear viscous damping using code‐based target spectra. Regression analysis is subsequently employed to develop generalised design equations (GDEs) suitable for design. Further investigations are made to address nonlinear viscous damping and the effect of the transverse component of seismic action in two‐degree‐of freedom (2DOF) systems under bidirectional excitation, making the procedure applicable to common bridge isolation schemes. GDEs constitute an alternative to equivalent linearisation approaches commonly adopted by codes, informing the selection among alternative isolation and energy dissipations schemes without requiring iterative analysis. The approach is incorporated in the Deformation‐Based Design methodology for seismically isolated bridges in a forthcoming paper.

Abstract.A performance-based design (PBD) procedure, initially proposed for the seismic design of buildings, is tailored herein to the structural configurations commonly adopted in bridges. It aims at the efficient design of bridges for multiple performance levels (PLs), achieving control over a broad range of design parameters (i.e. strains, deformations, ductility factors) most of which are directly estimated at the design stage using advanced analysis tools (a special type of inelastic dynamic analysis). To evaluate the efficiency of the proposed design methodology, it is applied to an actual bridge that was previously designed using a different PBD method, namely displacement-based design accounting for higher mode effects, thus enabling comparison of the alternative PBD approaches. Assessment of the proposed method using nonlinear dynamic analysis for a set of spectrum-compatible motions, indicate that it results in satisfactory performance of the bridge. Comparison with the displacement-based method reveals significant cost reduction, albeit at the expense of increased computational effort.

This is the accepted version of the paper.This version of the publication may differ from the final published version. In view of the grave socioeconomic consequences of earthquake damage to bridge structures, along with their critical role in modern and older road and rail networks, this article attempts to identify and summarise the current trends in the use of semi-active control technology in bridge engineering, as an enhanced seismic response control solution, combining increased adaptability and reliability, compared to passive and active schemes. In this context, representative analytical and experimental studies, as well as some full-scale applications of semi-active control devices are first reviewed and a brief description of relevant benchmark studies is subsequently presented, with a view to serving as a point of reference for further research and development. A framework of performance-based control principles aiming at the aforementioned objectives is finally set forth. Permanent

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A performance‐based design procedure is proposed for seismically isolated bridges with/without supplemental energy dissipation devices. Considering multiple performance levels (PLs), the proposed method initially identifies the critical hazard level and “near‐optimal” alternatives of the isolation system. Both performance and economy are evaluated based on the inelastic response of reduced‐degree‐of‐freedom (RDOF) isolation and energy dissipation systems. Nonlinear response history analysis (NLRHA) of the multi‐degree‐of‐freedom (MDOF) system is employed in successive design steps, corresponding to different PLs, to refine the design solution through the control of a broad range of material strains and deformations. The above characteristics aim to deliver a rigorous and broadly applicable design method that reduces the high computational effort characterising complex design frameworks, while addressing identified deficiencies of alternative displacement‐based methods. The efficiency of the proposed design methodology is demonstrated by applying it to an actual bridge that was previously designed for ductile behaviour. Alternative isolation and energy dissipation schemes are investigated. Assessment of the design through NLRHA reveals in all cases enhanced seismic performance and cost reduction in the substructure design, thus rendering base‐isolation an appealing design alternative.

Abstract. A performance-based design procedure is presented herein for seismically isolated bridges equipped with nonlinear viscous dampers (VDs