Journal of Earthquake Engineering

The concept of Isogeometric Analysis recently introduced by Hughes et al. [2005] is herein applied to the study of structural vibrations. In this framework, the favourable behaviour of the method is verified and compared with some classical finite element results. Numerical experiments are shown for structural one-, two- and three-dimensional problems in order to test the performance of this promising technique in the field of the analysis of natural frequencies and modes.

This paper presents a probabilistic method for seismic loss estimation. The method accounts for the dependence of the structural response on the ground-motion and on the mechanical properties through an approximate response model based on a limited number of nonlinear structural analyses using recorded ground-motions. This response model is the key element in keeping affordable the procedure that uses simulation to compute the distribution of monetary loss. The main advantage of the formulation is that all sources of uncertainty and correlation among loss terms are accounted for. The procedure is illustrated by way of an application to an RC arch bridge. The application highlights the need for further research on models that describe states of increasing damage in terms of repair actions.

In this paper, the seismic performance of a three- and a six-storey steel frame equipped with different bracing configurations is assessed. The bracing systems consist of traditional buckling-restrained steel braces and superelastic Nitinol shape-memory alloy (SMA) braces. Background on the behaviour of SMAs is provided and a state-of-the-art review of the applications of such new materials in earthquake engineering is presented. A uniaxial constitutive model for superelastic SMAs is then implemented into the finite element platform OpenSees and nonlinear dynamic analyses are performed. Finally, the seismic performance of the structures under investigation is judged through the evaluation of several response quantities, to determine the efficacy of the new bracing system in reducing earthquake-induced vibrations.

Dynamic nonlinear analysis of structures requires the seismic input to be defined in the form of acceleration time-series, and these will generally be required to be compatible with the elastic response spectra representing the design seismic actions at the site. The advantages of using real accelerograms matched to the target response spectrum using wavelets for this purpose are discussed. The program RspMatch, which performs spectral matching using wavelets, is modified using new wavelets that obviate the need to subsequently apply a baseline correction. The new version of the program, RspMatch2005, enables the accelerograms to be matched to the pseudo-acceleration or displacement spectral ordinates as well as the spectrum of absolute acceleration, and additionally allows the matching to be performed simultaneously to a given spectrum at several damping ratios.

A direct displacement-based design (DBD) procedure for structures that comprise both frames and walls is presented in this paper. Within the new procedure, strength proportions between walls and frames are assigned and are used to establish the design displacement profile before any analysis has taken place. Knowledge of the displacement profile and recommendations for the combination of frame and wall damping components enables representation of the structure as an equivalent single-degree of freedom system. The Direct DBD process is then utilised to set the required strength level which is proportioned to the structure in line with the initial strength assignments. To test the design methodology, two sets of 4-, 8,- 12-, 16- and 20-storey reinforced concrete structures are designed. The first set considers frame-wall structures in which the frames are parallel to the walls and the second considers structures in which link-beams connect from the frames directly onto the ends of the walls. A suite of time-history analyses are conducted to validate the methodology, which is seen to perform excellently.