Journal of Earthquake Engineering

Damage phenomena observed in structures subject to intense seismic events are the result of stiffness and strength degradation. This paper studies the damage assessment of hysteretic degrading structures described by means of the Bouc-Wen model, modified to represent the mechanical degradation induced by severe earthquakes. In order to consider randomness of seismic action, the analysis is performed by adopting a stochastic approach and the Park and Ang damage functional is also evaluated in stochastic way. A parametric analysis is carried out with the aim to analyse the effect of mechanical characteristics and measure parameters of earthquake intensity on seismic response and damage level. Damage spectra are finally obtained and they are used to develop, on the basis of the Performance Based Seismic Design, ductility demand spectra.

In this paper, the influence of the rotation speed on the earthquake response of rotors is investigated by means of a simple model with only two degrees of freedom. Some worth noticing properties of the eigenmodes and the transfer functions in the presence of solid gyroscopic effect are discussed. In particular, the importance of the relative contribution of the forward and backward modes is evaluated using basic properties of the transfer functions. In the case of a white noise excitation the backward mode contribution dominates the response, for high values of spin velocity. Depending on the frequency content of the excitation and the rotation speed, an important amplification of the response may occur due to gyroscopic effects, as a result of the amplification of the backward mode response. Nonlinear boundary conditions reduce, to some degree, the differences between the responses of rotating and non-rotating systems, but, even in this case, the importance of the contribution of the backward mode in the response appears clearly. Rotors immersed in a dense fluid with moderate confinement exhibit different behaviour and amplification is possible in the case of resonant response of the second forward mode.

In the last century alone two to three million people died in earthquakes; More than 240 000 perish in Tangshan earthquake in China, 20 000 in the Izmit [Ikeya, 2004] 50 000 in India Bhuj earthquake, 100 000 in Sumatra and 90 000 in Pakistan earthquakes. Earthquake engineering has progressed to the stage where it is now computationally practical and desirable to perform a dynamic analysis of most civil engineering structures. Such an analysis requires the engineer to create an accurate analytical model of the structures as well as prescribe an earthquake input excitation. The design earthquake input excitation for the site under consideration is usually prescribed in the form of response spectra or in the form of an ensemble of artificial earthquake acceleration time histories. There is every need for generating artificial accelerograms since recorded accelerograms are very limited at site. This paper proposes five neural network based models for the generation of artificial earthquake and response spectra using wavelet transforms (WT) and principal component analysis (PCA) where the recorded accelerograms are limited at site of interest. The proposed model is compared with Lee and Han's model. The data for 25 earthquakes are taken for training and 4 for testing. Just like response spectra, this is also a convenient way of obtaining the design solution to a structural dynamics problem and is certainly an important tool.

The M_w 7.1 Duzce earthquake occurred on 12 November 1999 along the North Anatolian Fault in northwestern Turkey. This paper documents observations from a field reconnaissance team, addressing two principal aspects of this significant earthquake: the recorded ground motions and the distribution and severity of the earthquake effects on the built environment. In general, the recorded ground motions from this earthquake were smaller than predicted by ground motion predictive equations available at the time of the event. One anomalous recording is presented and potential causes for this irregular motion based on observations from field reconnaissance are discussed. The effects of rupture directivity on the near-fault recordings are assessed and the effects of soil conditions on the recorded ground motions are examined. The patterns of building damage based on post-earthquake reconnaissance are presented for the most strongly shaken cities in the near-fault region: Duzce, Kaynasli, and Bolu. Damage in Duzce was concentrated in the southern part of the city, which is underlain by softer sediments. Damage in Bolu was distributed evenly throughout the city; whereas damage was concentrated on more recent alluvial sediments in Kaynasli. No evidence of liquefaction or ground failure was observed in the populated areas surveyed after the earthquake.

In the seismic design of steel frames, beam-to-column joints can be designed either as full strength joints, forcing the location of the plastic hinges at the beam ends, or as partial strength joints which have to dissipate the seismic input energy. Seismic codes provide specific design criteria for full strength joints, but there are no detailed recommendations dealing with partial strength connections. Therefore, in this paper, by means of a simplified model, such as a SDOF system, the requirements which partial strength joints have to possess, for designing steel frames characterised by seismic performances equivalent to those of steel frames with rigid full strength joints, are pointed out. Successively, starting from the above requirements, a new method for designing seismic resistant steel frames with extended end plate connections leading to the complete definition of the geometrical and mechanical parameters of the joints is proposed.

The paper presents an earthquake hazard study for Dubai, United Arab Emirates (UAE). The seismicity of the area is outlined and discussed in terms of available earthquake data and published earthquake catalogues. Strong motion estimation models are also discussed and a specific model is selected and extended to meet the defined requirements for the study. The hazard assessment is carried out to evaluate peak ground acceleration and uniform hazard response spectra corresponding to 5% and 2% probability of being exceeded in 50 years. Simulated earthquake ground acceleration records are derived for the purposes of dynamic response history analysis. The implications of the hazard from near and far earthquakes is explored with regard to the dynamic response of tall buildings and other long-period structures common in the study area.