Journal of Earthquake Engineering

The response of a secondary system mounted on a torsionally coupled yielding primary system under white-noise excitation is presented. The main objective is to examine the effect of rotary coupling and non-linearity of the primary structural system on the response characteristics of the linear secondary system in a stochastic environment. The responses are obtained by the frequency domain spectral analysis using a linearisation technique. The behaviour of the S-system is examined under a set of parametric variations. These parameters include the uncoupled lateral frequency, the eccentricity ratio, the ratio of uncoupled lateral to rotational frequencies, the damping ratio, and the hysteretic parameters for the primary structure. Also, they include the frequency, the damping ratio, the normalised eccentricity for the secondary system, and the mass ratio of the two systems. The results of the study indicate that the yielding of the primary system may result in an increased response of the secondary system under certain conditions, and that the rotary coupling of the primary system can have a significant influence on the responses of the secondary system.

A bridge knee joint having details representative of recent design procedures was tested under cyclic loading and found to perform poorly due to inadequate anchorage of the longitudinal column reinforcement. Repair and retrofit strategies were tested with excellent results obtained, and a redesigned joint also performed well. Reinforcement details and experimental results are presented for the four units.

An ensemble of 201 Greek strong motion components is analysed and the respective duration and instrumental energy characteristics are determined. A comparative study of these characteristics and their correlation with (i) Modified Mercalli Intensity measures and (ii) peak response and input energy measures of SDOF systems, reveal the most suitable ones which can serve as indicators of the damage potential of the ground motion. Predictive relations of these measures, valid for the Greek tectonic region, are also provided.

The Great Hanshin-Awaji Earthquake of 1995 has left traces of its intense seismic motion in granular soils at various places in Kobe, and these signs are found to be somehow correlated with the features of the disaster at those places. Strong ground shaking was responsible for a number of slope failures. Considerable displacements seem to have been built up even within nearly flat sandy soil deposits, a fact proven by the data regarding dislocated rings of manholes. Thus the importance of studying behaviours of granular soil experiencing this large strain emerges from the findings obtained through the investigation. Irreversible deformation of a granular material is mainly due to a change in its fabric. This process is accompanied by noticeable dilation, through which a certain amount of energy is consumed. It is therefore noted that ground velocity as well as acceleration is another important key which provides a stability index. On the basis of findings through experiments using a new visualisation technique, Laser-Aided Tomography (LAT), a simple approach for evaluating granular soil deformation built up during intense ground shaking is discussed.

The paper describes the formulation of a non-linear, two-dimensional beam finite element with bending, shear and axial force interaction for the static and dynamic analysis of reinforced concrete structures. The hysteretic behaviour of "squat" reinforced concrete members, in which the interaction between shear and flexural deformation and capacity is relevant for the overall structural performance, is emphasised. The element is of the distributed inelasticity type; section axial-flexural and shear behaviours are integrated numerically along the element length using a new equilibrium-based approach. At section level a "hybrid" formulation is proposed: the axial-flexural behaviour is obtained using the classic fibre discretisation and the plane sections remaining plane hypothesis, the shear response instead is identified with a non-linear truss model and described with a hysteretic stress-strain relationship. The latter contains a damage parameter, dependent on flexural ductility, that provides interaction between the two deformation mechanisms. The element has been implemented into a general-purpose finite element code, and is particularly suitable for seismic time history analyses of frame structures. Analytical results obtained with the model are compared with recent experimental data.

In October 1995 an earthquake with a magnitude of 7 on the Richter scale occurred in Sumatra, 450 km from Singapore. Tremors were felt by occupants of several buildings in Singapore and were recorded as an RMS acceleration value by instruments installed in a high-rise condominium. Based on this value and considering instrumental effects, site conditions and building characteristics, this paper investigates the ground motion accelerations and the building response.