Journal of Earthquake and Tsunami

This paper presents a large-scale numerical simulation of a reinforced concrete (RC) tunnel junction member using solid FEM. Particle discretization scheme (PDS), which uses two sets of non-overlapping characteristic functions to discretize displacement field and strain/stress field respectively, is employed to represent the multiple-cracking configurations of concrete. An efficient parallel FE program, called ADVENTURE, is used to implement PDS as well as a reformulated nonlinear concrete constitutive relation. A simplified tunnel junction member, in order to reveal its multiple-cracking behavior under the static load, is studied and the stochastic behavior of cracking is investigated; good agreements are achieved between the simulation results and experimental observations regarding the multiple cracking configurations.

To study the special behaviors of seismic responses regarding a cable-stayed bridge under an active fault earthquake, a novel numerical algorithm named Structure-Medium-Fault (SMF) Integrated Model, in which the interaction of the three parts can be considered, is proposed. The mechanical simplification of causative faults' rupture, numerical simulation of stress wave propagation and the artificial boundary conditions (ABC) for the infinite body laid the groundwork of this model. Initially, the mechanical model for the structures and earth medium was established. Afterwards, the equivalent initial stresses of causative seismic sources can be calculated according to the monitored data of active faults. Thirdly, the function of the equivalent initial stress of seismic source time was derived by the second derivation of Brune source function. Finally, the viscoelastic boundary was chosen for the model as ABC. A cable-stayed bridge (600 m main span) above the causative fault was analyzed using the novel model. Consequently, vertical effect, velocity pulse effect and directivity effect were all confirmed by the analytical results. The model can reflect the mutual influences of near-fault structures, medium and causative faults. The seismic responses of the bridge under a near-fault earthquake can thus be obtained.

The intensity measures of ground motions are closely related to the damage of bridge structures. However, it is difficult for engineers to select these parameters to predict the potential damage of cable-stayed bridges under earthquakes. This paper investigated the correlation between the intensity measures of far-fault ground motions and the damage of cable-stayed bridges. 322 far-fault ground motions were selected, and 26 available intensity measures in the literatures were chosen to carry out comparative analysis on a cable-stayed bridge with a single pylon. The nonlinear finite element model of this bridge was built, considering the stiffness degradation of concrete and low-cycle fatigue effect of steel. It is concluded in this study that velocity spectral intensity (VSI) is the optimal intensity measure for seismic damage analysis of cable-stayed bridges subjected to far-fault ground motions, followed by spectral acceleration at fundamental period and Housner intensity. Five commonly used intensity measures, namely peak ground acceleration (PGA), the ratio of PGA to peak ground velocity (PGA/PGV), specific energy density (SED), predominant period (T_p) and mean period (T_m), demonstrate low correlations with the bridge damage. In particular, there is very weak correlation between the conventionally used PGA and the seismic damage of cable-stayed bridges.