Journal of Earthquake and Tsunami

The concept of disaster resilience has received considerable attention in recent years and it is increasingly used as an approach for understanding the dynamics of natural disaster systems. No models are available in literature to measure the performance of natural gas network, therefore, in this paper, a new performance index measuring functionality of gas distribution network have been proposed to evaluate the resilience index of the entire network. It can be used for any type of natural or manmade hazard which might lead to the disruption of the system. The gas distribution network of the municipalities of Introdacqua and Sulmona, two small towns in the center of Italy which were affected by 2009 earthquake have been used as case study. Together the pipeline network covers an area of 136 km², with 3 M/R stations and 16 regulation groups. The software SynerGEE has been used to simulate different scenario events. The numerical results showed that, during emergency, to ensure an acceptable delivery service, it is crucial to guarantee the functionality of the medium pressure gas distribution network. Instead to improve resilience of the entire network the best retrofit strategy is to include emergency shutoff valves along the pipes.

This paper investigated dynamic responses of steel monorail bridges incorporating train-bridge interaction under strong earthquakes. Two types of steel monorail bridges were considered in the study: a conventional type with steel track-girder; an advanced type with composite track-girder and simplified lateral bracing system. During strong earthquakes, monorail train was assumed standing on the track-girder of monorail bridges. Observations through the analytical study showed that considering the monorail train as additional mass rather than a dynamic system in numerical modeling overestimated effect of the train load on seismic performance of monorail bridges. Earlier plastic deformations at the end bracing of the girder system absorbed seismic energy and reduced the stress at the pier base.

Basalt fiber reinforced polymer (BFRP) composites are regarded as promising structural strengthening material due to their environmental friendly and superior mechanical and chemical properties. In order to enhance the overall seismic performance of RC columns, a strengthening system is developed by applying BFRP composites with both near surface mounted (NSM) and confinement approaches. The variables taken into account consisted of the diameters and anchorage lengths of BFRP bars, as well as the confinement amounts of BFRP sheets. A total of eight column specimens including one control were tested subjected to simultaneous axial compression and cyclic bend. The structural performance such as load capacity, displacement, ductility, stiffness degradation, energy dissipation capacity, curvature and post-yield stiffness were investigated. The test results indicate that the combination of NSM and confinement techniques contributes to the comprehensive performance enhancement of RC columns, which lies in (1) constantly enlarging diameters of BFRP bars increases the yield and peak loads, the ultimate displacement, the initial and post-yield stiffness as well as the ductility, whereas it has no obvious influence on the yield displacement; (2) longer bonding length results in higher seismic performances although it makes no changes to the yield displacement, the post-yield stiffness, and the degradation of strength and stiffness as well; (3) the adoption of BFRP confinement significantly improves the ductility and the strength degradation performance; (4) the largest post-yield stiffness can be achieved by enlarging diameter to 12 mm, whereas the ductility and the strength degradation characteristics deteriorate due to the weakness of interfacial bonding between BFRP bars and concrete.

This paper presents multi agent simulation (MAS) which is developed to evaluate two social actions against earthquake disasters, mass evacuation and lifeline recovery. Mathematical problems for the verification and validation of the MAS codes are posed. A differential equation of an agent's position is used for the mass evacuation, and the mechanism of slowing evacuation processed is modeled. The lifeline recovery is regarded as a resource allocation problem, which maximizes lifeline users' benefit, by suitably dispatching engineers who repair damaged network segments. Several example problems are solved for the verification and validation as well as for the demonstration of the usefulness of the developed MAS codes.

During the 2011 Great East Japan earthquake occurring at the North–East pacific region, serious secondary disasters caused by collision of drifting containers or ships occurred in various structures when tsunami came. Drifting objects including large ships and tankers come in and out of ports in Japan. Disaster deterioration caused by drifting objects during earthquake and tsunami has become another problem. In this study, it is assumed that a large drifting ship collides with a large-span bridge in the gulf line during a tsunami. To investigate the impact behavior of the bridge during collision, tsunami simulations and nonlinear dynamic finite element analyses of the whole bridge during collision are performed. Based on the collision force calculations, an approximate analytical method is proposed, and the maximum size of drifting object which can result in the collapse of the whole bridge structure is calculated using this method.

The purpose of this research is to make clear the phase spectrum characteristic of earthquake motion. After the introduction of past researches we introduce the concept of fractional Brownian process (FBP). A simple method is proposed to determine the Hurst index and the variance of a given process characterized by the FBP. We find that the phase characteristic of earthquake motion can be expressed by this process which is a non-stationery function of the circular frequency with a constant correlation coefficient. Using several observed earthquake motion we demonstrate this fact and show the efficiency of newly founded result to simulate realistic earthquake motion phase and also compare simulated earthquake motions with those of observed ones. We also simulate design response spectrum compatible earthquake motions by simulating the earthquake motion phase using the identified Hurst index and variance of the given earthquake motion. We investigate the effect of hypocenter distance on the variance and Hurst index of earthquake motion phase, as well as on the mean gradient of earthquake motion phase with respect to the circular frequency.

Optimum positioning of newly installing seismographs along highway lines is discussed. First, we introduce a method to estimate the spatial distribution of earthquake intensity under the condition that several observation data of earthquake intensity are provided at given sensor locations. We also define a spatial index which indicates the estimation error level of the spatial distribution of earthquake intensity of which value becomes zero at the sensor locations. The optimum sensor location problems can be formulated as a minimization problem of this index value which is a function of the sensor locations and the prior information of the special distribution of earthquake intensity in the target area. The design parameters are locations of the sensors. Genetic Algorithm (GA) is used for the optimization. After a brief introduction of real coded GA, optimum sensor locations along highway lines are determined as to minimize the spatial index value by using this GA code.