Traveling wave effect on the seismic response of a steel arch bridge subjected to near fault ground motions

In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined, with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave （only time delay considered） effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also discussed.

Effective wave identification and interference analysis of the seismic reflection method in mines

Through discussion of the time-distance curve characteristics of the direct waveand from the front,side and rear of the reflection waves of the seismic reflection methodfor advanced exploration in mines,and analysis of several major interference waves inmines,the differences in time-distance curve,frequency,apparent velocity between theeffective wave and interference wave in the seismic reflection method for advanced explorationare obtained.According to the differences,the effective wave is extracted andthe interference wave is filtered and the system's precision and accuracy is improved.

Analysis on influence of seismic travelling wave effect on semi-active control for long-span rigid-continuous bridge

The analysis approach of semi-active control for long-span rigid-continuous bridge under seismic travelling wave input is established. Magnetorheological dampers are set on the positions of the bridge beatings. The semi-active control calculation and analysis are performed for a five-span rigid-continuous bridge under seismic travelling waves with different apparent surface velocities. The results indicate that travelling wave effect remarkably influences the uncontrolled seismic responses, the semi-active control seismic responses and vibration control effects for the long-span rigid-continuous bridge. It is disadvantageous to the responses of the beams and the piers under the travelling wave input with lower apparent surface velocity, and travelling wave effect can decrease the vibration control effects evidently. Therefore, the travelling wave effect should be considered for the selection of the parameter values of semi-active control system in order to get the designing control effect.

Spatial-temporal characterization of the San Andreas Fault by fault-zone trapped waves at seismic experiment site,Parkfield,California

In this article,we review our previous research for spatial and temporal characterizations of the San Andreas Fault(SAF)at Parkfield,using the fault-zone trapped wave(FZTW)since the middle 1980s.Parkfield,California has been taken as a scientific seismic experimental site in the USA since the 1970s,and the SAF is the target fault to investigate earthquake physics and forecasting.More than ten types of field experiments(including seismic,geophysical,geochemical,geodetic and so on)have been carried out at this experimental site since then.In the fall of 2003,a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth(SAFOD)site;the main-hole(MH)passed a~200-m-wide low-velocity zone(LVZ)with highly fractured rocks of the SAF at a depth of~3.2 km below the wellhead on the ground level(Hickman et al.,2005;Zoback,2007;Lockner et al.,2011).Borehole seismographs were installed in the SAFOD MH in 2004,which were located within the LVZ of the fault at~3-km depth to probe the internal structure and physical properties of the SAF.On September 282004,a M6 earthquake occurred~15 km southeast of the town of Parkfield.The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake.This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF,California,will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models,the fault models and the earthquake forecasting models in global seismogenic regions.

BOUNDED TRAVELING WAVE SOLUTIONS OF VARIANT BOUSSINESQ EQUATION WITH A DISSIPATION TERM AND DISSIPATION EFFECT

This article studies bounded traveling wave solutions of variant Boussinesq equation with a dissipation term and dissipation effect on them. Firstly, we make qualitative analysis to the bounded traveling wave solutions for the above equation by the theory and method of planar dynamical systems, and obtain their existent conditions, number, and general shape. Secondly, we investigate the dissipation effect on the shape evolution of bounded traveling wave solutions. We find out a critical value r^＊ which can characterize the scale of dissipation effect, and prove that the bounded traveling wave solutions appear as kink profile waves if ｜r｜≥ r^＊; while they appear as damped oscillatory waves if ｜r｜ 〈 r^＊. We also obtain kink profile solitary wave solutions with and without dissipation effect. On the basis of the above discussion, we sensibly design the structure of the approximate damped oscillatory solutions according to the orbits evolution relation corresponding to the component u（ξ） in the global phase portraits, and then obtain the approximate solutions （u（ξ）, H（ξ））. Furthermore, by using homogenization principle, we give their error estimates by establishing the integral equation which reflects the relation between exact and approximate solutions. Finally, we discuss the dissipation effect on the amplitude, frequency, and energy decay of the bounded traveling wave solutions.

Topographic effects on seismic response of long-span rigid-frame bridge under SV seismic wave

Seismic ground motions of two neighboring mountains and the free surface between them are calculated under the SV seismic waves with three different incident angles. The results are then taken as the inputs of multi-point seismic excitations for the foundation of a long-span bridge built over the valley in the analysis considering the integrated influence of traveling wave and topography. On the basis of a dynamic analytical method, a finite element model is created for the seismic responses of a four-span rigid-frame bridge of 440 m. The pier-top displacement and the pier-bottom internal force of the bridge are calculated. Then the results are compared with those considering traveling-wave effect only. The conclusions can serve as a seismic design reference for the structures located on the complex mountain topography.

Characterization Method of Explosion Seismic Wave

A new characterization method of explosion seismic wave is suggested on the basis of the analysis of experimental measured results. The seismic wave function is resolved into amplitude modulation part and random one. For the latter, the fractal dimension and the relevant characterization parameters are yielded by using the Weirstrass Mandelbrot (W M) fractal function. In contrast with conventional statistical parameters, the new set of parameters is independent of the chosen time length scales and the measuring instruments. A modeling example is presented which shows that the theoretical results are in agreement with the experimental results.

Effect of cyclotron resonance on ‘hot’ dispersion in a staggered double metallic grating sheet beam travelling wave tube

Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion equation considering both cyclotron resonance and Cherenkov resonance in a staggered double metallic grating traveling wave tube is deduced.Through the reasonable selection for geometric and electrical parameters, the numerical calculation and analysis of the ‘hot’ dispersion equation shows that the beam–wave interaction gain and frequency band with the cyclotron resonance enhancement effect are higher than those with only Cherenkov resonance radiation.

Application of passive source surface-wave method in site engineering seismic survey

Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the passive source surface-wave method is introduced into the site engineering seismic survey and practically applied in an engineering site of Shijingshan District. By recording the ubiquitous weak vibration on the earth surface, extract the dispersion curve from the surface-wave components using the SPAC method and obtain the shear-wave velocity structure from inversion. Over the depth of 42 m under- ground, it totally consists of five layers with interface depth of 3.31, 4.50, 7.23, 17.41, and 42.00 m; and shear-wave velocity of 144.0, 198.3, 339.4, 744.2, and 903.7 m/s, respectively. The inversion result is used to evaluate site classification, determine the maximum shear modulus of soil, provide basis for further seismic hazard analysis and site assessment or site zoning, etc. The result shows that the passive source surface-wave method is feasible in the site engineering seismic survey and can replace boreholes,shorten survey period, and reduce engineering cost to some extent.

Analysis of the role of diffraction in topographic site effects using boundary element techniques

The role played by the diffraction field on the problem of seismic site effects is studied. For that purpose we solve and analyze simple scattering problems under P and SV in-plane wave assumptions, using two well known direct boundary-element-based numerical methods. After establishing the difference between scattered and diffracted motions, and introducing the concept of artificious and physically based incoming fields, we obtain the amplitude of the Fourier spectra for the diffracted part of the response： this is achieved after establishing the connection between the spatial distribution of the transfer function over the studied simple topographies and the diffracted field. From the numerical simulations it is observed that this diffracted part of the response is responsible for the amplification of the surface ground motions due to the geometric effect. Furthermore, it is also found that the diffraction field sets in a fingerprint of the topographic effect in the total ground motions. These conclusions are further supported by observations in the time-domain in terms of snapshots of the propagation patterns over the complete computational model. In this sense the geometric singularities are clearly identified as sources of diffraction and for the considered range of dimensionless frequencies it is evident that larger amplifications are obtained for the geometries containing a larger number of diffraction sources thus resulting in a stronger topographic effect. The need for closed-form solutions of canonical problems to construct a robust analysis method based on the diffraction field is identified.

Present State of Explosion Seismic Wave Research and Primary Investigation on Its Characteristics

The present state and the significance of research on explosion seismic waves are discussed, and meanwhile the main contents and the basic problems to be solved in the study of explosion seismic waves are analyzed. The spectra characteristics of explosion seismic waves, functions of the isolated-seismic grooves and influences of the detonating methods on explosion seismic waves are investigated by experiments. The experimental method is introduced. Some experimental results are presented which are concerned with the influences of topographical conditions, explosive charges, ignition patterns, isolated-seismic grooves and the other related factors on the characteristics of seismic waves.

Amplification effect of near-field ground motion around deep tunnels based on finite fracturing seismic source model

Dynamic failure of rock masses around deep tunnels,such as fault-slip rockburst and seismic-induced collapse,can pose a significant threat to tunnel construction safety.One of the most significant factors that control the accuracy of its risk assessment is the estimation of the ground motion around a tunnel caused by seismicity events.In general,the characteristic parameters of ground motion are estimated in terms of empirical scaling laws.However,these scaling laws make it difficult to accurately estimate the near-field ground motion parameters because the roles of control factors,such as tunnel geometry,damage zone distribution,and seismic source parameters,are not considered.For this,the finite fracturing seismic source model(FFSSM)proposed in this study is used to simulate the near-field ground motion characteristics around deep tunnels.Then,the amplification effects of ground motion caused by the interaction between seismic waves and deep tunnels and corresponding control factors are studied.The control effects of four factors on the near-field ground motion amplification effect are analyzed,including the main seismic source wavelength,tunnel span,tunnel shape,and range of damage zones.An empirical formula for the maximum amplification factor(a_(m))of the near-field ground motion around deep tunnels is proposed,which consists of four control factors,i.e.the wavelength control factor(F_(λ)),tunnel span factor(F_(D)),tunnel shape factor(F_(s))and excavation damage factor(F_(d)).This empirical formula provides an easy approach for accurately estimating the ground motion parameters in seismicityprone regimes and the rock support design of deep tunnels under dynamic loads.

Modeling the Infection Disease (Covid-19) and the Effect of Vaccination

In this paper we provide different types of approach in mathematical biology about infection disease and understanding the dynamic of epidemic mathematical models specially in COVID-19 disease which first outbroke in China and fast spread around the world. We work in the connection between the mathematical models and the solution analytically and numerically. At first, we emphasize the Susceptible-Infectious-Recovered (SIR) models’ extension for policy significance. Then, we found the improved SIER model done by research. In third section, we examine the improved model when an appropriate vaccine has been found, we introduce the model of SIR with vaccine term which ends up with discussion and conclusion about the effect of vaccinate. The comprehension of COVID-19 transmission methods, structures, and characteristics is greatly aided by these mathematical models analytically and numerically.

Assessment of seismic ground motion amplification and liquefaction at a volcanic area characterized by residual soils

A seismic hazard was assessed related to site effects at Abbadia San Salvatore, central Italy, on the Mt. Amiata slopes, an ancient volcanic area characterized by residual soils(thick layers of loose to dense sands originated from weathering of the trachydacitic lavas). The seismic ground amplification and soil liquefaction related to these layers were recognized as the major seismic hazards for the area.Geological, geophysical, and geotechnical surveys were carried out on the volcanic rocks. The Horizontal-to-Vertical Spectral Ratio(HVSR) analysis of 252 noise measurements and 29 shear-wave velocity models of the subsoil allowed a seismic microzonation of the studied area, distinguished by thick weathered volcanic sands and shear-wave impedance contrast with respect to the seismic bedrock(volcanic bedrock). The differentiation of classified zones allowed recognition of areas characterized by residual(almost undisturbed) soils from those with soils probably affected by flowing water. The analysis of hazards revealed that peak acceleration by seismic amplification of ground motion exceeded the value set by the national rules(0.175 g) in a restricted area of the zone characterized by the most perturbed soils(Zone D);the potential occurrence of soil liquefaction was also greater in this zone. Finally, the study showed potential high hazards due to site effects of the volcanic mountainous area characterized by residual soils as opposed to an alluvial plain formed by volcanic debris where these effects have generally been more recognized.

Mechanism of Elastic Waves Reflection in Geological Media

Reflecting properties of layered geological media are substantiated in the framework of phonon-phonon mechanism of elastic wave propagation in porous media. In this scope the reflection coefficient is calculated using not impedances but impulses of phonons in adjoining porous media. Assuming for the first approximation that rocks do fulfill an average time equation we got an expression for the reflection coefficient via porosity factors of that geological medium. For calculation of reflection coefficient the wavelength is chosen as averaging line scale. These coefficients are calculated at every depth point for a set of frequencies in seismic range. Resulting curves have special depth points. Being cross-plotted in time-frequency space such points do form coherent units. These units we call effective boundaries, because they cause all reflections for the given media in the framework of considered model. Effective boundaries are not wide-band as for two half spaces but have a cutoff at some low frequency. Geological medium at a whole is characterized by the system of such effective boundaries that are capable to form a reflection waves field. To construct this field an algorithm is developed that solves the direct problem of seismic in the framework of effective boundaries theory. This algorithm is illustrated with vibroseis survey modeling for a specific geological section.

Effect of Soliton Propagation in Fiber Amplifiers

The propagation of optical solitons in fiber amplifiers is discussed by considering a model that includes linear high order dispersion, two photon absorption, nonlinear high order dispersion, self induced Ramam and five order nonlinear effects. Based on travelling wave method, the solutions of the nonlinear Schr dinger equations, and the influence on soliton propagation as well as high order effect in the fiber amplifier are discussed in detail. It is found that because of existing five order nonlinear effect, the solution is not of secant hyperbola type, but shows high gain state of the fiber amplifier which is very favourable to the propagation of solitons.

Simulation and Traffic Safety Assessment of Heavy-Haul Railway Train-Bridge Coupling System under Earthquake Action

Aiming at the problem that it is difficult to obtain the explicit expression of the structural matrix in the traditional train-bridge coupling vibration analysis,a combined simulation system of train-bridge coupling system(TBCS)under earthquake(MAETB)is developed based on the cooperative work of MATLAB and ANSYS.The simulation system is used to analyze the dynamic parameters of the TBCS of a prestressed concrete continuous rigid frame bridge benchmark model of a heavy-haul railway.The influence of different driving speeds,seismic wave intensities,and traveling wave effects on the dynamic response of the TBCS under the actions of the earthquakes is discussed.The results show that the bridge displacement increase in magnitude in the lateral direction is more significant than in the vertical direction under the action of an earthquake.The traveling wave effect can significantly reduce the lateral response of the bridge,but it will significantly increase the train derailment coefficient.When the earthquake intensity exceeds 0.2 g,the partial derailment coefficient of the train has exceeded the limit value of the specification.

地震波特性对岩质边坡放大效应的影响规律研究

为了研究地震波特性对岩质边坡放大效应的影响。采用黏弹性边界和等效节点力结合的输入方法,基于ABAQUS建立岩质边坡数值模型,分析了地震波幅值、频率和持时对岩质边坡加速度方法和反应谱放大的影响规律。研究结果表明,地震波频率对边坡放大效应影响最为显著,随着频率增加,坡顶处的放大系数显著增大;地震波幅值和持时对放大效应的影响较小。此外,反应谱放大峰值随地震波频率增加而增大,对应的周期变短。研究成果可为边坡工程的抗震设计提供参考。

Double-Frequency Microseisms on the Thick Unconsolidated Sediments in Eastern and Southeastern Coasts of United States: Sources and Applications on Seismic Site Effect Evaluation

This study presents a systematic analysis of double-frequency(DF) microseisms recorded on the unconsolidated sediments in the eastern and southeastern coasts of United States. For all recordings, the site effect parameters(predominant frequency(f_(0)), amplification factor and unconsolidated sediment thickness(UST)) are obtained by Nakamura method and the DF spectra are classified into five groups in terms of the DF peak patterns and the recording locations relative to the coastline. The frequencies and energy levels of the DF peaks in horizontal direction and the amplification factors are associated with the UST which is resulted from seismic site effect. By polarization analysis, the primary vibration directions of the DF peaks are identified and presented as great circles passing through the recording stations intersecting mainly along the continental slope. Correlation analyses of time histories of the DF energy and the ocean wave climate observed at buoys show that the low(<0.2 Hz) and high(>0.2 Hz) frequency DF microseisms are generated in the deep ocean and the continental shelf respectively. It is concluded that the continental slope plays a significant role in the generation of DF microseisms as it causes reflection of waves from the open ocean, initiating standing waves.

Modelling Large Scale Invasion of <i>Aedes aegypti </i>and <i>Aedes albopictus</i>Mosquitoes

The principle aim of this work is to simulate the invasion of two invasive mosquito species Aedes aegypti and Aedes albopictus in central Europe at a landscape scale. The spatial-temporal dynamics of invasion is investigated in dependence of predation pressure, seasonal variation of ambient temperature as well as human population density. The introduction of temperature dependent entomological parameters enables the simulation of seasonal pattern of population dynamics. The influence of temperature, predation pressure and human population density on invasion is studied in one-dimensional cases. In two dimensions, georeferenced parameters such as annual mean temperature and human population density are prepared by a geographical information system and introduced into the finite element tool COMSOL Multiphysics. The results show that under the current temperature, central Europe cannot become a permanent breeding region for Aedes aegypti. However, southwest Germany especially the regions along the Upper Rhine Valley may provide suitable habitats for the permanent establishment of Aedes albopictus. An annual temperature rise of two degrees would lead to dramatic increase of invasion speed and extension range of Aedes albopictus.