Vertical Spectra Research Articles

Soil dynamic response mapping and vulnerability analysis of earthquake hazard in Banda Aceh using HVSR method

Banda Aceh is a city with a high level of seismicity and earthquake risk. The seismicity level is mainly caused by two Sumatran Fault segments, i.e., the Aceh and Seulimeum Segments. Soft alluvium deposits aggravate the earthquake hazard in Banda Aceh. The presence of soft alluvium layers above the more rigid soil layer will cause earthquake wave amplification. This amplification phenomenon can increase the amplitude and energy of earthquake waves, making the earthquake more destructive.Therefore, dynamic response mapping and subsurface structure modeling are required to determine the soil characteristics of the research area. Such information is needed for the infrastructure and planning development of Banda Aceh City. This study obtained the subsurface model from microtremor data and a sequence of processing and modeling techniques. The process uses the Horizontal to Vertical Spectral Ratio method (HVSR). The resonance frequency and amplification values are identified from the ratio between the horizontal and vertical spectrum components depicted in the HVSR curves. Based on the obtained results, Banda Aceh has a predominant frequency values range of 0.54-11.72 Hz and an amplification range of 1.22-6.26. Low predominant frequency is mainly located in the study area’s southeast and center, which is associated with large sediment thickness. Meanwhile, high amplification values are mainly located on the study area’s southeast, middle, and northwest sides, which are associated with increased sediment depth and geological features in the form of swamp sediment. Then the value of seismic vulnerability (Kg ) can be obtained based on the predominant frequency and amplification value. In this study, the value of seismic vulnerability ranges between 0.72-31.77 area with relatively high vulnerability values in the middle, southeast, south, and southwest of the study area.

Vertical time-of-flight spectroscopy of ultracold neutrons

This paper describes the mathematical basis for analysis of vertical time-of-flight (TOF) measurements with ultracold neutrons (UCN). In contrast to conventional horizontal TOF, this enables spectroscopy of UCN incident on the chopper with kinetic energies below the neutron optical potential of the detector entrance window. Much of the treatment presented here is general, and may be applied to horizontal and vertical TOF data of stationary and time-dependent spectra. Transformation rules are given for the conversion of vertical TOF spectra into other spectra of interest, and some aspects of detection efficiency are discussed that are common to all vertical TOF measurements using detectors with entrance windows. Throughout the paper, examples are provided using experimental data from measurements at the SUN-2 prototype superthermal UCN source. The technical details of these experiments and a comprehensive characterization of the source will be published by the present authors in a later paper.

The low-lying electronic states of ScO2 and ScO2 −: a computational study

The low-lying electronic states of ScO2 and ScO2 – were studied using the SAC-CI method. The lowest six doublet states (X2B2, 12A1/22A′, 22A1, 12A2, 12B1/12A″, and 22B2) of ScO2 and the valence-bound singlet/triplet states (X1A1, 21A1/13A1, 11A2/13A2, 11B1/13B1, 11B2/13B2, and 21B2/23B2) of ScO2 – were optimised, and the relative energies among these electronic states were obtained. The electron detachment energies from the X1A1 state of ScO2 – to the lowest six doublet states of ScO2 and from the 13B2 state of ScO2 – to the X2B2 state of ScO2 can be compared with the previous experimental photoelectron spectra of ScO2 –. The vertical excitation spectra of ScO2 and ScO2 – were computed. The singlet/triplet dipole-bound states (1B2(DB)/3B2(DB)) of ScO2 – were found.

Correlation and Joint Distribution of Spectral Accelerations of Vertical Ground Motions

ABSTRACT This paper estimates a correlation model and joint distribution model of spectral accelerations of vertical ground motions based on the NGA-West2 ground motion database. The correlation model calculated via BC16 vertical GMPE in this study is compared with those published models via other vertical NGA-West2 GMPEs. It is verified that the calculated residuals of vertical ground motions at multiple periods follow the multivariate normal distributions via both a qualitative validation method and a set of quantitative validation methods. The correlation model and the joint distribution model of vertical spectral accelerations are the theoretical basis for research on the joint occurrence of spectral accelerations of vertical ground motions, and an example of applied research on joint occurrence of spectral accelerations of vertical ground motions is studied: the conditional mean spectrum of vertical ground motions. Finally, the effects of different vertical correlation models and ground motion prediction equations on vertical conditional spectra are investigated for wide application of the correlation model and the joint distribution model of spectral accelerations of vertical ground motions.

Effect of compressive residual stress and press fitting on residual life assessment of deep-rolled EA4T steel railway axles

Deep rolling surface strengthening is an effective way to introduce compressive residual stress (CRS) along the railway axle, which can improve the fatigue resistance of the material. The CRS field was rebuilt adopting the proportional-integral (PI) iteration method and the unit pressure method (UPM) to study the fatigue cracking behavior of deep-rolled EA4T railway axles. The remaining life prediction model and the stress intensity factor (SIF) solution method were then validated using simulations and testing with small-sized specimens. The remaining life of the EA4T railway axle was then calculated by applying a realistic vertical load spectrum. The results showed that CRS prevented crack propagation, enhanced the critical propagation size of railway axle cracks, and prolonged the remaining life of the axle. Additionally, the remaining life of the axle may not support the following maintenance period if a crack with an extendable size emerges at the unloading groove of the railway axle. This work provides a theoretical basis for the optimization of the non-destructive testing (NDT) interval of deep-rolled EA4T railway axles.

Probing Gravity Waves in the Middle Atmosphere Using Infrasound From Explosions

AbstractThis study uses low‐frequency, inaudible acoustic waves (infrasound) to probe wind and temperature fluctuations associated with breaking gravity waves (GWs) in the middle atmosphere. Building on an approach introduced by Chunchuzov et al., infrasound recordings are used to retrieve effective sound‐speed fluctuations in an inhomogeneous atmospheric layer that causes infrasound backscattering. The infrasound was generated by controlled blasts at Hukkakero, Finland, and recorded at the IS37 infrasound station, Norway in the late summers 2014–2017. Our findings indicate that the analyzed infrasound scattering occurs at mesospheric altitudes of 50–75 km, a region where GWs interact under non‐linearity, forming thin layers of strong wind shear. The retrieved fluctuations were analyzed in terms of vertical wave number spectra, resulting in an approximate power law that corresponds to the “universal” saturated spectrum of atmospheric GWs. The power law wavenumber range corresponds to vertical atmospheric scales of 33–625 m. The fluctuation spectra were compared to theoretical GW saturation theories as well as to independent wind measurements by the Saura medium‐frequency radar near Andøya Space Center around 100 km west of IS37, yielding a good agreement in terms of vertical wavenumber spectrum amplitudes and slopes. This suggests that the radar and infrasound‐based effective sound‐speed profiles represent low‐ and high‐wavenumber regimes of the same “universal” GW spectrum. The results illustrate that infrasound allows for probing fine‐scale dynamics not well captured by other techniques, suggesting that infrasound can provide a complementary technique to probe atmospheric GWs.

Features of vortex trace propagation for aircraft with propellers

The article presents the results of a study of the characteristics of the wake vortex of aircraft with turboprop engines. Using the example of the An-12 aircraft, it is shown that rotating propellers make a noticeable contribution to the propagation of the vortex trail behind the aircraft. This is proved by some studies, as well as numerous observations. It also describes a technique for studying the wake vortex of aircraft with propellers. The method is based on the method of discrete vortices. The relevance of such studies is due to the growing interest of carrier companies in aircraft with turboprop engines. It has been proven that when transporting passengers and cargo on such vessels over distances of 700–800 km, maintenance and fuel costs are reduced by about 30–40%. Therefore, the fleet of turboprop aircraft, such as An-22, An-70, An-12, as well as Tu-95, Il-38, C-130, etc., has been preserved so far. New turboprop aircraft are being developed and put into operation: A-400M, Il-114, Il-112M. The vortex trail behind such aircraft also poses a danger to other aircraft flying behind. A feature of the propagation of the wake vortex behind aircraft with propellers is the interaction of vortices coming off the airframe and vortices from the propellers. As a result, due to the rotation of all the screws in one direction, symmetry is broken in the propagation of vortices descending from the right and left halves of the wing. Therefore, it is important to understand how differently the vortices that descend from the airframe of an aircraft with turboprop engines behave. For the convenience of the study, the method of accounting for the effect of vortices from screws is integrated into a special calculation and software package, also based on the method of discrete vortices. In it, when calculating the characteristics of the wake vortex, the flight weight, speed and altitude of the aircraft, its flight configuration, atmospheric conditions, proximity of the earth, axial velocity in the core of the vortex and some other factors are taken into account. This complex has passed the necessary testing and state registration. A number of measures were carried out to validate and verify the developed complex, confirming the operability of the programs included in it and the reliability of the results obtained from it. The results of the study of the characteristics of the wake vortex behind the Antonov-12 aircraft in the form of vertical velocity spectra and fields of perturbed velocities at various distances from it are presented. It is shown that propellers noticeably affect the propagation of the wake vortex behind turboprop aircraft. This circumstance must be taken into account by the crews of aircraft flying behind such aircraft.

Vertical floor acceleration spectra for regular steel frame structures

The scope of this contribution is the assessment of the vertical peak component acceleration of single-degree-of-freedom (SDOF) oscillators attached to elastic moment-resisting steel frames subjected to recorded ground motions. These SDOF oscillators represent nonstructural components (NSCs) flexibly attached to the load-bearing structure whose acceleration demands correlate with their maximum strength demands. The results in terms of floor acceleration spectra show that the interaction between a vertically oscillating NSC and the structure is much more pronounced than for horizontally oscillating NSC of the same mass and natural frequency. This means that even for vertical NSCs with very small mass (in the case of the investigated eight-story frame 0.01% of the frame mass depending on the number of stories) a coupled analysis is required for a realistic prediction of the NSC acceleration demand. In a parametric study of vertical NSCs attached to steel frame structures of different number of stories, a median vertical peak component acceleration was observed up to 5.5 times larger than the vertical peak floor acceleration of the attachment node of the load-bearing structure and up to 20 times larger than the vertical peak ground acceleration. The amplification of the vertical acceleration response is thus of the same order of magnitude as for horizontal NSCs. This means that the vertical dynamic response of flexible NSCs cannot be neglected and should therefore be studied in more detail in the future.

Influence of seawater depth on offshore ground motion characteristics and seismic responses of sea-crossing cable-stayed bridges

This paper studies the effect of seawater depth on offshore earthquake motion characteristics and seismic response of bridges. By analyzing the offshore seismic data recorded by the K-NET during 2006–2021, the horizontal amplification coefficient spectrum and V/H spectral ratio of offshore ground motions were compared for various offshore stations at different seawater depths. Moreover, a numerical model simulating the propagation process of seismic waves in the seabed was developed to investigate the effects of seawater depth and site conditions on offshore ground motions. Finally, a site-seawater-pile foundation-cable-stayed bridge coupling model was created to study the influence of seawater depth on the seismic responses of sea-crossing cable-stayed bridges. The results reveal that the vertical response spectrum of offshore ground motion in deeper seawater is lower for periods longer than 0.3 s. The numerical models reveal that seawater has a suppression effect on the P wave near the resonance frequency of the seawater layer. Due to the hydrodynamic effect, the longitudinal bridge seismic response is significantly amplified. The amplification effect becomes more obvious with an increase in seawater depth. Therefore, it is important to consider the influence of the seawater layer in the seismic design of sea-crossing bridges.

Vertical floor spectra in low- and mid-rise elastic RC moment resisting frame buildings

To examine how floor spectral accelerations affect the design force of flexible Non-Structural Components (NSCs), the present study discusses the estimation of floor response spectra resulting from strong vertical seismic motion. 3-, 6-, 9- and 12-storey reinforced concrete buildings with moderately ductile moment-resisting frame systems, designed in accordance with the National Building Code of Canada [25] were selected for this research. 65 sets of historical records relating to 31 severe earthquakes from across the world were used to analyze the linear behavior of these structures. A constant amplification of the Vertical Floor Spectral Acceleration (FSAV) was observed along the building height. This amplification was noticeably elevated for slab nodes, especially at the center of the interior slab and in shorter buildings. Furthermore, the vertical component of the earthquake had a greater impact at shorter periods, since the maximum vertical acceleration occurred at periods lasting less than 0.35 sec. Finally, equations to estimate FSAV corresponding to the input vertical ground acceleration were proposed for typical code-conforming RC frame buildings.

Numerical study of the high-intensity heat conduction effect on turbulence induced by the ablative Rayleigh–Taylor instability

By adopting heat conduction of the Spitzer form in implicit large eddy simulations, the effect of high-intensity heat conduction on turbulence induced by the ablative Rayleigh–Taylor instability is studied in this paper. The height of the spike and bubble exhibit self-similar evolution with t2 dependence by the late stage of simulations, while heat conduction suppresses the coefficient of spike αs and slightly enhances that of the bubble αb. Heat conduction displays a strong damping effect for small-scale fluctuations of the temperature and density field, resulting in a much steeper slope for energy spectra in intermediate scales. The diffusion effect is responsible for the suppression of temperature fluctuations, and velocity dilatation is shown to be a possible route for heat conduction to affect density fluctuations. The impact of heat conduction on the velocity field is relatively weak, with vertical velocity spectra exhibiting classical Kolmogorov inertial range in intermediate scales. By comparing enstrophy profiles, it is found that vorticity tends to peak at the bubble side in cases with high-intensity heat conduction.

Momentum Flux and Vertical Wind Power Spectral Characteristics in the Troposphere and Lower Stratosphere Over Andøya, Norway as Observed by MAARSY

AbstractWe used the tropospheric and lower stratospheric 3D winds for four consecutive years (2017–2020) to study the momentum flux (MF) and vertical wind power spectra (VWP) over Andøya, Norway (69.30°N, 16.04°E) using the Middle Atmosphere Alomar Radar System. The spectra range from 3.5 days−1 > f > 30 min−1, which are categorized in terms of observed/ground‐based frequency (as the local inertial period is 13 h over Andøya), height ranges, and seasons. Our results indicate for the first time that (a) both the zonal and meridional MF display peaks around the inertial period (13 h) in the troposphere (1.80–12.00 km) during all seasons (with some exceptions), while VWP exhibits such features in the whole height range (1.80–18.00 km), (b) the minimum variability in MF, VWP, and kinetic energy is observed during summer, and (c) both the MF and VWP demonstrate height variation with maximum deviations below the tropopause.

Aircraft observations of gravity wave activity and turbulence in the tropical tropopause layer: prevalence, influence on cirrus clouds, and comparison with global storm-resolving models

Abstract. The tropical tropopause layer (TTL) is a sea of vertical motions. Convectively generated gravity waves create vertical winds on scales of a few to thousands of kilometers as they propagate in a stable atmosphere. Turbulence from gravity wave breaking, radiatively driven convection, and Kelvin–Helmholtz instabilities stirs up the TTL on the kilometer scale. TTL cirrus clouds, which moderate the water vapor concentration in the TTL and stratosphere, form in the cold phases of large-scale (> 100 km) wave activity. It has been proposed in several modeling studies that small-scale (< 100 km) vertical motions control the ice crystal number concentration and the dehydration efficiency of TTL cirrus clouds. Here, we present the first observational evidence for this. High-rate vertical winds measured by aircraft are a valuable and underutilized tool for constraining small-scale TTL vertical wind variability, examining its impacts on TTL cirrus clouds, and evaluating atmospheric models. We use 20 Hz data from five National Aeronautics and Space Administration (NASA) campaigns to quantify small-scale vertical wind variability in the TTL and to see how it varies with ice water content, distance from deep convective cores, and height in the TTL. We find that 1 Hz vertical winds are well represented by a normal distribution, with a standard deviation of 0.2–0.4 m s−1. Consistent with a previous observational study that analyzed two out of the five aircraft campaigns that we analyze here, we find that turbulence is enhanced over the tropical west Pacific and within 100 km of convection and is most common in the lower TTL (14–15.5 km), closer to deep convection, and in the upper TTL (15.5–17 km), further from deep convection. An algorithm to classify turbulence and long-wavelength (5 km < λ < 100 km) and short-wavelength (λ < 5 km) gravity wave activity during level flight legs is applied to data from the Airborne Tropical TRopopause EXperiment (ATTREX). The most commonly sampled conditions are (1) a quiescent atmosphere with negligible small-scale vertical wind variability, (2) long-wavelength gravity wave activity (LW GWA), and (3) LW GWA with turbulence. Turbulence rarely occurs in the absence of gravity wave activity. Cirrus clouds with ice crystal number concentrations exceeding 20 L−1 and ice water content exceeding 1 mg m−3 are rare in a quiescent atmosphere but about 20 times more likely when there is gravity wave activity and 50 times more likely when there is also turbulence, confirming the results of the aforementioned modeling studies. Our observational analysis shows that small-scale gravity waves strongly influence the ice crystal number concentration and ice water content within TTL cirrus clouds. Global storm-resolving models have recently been run with horizontal grid spacing between 1 and 10 km, which is sufficient to resolve some small-scale gravity wave activity. We evaluate simulated vertical wind spectra (10–100 km) from four global storm-resolving simulations that have horizontal grid spacing of 3–5 km with aircraft observations from ATTREX. We find that all four models have too little resolved vertical wind at horizontal wavelengths between 10 and 100 km and thus too little small-scale gravity wave activity, although the bias is much less pronounced in global SAM than in the other models. We expect that deficient small-scale gravity wave activity significantly limits the realism of simulated ice microphysics in these models and that improved representation requires moving to finer horizontal and vertical grid spacing.

Accuracy enhancement of laser-induced breakdown spectroscopy by polarization spectrum fusion

Laser-induced breakdown spectroscopy (LIBS) has been proven to be an effective way for online analysis of coal properties (such as ash content, volatile content, and calorific value), but the quantitative analysis accuracy still needs to be improved. Herein, a polarization spectral data fusion scheme was proposed to obtain more abundant spectral information and improve the performance of quantitative analysis models. First, the polarization effect of laser-induced coal plasma emission was analyzed using the Stokes parameters of the average spectra. Due to the partially polarized phenomenon of emission, fused data of PRLIBS (0°, 0) (horizontal plasma polarization spectra) and PRLIBS (90°, 0) (vertical plasma polarization spectra) was utilized to establish an efficient prediction model to obtain high prediction accuracy. For fusion models, the root mean square error prediction (RMSEP) of ash content, volatile content and calorific values were 1.497%, 0.595%, and 0.597%, respectively, and the coefficients of determination (R2) were 0.980, 0.968, and 0.978, respectively. Comparison with regression models for individual PRLIBS (0°, 0), PRLIBS (90°, 0), and LIBS data, the data fusion scheme significantly improved the performance of the prediction model. The improvement in model performance is due to the fact that there is no perfect correlation between PRLIBS (0°, 0) and PRLIBS (90°, 0), whilst polarization spectral fusion makes it possible to acquire more number of characteristic spectral lines with high importance score. The results demonstrated the feasibility of PRLIBS spectral fusion to provide better analytical results for ash content, volatile content, and calorific values of coal.

The Relationship between Horizontal and Vertical Velocity Wavenumber Spectra in Global Storm-Resolving Simulations

Abstract Several studies have reported vertical kinetic energy spectra almost white in horizontal wavenumber space with evidence of two maxima at synoptic scales and mesoscales, leaving the explanation of these maxima open. Processes known to influence the shape of the horizontal kinetic energy spectra include the superposition of quasi-linear inertia–gravity waves (IGWs), quasigeostrophic turbulence, and moist convection. In contrast, vertical kinetic energy has been discussed much less, as measuring vertical velocity remains challenging. This study compares the horizontal and vertical kinetic energy spectra and their relationships in global storm-resolving simulations from the DYAMOND experiment. The consistency of these relationships with linear IGW theory is tested by diagnosing horizontal wind fluctuations associated with IGW modes. Furthermore, it is shown that hydrostatic IGW polarization relations provide a quantitative prediction of the spectral slopes of vertical kinetic energy at large scales and mesoscales, where the intrinsic frequencies are inferred from the linearized vorticity equation. Our results suggest that IGW modes dominate the vertical kinetic energy spectra at most horizontal scales, whereas an incompressible, isotropic scaling of the continuity equation captures the relationship between horizontal and vertical kinetic energy spectra at small scales.

How Applicable Are Turbulence Assumptions Used in the Tidal Energy Industry?

As tidal current and marine hydro-kinetic energy converters start to be deployed in pre-commercial arrays, it is critical that the design conditions are properly characterised. Turbulence is known to influence fatigue loads and power production, so developers use turbulence models to generate unsteady flows in order to simulate device performance. Most such models construct a synthetic flow field using a combination of measured parameters and theoretical assumptions. The majority in use today are based on atmospheric flow conditions and may have limited applicability in tidal environments. In the present work, we compare key turbulence model assumptions (which are recommended by the tidal turbine standards and are used in design software) to turbulence measurements from two tidal test sites in Scotland and Canada. Here, we show that the two sites have different levels of conformity to theoretical models, with significant variability within nearby locations at the same site. The agreement with spectral models is shown to be depth-dependent. The vertical component spectrum is better represented by the Kaimal model, while the streamwise spectrum is better represented by the von Kármán model. With the exception of one site, the shear profiles follow a power law, although with a different exponent to that commonly assumed. Both sites show significant deviations from the theoretical length scales and isotropy ratios. Such deviations are likely to misrepresent the loads experienced by a device. These results highlight the turbulence characteristics at real deployment sites, which are not well represented by current models, and, hence, which must be determined using field measurements.

Adjustments to the law of the wall above an Amazon forest explained by a spectral link

Modification to the law of the wall represented by a dimensionless correction function ϕRSL(z/h) is derived using atmospheric turbulence measurements collected at two sites in the Amazon in near-neutral stratification, where z is the distance from the forest floor and h is the mean canopy height. The sites are the Amazon Tall Tower Observatory for z/h∈[1,2.3] and the Green Ocean Amazon (GoAmazon) site for z/h∈[1,1.4]. A link between the vertical velocity spectrum Eww(k) (k is the longitudinal wavenumber) and ϕRSL is then established using a co-spectral budget (CSB) model interpreted by the moving-equilibrium hypothesis. The key finding is that ϕRSL is determined by the ratio of two turbulent viscosities and is given as νt,BL/νt,RSL, where νt,RSL=(1/A)∫0∞τ(k)Eww(k)dk, νt,BL=kv(z−d)u*, τ(k) is a scale-dependent decorrelation time scale between velocity components, A=CR/(1−CI)=4.5 is predicted from the Rotta constant CR=1.8, and the isotropization of production constant CI=3/5 given by rapid distortion theory, kv is the von Kármán constant, u* is the friction velocity at the canopy top, and d is the zero-plane displacement. Because the transfer of energy across scales is conserved in Eww(k) and is determined by the turbulent kinetic energy dissipation rate (ε), the CSB model also predicts that ϕRSL scales with LBL/Ld, where LBL is the length scale of attached eddies to z=d, and Ld=u*3/ε is a macro-scale dissipation length.

Seismic effects of loess slopes using physical modeling and numerical simulation

A large shaking-table test of a loess slope with a geometric similarity ratio of 1:25 was established as a prototype model of the loess landslide in Yongguang Village, which occurred during the 2013 Minxian–Zhangxian M6.6 earthquake. Combined with finite-element–numerical-simulation software, the dynamic response characteristics of the loess slope were compared and analyzed under the action of the same Minxian horizontal seismic wave characteristics. The results show that the seismic waves observed in the model test and numerical simulation clearly exhibit non-linear amplification effects along the slope surface and in the loess vertical direction, reaching a maximum value at the top of the slope. The ground-motion acceleration waveforms observed in the model test and numerical simulation at each observation point of the slope were similar, and the horizontal peak ground acceleration (PGA) obtained from the numerical simulation at these locations was larger than that of the slope top. The horizontal aSimulated-max/aModel-max values ranged from 1.5 to 2.2 and the vertical aSimulated-max/aModel-max values were more discrete in the range of 0.5–2.7, while the horizontal and vertical-PGA-amplification factors at the slope surface were similar. The Fourier amplitude and main horizontal frequencies were mainly distributed between 0.1 and 12 Hz. The Fourier spectrum observed in the model test was approximately 0.5 Hz, while the main frequency of the vertical Fourier spectrum was approximately 4 Hz. Additionally, the main frequency of the horizontal and vertical Fourier spectra observed in the numerical simulation was approximately 2 and 1.2 Hz, respectively.

Relation Between Seated Person Vibrations and the International Roughness Index

Vertical vehicle feet/floor interface vibrations are typically not used to indirectly estimate road roughness. The relation for vehicle floor vibrations, the International Roughness Index (IRI), vehicle speed, and road roughness vertical displacement spectrum according to the ISO 8608: 2016 standard was previously derived only for the simulation of a reference quarter-car model. It was estimated using the in situ measurement of vibrations of a person sitting in a passenger car for different vehicle and road categories, vehicle speed, and road roughness. Vibrations at the feet/floor interface and seat surface of a seated passenger were evaluated with the frequency-weighted root-mean-square vertical acceleration according to the ISO 2631-1: 1997 standard. The results indicated that the simulated results for the quarter-car model may have substantially underestimated the ratio between the vehicle floor vibrations of a seated person and the IRI, but they were similar to seat surface vibrations.

Failure Mode Analysis of Bridge Pier Due to Eccentric Impact Based on Separation of Pier and Beam

By considering the near-field vertical seismic spectrum and calculating the change in vertical contact force between the main beam and the pier, the possible vertical separation contact condition of a bridge is deduced. By calculating the extreme value of the pier–beam vertical contact force and the longitudinal deformation of the pier under the structural separation, the influence of the separation on the failure of the pier is determined. Separation increases the risk of pier failure under compression, bending, and shear, and different separation times lead to different longitudinal responses from the pier, and the first failure mode is different. Therefore, it is of great significance to reasonably design bridges near faults.