Soil Dynamics and Earthquake Engineering最新文献

Geophones are typically arranged along the dam axis when seismic wave methods are used to detect latent hazards. Due to the complexity of the potential hazards and physical parameters inside the dam, the detection results may be inaccurate based on the seismic data in a single direction. The incorporation of seismic data perpendicular to the dam axis will effectively improve the detection accuracy. Mastering the propagation characteristics of seismic waves perpendicular to the earth-rock dam axis are necessitated for seismic data processing and interpretation yet remain a research gap, and the kinematic characteristics of various wave fields are underexplored. Here, an adaptive free boundary treatment scheme at the dam crest and slope is proposed based on the structural features of actual earth-rock dams, and the corresponding difference mode is provided. The full-wavefield simulation of seismic waves perpendicular to the dam axis is achieved using a finite-difference method with a spatial sixth-order and temporal second-order staggered grid. The kinematic characteristics of seismic wave propagation within the dam are elaborated. The layout of geophones perpendicular to the dam axis allows for recording the direct longitudinal wave and direct shear wave penetrating the dam, and surface wave reflection occurs at the crest corners and bottom corners. Influenced by the dam's slope structure, the path lengths of the reflected body waves vary irregularly depending on the locations of receiver points on the dam slope, resulting in irregular travel-time curves in seismic records.

This paper explores the fragility of pile-supported wharves to environmental hazards, notably climate change and corrosion, and underscores the critical need to understand the interplay between these factors when assessing structural safety. The research advocates for comprehensive methodologies that encompass climate change effects, aging, and time-dependent deterioration in evaluating the seismic fragility functions of pile-supported wharves. An examination of aging and seismic effects is performed on a representative pile-supported wharf at designated time intervals. This study highlights the pronounced impacts of climate change and corrosion on the structural integrity of concrete and steel in marine environments. Specifically, it considers effects such as sea level rise, increased temperatures, and heightened relative humidity on pile-supported wharves. Additionally, three corrosion pitting configurations in prestressed strands with and without climate change considerations are analyzed to determine their influence on the strength and ductility of materials, limit states, and ultimately, on the fragility curves. The findings indicate that climate change significantly exacerbates the corrosion of materials in pile-supported wharves, and increases failure probability. The relative increase in corrosion rate after 50 years due to climate change is found to be 94%.

To develop an effective pile foundation scheme for earthquake-prone regions, this study introduces a novel pile structure that integrates ultra-high-performance concrete (UHPC) with traditional prestressed high-strength concrete (PHC) pipe piles. The research focuses on assessing the impact of various connection forms between the pile and cap beam on the seismic performance of bridge substructures. Two 1/3-scale specimens were meticulously designed and tested: one featuring a cast-in-place (CIP) connection and the other incorporating precast assembly (PA) connection between the pipe pile and cap beam. Cyclic loading tests were conducted to evaluate the failure mode, lateral capacity, ductility, energy dissipation ability, residual displacement, rebar strain, curvature distribution and rotation of UHPC pipe piles with the two connection forms. The results indicate that the specimen with a CIP connection exhibits a higher horizontal load capacity and stronger energy dissipation ability, while the specimen with the PA connection displays superior self-centering ability, increased ductility, and causes less damage to the cap beam. Finally, finite element models were developed to analyze the effects of design parameters on the seismic performance of the pile connected by the two methods. This research may provide valuable design guidance for incorporating UHPC in pile foundations. To facilitate its practical implementation in engineering projects, further theoretical and experimental research is recommended in this paper.

In this paper, by using the wave function expansion (WFE) and the expansion of the cylindrical wave into plane wave (ECPW) methods, an analytical method for the dynamic response of a circular tunnel with segmental liner buried in the half-space soil to harmonic elastic waves is developed. The liner of the tunnel is supposed to consist of several segments and joints. Both the segments and joints are treated as open cylindrical shells, and the segment and joint shells together thus form an equivalent continuous shell (ECS) liner, and the thin shell theory is utilized to describe its vibration. The scattered wave field due to the presence of the tunnel and boundary of the half-space soil is divided into two parts, namely, the direct scattered wave field and secondary scattered wave field. The expressions for the direct scattered cylindrical waves in the soil is determined via the WFE method, while the secondary scattered waves form the boundary of the half-space soil are obtained by the ECPW method together with the application of the boundary condition along the soil surface. Applying the cylindrical shell theory on the ECS liner and using the Fourier series expansions for the variables and parameters of the ECS liner along the azimuthal direction together with introducing the Fourier component constitutive relation for the ECS liner, a system of equations for the Fourier component ECS displacements are derived with the differential equations for the ECS liner displacements. By using the system of equations, the expressions for the free and scattered wave fields and the continuity conditions at the interface between the liner and soil, the system of equations for the ECS liner coupled with the soil are derived. By using the developed analytical method for the tunnel, some results of the ECS tunnel under different incident waves are given.

Self-centering structures have become the focus of current research in earthquake engineering due to their excellent re-centering capability. The re-centering capability primarily influences the residual displacement of structures that is an essential index for assessing the performance of post-earthquake functional and withstand subsequent seismic events of structures. The main purpose of this paper is to investigate the re-centering capability of partially self-centering structures with flag-shaped hysteretic behavior subjected to near-fault pulsed ground motion. To this end, the current provisions on residual displacement of structures were first introduced. Then two self-centering energy dissipation braces (SCEBs) with fully re-centering capability and partially centering capability are developed, and their hysteretic behavior are investigated by quasi-static cyclic loading tests. To capture the flag-shaped hysteretic behavior of such self-centering structures, a mathematical restoring force model based on the Bouc-Wen model is developed. It is found that the self-centering capacity of a partially self-centering structure is inversely related to the energy dissipation capacity, resulting in a reciprocal effect on the maximum and residual deformations of the structure under earthquakes. The influence of the critical parameters (including the energy dissipation ratio (β), the post-yield stiffness ratio(α) and pulse period (T_p)) on the re-centering capability of the model is further investigated by using mathematical and statistical methods. Based on these results, the design recommended values of β for models with different α are given, furthermore, a simplified calculation formula for residual displacement of partially self-centering structures is established based on mathematical statistics.

This study applies the shock-waveform (SW) decomposition method, originally developed for mechanical shock analysis, to earthquake ground motions. It reveals a general shape similarity between the envelope of the Pseudo-Spectral Accelerations (PSAs) of SW decomposed components and the PSA of the corresponding ground motion. Based on this similarity, a novel method to determine the characteristic period $T_g$, the long-period transition period $T_D$, the shape correction period $T_{\beta }$, and the Design Response Spectrum (DRS) is proposed and evaluated. New methods to determine $T_g$, $T_D$ and $T_{\beta }$ from the signal decomposition perspective are integrated into the normalized DRS in Eurocode 8–2022, enabling the construction of the normalized DRS based on SW method (SWDRS). Furthermore, simple ground motion attenuation regression equations are derived to relate the parameters ($T_g$, $T_D$, $T_{\beta }$) and the corresponding spectral ordinates of the normalized SWDRS model with seismic magnitude and site conditions. The SWDRS model is validated by randomly selecting two sites in United States. For each site, the SWDRS is determined by using the attenuation regression equations and the DRS spectral plateau value from the official seismic hazard map. Comparisons between the SWDRS, the latest local DRS, and the severest historical PSA recorded at the specific site demonstrate that the SWDRS provides more accurate spectral values over intermediate- and long-period ranges for structural seismic design.

The randomness of material parameters and earthquake excitation greatly impacts the seismic stability of high concrete-faced rockfill dam (CFRD) slopes. However, no research has comprehensively analyzed the impacts of stochastic earthquake excitations, random parameters and their coupled effects on seismic stability of CFRD slopes and selected a multi-indicator evaluation criterion to carry out performance-based safety assessment. This paper develops a novel and comprehensive framework for evaluating the seismic stability of CFRD slopes based on the generalized probability density evolution method (GPDEM) with high efficiency and accuracy. The effects of three kinds of randomness on seismic stability of CFRD slopes were comprehensively compared and analyzed on the basis of multi-indices (safety factor (F_S), cumulative slip displacement and cumulative time with F_S < 1.0). Firstly, the nonlinear shear strength parameters of 40 high CFRDs were statistically collected to obtain the statistical characteristics of rockfill material strength parameters of actual CFRD projects. Secondly, three kinds of random samples were generated using generalized F-discrepancy (GF-discrepancy) method and Spectral expression-Random function (SERF) method. Then, the GPDEM was introduced to combine with three indices to perform the stochastic analysis and reliability evaluation. Finally, the fragility analysis of the CFRD slope was conducted. The results reveal that F_S is more sensitive to the ground motions randomness, while cumulative slip displacement and cumulative time with F_S < 1.0 are more sensitive to the material parameters randomness. The seismic safety evaluation of CFRD slopes based on multiple indices with full consideration of coupled randomness effects is necessary.

Irregularly designed structures frequently experience greater damage compared to regular buildings as a result of elevated torsional reactions and stress concentration, as indicated by evaluations of damage carried out subsequent to past seismic events. The irregularities in the plan configuration provide significant issues for building seismic design. One example of an irregularity is the re-entrant corners found in L-shaped structures, which can lead to early collapse by causing stress concentration from abrupt changes in stiffness and torsional response amplification. More than ever, a thorough investigation into the relationship between the issue of ground motion parameters (GMPs) and Damage is required because of the complex way that L-shaped buildings respond to earthquakes. The current study examines the relationship between a large number of commonly used GMPs and the associated damage for three-, six-, nine-, and twelve-story 3D buildings—that is, low-, mid, and high-rise structures—with asymmetric L-shaped plan layouts. The system of lateral load resistance that was used was Buckling Restrained Brace Frames (BRBFs). To assess a building's seismic performance, 15 bidirectional earthquake ground motions were applied using Nonlinear Time History Analysis (NTHA) for incident angles of 0°, 45°, 135°, 225°, and 315°. The structural response is reported in terms of the average and maximum inter-story drift as well as the total Park-Ang damage index. The relationship between GMPs and structural damage was then investigated using Pearson's correlation coefficient. The results indicate that the highest link with damage measurements is found for 3- and 6-story structures when looking at the spectral acceleration at the fundamental period, $S_a\left(T_1\right)$. However, PGD and SMV exhibit a stronger correlation than other GMPs for structures with nine and twelve stories. Additionally, Classification and Regression Trees (CART) is a decision tree algorithm used for predictive modeling. In this study suggested using CART (Classification and Regression Trees) algorithms to estimate the link between GMPs and Damage Indices. The findings demonstrate the ability of CART algorithms to extract the rules and correlations governing earthquake damage.

The current study focuses on deriving ground motion models (GMMs) for 21 ground motion parameters derived from data sourced from the Engineering Strong Motion (ESM) database. These parameters include Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), Peak Ground Displacement (PGD), PGV-to-PGA ratio, (V/H) PGA ratio Predominant Frequency ($F_p$), Central Frequency ($\Omega$), Spectral Parameter ($q$), Significant Duration ($T_{Sig}$), Root Mean Square Acceleration ($A_{rms}$), Arias Intensity ($I_a$), Cumulative Absolute Velocity (CAV), Characteristic Intensity ($I_C$), Acceleration Spectrum Intensity (ASI), Velocity Spectrum Intensity (VSI), Total Energy ($E_{acc}$), Spectral Centroid ($E_w$), Spectral Standard Deviation ($S_w$), Temporal Centroid ($E_t$), Temporal Standard Deviation ($S_t$), and Correlation between time and frequency [$\rho \left(t,\omega \right)$]. Both horizontal and vertical components are considered in this study. The inherent random effects within ground motion regression, encompassing inter-event, inter-site, inter-locality, and inter-region variabilities, are addressed using cross-nested mixed effect regression utilizing a non-parametric GMM approach employing Artificial Neural Network (ANN). Quantitative assessment of the models involves correlation coefficients for regression through the origin and error measures like mean squared error and mean absolute error. These findings of the assessment confirm reliable estimates of Ground Motion Parameters (GMPs). A comparison of GMPs computed using the proposed model and those reported in the literature indicated model's superior performance. Furthermore, satisfactory performance of the proposed GMM in ground motion simulation for the ESM region is demonstrated.