Earthquake Engineering and Engineering Vibration最新文献

The 2022 M6.9 Menyuan earthquake caused severe damage to a high-speed railway bridge, which was designed for high-speed trains running at speeds of above 250 km/h and is located right next to the fault. Bridges of this type have been widely used for rapidly constructing the high-speed railway network, but few bridges have been tested by near-fault devastating earthquakes. The potential severe impact of the earthquake on the high-speed railway is not only the safety of the infrastructure, trains and passengers, but also economic loss due to interrupted railway use. Therefore, a field survey was carried out immediately after the earthquake to collect time-sensitive data. The damage to the bridge was carefully investigated, and quantitative analyses were conducted to better understand the mechanism of the bridge failure. It was found that seismic action perpendicular to the bridge’s longitudinal direction caused severe damage to the girders and rails, while none of the piers showed obvious deformation or cracking. The maximum values of transverse displacement, out-of-plane rotation and twisting angle of girders reached 212.6 cm, 3.1 degrees and 19.9 degrees, respectively, causing severe damage to the bearing supports and anti-seismic retaining blocks. These observations provide a basis for improving the seismic design of high-speed railway bridges located in near-fault areas.

The single-station microtremor method is one of the fastest, most reliable, and cheapest methods used to identify dynamic soil properties. This study utilizes 49 single-station microtremor measurements to identify the dynamic soil properties of the Hilalkent quarter of the Yakutiye district in Erzurum. Soil dominant frequency and the amplification factor were calculated by using the Nakamura horizontal/vertical spectral ratio (H/V) method. While the soil dominant frequency values varied between 0.4 Hz and 10 Hz, the soil amplification factor changed between 1 and 10. Higher H/V values were acquired with lower frequency values. The vulnerability index (K_g) and shear strain parameters that are utilized to estimate the damage that may be caused by an earthquake were mapped. Especially in the west side of the study area, higher K_g values were observed. The shear strain map was created with 0.25 g, 0.50 g and 0.75 g bedrock accelerations, and soil types that lost elasticity during an earthquake were identified. The average shear wave velocity for the first 30 m (V_s30) was calculated. Finally, it was observed that the western part of the study area, which resulted in a higher period and higher H/V, higher K_g and lower V_s30 values, presents a higher risk of damage during an earthquake.

In this study, a novel equivalent damping ratio model that is suitable for reinforced concrete (RC) structures considering cyclic degradation behavior is developed, and a new equivalent linearization analysis method for implementing the proposed equivalent damping ratio model for use in seismic damage evaluation is presented. To this end, Ibarra’s peak-oriented model, which incorporates an energy-based degradation rule, is selected for representing hysteretic behavior of RC structure, and the optimized equivalent damping for predicting the maximum displacement response is presented by using the empirical method, in which the effect of cyclic degradation is considered. Moreover, the relationship between the hysteretic energy dissipation of the inelastic system and the elastic strain energy of the equivalent linear system is established so that the proposed equivalent linear system can be directly integrated with the Park-Ang seismic model to implement seismic damage evaluation. Due to the simplicity of the equivalent linearization method, the proposed method provides an efficient and reliable way of obtaining comprehensive insight into the seismic performance of RC structures. The verification demonstrates the validity of the proposed method.

A dynamic analysis of both twisting and regular towers is carried out to determine the results of considering soil-structure interaction (SSI) on high-rise buildings. In addition, the difference between the seismic performance of using twisting towers over regular ones is investigated. The twisting tower is a simulation of the Evolution Tower (Moscow). The towers’ skeletons consist of RC elements and rest on a reinforced concrete piled-raft foundation. The soil model is considered as multi-layered with the same soil properties as the zone chosen for the analysis (New Mansoura City, Egypt). The only difference between both towers is their shape in elevation. The whole system is modelled and analyzed in a single step as one full 3D model, which is known as the direct approach in SSI. All analyses are carried out using finite-element software (Midas GTS NX). Dynamic output responses due to three records of seismic loads are proposed and presented in some graphs. Based on the results, it is concluded that SSI has a considerable effect on the dynamic response of tall buildings mainly because of the foundation flexibility, as it leads to lengthening the vibration period, increasing the story drift and the base shear for both cases.

Replaceable flexural and shear fuse-type coupling beams are used in hybrid coupled shear wall (HCSW) systems, enabling concrete buildings to be promptly recovered after severe earthquakes. This study aimed to analytically evaluate the seismic behavior of flexural and shear fuse beams situated in short-, medium- and high-rise RC buildings that have HCSWs. Three building groups hypothetically located in a high seismic hazard zone were studied. A series of 2D nonlinear time history analyses was accomplished in OpenSees, using the ground motion records scaled at the design basis earthquake level. It was found that the effectiveness of fuses in HCSWs depends on various factors such as size and scale of the building, allowable rotation value, inter-story drift ratio, residual drift quantity, energy dissipation value of the fuses, etc. The results show that shear fuses better meet the requirements of rotations and drifts. In contrast, flexural fuses dissipate more energy, but their sectional stiffness should increase to meet other requirements. It was concluded that adoption of proper fuses depends on the overall scale of the building and on how associated factors are considered.

For real-time dynamic substructure testing (RTDST), the influence of the inertia force of fluid specimens on the stability and accuracy of the integration algorithms has never been investigated. Therefore, this study proposes to investigate the stability and accuracy of the central difference method (CDM) for RTDST considering the specimen mass participation coefficient. First, the theory of the CDM for RTDST is presented. Next, the stability and accuracy of the CDM for RTDST considering the specimen mass participation coefficient are investigated. Finally, numerical simulations and experimental tests are conducted for verifying the effectiveness of the method. The study indicates that the stability of the algorithm is affected by the mass participation coefficient of the specimen, and the stability limit first increases and then decreases as the mass participation coefficient increases. In most cases, the mass participation coefficient will increase the stability limit of the algorithm, but in specific circumstances, the algorithm may lose its stability. The stability and accuracy of the CDM considering the mass participation coefficient are verified by numerical simulations and experimental tests on a three-story frame structure with a tuned liquid damper.

Based on the domain reduction method, this study employs an SEM-FEM hybrid workflow which integrates the advantages of the spectral element method (SEM) for flexible and highly efficient simulation of seismic wave propagation in a three-dimensional (3D) regional-scale geophysics model and the finite element method (FEM) for fine simulation of structural response including soil-structure interaction, and performs a physics-based simulation from initial fault rupture on an ancient wood structure. After verification of the hybrid workflow, a large-scale model of an ancient wood structure in the Beijing area, The Tower of Buddhist Incense, is established and its responses under the 1665 Tongxian earthquake and the 1730 Yiheyuan earthquake are simulated. The results from the simulated ground motion and seismic response of the wood structure under the two earthquakes demonstrate that this hybrid workflow can be employed to efficiently provide insight into the relationships between geophysical parameters and the structural response, and is of great significance toward accurate input for seismic simulation of structures under specific site and fault conditions.

An efficient approach is proposed for the equivalent linearization of frame structures with plastic hinges under nonstationary seismic excitations. The concentrated plastic hinges, described by the Bouc-Wen model, are assumed to occur at the two ends of a linear-elastic beam element. The auxiliary differential equations governing the plastic rotational displacements and their corresponding hysteretic displacements are replaced with linearized differential equations. Then, the two sets of equations of motion for the original nonlinear system can be reduced to an expanded-order equivalent linearized equation of motion for equivalent linear systems. To solve the equation of motion for equivalent linear systems, the nonstationary random vibration analysis is carried out based on the explicit time-domain method with high efficiency. Finally, the proposed treatment method for initial values of equivalent parameters is investigated in conjunction with parallel computing technology, which provides a new way of obtaining the equivalent linear systems at different time instants. Based on the explicit time-domain method, the key responses of interest of the converged equivalent linear system can be calculated through dimension reduction analysis with high efficiency. Numerical examples indicate that the proposed approach has high computational efficiency, and shows good applicability to weak nonlinear and medium-intensity nonlinear systems.

In this work, a numerical study of the effects of soil-structure interaction (SSI) and granular material-structure interaction (GSI) on the nonlinear response and seismic capacity of flat-bottomed storage silos is conducted. A series of incremental dynamic analyses (IDA) are performed on a case of large reinforced concrete silo using 10 seismic recordings. The IDA results are given by two average IDA capacity curves, which are represented, as well as the seismic capacity of the studied structure, with and without a consideration of the SSI while accounting for the effect of GSI. These curves are used to quantify and evaluate the damage of the studied silo by utilizing two damage indices, one based on dissipated energy and the other on displacement and dissipated energy. The cumulative energy dissipation curves obtained by the average IDA capacity curves with and without SSI are presented as a function of the base shear, and these curves allow one to obtain the two critical points and the different limit states of the structure. It is observed that the SSI and GSI significantly influence the seismic response and capacity of the studied structure, particularly at higher levels of PGA. Moreover, the effect of the SSI reduces the damage index of the studied structure by 4%.

Several studies on functionally graded materials (FGMs) have been done by researchers, but few studies have dealt with the impact of the modification of the properties of materials with regard to the functional propagation of the waves in plates. This work aims to explore the effects of changing compositional characteristics and the volume fraction of the constituent of plate materials regarding the wave propagation response of thick plates of FGM. This model is based on a higher-order theory and a new displacement field with four unknowns that introduce indeterminate integral variables with a hyperbolic arcsine function. The FGM plate is assumed to consist of a mixture of metal and ceramic, and its properties change depending on the power functions of the thickness of the plate, such as linear, quadratic, cubic, and inverse quadratic. By utilizing Hamilton’s principle, general formulae of the wave propagation were obtained to establish wave modes and phase velocity curves of the wave propagation in a functionally graded plate, including the effects of changing compositional characteristics of materials.