Earthquake Engineering and Engineering Vibration最新文献

In this study, the instability and bifurcation diagrams of a functionally graded (FG) porous sandwich beam on an elastic, viscous foundation which is influenced by an axial load, are investigated with an analytical attitude. To do so, the Timoshenko beam theory is utilized to take the shear deformations into account, and the nonlinear Von-Karman approach is adopted to acquire the equations of motion. Then, to turn the partial differential equations (PDEs) into ordinary differential equations (ODEs) in the case of equations of motion, the method of Galerkin is employed, followed by the multiple time scale method to solve the resulting equations. The impact of parameters affecting the response of the beam, including the porosity distribution, porosity coefficient, temperature increments, slenderness, thickness, and damping ratios, are explicitly discussed. It is found that the parameters mentioned above affect the bifurcation points and instability of the sandwich porous beams, some of which, including the effect of temperature and porosity distribution, are less noticeable.

This paper presents an investigation of the seismic behavior of reinforced concrete (RC) structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design procedure. In this regard, the behavior of six prototype structures (with different heights and plan layouts) is investigated through nonlinear static and time history analyses, implemented in the OpenSees platform. The results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading stages. Moreover, the global response of the buildings is discussed in terms of some parameters, such as lateral overstrength due to the gravity flat slab-column frames. According to the nonlinear static analyses, in structures in which the slab-column connections were designed only for gravity loads, the slab-column connections exhibited a punching mode of failure even in the early stages of loading. However, the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318 (2019) was provided in the slabs at joint regions. Furthermore, despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures, a relatively significant overstrength was imposed on the structures by the gravity frames.

To quantify the seismic effectiveness of the most commonly used fishing line tie up method for securing museum collections and optimize fixed strategies for exhibitions, shaking table tests of the seismic systems used for typical museum collection replicas have been carried out. The influence of body shape and fixed measure parameters on the seismic responses of replicas and the interaction behavior between replicas and fixed measures have been explored. Based on the results, seismic effectiveness evaluation indexes of the tie up method are proposed. Reasonable suggestions for fixed strategies are given, which provide a basis for the exhibition of delicate museum collections considering the principle of minimizing seismic responses and intervention. The analysis results show that a larger ratio of height of mass center to bottom diameter led to more intense rocking responses. Increasing the initial pretension of fishing lines was conducive to reducing the seismic responses and stress variation of the lines. Through comprehensive consideration of the interaction forces and effective securement, it is recommended to apply 20% of breaking stress as the initial pretension. For specific museum collections that cannot be effectively protected by the independent tie up method, an optimized strategy of a combination of fishing lines and fasteners is recommended.

A seismic-induced landslide is a common geological catastrophe that occurs in nature. The Wangjiayan landslide, which was triggered by the Wenchuan earthquake, is a typical case in point. The Wanjiayan landslide caused many casualties and resulted in enormous property loss. This study constructs a simple surficial failure model based on the upper bound approach of three-dimensional (3D) limit analysis to evaluate the slope stability of the Wangjiayan case, while a traditional two-dimensional (2D) analysis is also conducted as a reference for comparison with the results of the 3D analysis. A quasi-static calculation is used to study the effect of the earthquake in terms of horizontal ground acceleration, while a parametric study is conducted to evaluate the critical cohesion of slopes. Rather than employing a 3D analysis, using the 2D analysis yields an underestimation regarding the safety factor. In the Wangjiayan landslide, the difference in the factors of safety between the 3D and 2D analyses can reach 20%. The sliding surface morphology as determined by the 3D method is similar to actual morphology, and the parameters of both are also compared to analyze the reliability of the proposed 3D method.

The horizontal to vertical spectral ratio (HVSR) methodology is used here to characterize pumice soils and to image the three-dimensional surface geometry of Guadalajara, Mexico. Similar to other Latin American cities, Guadalajara is exposed to high seismic risk, with the particularity of being the largest urban settlement in Latin America built on pumice soils. Methodology has not yet been tested to characterize subsoil depths in pumice sands. Due to the questionable use of traditional geotechnical tests for the analysis of pumice soils, HVSR provides an alternative for its characterization without altering its fragile and porous structure. In this work, resonance frequency (F₀) and peak amplitude (A₀) are used to constrain the depth of the major impedance contrast that represents the interface between bedrock and pumice soil. Results were compared with borehole depths and other available geotechnical and geophysical data and show good agreement. One of the profiles estimated on the riverbanks that cross the city, reveals different subsoil thickness that could have an impact on different site responses on riverine areas to an eventual earthquake. Government and academic efforts are combined in this work to characterize depth sediments, an important parameter that impacts the regulations for construction in the city.

The seismic performance of rubber concrete-layered periodic foundations are significantly influenced by their design, in which the band gaps play a paramount role. Aiming at providing better designs for these foundations, this study first proposes and validates the analytical formulas to approximate the bounds of the first few band gaps. In addition, the mapping relations linking the frequencies of different band gaps are presented. Furthermore, an optimal design method for these foundations is developed, which is validated through an engineering example. It is demonstrated that ensuring the superstructure’s resonance zones are completely covered by the corresponding periodic foundation’s band gaps can achieve satisfactory vibration attenuation effects, which is a good strategy for the design of rubber concrete layered periodic foundations.

This study aims to develop a damage-detection algorithm based on the electromagnetic wave properties inside a reinforced concrete structure. The proposed method involves employing two algorithms based on data measured using ground-penetrating radar—a common electromagnetic wave method in civil engineering. The possible defect area was identified based on the energy dissipated by the damage in the frequency-wavenumber domain, with the damage localized using the calculated relative permittivity of the measurements. The proposed method was verified through a finite difference time-domain-based numerical analysis and a testing slab with artificial damage. As a result of verification, the proposed method quickly identified the presence of damage inside the concrete, especially for honeycomb-like defects located at the top of the rebar. This study has practical significance in scanning structures over a large area more quickly than other non-destructive testing methods, such as ultrasonic methods.

The post-earthquake emergency period, which is a sensitive time segment just after an event, mainly focuses on saving life and restoring social order. To improve the seismic resilience of city road networks, a resilience evaluation method used in the post-earthquake emergency period is proposed. The road seismic damage index of a city road network can consider the influence of roads, bridges and buildings along the roads, etc. on road capacity after an earthquake. A function index for a city road network is developed, which reflects the connectivity, redundancy, traffic demand and traffic function of the network. An optimization model for improving the road repair order in the post-earthquake emergency period is also developed according to the resilience evaluation, to enable decision support for city emergency management and achieve the best seismic resilience of the city road network. The optimization model is applied to a city road network and the results illustrate the feasibility of the resilience evaluation and optimization method for a city road network in the post-earthquake emergency period.

This paper presents an air-coupled impact echo (IE) technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations. The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave, but it is the 1st order symmetrical (S1) mode Lamb wave at zero group velocity (S1-ZGV). Therefore, it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference. As a result, the technique reduces the effect of propagating waves, including the direct acoustic wave and ambient noise. It is named the Constant Phase IE (CPIE). The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques. The CPIE shows a performance advantage, especially in a noisy environment.

Steel-concrete composite structures (SCCS) have been widely used as primary load-bearing components in large-scale civil infrastructures. As the basis of the co-working ability of steel plate and concrete, the bonding status plays an essential role in guaranteeing the structural performance of SCCS. Accordingly, efficient non-destructive testing (NDT) on interfacial debondings in SCCS has become a prominent research area. Multi-channel analysis of surface waves (MASW) has been validated as an effective NDT technique for interfacial debonding detection for SCCS. However, the feasibility of MASW must be validated using experimental measurements. This study establishes a high-frequency data synchronous acquisition system with 32 channels to perform comparative verification experiments in depth. First, the current sensing approaches for high-frequency vibration and stress waves are summarized. Secondly, three types of contact sensors, namely, piezoelectric lead-zirconate-titanate (PZT) patches, accelerometers, and ultrasonic transducers, are selected for MASW measurement. Then, the selection and optimization of the force hammer head are performed. Comparative experiments are carried out for the optimal selection of ultrasonic transducers, PZT patches, and accelerometers for MASW measurement. In addition, the influence of different pasting methods on the output signal of the sensor array is discussed. Experimental results indicate that optimized PZT patches, acceleration sensors, and ultrasonic transducers can provide efficient data acquisition for MASW-based non-destructive experiments. The research findings in this study lay a solid foundation for analyzing the recognition accuracy of contact MASW measurement using different sensor arrays.