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Authors:Fakhar Muhammad Abbas, Norio Tanaka Abstract: Journal of Earthquake and Tsunami, Volume 16, Issue 01, February 2022. This study addresses the vivid internal flow structure variations through horizontal double-layered vegetation (HDLV) under subcritical flow conditions for an inland tsunami. The computational domain was built in ANSYS Workbench, while post-processing and simulation were performed using the computational fluid dynamics (CFD) tool FLUENT with the three-dimensional (3D) Reynolds stress model (RSM). Two alternative arrangements of HDLV were considered, namely Configuration 1 (short submergent layer [math] emergent layer (Lt)) and Configuration 2 (tall emergent layer [math] submergent layer (Ls)) along with varying flow depths. Strong inflections in velocity and Reynolds stress profiles were observed at the interface near the top of Ls, Whereas, these profiles were almost constant from bed to the top of vegetations inside Lt. A shear layer zone was formed above the top of Ls, which extended to the downstream region in Configuration 2 while it was restricted by Lt in Configuration 1. The normal Reynolds stresses at the bed were significantly greater within Ls in Configuration 2 than inside Lt in Configuration 1. Hence, Configuration 1 was performed relatively better than Configuration 2 in terms of reducing velocity within the vegetation, while Configuration 2 played a key role in attenuating the increased velocities and confining the shear layer above the short submergent layer. Citation: Journal of Earthquake and Tsunami PubDate: 2022-03-30T07:00:00Z DOI: 10.1142/S179343112250004X Issue No:Vol. 16, No. 01 (2022)
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Authors:Mohana Rajendran Abstract: Journal of Earthquake and Tsunami, Volume 16, Issue 01, February 2022. Ductility and energy dissipation capacity of the beam column joints are the two prominent characteristics which govern the stability of the entire structure constructed in the seismic prone areas. In this paper, the effect of potassium-activated geopolymer concrete in the exterior beam column joint application is investigated under low frequency cyclic loading. Numerical analysis has been done by using the finite element software Abaqus and compared with the experimental work. From the load deformation relationship, parametric studies are carried out in the aspects of ductility, stiffness degradation, energy dissipation capacity, drift ratio and cracking pattern. The use of potassium-activated geopolymer technology in the exterior beam column joint application resulted in the improved ductility, energy dissipation capacity with superior ultimate load carrying capacity of 1.05% over conventional cement reinforced concrete beam column joints with special confining reinforcement confirmed by IS 13920 due to the enormous polymerization activated by high molecular potassium ions. There is an improved energy dissipation capacity of 2.78% of potassium-based geopolymer specimen resulting in lesser number of non-structural cracks and 11.26% more deformation under 11.96% enlarged drift ratio than the conventional reinforced concrete specimen. From the observed results, it is clearly noted that the implementation of potassium-activated green polymer technology in the beam column joints possessed enhanced ductility characteristics to protect the structure susceptible to seismic environment and resulted in innovative, economical and sustainable mode of seismic-resistant building construction. Citation: Journal of Earthquake and Tsunami PubDate: 2022-03-30T07:00:00Z DOI: 10.1142/S1793431122500051 Issue No:Vol. 16, No. 01 (2022)
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Authors:Conghao Xu, Zhenhua Huang Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Understanding tsunami-induced scour at a pile breakwater is important for the foundation safety of this type of coastal defense structures. A series of wave-flume tests were performed for [math], with [math] being the gap size and [math] the pile diameter, to study the characteristics of the solitary-wave-induced local scour around a pile breakwater, including the scour-hole depth, scour-hole length, deposition sandbar height and the scoured volume. It was found that the jet flow through the gaps between piles caused the local scour around individual piles. A more or less two-dimensional deposition sandbar was found on the down-wave side of the pile breakwater in the later stage of the scour process. A new empirical equation was introduced to approximate the evolution of the depth of the scour hole induced by a series of solitary waves. The equation was verified by existing data reported in the literature for [math] and the new data reported in this study. Effects of the distance between piles on the characteristics of the local scour were discussed by comparing the results for [math] and 0.39. The comparison showed that the scour-hole depth and height of the sandbar for [math] were all noticeably larger than the corresponding values for [math]. Citation: Journal of Earthquake and Tsunami PubDate: 2022-05-05T07:00:00Z DOI: 10.1142/S1793431122400024
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Authors:Qifei Liu, Haiyang Zhuang, Qi Wu, Kai Zhao, Guoxing Chen Abstract: Journal of Earthquake and Tsunami, Ahead of Print. This paper systematically investigates the dynamic behavior of sandy soils mixed with recycled tire rubber over a wide strain range in the order of 10[math]–10[math], using combined resonant column and cyclic triaxial tests for measurement of the shear modulus and damping ratio. The experiment integrates small-strain tests using a resonant column apparatus and large-strain tests using a cyclic triaxial apparatus. The results demonstrated that the addition of rubber particles significantly enhances the linear elastic properties of the host sandy soils and improves the critical shear strain from which the rubber–sand mixtures change from linear to nonlinear stress–strain behavior. The critical shear strain is therefore introduced as the function of rubber content (RC), to identify the influence of RC on the strain-dependent dynamic properties of the host sandy soils. Then, a well-calibrated prediction formula is applied in conjunction with the concept of binary packing material to describe the behavior of the host sandy soils with various RC. Remarkably, the obtained normalized shear modulus and damping ratio vs. shear strain relationships address the limitations of existing testing methods to simultaneously capture the soil dynamic properties at low-strain (stiffness) and the large-strain (energy dissipation) regimes. The model constants can be simply determined through a unique set of explicit expressions which incorporate some basic index properties of the host sand and recycled tire rubber. In this regard, the proposed procedure provides a significant advantage in the evaluation of strain-dependent dynamic properties of rubber–sand mixtures in practice. Citation: Journal of Earthquake and Tsunami PubDate: 2022-04-22T07:00:00Z DOI: 10.1142/S1793431121400066
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Authors:W. Y. Sun, K. Qu, S. Kraatz, G. Y. Lan, C. B. Jiang Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Tsunamis, such as the 2004 Indian and 2011 Japan tsunamis, routinely cause severe damage along coasts. Coastal vegetation serves as an excellent, naturally occurring protection from tsunamis. However, prior studies focusing on the wave attenuation by vegetation assumed that solitary waves would adequately represent the major aspects of tsunamis. However, there are substantial differences between solitary tsunami waves with regards to their wave profiles and how it evolves with time. This study aims to improve our understanding of the wave-vegetation interactions by employing a more realistic wave profile (tsunami-like instead of solitary). This work uses measurements obtained during the 2011 Japan tsunami to parameterize the observed tsunami-like wave profile, which is then used to investigate the wave-vegetation interaction on a sloped beach, using a nonhydrostatic wave (NHWAVE) model. The work investigates the efficiency of vegetated sloped beach in mitigating the maximum run-up height and total wave energy as function of wave height, water depth, vegetation width, vegetation density and wave model (solitary vs. tsunami-like). Results show that a vegetated sloped beach is effective in reducing the wave energy of both kinds of waves. However, when a solitary wave is used, the vegetation patch is shown to be relatively better at attenuating wave energy and in reducing maximum run-up heights. The findings indicate that the solitary wave model overestimates protections afforded by coastal vegetation, and that it underestimates maximum run-up heights. The findings drawn from this study further broaden our understanding on the wave attenuation of tsunami surges and waves by a vegetated sloped beach. Citation: Journal of Earthquake and Tsunami PubDate: 2022-04-22T07:00:00Z DOI: 10.1142/S179343112140008X
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Authors:Jinghua Wang, Philip L.-F. Liu Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Tsunamis induced by megathrust in the Manila subduction zone impose alarming threats to the coastal cities in the northern South China Sea (SCS), and risk assessment of tsunami hazards in this region becomes demanding. One distinguishable geographic feature in this region is Dongsha Atoll, which is situated between the tsunami source zone and the China coastline. This study discusses the role of the Dongsha Atoll in modifying the tsunami impacts through numerical simulations of a group of synthetic tsunami events with [math]. Three types of representations for the Atoll in the numerical simulations are employed, specifically (i) the real topo-bathymetry of the Atoll is fully resolved (Model-1), (ii) the Atoll is removed (Model-2), and (iii) the Atoll is artificially represented by a cylinder (Model-3). The results show that without the Dongsha Atoll presence (Model-2), the tsunamis can induce a substantial increment of water level behind the Atoll and in the vicinity of the Pearl River Delta (PRD) region in China. While the results obtained by realistically modeling the Atoll (Model-1) show that a large amount of tsunami wave energy/momentum can be entrapped by the lagoon and slowly radiated to the ocean. The interactions between the tsunamis and the Atoll will lead to severe flooding on the Dongsha Island on the west bank of the Atoll. However, the peak water levels behind the Atoll and at the selected mainland coastal sites are reduced, indicating that the Dongsha Atoll can offer some degree of protection for the region in its behind. Meanwhile, a slightly smaller reduction of tsunami heights is reported in the simulations with the Atoll being represented by a cylinder (Model-3), implying that the reduction effects are sensitive to the representations of the Atoll. Therefore, the full model of the topo-bathymetry of the Dongsha Atoll is recommended for future tsunami risk assessments for both Dongsha Atoll and the mainland in the SCS region. Citation: Journal of Earthquake and Tsunami PubDate: 2022-04-22T07:00:00Z DOI: 10.1142/S1793431122400012
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Authors:Su Chen, Lei Fu, Zhijun Dai, Shiyang Chen, Xiaojun Li Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Accelerograms of 58 subduction zone earthquakes recorded by 25 K-NET coastal stations located in Sagami Bay and its adjacent regions were used to analyze the spectral properties of the source, propagation path, and site effects by using the generalized inversion technique. The inverted [math] values vary from 1.7[math]MPa to 17.4[math]MPa, with an average value of 4.89[math]MPa and a standard deviation of [math]. Although the depths of the selected earthquakes are confined to 30 km, which is similar to those of the crustal earthquakes, this study obtains an average [math] which coincides with the plate-boundary earthquakes rather than the crustal earthquakes. It implies that the stress condition of the plate-boundary region varies from the inland crust. The obtained [math] is similar to the previous studies. The [math] of the selected stations varies from 0.0479[math]s to 0.0904[math]s, indicating high-frequency attenuation for the coastal area. The inverted site response shows the systematic tendency for different site classes. The amplification levels of class A sites fluctuate around one between 1[math]Hz and 10[math]Hz. Class B sites indicate peak amplification at the resonant frequency distributed between 3[math]Hz and 10[math]Hz. Most of the Classes D and E sites have peak amplification below about 4[math]Hz. Using the inversion results as the input parameters of the stochastic finite-fault method, an [math] subduction zone earthquake was simulated. The resulting response spectra corresponded to the observations and confirmed that the inverted parameters are reasonable. Citation: Journal of Earthquake and Tsunami PubDate: 2022-03-30T07:00:00Z DOI: 10.1142/S1793431121400030
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Authors:Chunyu Wu, Dechun Lu, Chao Ma, Xiuli Du Abstract: Journal of Earthquake and Tsunami, Ahead of Print. The seismic performance of large underground structures can be evaluated from two perspectives, namely the horizontal interlaminar deformation and the vertical loading-carrying capacity. The current seismic analysis methods focus on the horizontal seismic performance with the interlaminar drift ratio as the evaluation index. It is difficult to fully reflect the vertical failure characteristics of the overall structure. This paper aims to develop an evaluation method to comprehensively evaluate the seismic performance of underground frame structures. The quantitative evaluation indexes, i.e. the vertical loading-carrying risk factor of columns and the vertical deflection risk factor of slabs, were defined to evaluate the seismic performance of underground frame structures. Then, the seismic performance evaluation method was established and the evaluation processes were described. Seismic response analysis of an underground frame structure with different spans on the upper and lower stories was conducted, and the seismic performance of the structural components and overall structure was quantitatively evaluated by using the proposed evaluation method. The seismic response laws of columns and slabs were analyzed and the potential failure mode of the structure was clarified. Furthermore, the failure mechanism of the structure was explained in detail. Numerical results presented that the proposed evaluation method can effectively identify the seismic-induced weak components and failure modes of underground frame structures, and thus has guiding significance for the seismic design of the underground frame structures. Citation: Journal of Earthquake and Tsunami PubDate: 2022-03-30T07:00:00Z DOI: 10.1142/S1793431121400042
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Authors:Yang Shi, Hong-Jun He, Yu Miao Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Numerous works have highlighted the importance of the site response analysis of vertical ground motion in the earthquake engineering field. However, most studies have focused on nonlinear site response analysis. Hence, the knowledge of the linear site response analysis of vertical ground motion is inadequate. In this study, we perform multidirectional linear site response analysis by applying the surface-to-borehole spectral ratio (SBSR) technique to the Kiban–Kyoshin strong-motion observation network (KiK-net) seismic data. We find the hyperbolic relationships between multiple natural frequencies and the corresponding fundamental frequency. We propose empirical formulas, which can reduce the error in the multiple natural frequencies estimated by a single-layer model. Moreover, a brief investigation is conducted to provide an extra evidence for a previous correction method to the horizontal-to-vertical spectral ratio (HVSR) technique. The results of this study provide the empirical tools and can be utilized as a reference for the multidirectional linear site response analysis based on seismic observations. Citation: Journal of Earthquake and Tsunami PubDate: 2022-03-30T07:00:00Z DOI: 10.1142/S1793431121400054
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Authors:Liu Zhong-Xian, Huang Zhen-En, Huang Lei, Sun Jun, Du Jian-Mei Abstract: Journal of Earthquake and Tsunami, Ahead of Print. In this study, the fast multipole indirect boundary element method (FM-IBEM) was adopted for solving the scattering problem of incident P-waves using a two-dimensional (2D) mountain terrain with large-scale random cracks. By adopting the FM-IBEM, this study resolves the bottleneck of the conventional boundary element method (BEM) for computing complex multi-degree-of-freedom models, and for the first time quantitatively analyzes the seismic wave scattering problem of large-scale narrow mountain cracks. After verifying the calculation accuracy, the horizontal and vertical displacement amplitudes of the mountain surface and its adjacent surface were accurately calculated. The results suggest the following: (1) Cracks significantly amplify the displacement amplitude of the mountain surface. The amplification mostly depends on the number of cracks and on the frequency of the incident P-wave. Compared with homogeneous mountains (no cracks), under the most unfavorable circumstances, the horizontal displacement is amplified more than 9.5-fold, while the vertical displacement is amplified more than 6.5-fold. (2) When the wave field passes through the crack area, a large amount of energy is trapped. Moreover, this energy is highly concentrated, which amplifies the local ground motion more than 7-fold. (3) The ground motion generated by the P-wave scattering by a mountain with large-scale random cracks exhibits a significant spatial difference. (4) The resonance of multi-order modes can emerge owing to large-scale random cracks. Compared with homogeneous mountains, the ground motion caused by the P-wave scattering by mountains with large-scale random cracks is much more severe in many cases. This phenomenon must be considered in practical seismic engineering applications. Citation: Journal of Earthquake and Tsunami PubDate: 2022-03-30T07:00:00Z DOI: 10.1142/S1793431121400078
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Authors:Gopala Krishna Rodda, Narsiram Gurjar, Dhiman Basu Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Recorded ground motion is nonstationary in both intensity and frequency contents. Two methodologies were reported by the authors elsewhere for generating spatially varying ground motion (SVGM), namely, (i) auto-spectral density (ASD)-based framework, and (ii) evolutionary power-spectral density (EPSD)-based framework. While the former framework imparts nonstationarity through a uniform modulation (that accounts for nonstationarity only in intensities), the latter framework accounts for nonstationarity in both intensity and frequency contents. Reported EPSD-based framework was modeled through a decay function and a random component and was investigated only in the context of horizontal ground motion. Reported EPSD-based framework made two strong assumptions that need further investigation: (i) spatial variation of the random component was assumed to be frequency independent; and (ii) phase-structure of the ground excitation simulated around the reference station (with seed motion) was assumed to be same as that of the seed motion. This paper investigates the possible impact of these two assumptions on the simulated SVGM through appropriately revising the framework and introducing the phase-structure accordingly. Possible effects of the phase-structure on structural demand are investigated through an idealized long-span bridge. Revised EPSD-based framework is next assessed against the vertical recordings of SMART1 array along with the auto-spectral density (ASD) framework. Though spectral representation is nearly identical in both the frameworks, the acceleration time series simulated using the revised EPSD-based framework matches the recorded data better when compared with the ASD-based framework. Possible effect of spatially varying vertical ground motion on the seismic design is investigated through the same idealized bridge model. Significant increase in the demand of axial force in piers and mid-span moment in the deck are observed. Although these inferences are contingent on the idealized example considered for illustration, the spatially varying vertical ground motion is expected to contribute significantly to the seismic design of long-span bridges. Citation: Journal of Earthquake and Tsunami PubDate: 2021-09-23T07:00:00Z DOI: 10.1142/S1793431122500038
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Authors:Cong Zhang, Lingkan Yao Abstract: Journal of Earthquake and Tsunami, Ahead of Print. Large surface water waves can be triggered in moraine-dammed lakes during earthquakes and may lead to the overtopping failure of moraine dams. In the earthquake-prone Himalayas, there are thousands of moraine-dammed lakes; their outburst may lead to catastrophic disasters (e.g. floods and debris flow), posing severe threats to humans and infrastructures downstream. This paper experimentally studied earthquake-induced water waves (EWWs) in moraine-dammed lakes and examined the effects of several factors (e.g. water depth, earthquake parameters, and uneven lake basin). The experimental results suggest that the EWWs positively correlate to the earthquake wave, and the maximum height of the EWWs increases by 10%–15% when the effect of the uneven lake basin is considered. Based on the experiment data, we derived a calculation equation to estimate the maximum amplitude of EWWs considering the basin effect, and proposed a fast risk assessment method for moraine lakes due to overtopping EWWs. Finally, based on the method, we assessed the failure risk of the moraine lakes located in the Gyirong river basin where the China–Nepal corridor crosses. The study broadens understandings of the risk source of moraine-dammed lakes. Citation: Journal of Earthquake and Tsunami PubDate: 2021-08-18T07:00:00Z DOI: 10.1142/S1793431122500014
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Authors:Yubing Wang, Shuang Shu, Yongxin Wu Abstract: Journal of Earthquake and Tsunami, Ahead of Print. The objective of this study was to investigate the liquefaction response of soil using the spatial variability of the shear modulus by considering different values of the coefficient of variation (COV) and the horizontal scale of fluctuation (SOF). For this purpose, a Monte Carlo simulation, combining the digital generation of a non-Gaussian random field with finite difference analyses, was utilized. Parametric studies were performed from the perspectives of the liquefaction area, excess pore water pressure (EPWP), and displacement at the ground surface. We found that a larger COV of the soil shear modulus was correlated with a slower reduction of liquefaction area and a lower EPWP ratio. To explain the influence from the perspective of the spatial distribution characteristics of the shear modulus, a deterministic model test was carried out. Additionally, it was found that the displacement history and the differential settlement at the end of shaking were regularly affected by the COV and the horizontal SOF, especially for large COV and horizontal SOF. Citation: Journal of Earthquake and Tsunami PubDate: 2021-08-18T07:00:00Z DOI: 10.1142/S1793431122500026
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Authors:Qunying Fan, Rui Pang, Bin Xu, Mingyuan Jing Abstract: Journal of Earthquake and Tsunami, Ahead of Print. As a relatively new means of transportation, the subway has become an important tool for the sustainable development of many cities. Being buried deep in soil under the weight of vital infrastructure, subway stations can be vulnerable to seismic excitations. Considering the high randomness of ground motions, it is important to research the failure probability and seismic performance of the subway station based on stochastic dynamic analysis. In this paper, a probability density evolution method (PDEM) coupled with a spectral representation random function is used to analyze the stochastic dynamic response and seismic probability of a subway station. First, according to the improved power spectral density model and the seismic design code of urban rail transit structures in China (GB 50909-2014), a set of nonstationary ground motions consistent with the code spectrum are obtained. Then, a great deal of deterministic dynamic calculations for Daikai subway station considering soil–structure interaction based on elastic–plastic methods are performed. In addition, the nonlinear stochastic response analysis and the dynamic probability analysis are obtained for the subway station by solving the PDEM equation. Finally, the probability density function (PDF) and cumulative distribution function (CDF) of the subway station under stochastic earthquake excitations are obtained based on three performance indices, including drift angle in the middle column, relative vertical displacement between floor and roof, and damage area ratio (DAR). The results show that the stochastic dynamic analysis and the probability density evolution method can analyze seismic response and evaluate seismic performance of subway stations effectively. The proposed method will serve as an effective tool for the seismic design of underground structures. Citation: Journal of Earthquake and Tsunami PubDate: 2021-07-26T07:00:00Z DOI: 10.1142/S1793431121400017
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Authors:Chunyi Cui, Zhimeng Liang, Chengshun Xu, Yu Xin, Benlong Wang, Kun Meng Abstract: Journal of Earthquake and Tsunami, Ahead of Print. According to the theories of wave propagation in visco-elastic continuum and Rayleigh-Love rod, a simplified model in axisymmetric conditions for the longitudinal vibration of large-diameter pipe pile (LDPP) in radially heterogeneous surrounding soil with viscous damping is presented. The relevant analytical solution for dynamic impedance at pile head is derived by using complex stiffness transfer method, which is also validated via independent comparisons with previous solutions. Besides, parametric analyses are carried out to reveal both the radial heterogeneity of surrounding soil and the lateral inertia effect of pile shaft on the dynamic impedance of LDPP. The obtained analytical solutions are suitable for the longitudinal vibration issues of floating LDPP in visco-elastic surrounding soil with radial heterogeneity, which can be conveniently degenerated to describe the longitudinal vibration of a floating solid pile in soil with radial heterogeneity as well as a floating LDPP or solid pile in radially homogenous soil. Citation: Journal of Earthquake and Tsunami PubDate: 2021-07-26T07:00:00Z DOI: 10.1142/S1793431121400029
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