This paper focuses on the ultimate state of three-story wood dwellings with high aspect ratios, which are increasing in Japan’s urban areas. Using shaking table test results from the 2019 full-scale shaking table test, a comprehensive study is conducted on the accuracy of evaluating ultimate state through the story shear failure mode at the first story, the tension fracture mode at the wall base of the first story, and foundation sliding mode on the soil. Methods evaluating the dynamic response behaviors of the building systems are also investigated. In the test, the current Japanese seismic design guidelines were applied, and two Grade-3 buildings were prepared. One adopted the Post-and-Beam structure (A-building), and the other the Shear-Wall structure (B-building). A series of tests planned very different physical boundary conditions surrounding their reinforced concrete (RC) mat foundations. The sills, column bases and wall bases of the upper wood structures were anchored to the RC foundations by steel anchor bolts, according to the current Allowable Stress Design (ASD) requirements. In the first stage, A-building equipped a Base-Isolation system, while B-building represented a generic foundation constructed on a 1.5m-height real soil ground by preparing a rigid soil box (Foundation-Soil system). In the second stage of A-building and B-building, the foundation was firmly fixed (Fixed-Foundation system), and shaking table motions were fully applied to the foundations. The entire test system was setup on the large shaking table facility at E-Defense, and a series of tests were conducted using JMA-Kobe motion and JR-Takatori motion recorded in the 1995 Kobe earthquake as Maximum-Considered-Earthquake motions. Confirmed was the change in the structural mechanism due to the upper structural systems and the foundation boundaries. Regarding the upper wood structure performance in the Fixed-Foundation system, a story shear failure mode was observed at the first story in A-building, while a tension fracture mode at the base of the first story in B-building. This difference of failure mode is difficult to determine with ASD. The maximum strength were more than four times higher than the ASD base shear force. Tension fracture capacity at the wall base was mainly enhanced by the presence of the steel anchor bolts. Regarding the foundation performance in Foundation-Soil system of B-building, a horizontal displacement up to 240mm was observed between the foundation and soil when JMA-Kobe 100% was applied. A response reduction effect was observed in the upper wood structure, similar to the Base-Isolation system of A-building. The initial friction and cyclic friction strength capacities between the foundation and soil were quantitatively evaluated considering the horizontal twodirectional sliding. The representative test results were converted to the corresponding SDOF systems based on the first mode response assessment. In the Fixed-Foundation system, the dynamic response characteristics of the upper wood structures were properly represented using Ibarra-Medina-Krawinkler pinching model in the equivalent SDOF system.
The widespread threat posed by slope structure failures to human lives and property safety is widely acknowledged. Additionally, natural soil often displays spatial variability due to geological deposition and other factors. Therefore, predicting the seismic response of slopes subjected to ground motions and inversely analyzing the spatial distribution of soils remains an unresolved issue. In the present work, a shaking table experimental test is first designed and carried out, in which a soft-soil slope dynamic system is established. To capture the seismic response of the soft-soil slope, specifically the experimental characteristic of acceleration and soil pressure response in both spatial domain and time domain, a series of sensors were pre-embedded in the slope. Subsequently, a model updating approach is proposed for slope seismic analysis that incorporates spatial variability of soil. In addition, to enhance computational efficiency, the dimensionality reduction of Karhunen–Loève expansion method is introduced to reduce inverse analysis parameters. On the basis of 34 samples collected from experimental data, it is shown that near-fault pulse-like ground motions deliver greater concentrated energy, causing more severe damage to slope structures, especially the topsoil layer. Furthermore, using data obtained from a shaking table test subjected to ground motion Recorded Sequence Number 158H1 from the Pacific Earthquake Engineering Research Center NGA-West2 database as an example, it is also shown that the proposed approach demonstrates high accuracy in predicting the spatial distribution of the maximum shear modulus in soil slope dynamic systems. The present work not only addresses the challenges posed by mainshock–aftershock effects but also highlights the potential of model updating approaches to enhance the understanding of slope behavior under seismic loading conditions.
Resilience assessment is a widely used method to evaluate the ability of an object (e.g., an individual structure, or a system consisting of multiple interacting structures) to withstand, recover from, and adapt to disruptive events. This paper proposes a novel concept of “nonresilience curve,” which measures the nonresilience (complement of resilience) of an object of interest conditional on a specific hazard intensity. It is by nature an extension of the well-established fragility curves, integrating the multiple damage states of a posthazard object. The applicability of the proposed nonresilience curve to individual structures and systems (including series systems, parallel systems, and more general and complicated systems) has been demonstrated in this paper. It is also preliminarily shown that the shape of the cumulative distribution function of a lognormal distribution is suitable to approximate the nonresilience curve, if only limited data points associated with the target nonresilience curve are available. Since the nonresilience curve is a function of the hazard intensity measure (IM), one can estimate the nonresilience of an object in a fully probabilistic manner by additionally taking into account the uncertainty associated with the IM. The proposed nonresilience curve can be further extended to formulate nonresilience surface, which is a joint function of both the IM and the available resource that supports the posthazard recovery process. The nonresilience curve is promising to be adopted in engineering practice for resilience assessment and resilience-based design of civil structures and infrastructure systems.
Tunnel-soil-pile interaction (TSPI) is a vital issue during seismic excitation because of the evaluation of the interactive structural behaviors of the tunnel. This study derives analytical formulae for the proposed TSPI model under transverse horizontal shear, vertical shear, and body waves, considering a series of piles along the tunnel’s longitudinal axis. For this reason, the soil medium is considered to be an isotropic, homogeneous, elastic, and infinite. Also, the tunnel is assumed to be a beam element to connect to the series of piles by the linear elastic springs. Parametric studies of proposed formulae show the parabolic and exponential variations of tunnel forces and soil pressures when increases the number of piles. Also, recalculated tunnel moments of previous studies by using proposed formulae vary closely, which may indicate the accuracy of the present formulations. Similar variations are obtained for the previous field study verification by the present formulations. Therefore, the design charts and graphs are addressed in the present research which may be used as a standard to enhance this research in the future.
Site resonance frequency is a crucial parameter for estimating site effects. However, there is currently no consensus on how to identify the bedrock interface to obtain the site resonance frequency. In this study, we identified 43 stations that can be regarded as one-dimensional sites from the KiK-net network in Japan, which consists of 699 stations. By analyzing the horizontal-to-vertical spectral ratio and surface-to-borehole spectral ratio of strong motion observation recordings, the fundamental resonance frequency (f0) of these 43 sites was determined. Subsequently, the correlation between the f0 values obtained from theoretical noise horizontal-to-vertical spectral ratio (NHV) with different bedrock interfaces and the f0 values determined from observation was analyzed. The conclusion shows that the f0 is primarily influenced by shallow interfaces with high S-wave impedance contrasts (ICs). Specifically, when the bedrock interface is taken as the interface with ICs greater than 2.5 that appears for the first time, or the interface with ICs greater than 1.5 that appears for the second time, there is a strong correlation (greater than 0.86) between the f0 values obtained from theoretical NHV and from observation. These findings can provide a quantitative reference for accurately determining the fundamental resonance frequency.
On February 6, 2023, the Republic of Turkey experienced a rare occurrence of two successive earthquakes, each with a magnitude exceeding 7.0. The Disaster and Emergency Management Agency (AFAD) swiftly shared the strong motion records, thereby enriching the global database of near-fault strong motion records. Identification of permanent displacement is essential for effectively utilizing these records. In this study, we refined the permanent displacement identification method, which combines the Hermit interpolation baseline correction with flatness determination by incorporating a low-pass filter. Following this, we compared four permanent displacement identification methods, including our improved approach. We applied these to the strong motion record of station 4404 and compared the results with the Global Positioning System coseismic displacement. At the same time, we used field investigation data to verify the effectiveness of our improved method, studying its applicability for both single-wave packet and multiwave packet records. The conclusions are the following: the improved method provides a more reasonable and effective means of identifying permanent displacement. When the peak ground acceleration (PGA) exceeds 1 g, the permanent displacement identifications from the four methods differ significantly. The discrepancy in permanent displacements identified by the four methods in the horizontal direction is larger than that in the U–D direction. For the record with the largest PGA (station 4614), our improved method yields more reasonable results compared with other techniques. Furthermore, the choice of segmentation time nodes in the velocity time history significantly affects the identification of permanent displacement.
Ground motion recording with peak ground acceleration (PGA) exceeding 1.43 g was observed at the Yamamoto (MYGH10) station during the MW 7.1 Fukushima earthquake off the east coast of Honshu, Japan, in February 2021. In this study, we investigated the site amplification effect and nonlinear site response at the MYGH10 site using the horizontal-to-vertical spectral ratio (HVSR) and surface-to-borehole spectral ratio (SBSR), respectively. The site transfer function of station MYGH10 was presented using HVSRs (HVSR on the ground surface) and SBSR at different frequency bands. The dominant contributing frequency band of the PGA was determined by increasing the high cutoff frequency of the bandpass filter when filtering the acceleration recording, which was used to interpret the anomaly of the PGA by combining it with the site characteristics. We found an obvious site effect below the downhole sensor through the HVSRb (HVSR on the downhole bedrock) and determined the influence of the frequency band of the downhole site on ground motion. In addition, substantial discrepancies in the frequency and amplitude between the spectral ratio curves for the Fukushima mainshock records and the weak historical motions were identified. The calculated values of the degree of nonlinearity suggested that a strong nonlinear site response occurred at station MYGH10. Finally, the recovery of the site after strong shaking was evaluated by using the average spectral ratio curves of several aftershock records.
As structural seismic damage develops, the internal force transfer and damage weight relationship of component are constantly changing, and the fixed weighted coefficient is adopted by the traditional weighted method, which cannot reflect the changes in the structural damage state. The structure is a network formed by connecting a large number of components, and the network state undergoes complex changes with the development of component damage. In this paper, a novel method for component damage transfer to structural seismic performance loss is proposed using network shortest paths. First, a directed weighted complex network based on force transfer direction and component stiffness is constructed for reinforced concrete (RC) frame structures. Then, the component damage is calculated by the degradation of its stiffness and is used to update the weight distribution of the damage network. Finally, the structural performance loss is evaluated by the degradation of damage network efficiency. Results show that the proposed method with an updated component weight relationship is able to reflect the true loss of structural performance according to the finite element dynamic elastic-plastic analysis of RC frame structures. For the structural performance loss degree (none, slight, moderate, severe, complete), the proposed method and the weighted method both exhibit high accuracy (number correctly classified/total number of samples) when structural performance loss is none, severe, or complete loss. The accuracy of the proposed method is significantly higher than that of the weighted method when structural performance loss is slight and moderate loss, with 58.1% and 84.2% improvement, respectively. For structural typical damage modes (global, local, and weak layer damage mode), the proposed method and the weighted method both exhibit high accuracy when structures exhibit global damage mode. The accuracy of the proposed method is significantly higher than that of the weighted method when structures exhibit local and weak layer damage mode. The accuracy of the proposed method is stable at 95.2%, while the accuracy of the weighted method is 76.2% and 70.2%, respectively. Overall, the weighted method exhibits high accuracy when structural performance loss is less than slight loss or greater than moderate loss, while the proposed method exhibits high accuracy throughout the entire process of structural performance loss, especially in moderate loss.
The spatial variation of ground motion may significantly aggravate the seismic damage of large-scale structures such as nuclear buildings. Establishing the seismic wave field with spatial features is the basis and key to seismic analysis of large-scale complex structures. For the nuclear island buildings, which are arranged close to each other, the influence of structure–soil–structure interaction (SSSI) and incoherent motion on the structural seismic response should be considered. Taking a domestic nuclear power project as an example, the seismic response analyses under incoherent seismic motion and coherent seismic motion are carried out respectively. The seismic motion incoherency effects on the nuclear island buildings on the common raft and the adjacent seismic category I structure are explored by comparing the results of the in-structure response spectrum (ISRS) at key elevations. The results indicate that the seismic motion incoherency does not change the trend of the response spectrum curve and the dominant frequency. Both the peak acceleration and zero-period acceleration of ISRS are changed to some extent. Overall, seismic motion incoherency has a more significant impact on the ISRS of nuclear buildings with smaller volumes.