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CONTENTS
Volume 30, Number 3, March 2026
 

Abstract
Soil liquefaction is a key factor leading to building instability and foundation failure during earthquakes. To reveal the influence mechanism of the liquefiable soil layer on surface acceleration response spectra during the "pre-liquefaction" and "post-liquefaction" stages, this study established a 30 m total thickness liquefaction site soil column model using OpenSees. The "surface response spectrum intensity ratio" served as the core indicator to quantitatively analyze the effects of soil layer parameters and ground motions. The results indicate that: (1) Spectra differences between sites are minimal per-liquefaction but become significant post-liquefaction, showing a clear isolation effect. (2) Post-liquefaction site, regardless of the soil layer distribution, the spectra intensity ratios for both short-period (0.01-0.3 s) and long-period (0.8-10 s) ranges are less than 1, reflecting an isolation effect. (3) The spectra intensity ratio increases with the relative density of the liquefiable soil layer and decreases as a power function with increasing thickness and depth. When the thickness ratio (liquefiable soil layer thickness/total soil layer thickness) and depth ratio (liquefiable soil layer depth/total soil layer thickness) are less than 0.1, the growth rate of the isolation effect is the fastest; when the ratios exceed 0.4, the isolation effect stabilizes and reaches its maximum. (4) As the peak ground acceleration (PGA) of the input ground motion increases, the spectra intensity ratio gradually decreases under non-pulse ground motions, while it first decreases and then increases under pulse ground motions. The findings of this study can provide some reference for the seismic design of liquefiable sites.

Key Words
liquefaction soil layers; nonlinear numerical analysis; post-liquefaction surface response spectra; surface response spectra intensity ratios

Address
Dongsong Song: 1) Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China; 2) Key Laboratory of Earthquake Disaster Mitigation, Ministry of Emergency Management, Harbin, China; 3) State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structure, Shijiazhuang Tiedao University, Shijiazhuang, China
Hongshuai Liu: 1) Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China; 2) Key Laboratory of Earthquake Disaster Mitigation, Ministry of Emergency Management, Harbin, China; 3) College of Civil Engineering and Architecture, Hebei University, Baoding, China

Abstract
This paper presents a method of evaluating post-earthquake strength of steel moment-resisting frames based on fishbone model using acceleration data. Fishbone model is a simplified frame model used for simulating the structural behavior of steel moment-resisting frames, and it enables to explicitly identify the stiffness parameters of beams and column bases using model updating approaches. First, the stiffness of column bases and beam ends are identified by the model updating method using incomplete modal data identified from acceleration measurements. Then, the strength parameters of column bases and beam ends are calculated based on the identified stiffness values. Thirdly, post-earthquake strength is assessed through Pushover analyses and Incremental Dynamic Analysis (IDA) of updated fishbone models using OpenSees software. Finally, the practical applicability of the proposed method is investigated through the shaking table tests of a large-scale 3-story, 2-bay steel frame specimen. The results demonstrate that the fishbone model not only is competent to predict the accelerations, displacements, and story drift ratios of the structures but also effectively evaluates the post-earthquake strength of the steel frames. In addition, the fishbone model emerges as a reliable alternative to the conventional concentrated plastic hinge model for the assessment of the strength of steel moment-resisting frames after earthquakes.

Key Words
acceleration data; fishbone model; model updating; post-earthquake strength assessment; steel frame

Address
School of Civil Engineering, Chongqing University, Chongqing 400045, China

Abstract
The actual earthquake is multi-directional, and the interaction between soil and structure (SSI) will further increase the complexity of structures seismic response under multi-directional earthquake, in order to improve the seismic safety of liquid storage tank (LST), examining the 3-dimensional isolated LSTs dynamic reactions to soil-structure interaction is essential. In this paper, a hybrid 3D isolation system combining horizontal rubber bearings with vertical damping springs is investigated. A numerical model using finite element method with acoustic fluid elements and nonlinear isolator properties is constructed. Key response quantities, including sloshing wave height, liquid pressure, and tank shell stresses, are co MPared under near-field and far-field multi-directional seismic excitations. The results show that the maximum response position changes under multi-directional earthquakes. The dynamic responses of the non-isolated LST change dramatically as the number of seismic input directions increases, whereas the 3-dimensional isolated LSTs dynamic responses barely alter. The 3-dimensional isolation has an amplification effect on the height of the liquid sloshing waves, which in some cases exceeds the designated wall height, raising concerns regarding overtopping risk and the structural adequacy of the top ring. Nevertheless, it exhibits a steady damping effect on the bulk of seismic responses. 3-dimensional seismic isolation can provide an effective way for the earthquake prevention and disaster reduction of LSTs under multi-directional earthquakes.

Key Words
3-D isolation; dynamic response; liquid storage tank; multi-directional earthquake; soil-structure interaction

Address
Wei Jing: 1) Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education, Lanzhou University of Technology, Lanzhou, 730050, PR China; 2) Ningxia Center for Research on Earthquake Protection and Disaster Mitigation in Civil Engineering, Yinchuan 750021, PR China
Mengqi Yan, Shuang Tian: Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education, Lanzhou University of Technology, Lanzhou, 730050, PR China
Wenwei Yang: 1) School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan 750021, PR China; 2) Ningxia Center for Research on Earthquake Protection and Disaster Mitigation in Civil Engineering, Yinchuan 750021, PR China

Abstract
In this paper, a new generalized model of dual-fractional two-temperature nonlocal thermoelasticity is developed to investigate the reflection and dispersion of plane waves in a rotating medium under initial stress. The governing equations of motion, constitutive relations, and heat conduction are reformulated using the Atangana-Baleanu fractional derivatives of two distinct orders, representing two independent memory-dependent heat transport mechanisms associated with the thermodynamic and conductive temperature fields. This framework extends the classical and nonlocal thermoelastic theories by incorporating simultaneous nonlocal spatial interactions and dual fractional temporal relaxation. The combined effects of nonlocality, rotation, initial stress, and fractional orders on the phase velocity, attenuation coefficient, specific loss, and reflection coefficients of longitudinal (P), shear vertical (SV), and thermal (T) waves are analyzed. The results reveal that decreasing fractional orders intensifies thermal memory, enhances attenuation, and shifts reflection peaks, leading to pronounced dispersion and energy redistribution across the boundary. Numerical simulations using aluminum-like material parameters demonstrate strong sensitivity of wave characteristics to fractional parameters and nonlocal coupling, offering new insights into microstructured, rotating, and thermally diffusive materials such as semiconductors and functionally graded solids.

Key Words
dispersion; dual-fractional thermoelasticity; initial stress; nonlocal elasticity; plane wave reflection; two-temperature theory

Address
Amal Al-Hanaya, Wedad Albalawi, Shreen El-Sapa: Department of Mathematical Sciences, College of Science, Princess Nourah bint Abdulrahman University, Riyadh, 11671 Saudi Arabia
Khaled Lotfy: 1) Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt; 2) National Committee for Mathematics, Academy of Scientific Research and Technology, Egypt
Alaa A. El-Bary: 1) National Committee for Mathematics, Academy of Scientific Research and Technology, Egypt; 2) Arab Academy for Science, Technology and Maritime Transport, P.O. Box 1029, Alexandria, Egypt; 3) Council of Future Studies and Risk Management, Academy of Scientific Research and Technology, Egypt

Abstract
Seismic vulnerability in earthquake-prone areas is a key concern; choosing a suitable response reduction factor (R-factor) is crucial for assessing the seismic performance of reinforced concrete structures. This study presents a comprehensive analysis of the effects of the Response Reduction Factor (R-factor) on the seismic vulnerability of symmetrical buildings with 3 to 20 stories at different seismic intensities (DBE and MCE). The buildings are designed for varying R factors, ranging from 3 to 6, and the non-linear response parameters have been evaluated using both pushover and time-history analyses. The fragility curves of the buildings are developed according to the Hazus manual, and the probability of damage is estimated for each case. A unique relationship has been established between DI and SVI. The results indicate that both the height of a building and the R-factor collectively influence its seismic vulnerability. The result shows that the collapse damage of buildings increases by up to 20% when the R factor is increased from 3 to 6, and by 16% when the building height is increased from 3 storeys to 20 storeys. From the combination of height and R-factor on the selected models, it has been observed that buildings up to 15 stories can be safely designed with an R-factor of up to 6. In contrast, for a 20-storey building, the maximum recommended R factor is 5 because a 20-storey building with R=6 experiences more than 30% collapse damage. The DI value exceeds 3, and the SVI value exceeds 0.7 at the MCE level of earthquake. Finally, a 3d graph has been prepared, which shows the combined effect of height and R factor value, which can help to make a decision about the selection of R factor for multistoried buildings based upon seismic vulnerability as per performance level and damage states criterion.

Key Words
building's height; damage index; fragility curves; probability of damage; pushover analysis; response reduction factor; seismic vulnerability assessment; seismic vulnerability index; spectral displacement

Address
Civil Engineering Department, Motilal Nehru National Institute of Technology Allahabad, Prayagraj-211004, UP, India

Abstract
Near-fault ground motions are often influenced by forward rupture directivity effects, which may generate distinctive long-period velocity pulses and substantially increase seismic demands compared to far-field records. However, conventional design spectra prescribed in seismic codes generally fail to incorporate these near-fault characteristics, potentially resulting in unconservative structural designs. This study examines the spectral amplification associated with near-fault effects and introduces a coefficient-based modification approach derived through regression analysis. A total of 20 ground motion records from the 6 February 2023 Mw 7.7 Pazarcik earthquake were employed - 10 near-fault and 10 far-field - and to account for the bidirectional nature of seismic excitation, both the East-West (EW) and North-South (NS) components were analyzed separately, yielding 40 datasets. Five-percent-damped elastic acceleration response spectra were computed using the Newmark-Beta method across a broad period range, after which average spectra for the near-fault and far-field groups were compared and spectral ratios were calculated to quantify amplification due to fault proximity. The period range was classified into short (T<0.5 s), medium (0.5 s<=T<= 3 s), and long (T>3 s) intervals, and constant amplification coefficients were determined for each category. A regression-based model was further developed to represent the amplification trend as a function of period. An overall spectral modification factor of 1.47 was identified, and when applied to design spectra, this coefficient effectively reduced discrepancies between code-based and response spectra, mitigating potential underestimations. These findings emphasize the importance of explicitly incorporating near-fault effects in seismic design procedures.

Key Words
coefficient-based modification; near-fault ground motions; Pazarcik earthquake; seismic design; spectral amplification

Address
Ömer Faruk Nemutlu: Civil Engineering Department, Faculty of Engineering and Architecture, Bingol University, Bingol, Türkiye
Mohamed Freeshah: Civil and Environmental Engineering Department, College of Engineering, United Arab Emirates University, Khalifa Bin Zayed St., Al Ain P.O. Box 15551, United Arab Emirates

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