Earthquake

Seismic fragility evaluation of box deck concrete bridge equipped with shape memory alloy under bi-directional earthquake loading

Abtin Abiari, Sasan Motaghed, Hadi Sayyadpour, Nasrolla Eftekhari — Wed, 22 Jan 2025 09:52:05 +0800

Bridges are one of the most important elements of the transportation system in all countries. The collapse of a bridge or the time required for the repair of a damaged bridge can lead to traffic disruption and relief operation suspension that in turn results in the increased earthquake cascading tertiary effects. Therefore, reducing the vulnerability of bridges has always been the focus of engineers. The use of shape memory alloys (SMA) is one of the new solutions that have been presented and received attention in this field. The purpose of this research is to investigate the effects of using SMAs on the seismic behavior of straight box deck concrete bridges. For this purpose, a typical box deck concrete bridge is considered, and in the area of the plastic hinges of the bridge piers, the longitudinal steel bars are replaced with nickel-titanium SMA bars. The studied bridge is analyzed in two cases with and without the use of SMA under the effect of 3 categories of acceleration time histories, consisting of 120 strong ground motion records. Finally, the fragility curves for the maximum drift ratio and residual drift ratio values are calculated. The results show that the use of nickel-titanium SMA bars increases the maximum drift ratios and reduces the residual drift ratios. In this way, the permanent deformations will be decreased.

New trends in earthquake prediction – A case study of AI performance

Boyko Ranguelov — Wed, 22 Jan 2025 09:53:57 +0800

The short term earthquake prediction problem is considered not solved yet. The new trends on this topic are related to the intrusion of the Artificial Intelligence (AI) with believes it can help significantly to the solution. The case study of an experiment in China during 2023 and published in BSSA (https://pubs.geoscienceworld.org/ssa/ bssa/articleabstract/113/6/2461/627949/Earthquake-Forecasting-Using-Big-Data.) deals with the results critically assessed of the achievements in time, distance and magnitude of forthcoming earthquakes in a test area in China. Some other cases are also presented to help the reader to enter the last published development in the mass media of the topic and some speculations on it. The conclusions are that the proclaimed unprecedented accuracy of predicted parameters of forthcoming seismic events is strongly overestimated.

Performance and safety assessment of steel structures in substations using nonlinear time-history analysis

Md RezarsMia, Kamal Hosen — Thu, 13 Mar 2025 09:34:08 +0800

Electrical substations control voltage and the flow of electric energy, assuring optimal electricity transmission from generation plants to users. A detailed performance evaluation of the substation's structures is crucial to deciding whether to demolish or repair. This study analyzed a 200 KV substation's steel structure in China to find an efficient assessment strategy. Structural data and dimensions have been carried out through a holistic site inspection. Different laboratory tests have been conducted to evaluate the material's strength. The finite element method (FEM) has been utilized to develop the structural model, and nonlinear static and time-history analysis has been done with STAAD.Pro-2023. To assess the structural safety of the steel structure, necessary factors such as time-frequency, mode shape, deflections, and strength capacity ratios were studied. Structural data was found from structural analysis, and the Structure's present condition was compared with its initial conditions and allowable limits. The study's findings show a 15% reduction in natural frequencies and extended structural periods, indicating material degradation and potential reductions in dynamic resilience. The strength capacity ratio of the steel structure members was lower than the initial condition.

Impact of earthquakes on soil chemical properties: A Review of mechanisms, changes, and implications for environmental and structural resilience

Shoma Hore, Mosharof AlAlim, Ripon Hore,PhD — Thu, 20 Feb 2025 09:33:08 +0800

The response of soil chemical properties to seismic events has gained significant attention in recent years due to its potential impact on both the environment and infrastructure. Earthquakes can alter the chemical composition of soils, leading to changes in their mechanical properties, which may subsequently affect the stability of embankments, retaining walls, and other civil infrastructure. This review presents a comprehensive analysis of the chemical changes in soils following earthquake events, with a particular focus on the factors influencing these changes and their implications for engineering applications. The paper examines the underlying mechanisms that govern soil behavior during and after seismic events, including liquefaction, soil consolidation, and contamination from hazardous materials. Furthermore, it highlights the importance of post-earthquake soil chemical analysis in assessing potential hazards, such as the release of harmful substances, and offers recommendations for improving soil management strategies in earthquake-prone regions. By reviewing both experimental studies and field observations, this research aims to provide a deeper understanding of the complex relationship between seismic activity and soil chemistry. The novelty of this review lies in its systematic approach to integrating chemical analysis and seismic impacts on soils, offering valuable insights for engineers, environmental scientists, and policymakers involved in disaster risk management and mitigation. Ultimately, this review serves as a foundational resource for enhancing earthquake-resilient infrastructure in geologically active areas.

Review of earthquake-induced liquefaction potential in reclaimed urban areas: Insights from Dhaka city

Md. RiadArefin, Ahsan HabibShapon — Thu, 20 Feb 2025 09:33:12 +0800

This review paper examines the potential for earthquake-induced liquefaction in reclaimed urban areas, with a focus on Dhaka City as a case study. Rapid urbanization and land reclamation in Dhaka have increased concerns about the stability of reclaimed lands during seismic events. This paper synthesizes findings from prior studies, focusing on geotechnical parameters such as SPT-N values, cone tip resistance, local friction, and friction ratio. Key influencing factors, including peak ground acceleration, earthquake magnitude, soil type, and reclamation methods, are analyzed to assess their role in liquefaction susceptibility. Evidence suggests that areas reclaimed with dredged soil, especially at shallow to moderate depths, are more prone to liquefaction under seismic loading. Variability in parameters such as over-consolidation ratio, lateral earth pressure, and internal friction angle highlights the need for localized investigations. This review emphasizes the importance of integrating advanced geotechnical techniques and seismic risk assessments to ensure the resilience of reclaimed urban areas.