Seismic risk assessment of code-noncompliant reinforced concrete (RC) frames faces significant challenges due to structural heterogeneity and the complex interplay of site-specific hazard conditions. This study aims to introduce a novel framework that integrates three key concepts specifically targeting these challenges. Central to the methodology are fragility fuses, which employ a triplet of curves-lower bound, median, and upper bound-to rigorously quantify within-class variability in seismic performance, offering a more nuanced representation of code-noncompliant building behavior compared to conventional single-curve approaches. Complementing this, spectrum-consistent transformations dynamically adjust fragility curves to account for regional spectral shapes and soil categories, ensuring site-specific accuracy by reconciling hazard intensity with local geotechnical conditions. Further enhancing precision, the framework adopts a nonlinear hazard model that captures the curvature of hazard curves in log-log space, overcoming the oversimplifications of linear approximations and significantly improving risk estimates for rare, high-intensity events. Applied to four RC frame typologies (2-5 stories) with diverse geometries and material properties, the framework demonstrates a 15-40 % reduction in risk estimation errors through nonlinear hazard modeling, while spectrum-consistent adjustments show up to 30 % variability in exceedance probabilities across soil classes. Fragility fuses further highlight the impact of structural heterogeneity, with older, non-ductile frames exhibiting 25 % wider confidence intervals in performance. Finally, risk maps are presented for the four frame typologies, making use of non-linear hazard curves and spectrumconsistent fragility fuses accounting for both local effects and within-typology variability.

This study aims to assess the effectiveness of inter-storey isolation structures in reducing seismic responses in super high-rise buildings, with a focus on analyzing the impact of soil-structure interaction (SSI) on the dynamic performance of the buildings. Utilizing the lumped parameter SR (Sway-Rocking) model, which separately simulates the overall displacement of the super high-rise structure and the rotational motion of the foundation, the dynamic characteristic parameters of the simplified model are derived. The natural frequencies of the system are calculated by solving the equations of motion. The study examines the influence of parameters such as soil shear wave velocity and structural damping ratio on the dynamic response of the structure, with particular emphasis on displacement transfer rates. The findings indicate that inter-storey isolation structures are highly effective in reducing displacement responses in super high-rise buildings, especially when considering SSI effects. Specifically, for high-damping inter-storey isolation structures, modal frequencies decrease as soil shear wave velocity decreases. In non-isolated structures, the damping ratio increases with decreasing soil shear wave velocity, whereas for isolated structures, the damping ratio decreases, with a more pronounced reduction at higher damping ratios. Increasing damping significantly reduces inter-storey displacement and damage indices. However, under low shear wave velocity conditions, inter-storey isolation structures may experience increased displacement and damage.

Destructive earthquakes result in significant damage to a wide variety of buildings. The resulting damage data is crucial for evaluating the seismic resilience of buildings in the region and investigating urban resilience. Field damage data from 38 destructive earthquakes in Sichuan Province were collected, classified, and statistically analysed according to the criteria of the latest Chinese seismic intensity scale for evaluating building damage levels. Meanwhile, the construction features and seismic damage characteristics of these buildings were also examined. These results facilitated the development of a damage probability matrix (DPM) for various building typologies, such as raw-soil structures (RSSs), stone-wood structures (SWSs), brick-wood structures (BWSs), masonry structures (MSs), and reinforced concrete frame structures (RCFSs). The damage ratio was employed as the parameter for vulnerability assessment, and a comprehensive analysis was performed on the differences in damage levels among all buildings in various intensity zones and time frames. Furthermore, the DPMs were further refined by simulating additional data from high-intensity zones to more accurately represent the seismic resistance of existing buildings in multiple-intensity zones. Vulnerability prediction models were developed using the biphasic Hill model, which elucidates varying damage trends across different construction typologies. Finally, empirical fragility curves were established based on horizontal peak ground acceleration (PGA) as the damage indicator. This study is based on multiple seismic damage samples from various regions, accounting for the influence of earthquake age. The DPMs, representative of the regional characteristics of Sichuan Province, were developed for different building types. Furthermore, multidimensional vulnerability regression models and empirical fragility curves are established based on these DPMs. These models and curves provide a theoretical foundation for seismic disaster scenario simulations and the seismic capacity analysis of buildings within Sichuan Province.

Screw piles are uniquely-shaped concrete piles with screw threads that have been widely used in various fields, including construction, structural design, and geotechnical engineering. Research on the dynamic characteristics of screw piles under vertical loads is limited compared with that investigating traditional circular piles. This report describes an analytical solution that has been developed to investigate the dynamic features of a screw pile under a longitudinal load while considering the cushion cap effect. The Laplace transform and Potential functions are applied to decouple the three-dimensional wave equations of the soil. The dynamic response of the screw pile is deduced using a modified impedance transfer function method. Finally, the cushion cap displacement and velocity in the frequency domain are determined by combining the initial conditions. The analytical solutions are compared with field-measured curves to validate the developed method. The results indicate that the soil around the pile can be regarded as a threedimensional continuous medium to simulate the radiation-damping effect as the wave propagates outward. The cushion cap reduces the screw pile damage caused by resonance, particularly in the low-frequency range. Considering the effects of vibrational loads, a screw pile should employ a large lightweight cushion cap, i.e., with the largest reasonable dimensions and with concrete materials that are as light as possible. The results of this study provide a theoretical basis for designing a dynamic foundation of a screw pile.

On February 6, 2023, two devastating seismic events, the Kahramanmaras, earthquakes, struck the Eastern Anatolian Fault Line (EAF) at 9-h intervals. The first earthquake, with a moment magnitude (Mw) of 7.7, struck the Pazarc & imath;k district, followed by a second earthquake with a moment magnitude (Mw) of 7.6 in the Elbistan district, both within the Kahramanmaras, province. These dual earthquakes directly impacted eleven provinces in Eastern and Southeastern Anatolia leading to significant loss of life and extensive damage to property and infrastructure. This study focuses on revealing the main parameters causing to the collapse of reinforced concrete (RC) buildings by examining their compliance with legislation and earthquake codes in force at the time of construction. For this purpose, detailed examinations such as field observations, collection of general information and official documents about the buildings, determination of material properties and soil characteristics, and three-dimensional finite element (FE) analysis of 400 totally collapsed RC buildings in the Kahramanmaras,, Ad & imath;yaman, Hatay, and Gaziantep provinces, which were among the cities affected by the Kahramanmaras, earthquakes were performed. The findings of this study contribute to a better understanding of the seismic deficiencies of buildings in earthquake-prone regions and provide information on which strategies to develop to increase the resilience of buildings with similar characteristics in other earthquake regions against future seismic events. Considering that the time from the beginning of the construction of the building until its completion consists of several stages, it can be seen that 43.58 % of the errors that cause damage and collapse of the buildings in this study are made in the construction stage, 25.57 % in the FE analysis stage, 24.77 % in the license stage, and 6.07 % in the after construction stage. Thanks to the development process of earthquake codes, regulations in building inspection practices and easier access to quality materials have greatly reduced the damage and collapse of buildings constructed in recent years.

This study quantifies the seismic fragility assessment of shallow-founded buildings in liquefiable and treated soils, enhanced by drainage and densification, considering both short-and long-term behaviors. A conceptual framework is proposed for developing seismic fragility curves based on engineering demand parameters (EDPs) of buildings subjected to various earthquake magnitudes. The framework for establishing seismic fragility curves involves three essential steps. First, nonlinear dynamic analyses of soil-building systems are performed to assess both the short-term response, which occurs immediately following an earthquake, and the longterm response, when excess pore water pressure completely dissipates, and generate a dataset of building settlements. The seismic responses are compared in terms of excess pore water pressure buildup, immediate and residual ground deformation, and building settlement to explore the dynamic mechanisms of soil-building systems and evaluate the performance of enhanced drainage and densification over short-and long-term periods. Second, 38 commonly used and newly proposed intensity measures (IMs) of ground motions (GMs) are comprehensively evaluated using five statistical measures, such as correlation, efficiency, practicality, proficiency, and sufficiency, to identify optimal IMs of GMs. Third, fragility curves are developed to quantify probability of exceeding various capacity limit states, based on structural damage observed in Taiwan, for both liquefaction-induced immediate and residual settlements of buildings under different levels of IMs. Overall, this study proposes a rapid and straightforward probabilistic assessment approach for buildings in liquefiable soils, along with remedial countermeasures to enhance seismic resilience.

Despite the complexity of real earthquake motions, the incident wavefield excitation for soil-structure interaction (SSI) analysis is conventionally derived from one-dimensional site response analysis (1D SRA), resulting in idealized, decoupled vertically incident shear and compressional waves for the horizontal and vertical components of the wavefield, respectively. Recent studies have revealed potentially significant deviation of the 1D free-field predictions from the actual three-dimensional (3D) site response and obtained physical insights into the mechanistic deficiencies of this simplified approach. Particularly, when applied to vertical motion estimation, 1D SRA can lead to consistent overprediction due to the refraction of inclined S waves in the actual wavefield that is not correctly accounted for in the idealized vertical P wave propagation model. However, in addition to the free-field site response, seismic demands on structures and non-structural components are also influenced by the dynamic characteristics of the structure and SSI effects. The extent to which the utilization of vertically propagating waves influences the structural system response is currently not well understood. With the recent realization of high-performance broadband physics-based 3D ground motion simulations, this study evaluates the impact of incident wavefield modeling on SSI analysis of representative building structures based on two essential ingredients: (1) realistic spatially dense simulated ground motions in shallow sedimentary basins as the reference incident motions for the local SSI model and (2) high-fidelity direct modeling of the soil-structure system that fully honors the complexity of the incident seismic waves. Numerical models for a suite of archetypal two-dimensional (2D) multi-story building frames were developed to study their seismic response under the following incident wavefield modeling conditions: (1) SSI models with reference incident waves from the 3D earthquake simulation, (2) SSI models with idealized vertically incident waves based on 1D SRA, and (3) conventional fixed-base models with base translational motions from 1D SRA. The impact of these modeling choices on various structural and non-structural demands is investigated and contrasted. The results show that, for the horizontal direction, the free-field linear and nonlinear site amplification and subsequent dynamic filtering of the base motions within the structure can be reasonably captured by the assumed vertically propagating shear waves. This leads to generally fair agreements for structural demands controlled by horizontal motions, including peak inter-story drifts and yielding of structural components. In contrast, vertical seismic demands on structures are overpredicted in most cases when using the 1D wavefields and can result in exacerbated structural damage. Special attention should be given to the potentially severe vertical floor accelerations predicted by the 1D approach due to the combined effects of fictitious free-field site amplification and significant vertical dynamic amplification along the building height. This can pose unrealistic challenges to seismic certification of acceleration-sensitive secondary equipment necessary for structural and operational functionality and containment barrier design of critical infrastructures. It is also demonstrated that vertical SSI effects can be more significant than those in the horizontal direction due to the large vertical structural stiffness and should be considered in vertical floor acceleration assessments, especially for massive high-rise buildings.

Determining the optimal damping value of the isolation system in tall structures is challenging as it requires parametric studies and time-consuming nonlinear time-history analyses. Consequently, the influence of different parameters, such as displacement limitation, on the optimal damping of isolators in tall structures remains unclear. This study aims to investigate the optimal damping of isolators in tall structures under two scenarios: a) changing the displacement capacity of the isolators in proportion to the increase of damping (variable gap); b) maintaining a constant displacement capacity of the isolators as the damping increases (constant gap). The study also explores the influence of two additional parameters on the optimal damping of the isolation system, namely the ratio of isolator to superstructure period (TM/TS) and the soil type. The optimal design procedure is illustrated with reference to a case-study 14-story isolated steel structure with an ordinary concentrically braced frames (OCBF) system, isolated with the triple friction pendulum isolator (TFPI) system. The modified endurance time (MET) method is utilized to analyze the seismic response of the case-study structure under increasing levels of earthquake hazard. The analysis reveals that increasing damping in both constant and variable gap modes can effectively reduce the damage level of the structure. However, the effectiveness of increasing damping is limited and influenced by factors such as soil softness and the TM/TS ratio. The optimal damping values are determined based on the desired performance levels for both structural and nonstructural acceleration-sensitive components.

This review explores the influence of soil-structure interaction (SSI) on the seismic response of structures, employing Latent Dirichlet Allocation (LDA) to identify research trends and thematic clusters. Key topics include the dynamic response of buildings, nonlinear modeling approaches, soil-foundation interaction, and performance-based seismic evaluation. SSI significantly modifies structural behavior, influencing vibration characteristics, wave propagation, and energy dissipation. Building parameters, soil stiffness, and foundation type were identified as critical factors impacting seismic performance. Advanced nonlinear modeling techniques, such as finite element analysis and optimization algorithms, have enhanced the accuracy of SSI simulations, enabling detailed assessments of soil-structure dynamics and damage probabilities. Innovations like gravel-rubber mixtures for seismic isolation and tuned mass dampers integrated with SSI were highlighted for their effectiveness in mitigating seismic impacts. The review highlights the necessity of incorporating SSI into design frameworks to address dynamic amplification, site-specific conditions, and fragility variations. However, critical gaps remain, particularly in large-scale fragility modeling, multi-hazard assessments, and experimental validations. These gaps highlight the need for further integration of SSI effects into seismic risk analyses and design codes. Future research should prioritize multi-disciplinary approaches that bridge theoretical advancements and practical applications to enhance structural resilience in seismically active regions. This study provides a comprehensive foundation for advancing SSI-informed seismic design practices and improving the safety and sustainability of infrastructure.

This study evaluates the impact of varying bedrock depths on local site amplification factors and their consequent influence on the vulnerability of buildings under seismic actions. An index-based methodology is implemented to analyze the seismic vulnerability of old masonry buildings in the historic center of Galata, & Idot;stanbul. As part of a site-specific analysis, soil models are developed to replicate a dipping bedrock at six different depths varying between 5 and 30 m beneath the ground surface. Consequently, potential damage scenarios are generated employing a seismic attenuation relation and damage distributions are compared for the cases with/without amplification effects. The findings point out that, the structural response undergoes the greatest amplification at a bedrock depth of 20 m, exceeding 1.6 and attaining its maximum value of 2.89 at the structural period of 0.22 s. The maximum shift in damage grades occurs for buildings with natural periods between 0.16 and 0.20 s on 15 m bedrock depth, whereas, for longer periods, the greatest increase occurs at 20 m bedrock depth compared to the scenarios without site amplification. As a result, this study emphasizes the significance of site-specific conditions that might amplify structural response and consequently, increase the seismic damage level in assessing the vulnerability of built heritage. By integrating geo-hazard-based evaluation into the large-scale seismic assessments, this study offers a framework for more accurate damage forecasting and highlights the need to include local site amplification effects in seismic risk mitigation plans, enhancing strategies for preserving built heritage.