Shallow cut-and-cover underground structures, such as subway stations, are traditionally designed as rigid boxes (moment-resisting connections between the main structural members), seeking internal hyperstaticity and high lateral (transverse) stiffness to achieve important seismic capacity. However, since seismic ground motions impose racking drifts, this proved rather prejudicial, with great structural damage and little resilience. Therefore, two previous papers proposed an opposite strategy seeking low lateral (transverse) stiffness by connecting the structural elements flexibly (hinging and sliding). Under severe seismic inputs, these structures would accommodate racking without significant damage; this behaviour is highly resilient. The seismic resilience of this solution was numerically demonstrated in the well-known Daikai station (Kobe, Japan) and a station located in Chengdu (China). This paper is a continuation of these studies; it aims to extend, deepen, and ground this conclusion by performing a numerical parametric study on these two stations in a wide and representative set of situations characterised by the soil type, overburden depth, engineering bedrock position, and high- and lowlateral-stiffness of the stations. The performance indices are the racking displacement and the structural damage (quantified through concrete damage variables). The findings of this study validate the previous remarks and provide new insights.

The seismic resilience of underground structures is one of the critical issues for the development of resilient cities. However, existing assessing methods for assessing the seismic resilience of underground structures do not comprehensively address their seismic capacity and post-earthquake recoverability. This paper developed a seismic resilience index and framework for assessing the seismic resilience of underground frame structures by considering both the damage and functionality of underground structures caused by earthquakes, as well as the processes involved in repairs. The seismic resilience index was developed by quantifying the resist resilience and recovery resilience, which can be used to describe the robustness, redundancy, and resourcefulness of the seismic resilience. Then the assessing procedure for this method is presented step by step. Additionally, a case study was conducted to assess the seismic resilience of a frame subway station, focusing on the economic losses associated with earthquakes. The study also discusses the improvements in seismic resilience achieved through the use of reinforced concrete truncated (RCT) columns. Results indicate that RCT columns can significantly enhance the seismic resilience of underground structures. The reasonability and quantifiability of the developed method were compared with existing methods, demonstrating its effectiveness. Furthermore, the developed assessing method can be extended to assess the seismic resilience of underground structures after quantifying their operational functionality.

The recurring occurrence of seismic hazards constitutes a significant and imminent threat to subway stations. Consequently, a meticulous assessment of the seismic resilience of subway stations becomes imperative for enhancing urban safety and ensuring sustained functionality. This study strives to introduce a probabilistic framework tailored to assess the seismic resilience of stations when confronted with seismic hazards. The framework aims to precisely quantify station resilience by determining the integral ratio between the station performance curve and the corresponding station recovery time. To achieve this goal, a series of finite element models of the soil-station system were developed and employed to investigate the impact of site type, seismic intensity, and station structural type on the dynamic response of the station. Then, the seismic fragility functions were generated by developing the relationships between seismic intensity and damage index, taking into account multidimensional uncertainties encompassing factors such as earthquake characteristics and construction quality. The resilience assessment was subsequently conducted based on the station's fragility and the corresponding economic loss, while also considering the recovery path and recoverability. Additionally, the impacts of diverse factors, including structural characteristics, site types, functional recovery models, and peak ground acceleration (PGA) intensities, on the resilience of stations with distinct structural forms were also discussed. This work contributes to the resilience-based design and management of metro networks to support adaptation to seismic hazards, thereby facilitating the efficient allocation of resources by relevant decision makers.

The current Indian Standard Seismic Code IS 1893: Part 1 (2016) for general buildings lacks detailed guidelines on modeling soil-structure interaction (SSI) in the estimation of seismic demand and earthquake-induced damage in reinforced concrete buildings. Therefore, this study aims to investigate the effects of SSI, with a focus on its nonlinear behavior, on the seismic demand of ductile reinforced concrete frames designed as per IS 1893: Part 1. The selected RC buildings are designed for second-highest seismic risk zone in India and represent short, medium, and long-period structures commonly found across Indian sub-continent. The influence of SSI is studied for soil type II and type III, as specified in the Indian Code, which corresponds to medium stiff and soft soil sites, respectively. Using a nonlinear Winkler-based model, numerical finite element models of linear and nonlinear SSI have been developed for isolated shallow foundations. This study utilizes the results of incremental dynamic analysis to evaluate the fragility parameters for code specified performance limit states. Further, the estimated fragility parameters are integrated with the regional hazard curve coefficients to quantify the annual exceedance probability of specified damage levels. The simulation results highlight the critical impact of nonlinear SSI on the earthquake resilience of IS code designed low- to high-rise reinforced concrete buildings. Notably, the percentage increase in estimated fragilities is higher for low-rise buildings than high-rise buildings when subjected to ground motions on soil sites. Additionally, the vulnerability to failure of these buildings elevates significantly when they are analyzed on soft soil sites compared to medium soil and bedrock sites. Therefore, it is recommended to account for the significance of nonlinear SSI while assessing the expected structural performance and fragility of IS 1893: Part 1 designed stiff low- to medium-rise reinforced concrete buildings, as this step can substantially enhance the resiliency of such buildings in the aftermath of a disastrous earthquake.

This study investigates the seismic performance of a theoretical hospital building designed as a Fixed-Base (FB) structure according to TSC-2018 (Turkish Seismic Code) and evaluates its behavior under three scenarios: FixedBase (FB), Soil-Structure Interaction (SSI), and Base-Isolated (SSI+ISO). The study employs Nonlinear Time History Analysis (NLTHA) using scaled acceleration records, including one from the 2023 Maras, earthquake. Structural performance is assessed based on maximum roof displacements, interstory drift ratios (IDR), and isolator displacements. Results show that base isolation systems significantly reduce drift demands and roof displacements, keeping the structure within slight damage limits even under extreme seismic loads. In contrast, SSI effects amplify interstory drift demands, increasing the likelihood of exceeding moderate damage thresholds. The analysis highlights the Maras, Education and Research Hospital, which suffered severe damage and became non-operational during the 2023 Kahramanmaras earthquake. This outcome underscores the limitations of fixedbase designs in regions with soft soil conditions and the necessity of incorporating base isolation systems to improve seismic resilience. The findings emphasize the importance of mandatory adoption of base isolation systems in hospital designs, proper consideration of SSI effects, and the retrofitting of existing hospital buildings to meet modern seismic code requirements (TSC-2018) and prevent similar failures in future seismic events.

The subterranean environment of tunnels poses considerable uncertainty as tunnel structures are ensconced in soil, unlike their above-ground counterparts. This significantly complicates tunnel risk assessment during earthquakes. This study introduces a novel method that integrates multiple damage indices to evaluate the seismic resilience of tunnels. Initially, seismic attenuation is introduced to calculate earthquake exceedance probabilities for various tunnel damage indicators, employing finite element methods (FEM). A robustness evaluation criterion scale value is established based on the amalgamation of multiple tunnel damage indices. Standard Cloud Models are then generated utilising the robustness evaluation criteria. Subsequently, the independent and correlated weights of the robustness evaluation indices are determined using the CRITIC-G1 and decision-making trial and evaluation laboratory (DEMATEL) methods, respectively. A game theory (GT) method is then utilised to amalgamate and allocate weights to these robustness evaluation indices. The evaluation Cloud Models are subsequently generated using a backward cloud generator, based on the division of damage grades for the evaluation criteria and combination weights. Finally, the robustness grade is determined by comparing the similarities between the standard and evaluation Cloud Models. The repair time of the tunnel is quantified using a repair function based on robustness grades. The efficacy of the seismic resilience assessment method is discussed based on three hypothetical cases, providing valuable guidance for assessing the seismic resilience of underground structures.

This study underscores the critical need to integrate changing climatic conditions into corrosion models for civil engineering infrastructures, particularly highway bridges, given the potential reduction in structural performance post-seismic events. The paper introduces a novel framework for assessing the seismic resilience of deteriorated highway bridges in the context of changing climatic conditions. The framework is demonstrated on a non-seismically designed simply supported highway bridge situated near the sea in a seismically active region of Gujarat, India. An improved corrosion deterioration model is used that considers the impact of climate change and non-uniform pitting corrosion for evaluating the deterioration of RC bridge components. A detailed threedimensional finite-element model of the case-study bridge is developed that can accurately simulate various failure modes of corroding bridge piers. Time-varying seismic fragility curves are developed using damage limit states and probabilistic seismic demand models while considering the influence of climate change. Bridge seismic resilience is estimated by aggregating the seismic vulnerability, losses, and recovery functions. Results show that incorporation of changing climatic factors will considerably reduce the seismic resilience of the 75-year corroded bridge up to 56 %. Finally, a comparison of seismic fragility and resilience is carried out using the proposed and conventional corrosion deterioration model to evaluate the significance of considering the effects of climate change in the seismic resilience assessment framework.

The dynamic response for different earth-retaining walls having geogrid as a reinforcement, combined with cohesionless granular material for backfill to mitigate earth pressure, has been examined through scale-down shaking table experiments and full-scale 3D FE analysis, utilizing ABAQUS as the finite element software. The scale factor is 1/4th for scaled-down. This study included various physical modelling experiments using different geogrid-reinforced earth retaining (GRER) walls (1 m height, 7.5 cm, thickness, and length 1 m). Additionally, comprehensive 3D finite element analysis were conducted with the configurations measuring (4 m, height 0.3 m, thickness, and length 4 m). This study examines hollow prefabricated concrete panels with shear key (PC-W), stone masonry walls of gravity type (GM-W), and traditional reinforced concrete (RC-W) walls. It also presents comparative investigations, such as lateral horizontal displacement of the wall, lateral pressure to the backfill, backfill soil settlement, and settlement of the wall foundation of various (GRER) walls. The accuracy of the Finite Element simulation framework has also been assessed in the shaking table experiment, as well as the FE analyses. According to the results, a PC-W wall with a shear key is the most effective type because it shows more resistance toward displacement. As per the comparison of the test models, GRER walls' seismic response was more affected by the earthquake waves from the far field having long-term high acceleration values. In contrast, seismic waves from the close field had a smaller impact on the walls' seismic response. However, the geogrid could improve the GRER seismic resilience deformation. Geogrid layers may reduce backfill pressures and backfill settlements. The geogrids located in the central portion within the reinforced soil and the geogrid roots connected to the walls were essential to the seismic design of the geogrid-reinforced earth retaining wall. To evaluate the reliability of the findings, the models have a predicted R2 variance below 0.1, indicating a consistent relationship between these two variables.

This paper examines the effects of near-field pulse-like earthquake ground motions (GMs) on the seismic resilience, repair cost and time, and structural collapse risk of low-to-high-rise selected multi-story RC structures with special moment-resisting frames (SMRFs) and shear walls. Selected 5-, 10-, and 15-story structures are designed based on a seismically active region where pulse-like GMs are more likely to occur. Two different sets of near-field GMs are chosen based on the recommendations of FEMA P-695 to conduct nonlinear dynamic analyses. Subsequently, the methodology provided in FEMA P-58 is adopted to perform a comprehensive seismic performance assessment at various hazard levels. It is shown that the consideration of the effects of near-field pulse-like GMs can considerably increase the risk of structural collapse in RC shear wall systems, based on the ratio of the pulse period of ground motion records to the elastic first mode period, in comparison to the near-field GMs without a pulse. It is concluded that the stated ratio is a crucial parameter to assess the risk to the life safety (LS) of low-to-high-rise RC buildings. For frequently occurring seismic intensities, repairable damage to nonstructural elements is the main factor contributing to the total expected economic loss in the studied buildings, irrespective of the selected GM set and the number of stories. In addition, the contribution of collapse and demolition due to residual drift in the estimation of repair time is significant for pulse-like GMs.

The stabilizing pile represents a promising solution for enhancing the seismic resilience of unsaturated slopes. This study introduces a novel analytical framework for assessing the stability of unsaturated slopes reinforced with piles, amalgamating the minimum potential energy approach with the pseudo-dynamic method. The formulation of the external potential energy arising from the self-weight of the landslide mass and seismic forces is derived. Furthermore, traditional plasticity theory is extended to unsaturated soil slopes to account for the augmenting influence of matric suction on the lateral pressure exerted by stabilizing piles. The efficacy of reinforcing unsaturated soil slopes with piles is gauged through the definition of the safety factor (SF), delineated as the ratio of resistance moment to sliding moment. Additionally, a fresh interpretation of the critical slip surface (CSS) for unsaturated soil slopes is proposed, alongside an original criterion for identifying CSS, introduced herein for the first time. The validity of the proposed methodology is substantiated through examination of three case studies, yielding results indicative of its efficacy and rationality. The analysis underscores the substantial fortifying impact of matric suction on the stability of unsaturated slopes, as well as the reinforcing influence of piles. Moreover, an exploration into the ramifications of seismic and pile-related parameters on slope performance and CSS is conducted. In conclusion, this approach serves as a valuable reference for the design of unsaturated slopes fortified with stabilizing piles.