Seismic Conditions Research Articles

Model updating of highway slope under seismic intensity conditions considering spatially varying soils

Abstract Understanding the mechanisms underlying earthquake-induced landslides and assessing seismic responses are crucial for effective mitigation strategies. Earthquakes typically involve a mainshock followed by aftershocks, posing challenges to structures weakened by the mainshock. Highway slope structures, especially those in unsaturated soft-soil slopes, are vulnerable to aftershocks, amplifying the damage caused by the mainshock-aftershock (MSAS) sequence. While existing research primarily focuses on the effects of mainshocks on certain structures, there is a notable gap regarding the damage sustained by unsaturated slope structures under MSAS conditions. Addressing this gap is vital for comprehensive risk assessment and mitigation. To address these challenges, we propose a stochastic model updating approach for seismic reliability analysis. This approach integrates subset simulation with adaptive Bayesian updating and dimensionality reduction using the Karhunen–Lòeve expansion. Shaking table tests on a slope structure with unsaturated red clay soil are conducted to investigate the effects of matrix suction on performance degradation and failure mechanisms. The results reveal spatial variability in soil property parameters, underscoring the need to incorporate this variability into inverse analyses. Traditional deterministic methods or probability-based approaches may overlook such variability. Also, the results indicated our proposed approach enables effective prediction of seismic responses for unsaturated slopes subjected to MSAS sequences. By considering spatial variability and the effects of matrix suction, our method offers a comprehensive framework for seismic reliability analysis of unsaturated slope structures.

Performance Assessment of Reinforced Concrete Bridges Under Coupled Horizontal and Vertical Ground Motions Using Fragility Surfaces

ABSTRACT The objective of this study is to explore the seismic fragility of reinforced concrete bridges, specifically in response to the vertical components of ground motions, utilizing fragility surfaces. The examination of bridge responses involves the application of optimally selected intensity measures through three-dimensional nonlinear time-history analyses, encompassing uncertainties in both superstructure materials and soil–structure interaction effects. In this investigation, an extended Probabilistic Seismic Demand Model (e-PSDM) is employed, leveraging fragility surfaces to concurrently consider vertical and horizontal excitations. The results obtained from this approach are compared with traditional fragility curves. This study emphasizes Pile-cap displacement and drift ratio as pivotal engineering damage parameters, acknowledging their sensitivity to the influences of both soil–structure interaction effects and vertical ground motion. The fragility surfaces derived from the study reveal a correlation between increased vertical spectral accelerations and elevated probabilities of surpassing both slight damage and collapse limit states. These observations underscore the critical significance and practical utility of fragility surfaces in the context of performance-based seismic assessment and design for reinforced concrete bridges. The findings from this research contribute valuable insights into the nuanced behaviour of reinforced concrete bridges under seismic conditions, emphasizing the relevance of incorporating vertical components in fragility assessments for a more comprehensive understanding of structural vulnerability.

Study on rock block seismic sliding using three‐dimensional discontinuous deformation analysis

AbstractThe seismic sliding of rock masses is an important phenomenon that is widely involved in earthquake geological hazards. Practical seismic sliding is a three‐dimensional problem, namely, the seismic loads may act in any direction and the rock masses may move in an arbitrary direction relative to the sliding plane. In the present work, the functions of two different seismic loading methods, that is, loading as body force time histories to the sliders or as displacement time histories to the base, are added to the program of the three‐dimensional discontinuous deformation analysis (3D‐DDA) method that is based on the contact theory to study the seismic sliding of rock blocks. The theoretical solutions of single‐block sliding on an incline under the two seismic loading methods are derived. By comparing the 3D‐DDA results of single‐block seismic sliding with the corresponding theoretical results, and comparing the 3D‐DDA results of seismic sliding of three‐stacked‐blocks under the two seismic loading methods, the correctness of 3D‐DDA for seismic sliding simulations is validated. Thereafter, the influence of three‐dimensional seismic components on single‐block sliding, and the movement of block groups under different seismic load conditions are investigated by 3D‐DDA simulations, which indicate the importance to consider rock mass seismic sliding as a three‐dimensional problem and the capability of 3D‐DDA for its analysis. This work builds a meaningful basis for the further numerical simulation study on the earthquake‐induced rock mass movements by 3D‐DDA.

Longitudinal Seismic Response of Metro Tunnels Crossing a Fault with Multi-Slip Surfaces

There are multiple seismic fault zones near Xi’an in China, among which the Li Piedmont Fault has multiple slip surfaces. A 3D finite element dynamic Soil–Fault–Tunnel model was established based on the engineering background of the Xi’an Metro tunnel orthogonally crossing the Li Piedmont Fault. The input seismic loads used the Chi-Chi, El-Centro, and artificial seismic waves, and the latter was artificially synthesized based on seismic conditions and site conditions of actual engineering. The Chi-Chi seismic wave with larger PGV/PGA and wider acceleration-sensitive area is a near-field seismic wave, while the others are far-field seismic waves. The seismic loads were transformed into the equivalent nodal force on the boundary nodes of the model, and nonlinear dynamic calculation was carried out to obtain the longitudinal seismic response of the structure. The main results show that the fault amplifies the seismic response of the tunnel, and the tunnel at the position of the fault slip surfaces is more vulnerable to failure, especially near the slip surface between the hanging wall and the fault, where the maximum acceleration, soil pressure, and internal force of the tunnel structure occur. In addition, the seismic response of the tunnel and soil caused by near-field seismic motion is significantly stronger than that caused by far-field seismic motion.

Seismic performative analysis of a 200-year-old Masonry Heritage Structure in India

A structural assessment study on the “Humayun Palace” in Tamil Nadu, a cultural heritage structure, constructed in the early 1700’s was done. Based on the original design documentation collected through records, a static analysis model of the building was generated. This structure is a 3-storey building and details of all the provisions from the slab system to the roof tiles were made. The results developed by these models, aimed at fully understanding the original design concept of the various members, as well as at evaluating their current static and seismic safety conditions, are reported in this paper. This analysis was examined using E-TABS software, whose geometric limitations lead to minor encumbrances. Some complex geometric façade features were approximated to convenience and overcome. The results of the analyses highlight safe conditions and good performance objectives in general, but for some important exceptions. The overall satisfactory performance may be attributed to the overdesigning with excessive safety factors carried out by builders of that century, enabling the structure to withstand conditions way past its intended life. However, the question as to how well the structure will hold good in the future is hypothetical. It is for the same reason that the Public Works Department has allocated nearly 96 crore rupees for the rehabilitation of the same. This investigation is synchronous with the objectives of the said rehabilitation project and has established an exhaustive analysis of the structural health of the structure.

A novel constitutive model for the concrete face slab of a CFRD and the numerical simulation of its seismic behavior

AbstractWith the rising demand for hydropower energy, China has built numerous concrete‐faced rockfill dams (CFRDs) with considerable heights. The potential failure pattern of the concrete face slab is the key to the safety of the anti‐seepage system. However, engineers commonly employ an elastic relationship to model the concrete face slab for simplicity, which induces inaccurate estimation of the face slab's stresses, especially under seismic conditions. On the other hand, the existing elastoplastic models for concrete often require complex derivation of the necessary formula and thus are difficult to apply to finite element (FE) analysis. Under the comprehensive action of the upstream water, supporting rockfill, and surrounding mountains, the damage mode of the quasibrittle concrete slab is not a tensile mode but a compressive shearing mode. Therefore, it is urgent to establish an elastoplastic model that is adapted to the actual working environment of the slab and easy to apply. To this end, a generalized plasticity model is developed within the phenomenology modeling concept, which is validated at both the experimental level and application level. The results indicate that three‐dimensional stress‒strain behaviors, such as the strength nonlinearity, prepeak dilatancy, and postpeak softening, can be effectively captured. In addition, the seismic characteristics of a 200‐m high CFRD are numerically investigated. The findings show that the slab's stress accumulation can be reflected during the earthquake and that the final stress distribution conforms to the field observations. The conclusions of this paper provide a reliable reference for the seismic resistance design of CFRDs.

Parametric Optimization of Circular Elevated Water Tanks Under Various Capacities and Seismic Conditions

The elevated water tank comprises important structural elements which includes slabs, beams, columns, and footings, facilitating the transfer of loads amongst these contributors and subsequently to the subgrade of the soil. This paper goals is to comprehensively analyze the structural behaviours exhibited by elevated water tanks underneath various loading conditions. The behaviours of multiplied water tanks variety underneath various styles of loadings, inclusive of dead, live, and seismic loads, that are comprehensively analyzed. This paper primarily aims to conduct a hydrostatic evaluation of circular water tanks and emphasizes the necessity of a parametric study. To obtain this goal, 2, 2.5, and 3 lakh litters of tanks are being considered for the analysis which are all examined underneath area III seismic situations whilst keeping a normal height and varying diameters during the simulation. The examination focuses on carrying out a comparative evaluation of critical structural parameters, such as moment, maximum displacement, and maximum base shear. By means of analysing those parameters across various tank capacities, precious insights into the structural reaction of circular elevated water tanks under seismic loading conditions are gained. Those findings contribute to enhancing the design and overall performance of such structures, enhancing their resilience and protection in earthquake-susceptible regions.

Mathematical modeling for assessing the seismic response of buildings in Al Hoceima

The purpose of this paper is to apply structural dynamics principles to conduct a comprehensive mathematical analysis of how buildings respond to earthquakes, with a particular focus on the dynamic behavior of a reinforced concrete structure in the city of Al Hoceima, located in the north of Morocco, which is subjected to frequent seismic activity. Considering various parameters such as building configurations, materials, soil characteristics, and seismic conditions, we will build a mathematical model for response of structures to earthquakes and conduct numerical experiments using ETABS software on a typical building in this region with a G+2 house elevation.

Settlement Prediction of Ring Foundation under Seismic Conditions

Settlement Prediction of Ring Foundation under Seismic Conditions

Pertinent Emplacement of Shear Walls to Diminish the Torsional Effects in Asymmetric-RC Framed Buildings

In seismic conditions, asymmetric structures typically experience lateral deflection. The magnitude of this deflection is dependent on various factors, including the configuration of the structural system, the mass of the structure, and the mechanical properties of the materials used. One critical factor that can reduce a structure's seismic resistance is torsion irregularity. To combat this, shear walls can be installed in the pertinent location to provide stability and stiffness to the structure. This study explores the seismic analysis of a G+10 storey asymmetric RC frame-shear wall structure using the response spectrum method as per ASCE7-16. The study encompasses six models with varying shear wall placements, with the initial model lacking a shear wall. The results are compared, and recommendations are made to avoid torsional irregularity destruction under seismic loads. Based on the analysis, Model-2 (shear wall in the periphery) shows the worst condition from the 1st storey through the 11th storey, possibly due to maximum eccentricity in upper storeys. In contrast, Model-5 (shear wall in core and corners) shows the best performance among all models, likely due to increased stiffness in the corners and core of the structure. Overall, this study contributes to the advancement of structural engineering practices by enhancing the understanding of complex interplay between torsional irregularity, shear wall placement, and structural asymmetry.

Mechanically Stabilized Earth (MSE) retaining wall at hotel in Bariloche City

In the city of Bariloche, Argentina after heavy rains, among other things, a slope failure occurred. At the top of it there were gabions, which, due to the loss of stability, together with a large mass of soil and trees, collided tragically against the facilities of the Hotel. This article describes the use of geosynthetics for the construction of a 20m high MSE (Mechanically Stabilized Earth) retaining wall in order to contain the slope soil. At the same time, the consequent drainages for water runoff and the release of hydrostatic pressures needed to be considered. Instead of gabions, a wall made of prefabricated concrete blocks was proposed, along with PVA geogrids for slope stabilization and soil reinforcement. Due to the large size of the slope, a stepped wall with six terraces was proposed, which would later be naturally vegetated. Each wall was locally dimensioned for a specified height, and then a global stability verification of the structure was carried out.The inclusion of geosynthetic reinforcements in the soil for the construction of a reinforced wall results in a material with better mechanical characteristics. This solution offers significant technical and economic advantages, increasing the shear strength of the system (ensuring stability), reducing the deformability of the structure (both in static and seismic conditions), and saving construction time and material. Thanks to their excellent interaction properties, reinforcement geosynthetics (flexible elements with stiffness and tensile strength) work together with the soil, connecting the potentially "unstable" region (active zone) with the "stable" region (passive zone) for a given failure surface. Furthermore, the system flexibility and adaptability allowed the structure to be adapted in an aesthetic way, respecting the site architecture and environment.

Constitutive Modelling of the Cyclic Response of Unsaturated Soils: A Discussion of the State‐of‐Art

Site response analysis (SRA) is an important aspect of seismic design that considers the impact of local site conditions on the ground response during earthquakes and plays a key role in the design of structures that interact or are made with soil. Although previous studies have demonstrated that factors such as the degree of saturation influence the site response, incorporating partial saturation into analysis has not been widely practiced. Numerical analysis tools exist; however, they are often unable to directly assess the influence of partial saturation, especially under seismic conditions. This is often caused by the missing implementation of constitutive models and finite elements able to account for partial saturation of soils under cyclic conditions. For this reason, a review of the most common constitutive models developed with a view to describing unsaturated soil behaviour subjected to cyclic loads is presented, followed by a critical discussion on their applicability to finite element frameworks, with the aim of providing a wide panorama of the available constitutive platforms suitable for implementation in numerical codes. Therefore, we present and discuss the mechanical and hydraulic properties of the constitutive models that can be applied to the analysis of boundary value problems, and specifically for SRA, focusing on partially saturated soils under cyclic loading conditions. It was observed that many constitutive model frameworks for cyclic loadings are based on the bounding surface or two‐surface theories, and some of them are coupled with hydraulic behaviour through the Soil Water Retention Curve (SWRC) or its variations. Two main approaches were identified based on the mechanical features, while regarding the hydraulic behaviour, the main distinction lies in the selected SWRC. Furthermore, certain constitutive models have been implemented in finite element software for numerical analysis of geotechnical earthquake engineering problems.

Design of rigid inclusions in seismic conditions

Design of rigid inclusions in seismic conditions

Seismic Deformation Response Analysis of Shallow Buried Section at the Entrance and Exit of River Crossing Tunnel

Ensuring the safety of tunnel structures in unique underwater environments is of paramount importance. This study focuses on the entrance section of a river-crossing tunnel, characterized by shallow burial depths with significant variations. The tunnel structure faces challenges related to structural weakening, and its deformation response exhibits specific characteristics under seismic loads. Numerical simulation software was employed to model and calculate the deformation response of the shallowly buried entrance section under seismic load conditions, assessing the impact of changes in tunnel structural strength and burial depth. The results reveal the following key findings: (1) As the tunnel structure weakens, structures of varying strengths primarily experience vertical deformation under seismic loads, followed by horizontal deformation. Furthermore, as the tunnel structure’s strength decreases, it exhibits an increasing trend in deformation. Routine maintenance should prioritize locations where the tunnel structure weakens, implementing timely reinforcement measures to ensure adequate load-bearing capacity. (2) Considering the influence of tunnel structural burial depth, lateral deformation values rank in descending order from largest to smallest, including the tunnel bottom, middle carriageway, middle of the tunnel, and tunnel vault, while the overall lateral deformation of the tunnel is not significant, it decreases as the structural burial depth increases. (3) In relation to tunnel structural burial depth, vertical deformation values generally exceed horizontal deformation values. Sections with the highest to lowest deformation values are the tunnel bottom, middle lane of the tunnel, middle of the tunnel, and position of the tunnel vault. With increasing burial depth, the vertical deformation values decrease at a slower rate than horizontal deformation. The tunnel structure demonstrates a higher sensitivity of lateral deformation to changes in burial depth factors.

Design experiences of MSE structures under complex conditions in a highway project

The design and construction of Mechanically Stabilized Walls (MSE) have had a great boom in Guatemala in recent years. Central America’s largest private infrastructure road project has required the construction of more than 30,000 m2 of MSE structures under extreme seismic, topographical, and hydrological conditions. Considering that Guatemala has been a country with very high seismicity and the project being on a good percentage of slopes on the margins of a river, made both the design and construction of the project face great challenges. The project consists of tier walls, walls with upper slopes, walls supported on extremely steep slopes and walls with heights that can reach more than 20 meters. Many of these structures have critical hydraulic and global stability conditions. There are three case studies of walls, that by their complexity deserve to be considered for further study and from which there are many lessons for the future use of mechanically stabilized structures in the face of complex conditions.

Design experiences of MSE structures under complex conditions in a highway project

The design and construction of Mechanically Stabilized Walls (MSE) have had a great boom in Guatemala in recent years. Central America’s largest private infrastructure road project has required the construction of more than 30,000 m2 of MSE structures under extreme seismic, topographical, and hydrological conditions. Considering that Guatemala has been a country with very high seismicity and the project being on a good percentage of slopes on the margins of a river, made both the design and construction of the project face great challenges. The project consists of tier walls, walls with upper slopes, walls supported on extremely steep slopes and walls with heights that can reach more than 20 meters. Many of these structures have critical hydraulic and global stability conditions. There are three case studies of walls, that by their complexity deserve to be considered for further study and from which there are many lessons for the future use of mechanically stabilized structures in the face of complex conditions.

Neural Function Desynchronisation in Left and Right Dorsolateral Prefrontal Cortices During Virtual Reality Earthquake Video Viewing.

During natural disasters such as earthquakes, individuals are required to evacuate calmly amidst significant emotional distress, presenting a considerable challenge. Very few studies have measured emotional responses during disasters, and the emotional responses and brain activity during natural disasters are poorly understood. Therefore, this study aimed to investigate emotional responses during an earthquake using immersive virtual reality (VR), focusing on changes in neural connectivity in the left and right dorsolateral prefrontal cortices (DLPFCs). We measured changes in total haemoglobin concentration (Δtotal-Hb) using 2-channel near infrared spectroscopy (NIRS) while 24 healthy young adults viewed earthquake and neutral videos through a head-mounted display (HMD). Spearman's correlation analysis was applied to the time variation in Δtotal-Hb in the left and right DLPFCs, independently for seismic or neutral video conditions. The findings revealed a negative correlation between the left and right total haemoglobin concentration changes during the earthquake video (ρ=-0.53). Conversely, individuals exposed to the neutral video exhibited a positive correlation (ρ=0.75). The present steady-state analysis suggests that emotional changes induced by virtual earthquake videos disturbed steady-state neural synchronisation between the left and right DLPFCs.

Effect of Water Immersion on the Seismic Isolation Performance of Castable Polyurethane Bearing

This study performs a 120-day water aging simulation on castable polyurethane (CPUE) bearings and tests them at 30-day intervals for vertical load-bearing performance and 100% horizontal shear performance. The results indicated that the CPUE bearings achieved full water aging after 120 days of water immersion. Besides, the vertical stiffness, horizontal shear stiffness, and equivalent damping ratio decreased by 10.3%, 16.8%, and 10.0%, respectively. Moreover, the study investigates the hydrolysis mechanism of CPUE bearings using Atomic force microscopy (AFM) and cross-linking density (NMR) tests. Subsequently, it develops models for unaged CPUE bearings (CPUE-un) and fully water-aged bearings (CPUE-aged), selecting unaged test results for CPUE-un and the test results from 120 days of water immersion for CPUE-aged. Within the study context, a representative high-pier continuous girder bridge serves as the basis for evaluating the effects of seismic conditions on the CPUE-un and CPUE-aged bearing bridge systems. The findings demonstrate that water-aged CPUE experiences significant material softening, with bearing deformations increasing by 14.99%, 34.06%, and 46.65% at 0.3, 0.6, and 0.9 g peak ground acceleration (PGA), respectively. The likelihood of damage to water-aged bearings increased under seismic influence, while the impact on piers was less pronounced. This research provides a valuable reference for the application of CPUE bearings in humid environments.

Experimental study on the effect of different cement content on the improvement of dynamic characteristics of seismic-prone poor soil.

The improvement of sandy soils with poor seismic properties to modify their dynamic characteristics is of great importance in seismic design for engineering sites. In this study, a series of dynamic tests on sandy soils sandy soils with poor seismic conditions were conducted using the GCTS resonant column system to investigate the improvements effects of different cement contents on dynamic characteristic parameters. The research findings are as follows: The cement content has certain influences on the dynamic shear modulus, dynamic shear modulus ratio, the maximum dynamic shear modulus, and the damping ratio of sandy soils with poor seismic properties. Among them, the influence on dynamic shear modulus is limited, while the damping ratio is significantly affected. The addition of cement to seismic-poor sandy soils significantly enhances their dynamic characteristics. The most noticeable improvement is observed when the cement content is 8%. Through curve fitting analysis, a relationship equation is established between the maximum dynamic shear modulus and the cement content, and the relevant parameters are provided. A comparative test between the improved soils and the remolded soils reveals that the addition of cement significantly improves the seismic performance of the poor soils. The recommended values for the range of variation of the dynamic shear modulus ratio and damping ratio are provided, considering the effect of improvement. These research findings provide reference guidelines for seismic design and engineering sites.

A Comprehensive Analysis of Column Optimization for Circular Elevated Water Tanks in Seismic Environments

Water storage is critical everywhere, especially in places where there is a severe water shortage. Understanding its vital significance, water storage projects are receiving more attention in an effort to guarantee regular availability to this resource that is necessary for daily existence. The study explores the complex dynamics of raised water tanks and describes the structural details of slabs, beams, columns, and footings. These element channel loads carefully to the soil sub-grade, allowing their complex interaction. The study focuses into many load types, including seismic, living, and dead, and as a result, the analytical framework reveals the dynamic behaviours of the water tank. The main aim of this research project is to perform a thorough hydrological investigation of circular water tanks. Furthermore, the study presents the findings from a thorough analysis of round raised water tanks, with a focus on column optimisation. The research examines different column arrangement with capabilities that remain constant across the range, from 10 to 14 columns. In the context of Zone II seismic conditions, the study preserves relative integrity by keeping heights and diameters constant. By conducting a detailed analysis of crucial structural considerations, such as maximum bending moment, maximum displacement, and base shear, the study aims to clarify the subtle performance characteristics present in circular elevated water tanks under seismic loading scenarios.