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Offshore foundations usually experience long-term cyclic loading, where the weakly bound water at the soil-structure interface can be transformed into free water. The free water enriched at the soil–structure interface would influence the mechanical characteristics of the soil near the interface, weakening the interface strength and posing a significant threat to the safety and stability of offshore foundations. This study proposed a novel concept, i.e. the characteristic water film thickness, to quantify the enrichment degree of water film at the soil–structure interface under cyclic loading. A series of cyclic shearing tests were carried out by using self-developed cyclic loading equipment combined with a small constant temperature centrifuge. The influence of different clay and salt contents on the characteristic water film thickness was investigated and analyzed. It was found that both the kaolin and salt contents significantly impacted the characteristic water film thickness, where it was positively correlated with the kaolin content while negatively correlated with the salt content. The research outcome enriched the understanding of the weakening mechanism underlying the load and deformation transfer between soil–structure interface. [ABSTRACT FROM AUTHOR]

High-speed railway is expanding drastically in Sweden, necessitating new technology, and improvements of existing structures. End-shield bridges are a common and under-tested bridge type in Sweden. Their dynamic performance is significantly impacted by their boundary conditions due to the soil–structure interaction (SSI) and their large masses cantilevering beyond the footings. A specific end-shield bridge was tested under low (5 kN) and high (20 kN) amplitude-forced hydraulic excitation for a wide range of frequencies. Several train passages for typical passenger trains, 'X62', were measured with the same experimental setup. The results were analysed to isolate the significant modes of the system and the natural frequencies. A full 3D numerical model was calibrated and updated in Abaqus, along with a brief sensitivity study to determine the most influential parameters. Finally, the response to passing trains and Eurocode design HSLM trains was calculated. The experimental study showed that higher loading amplitudes resulted in higher damping and lower natural frequencies. The numerical analysis showed that for this bridge type the SSI cannot be neglected and can be successfully introduced in the model. [ABSTRACT FROM AUTHOR]

The mutual interaction between base isolation (BI) and soil–structure interaction (SSI) needs to be considered in design applications. In the literature, the key parameters that may affect such interaction have been rarely considered. Closed formulations for the assessment of the mutual role of BI and SSI have not been proposed yet. The paper aims to cover this gap by considering a 3DOF model to propose closed relationships with the most significant parameters (structural period, isolation ratio and shear wave velocity). The outcomes show that there are two different interactions. When soil deformability and structural stiffness are not significant, the isolation ratio may be used as a main parameter. However, when the foundation soil is particularly deformable and structures are significantly rigid, a more complex relationship needs to be considered. Parametric case studies have been performed with different structures, three isolation ratios and several soil conditions (soil A, B, C and D). [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive method for analyzing prestressed concrete bridges subjected to multiple concurrent dynamic loads, incorporating soil–structure interaction (SSI) and seismic wave propagation effects. The study develops a comprehensive numerical framework that simultaneously accounts for traveling seismic waves, train-induced vibrations, and soil–foundation dynamics. Three-dimensional finite element modeling captures the complex interaction between the bridge structure, foundation system, and surrounding soil medium. The investigation considers the spatial variability of ground motion and its influence on the bridge's dynamic response, particularly examining how different wave velocities and coherency patterns affect structural behavior. Advanced material constitutive models based on damage mechanics theory are implemented to represent both linear and non-linear structure responses under dynamic loading conditions. The analysis reveals that traditional simplified approaches, which neglect SSI, train, and seismic loading combinations, and traveling wave effects may significantly misestimate the structural demands. The results demonstrate how wave passage effects can either amplify or attenuate the combined response depending on the relationship between seismic wave velocity, the frequency content of the ground motion recordings, and the local soil conditions. These findings could contribute to the development of more reliable design methodologies for prestressed bridges in seismically active regions with significant railway traffic. [ABSTRACT FROM AUTHOR]

AbstractThe design of shallow foundations at the ultimate limit state is conventionally performed assuming a foundation structure that does not undergo any yielding, although current technical standards require the investigation of any possible rupture mechanism, including combined rupture in the soil and in the foundation structure. The aim of this work is to study the practical implications of including the analysis of combined rupture mechanisms (involving both soil and foundation structure) in shallow foundation design under drained and undrained conditions within the framework of current technical standards. Two case studies are presented and tackled with a recent novel strategy for numerical simulations. It is shown that conventional foundation design methods may not be reliable when evaluating internal actions within a spread foundation, hence foundation yielding may not be correctly detected, implying that the bearing capacity of a foundation can be severely overestimated in conventional practice, in particular under drained conditions. On the other hand, foundation yielding can be exploited to reduce the amount of needed reinforcement, while still satisfying both geotechnical and structural technical standards. [ABSTRACT FROM AUTHOR]

Background: Pile foundations, whether precast or cast-in-situ, are widely used in essential structures such as bridges and jetties. The common materials for pile fabrication include concrete, steel, and wood. However, these materials can deteriorate in harsh environments such as seawater and salty soil, affecting the integrity and service life of the pile-foundation systems. Problem: Traditional solutions, like using concrete piles confined with steel jackets, increase service life but are costly. The engineering community is exploring fiber reinforced polymer (FRP) as an alternative due to its noncorrosive nature and resistance to harsh environments. However, the relatively short track record of FRP raises concerns about its behavior under non-normal conditions, such as seismic events. Objective: To present a numerical assessment of the seismic behavior of an offshore bridge supported by a GFRP-filled tube pile group, considering the soil-structure interaction (SSI) and dynamic behavior of the composite system. Methods: The study involves a detailed proposed methodology for assessing the structure under earthquakes with different soil profiles. A numerical model is developed to evaluate the dynamic response and interaction between soil and the GFRP-filled tube pile group. Results: The results verify the expected benefits of using GFRP in pile foundations, focusing on the effects on the lateral capacity of structures under seismic conditions. Conclusion: The study contributes to understanding the feasibility and performance of GFRP-filled tube piles in offshore bridge foundations under seismic loads, providing insights into their potential advantages and limitations. [ABSTRACT FROM AUTHOR]

This study centers on the crucial determination of the mobilized friction angle between soil and various materials, including steel and concrete, to enhance the modeling of soil-structure interaction. The primary objective of the current investigation was to assess the interfacial friction between calcareous and silica sands when interacting with concrete or steel surfaces. To achieve this, direct shear tests were conducted to examine the impacts of relative density (Dr), surface roughness (Rn), and shearing direction. The test results reveal that the shear strength of calcareous sand surpasses that of silica sand when considering a specific Rn. Furthermore, the interface friction of both sand types escalates with an increase in normal stress and Rn, with higher values observed in interactions with steel plates. Notably, the friction angle ratio (the interaction friction angle over the pure sand friction angle) demonstrates minimal dependence on the sand type. The most pronounced divergence in the friction angle ratio is evident at the maximum Rn value, which increases alongside Rn values for both calcareous and siliceous sands. With increasing Rn values, the maximum shear strength, contingent on normal stress and relative density, also rises. The influence of relative density on the interaction friction angle diminishes with escalating surface roughness. [ABSTRACT FROM AUTHOR]

Tuned mass dampers (TMDs) are a useful control of vibrations for tall buildings and can be considered equal to burdens such as breezes and earthquakes. The better limits for TMD are to reduce the earthquake vibrations of tall buildings including soil–structure interaction (SSI) influences. This study proposes the multi-objective Black Widow Optimization (BWO) with Elman neural network (ENN) computation that is brought on to find the optimal limits of TMD. Considering that this proposed model analyzed the mass, stiffness, and damping ratio of TMD to get the maximum accelerations and displacement of 40 story building model, from the execution results, starting from this proposed BWO–Elman model to the expected methodology, the most outrageous TMD limits are better, likewise, the reduction of acceleration and displacement are 25% and 19.86% in the proposed study. This study assists the researchers with a better understanding of earthquake vibration and leads the fashioners to achieve superior TMD for tall designs. The impact of vibration control on the displacements and accelerations of both controlled and uncontrolled buildings is investigated in this work. It uses a MATLAB software technique to analyze their modal replies, moreover, this proposed optimal TMD model is compared with conventional techniques by acceleration and stiffness parameters. [ABSTRACT FROM AUTHOR]

This article proposes an advanced nonlinear soil-structure interaction methodology, for the seismic analysis of a nuclear structure. To do so, a study is performed on a nuclear reinforced concrete structure considering the effects of the nonlinearity due to the sliding and rocking at the soil-structure interface, under a Beyond Design Basis Earthquake. A tridimensional numerical model based on the Finite Element Method is developed for the structure and the soil. The model of the structure considers composite materials to describe all the structural members, taking full advantage of the modelling capabilities of the finite element method. The soil layers are modelled assuming their degraded properties due to the propagation of the seismic ground motion. An innovative approach to achieve spectral matching at the surface of the FEM soil model after propagation from the bedrock has been successfully implemented. The seismic analysis on the structure has been performed by considering three hypotheses for the contact between soil and structure: fixed-base, fixed contact and sliding-rocking contact. Insights are provided after comparing floor spectra for the contact approaches assessed in this research, calculated at the systems and components' locations at the nuclear structure. Finally, a statistical approach for the soil properties allows to study the effects of these uncertainties on the structural response. [ABSTRACT FROM AUTHOR]

This work explores earthquake-induced kinematic bending in the so far unresolved case of a pile embedded in a two-layer soil with a thin surface layer. The problem is treated analytically by means of a generalised Winkler model, which in addition considers the effect of boundary conditions at the pile head over earlier contributions on the subject. Novel analytical closed-form expressions of the kinematic bending moment at the pile head and at the interface between the two soil layers are provided for both fixed- and free-head piles. The analytical solutions are validated through a rigorous finite-element model, which proves a remarkable accuracy in the static regime. While for interface bending the past literature indications for the dynamic coefficient make the proposed formula accurate for both shallow and deep interface, a novel dynamic interaction factor, describing dynamic effects for pile-head bending, is introduced. A numerical example provides guidance on application of the formulae in real design scenarios. [ABSTRACT FROM AUTHOR]

This article presents an innovative structural system for offshore wind turbines supported on monopiles. The novelty of this system lies in its enhancement of the lateral stiffness of the tubular tower through the incorporation of an outrigger system, widely employed in high-rise buildings. This novel system is modeled as a Timoshenko beam-column element under both static and dynamic loading scenarios, incorporating geometric nonlinearity and accounting for the effect of soil-structure interaction. A comprehensive numerical analysis was conducted to evaluate the system's behavior under various static and dynamic load cases, utilizing soil data from the Red Sea region of Egypt. A modal analysis is also incorporated to investigate the eigenmodes of the proposed system. This study offers valuable insights for designers and researchers, providing guidelines and diagrams for the implementation of the proposed system. [ABSTRACT FROM AUTHOR]

The safety of an isolated structure built on the soft soil ground under the action of earthquakes is of major concern because the current seismic design of isolated structures has not considered the motions of the foundations caused by the effects of the soil‐isolated structure dynamic interaction (SISI). On this basis, a shaking‐table test method for base‐isolated structures on change of soil foundation stiffness was proposed and implemented. The foundation stiffness was controlled by the duration compression ratio and intensity of the input ground motion based on the influence of the increase in the excess pore water pressure ratio on the stiffness of the saturated sandy foundation. Meanwhile, the influence laws of foundation stiffness on the dynamic characteristics of base‐isolated structures were summarized and analyzed. The results showed that the first‐order natural frequency of base‐isolated structures on change of foundation stiffness decreased with an increase in the relative stiffness ratio of the structure–soil foundation (Rs), while its damping ratio increased significantly. The seismic isolation efficiency of the seismic isolation layer and the amplification effect on the rotational angular acceleration of the pile cap were significantly weakened. Meanwhile, under the same conditions, for the soil foundation with relatively small stiffness, the amplitudes of the bending moment and horizontal lateral displacement in the middle and upper parts of the pile remarkably increase because of the effects of the ISI. The research results of this test provide a certain scientific basis and reference for the seismic design of base‐isolated structures considering the SISI effects. [ABSTRACT FROM AUTHOR]

Since the Fukushima nuclear incident in 2011, the focus on nuclear safety has intensified significantly, leading to heightened demands for nuclear power plant modeling to go beyond the mere dynamic analysis of soil–structure interaction (SSI) or fluid–structure interaction (FSI). In current engineering practice, FSI is typically described using simplified forms, such as loads or added mass. However, this approach lacks a comprehensive analytical framework that integrates refined FSI analysis with soil–structure interaction (SSI). This study analyzes the dynamic response of the nuclear island structural system using a fully coupled fluid–structure–soil interaction (FSSI) model. The effectiveness and validity of the model are verified through case comparisons. Simulations were conducted using the parameters of five different types of nuclear power engineering sites for both homogeneous and layered foundations. The results indicated that the hydrodynamic pressure response and acceleration amplification of layered foundations significantly exceeded those of homogeneous foundations, underscoring the importance of considering layered sites in the comprehensive complex modeling of nuclear power projects. [ABSTRACT FROM AUTHOR]

This paper presents an innovative seismic isolation system for the structure and unbounded rubber soil. The dynamic interaction of the rubber soil and structure is considered. The rubber soil mixture is constituted by rubber particles and clay. The pollution problem of wast rubber is solved effectively. The rubber soil is firstly introduced into the ordinary unbounded foundation. According to the composite material theory and hybrid law, the rubber soil modulus formulation is derived by two-phase modulus innovatively. By employing the standard viscous boundary method, the radiation damping of unbounded rubber soil is considered. And then, the novel wave propagation equation of unbounded rubber soil is derived. Based on the cylindrical expansion wave and cut-off wave assumptions, the normal and tangential boundary condition equations are derived, respectively. The interaction force causing by earthquake on the rubber soil and structure is modeled. Numerical examples are presented to demonstrate the effectiveness and reliability of the proposed method for the rubber soil and structure interaction model. The seismic response of the rubber soil and structure system is discussed. Excellent seismic performance of rubber soil is confirmed. The influence of the rubber soil content and thickness are discussed in detail. [ABSTRACT FROM AUTHOR]

Full-scale physical modelling was used to evaluate the response of modular polymer stormwater collection structures when subjected to design-truck loading that was sustained for 1 week (i.e. a parked vehicle) and when buried with minimum soil cover. Surface loading was applied on a steel load pad that simulates one-half of the AASHTO design-truck single-axle that was held constant for 1 week to assess the stability of the buried system and demand on the platen and column components of the modules to allow independent load rating of the buried structure. No collapse or limiting state occurred. The 1-week creep buckling resistance was found to be nearly four times the factored column demand to 1-week loading for both module types. New insight into the time-dependent behaviour of the soil–structure system was gained by comparing the buried response to creep tests conducted on isolated columns and platens. The response of the buried soil–structure system was less severe than unconstrained creep. Column loads were found to not increase with time. Bending deflections increased by 1.04 to 1.26 times when buried rather than by 3.0 to 3.4 times for unconstrained creep as platen creep when buried was greatly restrained by the soil. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of soil-structure interaction on the dynamic behavior of structures subjected to seismic movements. A 2D model of a simple minaret, 18.4 meters tall with a width and length of 3.5 meters, was analyzed using the SAP2000 V21 finite element software. Two types of seismic loading were applied: the response spectrum of Algerian seismic regulations (RPA 99 version 2003) for low seismicity (zone: Z1), and accelerograms measured at the Keddara site in Boumerdès, Algeria, in 2003. The soil foundation is classified as type S3 (loose soil), and the analysis included conditions both with and without soil-structure interaction. The results indicate significant impacts of soil-structure interaction: the inclusion of soil effects led to a 25% reduction in base shear and a 15% increase in the fundamental period of the structure compared to the reference model without soil interaction. Additionally, nodal horizontal displacements at the top of the building increased by 40% when accounting for soil-structure interaction, affecting the overall stability and design considerations. This study underscores the importance of incorporating soil-structure interaction in the design process, as neglecting these effects could lead to underestimating the seismic demand and potentially compromise structural integrity. [ABSTRACT FROM AUTHOR]