This paper presents a data-driven model updating framework to estimate the operational parameters of a laterally-impacted pile. The goal is to facilitate the estimation of soil-pile interaction parameters such as the mobilized mass and stiffness, as well as geometrical data such as embedded pile length, using output-only information. Accurate knowledge of mass, stiffness, and pile embedded length is essential for understanding foundation behavior when developing digital-twin models of structures for the purpose of damage detection. The method first employs subspace identification to determine modal parameters and quantifies their uncertainties using output-only data. The covariance matrix adaptation evolution strategy (CMA-ES), a stochastic evolutionary algorithm, is subsequently used to update the model. The effectiveness of the approach is demonstrated through its application to numerical models in this paper, to quantify errors, and subsequently to data from a documented full-scale field test of a pile subjected to an impact load. The work underscores the potential of statistical updating in advancing the accuracy and reliability of soil-structure interaction parameter estimation for systems where only output data might exist.

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.

In recent years, researchers have taken advantage of the nonlinear characteristics of the underlying soil to mitigate the excessive seismic force demands on the superstructure under earthquake excitation. For this purpose, the conventionally designed foundation can be replaced with rocking foundation. This is achieved by under proportioning the shallow foundation. Although the mechanism of rocking foundations has been well documented, there remains a gap in developing a methodology for reduction of foundation sizes in multi storey Reinforced Concrete (RC) shear wall framed structure. Therefore, this study focuses on the seismic responses of a shallow foundations supporting a multistorey RC shear wall framed structure. The foundation for RC shear wall is proportioned by gradually reducing the earthquake load considered for the foundations to enhance the increased rocking effect and to mitigate seismic force demands. Thereafter, key parameters responsible for seismic behavior of sub-structure are being compared with conventionally designed foundation with increasing foundation rocking, by varying type of underlying soil and with increasing height. Seismic behavior obtained by implementing a series of nonlinear time history analyses indicates that the foundation rocking greatly influences the dynamic properties. With increasing degree of foundation rocking, natural fundamental period of the overall structure gets lengthened, with decreasing peak roof acceleration, thereby mitigating the peak base moment and base shear experienced at the shear wall compared to conventionally designed foundation. On the other hand, it is observed that there is an increase in roof displacement and shear wall settlement at the foundation level. It is found that the foundation of shear wall can be designed by considering 40%, 60% of earthquake loads for zone V and zone II structural designs, respectively without encountering excessive settlements. From the sensitivity analysis it is highlighted that the foundation size and design seismicity impact the base shear contribution ratios between shear wall and column members, fundamental natural period and foundation settlement.

Resonance occurs when the natural frequency of an offshore wind turbine matches its rotational or blade passing frequency, potentially causing severe structural damage. Existing research on the resonance frequency characteristics of offshore wind turbines has mainly focused on elastic analysis, neglecting the nonlinear dynamic interaction between the foundation and soil. Based on the dynamic Winkler foundation model, the hyperbolic soil resistance around the pile-lateral displacement (p-y) backbone curve was used to consider the stiffness nonlinear of the pile-soil system. The shear strain-dependence of hysteretic damping was considered for soil energy dissipation. A simplified nonlinear frequency domain analysis method for calculating the resonance frequency of monopile-supported offshore wind turbines was proposed. The validity of the method was confirmed through comparisons with model test results and field measurements from the Lely (A2) offshore wind turbine. A parametric study was conducted to investigate the influence of sand density, pile length and pile diameter on the nonlinear resonance frequency of offshore wind turbines. The results show that the resonance frequency of the offshore wind turbine system decreases with increasing loading amplitude. Additionally, the influence of soil nonlinearity on the resonance frequency for systems is more obvious when the sand is looser, the pile length is shorter, or the pile diameter is smaller.

Differential frost heaving can damage buried pipelines, with catastrophic outcomes. It is necessary to consider the interactions between the pipeline and soil as well as the stress characteristics of frost heaving. In this study, a mechanical behavior model of buried pipe suffering from frost-heaving force based on the Winkler elastic foundation beam theory is proposed. The concept of a frost heaving spring is proposed to replace the foundation spring of Winkler's theory. The frost heaving spring is a pre-compression spring that is dependent on the relationship between the frost-heaving force and frost heaving amount, the frost heaving state is similar to precompressed spring resilience. Since the pipeline is continuous, soil in the non-frost-heaving area is squeezed by the pipeline and generates a corresponding elastic response. Modeling mechanical behavior of buried pipe suffering from frost-heaving force based on a linear frost heaving spring assumption provided analytical solutions under two conditions. Results show that the modeled pipeline deformation and stress values conformed well to measured data of Huang Long and Caen test. The proposed model is mathematically simple and easy to apply to studies of mechanical behavior of buried pipe suffering from frost-heaving force.

Dynamic soil-structure interaction (SSI) is an important field in civil engineering with applications in earthquake engineering, structural dynamics, and structural health monitoring (SHM). There is an ongoing need for the development of numerical methods that can accurately estimate SSI parameters to model these systems. In this paper, a Frequency Response Function (FRF)-based model updating method is developed that can estimate the embedded length of foundation piles, in addition to the mobilized soil mass and stiffness, when a lateral impact load is applied. Knowledge of the embedded length of piles is very important for modelling foundation behaviour, and may not be readily available from as-built construction information. For example, if developing reference damage models or digital twins of foundation structures, full knowledge of the pile geometry is required. The work in this paper develops a two-stage iterative model updating method, which utilizes FRF data obtained at the pile ' s head as a result of an applied lateral impact load. The method uses information from the 1st mode of vibration to estimate the mobilised soil mass and stiffness, and subsequently uses information from the 2nd mode of vibration to estimate the embedded length. To appraise the approach, impact tests are numerically simulated on a number of 'piles ' (numerical spring-beam systems) with varying length/diameter ( L/D ) ratios to derive FRFs, whereby the models have known length and dynamic properties. These FRFs are then used as targets in the model updating approach, which iteratively varies the properties of a numerical model of a pile to obtain a match in the FRF data, and subsequently estimates the mobilised stiffness, mass, and embedded length. The results of the analyses illustrate that by minimising the difference in the first and second FRF peaks between the target and estimated FRFs, the method can accurately estimate the mass, stiffness and embedded length properties of the test 'piles ' . The performance of the approach against numerical case applications is assessed in this paper, as the properties of these systems are known in advance, facilitating quantification of the errors and performance. The developed method requires further validation through full-scale testing to confirm its effectiveness in real-world scenarios.

This study uses a two -stage finite element method to analyze offshore wind turbine (OWT) support structures under soil liquefaction during earthquakes. First, a three-dimensional cuboid u -p analysis with the soil cap yield criterion provides time -history soil accelerations and pore water pressure ratios. The second stage models the OWT support structure using traditional finite element methods, incorporating seismic displacement fields into p -y, t -z, and q -z nonlinear springs, with excess pore water pressure ratios reducing their stiffness. Numerical simulations were performed on 10, 15, and 20 MW OWT structures, yielding key insights. Ground accelerations near the soil surface cause frequent soil liquefaction, effectively mitigating seismic forces on the OWT foundation. When pile length is sufficient, the analysis with the u -p model requires less steel than traditional methods without considering soil liquefaction. Moreover, the reduction in sandy soil stiffness extends into deeper layers, making settlement a critical concern during soil liquefaction. Analysis accounting for soil liquefaction consistently reports greater settlements than traditional approaches. Consequently, the critical factor for deep pile OWT support structures with regard to soil liquefaction is foundation settlement rather than the design of the steel structure section.

In shield tunneling, the joint is one of the most vulnerable parts of the segmental lining. Opening of the joint reduces the overall stiffness of the ring, leading to structural damage and issues such as water leakage. Currently, the Winkler method is commonly used to calculate structural deformation, simplifying the interaction between segments and soil as radial and tangential Winkler springs. However, when introducing connection springs or reduction factors to simulate the joint stiffness of segments, the challenge lies in determining the reduction coefficient and the stiffness of the springs. Currently, the hyperstatic reflection method cannot simulate the discontinuity effect at the connection of the tunnel segments, while the state space method overlooks the nonlinear interaction between the tunnel and the soil. Therefore, this paper proposes a numerical simulation method considering the interaction between the tunnel and the soil, which is subjected to compression rather than tension, and the discontinuity of the joints between the segments. The model structure and external load are symmetrical, resulting in symmetrical calculation results. This method is based on the soft soil layers and shield tunnel structures of the Shanghai Metro, and the applicability of the model is verified through deformation calculations using three-dimensional laser scanning point clouds of sections from the Shanghai Metro Line 5. When the subgrade reaction coefficient is 5000 kN/m3, the model can effectively simulate the deformation of operational tunnels. By adjusting the bending stiffness of individual connection springs, we investigate the influence of bending stiffness reduction on the bending moment, radial displacement, and rotational displacement of the ring. The results indicate that a decrease in joint bending stiffness significantly affects the mechanical response of the ring, and the extent and degree of this influence are correlated with the joint position and the magnitude of joint bending stiffness.

Existing studies on soil-pipe interaction due to tunneling mainly focus on short-term responses. However, in areas with high water tables and low permeability soil, long-term ground movement and associated pipe responses may occur due to dissipation of excess pore pressure generated during tunnel construction. In this paper, a Winkler solution with time-varying subgrade modulus and the corresponding greenfield soil displacement formula are developed to investigate the tunneling effects on existing pipelines. The pipe is considered as an infinite Euler beam of finite width resting on a poroelastic half-space, and adhesion and drainage effects between the pipe and soil are considered using bounding techniques. The greenfield consolidation settlement is evaluated using a modified Gaussian curve. The findings indicate that the subgrade modulus decreases while greenfield soil displacement increases during the consolidation process. The time-dependent behavior of the subgrade modulus is governed by the drainage condition at the pipe-soil interface, whereas the greenfield soil displacement is primarily influenced by the drainage condition at the tunnel-soil interface. The study reveals that the bonded contact condition, hydraulic boundary condition, and displacement constraint conditions all influence the bending moment of the pipe.

为克服现有冬季输水梯形渠道冻胀力学模型未充分考虑冻结区与水下非冻结区差异,以及未考虑土体连续性的不足,该研究根据冻土与非冻土剪切刚度的不同,冻结区采用Pasternak双参数弹性地基梁模型,而非冻结区采用Winkler模型,综合Pasternak模型考虑土体连续性及Winkler模型易于求解、所需参数少的优点,提出联合Winkler-Pasternak模型的冬季输水梯形渠道冻胀力学分析方法。以新疆玛纳斯河流域某冬季输水梯形渠道为例,计算渠坡衬砌板法向变形,并将本文模型、Winkler模型、Pasternak模型计算结果与观测值进行了对比分析,最后计算了衬砌板截面弯矩及上表面应力分布。结果表明:衬砌板法向变形可分为冻胀段、沉降段及冻胀-沉降过渡段三个部分,三种模型计算结果均能较好地反映衬砌板法向位移基本变化趋势,且本文模型计算结果与实测值更加接近,表明了模型合理性。衬砌板易开裂位置位于冻土区距离水位线10.0%～23.3%坡板长处,与工程实际相符。该研究可为寒区冬季输水梯形渠道抗冻胀设计提供科学参考与理论依据。