Soil Pile Structure Interaction Research Articles

Numerical Validation of Fully Coupled Nonlinear Seismic Soil–Pile–Structure Interaction

While many researchers have broadly studied soil–structure interaction (SSI) problems to comprehend SSI effects on the overall system’s behavior, some critical numerical modeling issues have not been sufficiently investigated to achieve the most accurate results. Furthermore, most scholars have not provided detailed explanations of the validation process for their proposed numerical models. Modeling pile foundations in a three-dimensional (3D) continuum system in a fully coupled manner is often challenging for engineers who do not specialize in structural and geotechnical earthquake engineering, as it can be very time-consuming and complicated. Therefore, this work aims to validate a finite element model of seismic soil–pile–structure interaction (SPSI) problems in a continuum soil body by comparing the results of numerical models with those of a centrifuge test and computed numerical simulations available in the literature. In this regard, several newly developed elements in OpenSees (Version 3.6.0) are tested. The results of this work demonstrate a closer alignment with prior experimental research findings. It is believed that providing detailed numerical modeling and validation processes will assist researchers in better understanding crucial issues in modeling soil–pile–structure interaction problems.

Assessing seismic mitigation schemes of tuned mass dampers for monopile offshore wind turbine including pile–soil–structure interaction

The study of a monopile offshore wind turbine with the soil–structure interaction effect is most challenging in structural design under multiple hazards, i.e., the combined wind, sea wave, and earthquake excitations. Different arrangements of passive tuned mass dampers (TMDs) were used to mitigate the service and seismic loads affecting an offshore wind turbine (OWT) including the pile–soil–structure interaction (PSSI) effect. Different schemes of passive TMDs, placed at the top of the OWT tower or also at the center of gravity (CG) of the OWT tower or at the connection between the OWT tower and monopile, were tested. Various arrangements of TMDs including the proposed herein top radial TMDs arrangements have been investigated to determine their validity in resisting vibrations resulting from service and earthquake loads. The lateral displacements, shear forces and bending moments in both horizontal directions and the axial forces all over the OWT tower and monopile heights were recorded to compare the performance of each mitigation scheme of TMDs. The comparison results showed that the TMDs placement should be at the top of the OWT tower and the top radial 6 TMDs arrangement was found to be the most effective mitigation scheme for all straining actions in the tower and the monopile of the OWT subjected to service and earthquake loads.

Effects of constitutive soil models on the seismic response of an offshore jacket platform in clay by considering pile-soil-structure interaction

Offshore jacket platforms are widely used for wind energy generation and gas and oil field development. The South Pars gas field, located in the Persian Gulf, stands as one of the largest gas fields in the world. This gas field is situated in a seismically active region predominantly characterized by clay soil. Considering the significant impact of clay soil on the seismic response of offshore structures and their vulnerability to damage, it is essential to conduct comprehensive studies on the seismic behavior of offshore structures in this particular area while considering the nonlinear behavior of soil and pile-soil-structure interaction (PSSI). However, due to the laboratory limitations, it is difficult to experimentally investigate the seismic behavior of these structures on a real scale by considering the actual soil environment. This paper aims to adopt a nonlinear kinematic hardening model for clay in Abaqus software and calibrate this model parameters for the South Pars gas field region to carefully investigate the effects of nonlinear behavior of soil and PSSI on the seismic response of an offshore jacket platform. In addition, the perfectly elasto-plastic Mohr-Coulomb model is employed as a simple and common constitutive soil model to compare the results. To achieve the study goals, firstly, the numerical modeling techniques are validated. Subsequently, the main parameters of the nonlinear kinematic hardening model are calibrated for the South Pars gas field region, which has not been done for this region in previous works. Detailed numerical models, including the fixed-base model and the pile-soil-structure (PSS) model, are then developed and analyzed using different selected ground motion records. The results indicate that considering the effect of PSSI has a significant effect on the seismic responses of the structure. Moreover, PSSI effect has a great dependence on the constitutive soil model. The results of this study are expected to provide useful insights into the seismic design of offshore structures in similar geological conditions.

Nonlinear Analysis for Investigating Seismic Performance of a Spun Pile-Column of Viaduct Structure

Slab-on-pile SOP viaducts have been constructed on several highways and railways in Indonesia, but there are certain doubts about some practical structural seismic design concepts. Therefore, this study aims to investigate the seismic performance of a single spun pile column for the SOP viaduct using nonlinear analysis. The essential variables used include the effect of top pile reinforced concrete infill treatment, soil-pile structure interaction (SPSI), and different response modification factors (R). Moreover, the single spun pile column was designed as a macro model with a force-based beam-column element having a fiber section in the plastic hinge. The static pushover analysis and quasi-static cyclic were also conducted to determine the displacement limit state and the equal viscous damping, respectively. Furthermore, seven pairs of ground motion excitations were used to investigate seismic performance in line with ASCE 7-10 and ASCE 61-14. The results showed that the implementation of the top-pile reinforced concrete infill treatment slightly reduced seismic response but evoked more severe pile curvature in the embedded zone. In addition, the behavior and seismic performance were slightly better than those without treatment when considering the SPSI. This study recommends the spun pile column for the SOP viaduct with a response modification factor of 1.5 to avoid probable brittle failure occurrence under earthquake load. Doi: 10.28991/CEJ-2023-09-07-02 Full Text: PDF

Numerical Analysis on Effects of Soil Improvement on Pile Forces on Existing High-Rise Building

Nowadays, seismic codes are regularly updated with new knowledge and a better understanding of the earthquake phenomenon. With these updates, existing buildings require a reevaluation of their stability and a process of reinforcement and/or retrofitting. This study investigated the effects of two types of ground improvement which use cement-mixing soil surrounding the foundation structure to reduce and redistribute forces acting on piles. This is especially important when the reevaluation of high-rise buildings leads to increased forces in the piles. Typically, buildings are designed while assuming fixed base boundary conditions at the foundation level, without considering soil–pile–structure interaction (SPSI). SPSI significantly influences the response of high-rise buildings supported by soft soil. Increasing the lateral resistance of the surrounding soil can reduce the influence of SPSI. In this study, a detailed dynamic numerical analysis was used to investigate the dynamic response of an SPSI system of a high-rise building under seismic load. A dynamic analysis was conducted on a modified layout of a real building, using real-time earthquake motion. The finite element program DIANA FEA was used to perform nonlinear 3D FEM numerical simulations, taking into account the essential SPSI phenomena, gap-slip between the piles and the soil, and free-field boundary conditions. A comparison of the data suggests that the bending moment and shear forces in the piles are reduced in magnitude and evenly distributed along the upper part of the pile, which reduces the stress concentration of the bending moment and shear forces at the contact between the piles and the pile cap.

Comparison of Pile–Soil–Structure Interaction Modeling Techniques for A 10-MW Large-Scale Monopile Wind Turbine Model Under Wind and Wave Conditions

Comparison of Pile–Soil–Structure Interaction Modeling Techniques for A 10-MW Large-Scale Monopile Wind Turbine Model Under Wind and Wave Conditions

Substructure Pseudo-Dynamic Test Study for a Structure Including Soil–Pile–Structure Dynamic Interaction

An improved Penzien model is proposed in this paper as a simplified model of soil–pile–structure interaction. The dynamic nonlinearity of soil under earthquake excitation is simulated by ANSYS in a free-field model and added to the original Penzien model. The improved Penzien model uses the finite element software ANSYS 2021 to simulate the dynamic nonlinearity of soil. The improved Penzien model is then used as a simplified calculation model of the numerical substructure. A substructure pseudo-dynamic test based on the improved Penzien model is carried out. The realization of the substructure pseudo-dynamic test verifies the feasibility and effectiveness of this method, which provides a convenient test method for the study of soil–pile–structure interaction in general laboratories. Soil and structure interaction reduces the acceleration of the structure, and the response exhibited a hysteresis phenomenon because of the nonlinear characteristics of the soil. The influences of soil–pile–structure interaction on velocity and displacement are very complex. The conclusions are reasonable, which proves that the substructure pseudo-dynamic test method of soil–pile–structure dynamic interaction using the improved Penzien model is feasible.

Numerical and Experimental Analysis of Seismic Soil Pile Structure Interaction

The fundamental design of the piles is finished by static analysis, but particularly in seismically dynamic locales, the last configuration requires dynamic study. Dynamic soil-pile-structure interaction analyses require the stress-strain conduct of soils under dynamic loading conditions. The material nonlinearity can be addressed by comparable linear or completely nonlinear strategies. The correlation of these methodologies in the free-field site reaction analyses has been concentrated in recent years. In any case, the impacts on the soil-pile-structure interaction analyses have not been illustrated. In this study, a well-known centrifuge test was demonstrated and analyzed in the frequency domain (ACS SASSI) and in the time-domain (FLAC 3D) for equivalent-linear and fully nonlinear methods, respectively. The soil space was displayed with solid components in the projects, while the structural beam elements were utilized for the pile and the superstructure. The scaled speed acceleration time history of the Kobe earthquake was applied to the lower part of the soil-pile-structure model, and the acceleration-time histories were acquired at the ground surface and the superstructure. The outcomes obtained from the ACS SASSI and the FLAC 3D were compared with the centrifuge test. As per the outcomes, the peak ground and the superstructure accelerations were close to the experimental outcomes; however, the periods at the peak spectral accelerations were slightly different from the test results. The difference is more pronounced in SASSI than in FLAC, which may be attributed to the solution methods. Apart from the solution methods, the difference might be the inability to fully simulate the complex centrifuge test.

Soil-Pile-Structure Interaction (SPSI) in Bridges: A Review

Response of soil influencing motion of pile supported structures or vice-versa is called Soil-Pile-Structure Interaction (SPSI). A part of SPSI is considered beneficial for the structure wherein it increases damping, and period of vibration. This study provides a comprehensive review addressing SPSI in bridge structures. Past research in this field has typically emphasised on Soil-Structure Interaction (SSI), rather than SPSI. An attempt is made here to compile the work done so far in this field. Detailed study, based on discretising the considered models in various articles, and the method for determining the stiffness of the underlying soil was carried out. The articles in this study were carefully chosen such that even if they have not considered SPSI, their models were worth reporting in this study. Response of soil and structure on the application of earthquake ground motion was also studied and discussed here with emphasis given on calculation of stiffness of soil and the interaction between them. It was observed that the material/spring used for modelling of soil is of utmost importance. The theories for the calculation of stiffness of the soil material for different locations of the pile length are also discussed. Few studies have also considered the vertical component of earthquake ground motion in the past. A detailed justification regarding the selection of method of analysis such as linear or non-linear analysis, and adopted approaches for analysis such as discrete or continuous approaches, and their overall influence on the study was observed, and reported here in a concise manner. This article primarily aims to summarize the previously published researches on SSI and SPSI, including their advantages and issues over the structure.

Seismic response analysis of high-rise frame-core tube building on fluid-saturated soil considering soil-pile-structure interaction

This paper proposed a three-dimensional (3D) refined finite element method (FEM) to determine seismic responses of the high-rise buildings resting on fluid-saturated soil considering the soil-pile-structure interaction (SPSI) and the dynamic characteristics of two-phase media, using a user-defined element with ABAQUS. The theory and method to develop the FEM were introduced in detail, including the user-defined element, material constitutive models, boundary conditions, earthquake input methods, specific implementation procedures, and verifications. Then, the FEM was adopted to investigate the seismic responses of a 51-story high-rise building with a frame-core tube system subjected to six earthquake records. Discussions were conducted on the acceleration, displacements, inter-story drifts, story shear force, and damage behavior to interpret the seismic characteristics of the superstructure. A fixed-base model was also considered to reveal the SPSI effect under the same conditions. The results demonstrate that the SPSI lightens acceleration and total story shear force but amplifies displacements, inter-story drifts, and column shear force. Without regard to the SPSI, no apparent change appears for the damage of floor plates, whereas the core tube suffers more severe damage than under the SPSI conditions. For high-rise buildings, the SPSI does not always provide conservative seismic performance evaluations. It is of fundamental importance to include the SPSI effect during the performance-based seismic design of high-rise buildings for comprehensive understanding. The proposed FEM can also be access to seismic SSI analysis for other types of structures in the saturated field.

Assessing seismic response equivalency for fixed pile-founded offshore platforms utilizing PSDA and IDA

Detrimental seismic effects on offshore platforms safety and serviceability highlight the necessity of these infrastructures fundamental seismic investigations that contribute to the design and maintenance of reliable structures. To this end, probabilistic seismic response evaluation of fixed pile-founded offshore platforms utilizing probabilistic seismic demand analysis (PSDA) has been employed. Housner Intensity-Drift Ratio as the derived optimal pair -in which engineering demand parameters (EDPs) are calculated, given the ground motion intensity measures (IMs)- is chosen. A selection of optimal IM–EDP pairs is made based on the criteria of practicality, effectiveness, efficiency and sufficiency. In this study, equivalency of the results is evaluated comparing the same IM-EDP pairs against the method of incremental dynamic analysis (IDA). Furthermore, another objective of this assessment is to investigate the appropriate number of required ground motion records according to which structural seismic responses are not over/underestimated. The uncertainties associated with fixed pile-founded offshore platform brace configurations, besides the effect of soil-pile-structure interaction (SPSI) are thoroughly considered, generating more accurate and vigorous results. The findings of this study demonstrate that seismic responses resulted from IDA approach utilizing 12 ground motion records scaled 7 times matches well with those derived from PSDA.

Effect of Soil Damping on the Soil–Pile–Structure Interaction Analyses in Cohesionless Soils

Pile foundations in earthquake-prone regions must be analyzed and designed considering the dynamic loads. In the fully nonlinear dynamic analyses, the soil nonlinearity can be considered using the modulus degradation curves in the total-stress approach, and the soil damping is controlled by the unloading/reloading rule. Several researchers have investigated the effect of soil damping on the free-field soil response analyses, but the effect on the soil–pile–structure system response has not been studied thoroughly. In this study, the nonlinear elastic method (hyperbolic model) and the elastoplastic Mohr–Coulomb (MC) models were implemented to investigate the effect of soil damping on the pile and structure response. Dynamic soil–pile–structure interaction analyses were performed by simulating two different centrifuge tests published in the literature, and the analysis results were compared with the centrifuge test results. The analyses with the low-intensity input motions showed that the superstructure accelerations and the bending moments in the single pile were estimated with reasonable accuracy. However, the superstructure accelerations might be underestimated under high-intensity motions, especially in the MC model. Additional analyses were performed under six earthquake records. The constitutive models (MC and hyperbolic) may significantly vary the maximum structural acceleration and pile maximum moments (up to 50%). As a result, the responses of the superstructure and the pile in soil–pile–structure interaction problems are highly dependent on the soil constitutive model that must take the damping into account accurately; in turn, due account must be given to the selection of the constitutive model.

Seismic Performance Assessment of Semi Active Tuned Mass Damper in an MRF Steel Building Including Nonlinear Soil–Pile–Structure Interaction

Seismic Performance Assessment of Semi Active Tuned Mass Damper in an MRF Steel Building Including Nonlinear Soil–Pile–Structure Interaction

3D seismic response characteristics of a pile-mat-founded AP1000 nuclear-island building considering nonlinear hysteretic behavior of soil

Given the increase of nuclear power plants, it has become unavoidable for the pile-supported nuclear-island buildings to be constructed on the coastal deposits potentially influenced by strong earthquakes. The coupling influences of the hysteresis nonlinearity of soil and the soil-pile-structure interaction (SPSI) have not yet been considered comprehensively in the seismic response analysis of the nuclear-island building, although it is a vital issue. On the basis of a newly-developed generalized non-Masing hysteretic constitutive model, a 3D integrated simulation method is proposed to evaluate the seismic responses of the pile-mat-founded nuclear-island building system subjected to multidirectional earthquake motions. This integrated method involves an explicit parallel algorithm framework, comprising the nuclear-island building modeling, the pile-mat foundation modeling, the inhomogeneous soil domain modeling, and the artificial boundary condition. The bedrock records of near-field, moderate-far field and far-field earthquake scenarios are assumed for determining the bedrock motions of the ultimate and operational safety earthquakes. For an actual pile-mat-founded AP1000 nuclear-island building, the simulation results show the complexity and significance of the coupling effect of the site, the tridirectional earthquake shaking, and the secondary nonlinearity of soil. Such a complex coupling effect significantly increases the seismic responses of the pile-mat-founded nuclear-island building. A notable finding is that the scenario earthquakes with abundant long period components may have more destructive potential to the pile-mat-founded nuclear-island buildings than the scenario earthquakes with characteristics of abundant short period components and shorter durations. The results provide insights into the seismic design of the pile-mat-founded nuclear-island buildings, which could guide the design and construction of such similar facilities in the high seismic intensity regions.

Vibration control of midrise buildings by semi-active tuned mass damper including multi-layered soil-pile-structure-interaction

Semiactive tuned mass dampers (STMD) can be used in mid-rise buildings to control seismic excitations during continuous operation. Numerous studies have been conducted to investigate the performance of STMDs without considering the soil-pile-structure interaction (SPSI). When modeled with a fixed base, the characterization of STMD can be significantly misleading and doesn’t necessarily result in a conservative design. In order to evaluate the impact of SPSI on the performance of STMD under seismic loading, mid-rise steel buildings on layered soil were analyzed using the three-dimensional finite element software Opensees. The effects of changes in geotechnical parameters such as shear strength and stiffness were also studied. The results showed that the efficiency of STMD is significantly reduced and the structural accelerations and displacements are increased with the inclusion of SPSI. A progressive increase in the displacements of the top storeys were also observed when the SPSI effect was considered. The reduction in the base shear was attributed to the mobilised passive force around the piled foundations when SPSI was considered in the analysis models.

Seismic response of a tall tower on deep soil – A case study

The DYNAMIC response of a 100 m tall tower on a deep soil deposit is studied. The considered tower model is investigated for different loading/boundary conditions present at the base. The analyses are carried out using a finite element program SAP 2000. To demonstrate the effect of soil depth on the estimated seismic response of the tower, three different soil depths are considered. In order to study the effect of structural inelasticity and period elongation on the estimated seismic response of the structure, a yield strength ratio, Ry equal to 4 is also considered. The study primarily shows that soil-pile-structure interaction (SPSI) may increase or decrease the base shear and lateral deflection of the structure, in different directions and for different depths of soil strata. The sensitivity of the SPSI effects to the dynamic characteristics of the ground motion and structure has been brought out in the present case study. It is concluded that the effect of soil depth on seismic response of the structure is not monotonic and the role of ductility demand on superstructure in SPSI effects is important.

Optimal ground motion intensity measure selection for probabilistic seismic demand modeling of fixed pile-founded offshore platforms

The safety and serviceability of fixed pile-founded offshore platforms during and after an earthquake will ensure their continuous operation and prevent irreparable economic and environmental loss in a seismically prone area. The probabilistic seismic demand model is a performance-based earthquake engineering design method for offshore platforms. The level of uncertainty in PSDMs depends on the selected seismic intensity measures (IMs), although these models are traditionally conditioned with a single IM. The optimal IM selection used in the present study has not yet been investigated for offshore platforms. Because of the geometrical uncertainties of these types of structure, they were examined using 3D models of five braced configurations of fixed pile-founded offshore platforms by considering the soil-pile-structure interaction (SPSI). Twenty-seven optimal IMs were chosen with regard to their effectiveness, efficiency, practicality, proficiency, sufficiency, relative sufficiency, and hazard computability assessments. Probabilistic seismic demand analysis was performed and each model was subjected to 80 unscaled ground motions. The optimal velocity-related IMs performed well, especially those for the Housner intensity (HI) and velocity spectrum intensity (VSI) for predicting a fixed pile-founded offshore platforms response measured in terms of drift ratio and differential settlement. On the other hand, peak ground velocity (PGV) and HI for the ductility demand parameter present optimal pairs. These most informative IMs were able to provide improved probabilistic seismic demand models (PSDMs) and accurate fragility analysis of the structures.

Shaking table test and simulation of 12-story buildings with metallic dampers located on soft soil

In this study, shaking table tests are carried out on 12-story reinforced concrete frames with metallic dampers located on soft site, and the corresponding fixed-base structures with metallic dampers are also proposed for comparison. The superstructure is connected with the 3-by-3 pile foundation by the pile cap in a designed shear laminar container, which exhibits a good ability of reducing the boundary effect. Three earthquake inputs, which include one artificial earthquake (Shanghai bedrock wave) and two recorded Kobe and Chi-Chi earthquakes with various peak ground accelerations (PGAs) are used in the shaking table test. A series of investigation are carried out on the test phenomenal, which consist of dynamic characteristics of the models, seismic analysis of the soil, and also the working mechanism of pile-soil-structure interaction (PSSI). Then, the hysteretic behavior and aseismic performance of metallic dampers in the PSSI system and fixed-base condition are compared. Finally, a nonlinear three-dimensional finite element model is built to establish a proper numerical method for the PSSI system with metallic dampers. The experimental and simulation results indicate that the PSSI system has longer periods, larger damping ratio and less decreasing degree of frequency after tests than the fixed-base condition. Meanwhile, under these earthquakes, PSSI tends to reduce the structural peak acceleration, story shear force and the elastic displacement. However, the total deformation of the superstructure is amplified significantly due to the rocking and translational deformation in PSSI system. Moreover, the hysteretic performance of the metallic dampers are degraded greatly by PSSI effect. Therefore, the PSSI effect should be considered in the design of tall buildings with metallic dampers, because the seismic analysis of the structure may be unrealistic and the performance of the metallic dampers may be overrated when it is ignored.

Seismic behaviour of piles in non-liquefiable and liquefiable soil

This paper investigates the nonlinear soil–pile–structure interaction employing three-dimensional nonlinear finite element models verified with the results of large-scale shaking table tests of model pile groups-superstructure systems. The responses of piles in both liquefiable and non-liquefiable soil sites to ground motion with varying intensities were evaluated considering both kinematic and inertial interaction. The calculated piles and soil responses agreed well with the responses measured during the shaking events. The numerical models correctly predicted the different pile deformation modes that were exhibited in the experiments. The finite element analysis was then employed to perform a parametric study to evaluate the kinematic and inertial effects on the piles' response, considering different ground motion Intensity and piles characteristics. It was found that the bending moment of piles in the liquefiable site increases significantly, compared to the non-liquefiable site, due to the loss of lateral support of the liquified soil, and the maximum bending moment occurs at the interface between the loose and dense sand layers. The inertial interaction contributes the most to the bending moments at the pile top and the interface between the top clay and liquefied loose sand layers. For piles with a larger diameter, the bending moment due to kinematic interaction increases significantly, and the bending moment distribution corresponds to short (rigid) pile behaviour. In addition, the piles at the saturated site displace laterally as a rigid body during strong ground motions because the pile base loses the lateral support due to the soil liquefaction. Finally, the kinematic interaction effect becomes more significant for piles with higher elastic modulus.

Sensitivity of fatigue assessment for offshore jacket platform to different pile–soil–structure interaction models

ABSTRACT One of the main factors that affect the response of fixed offshore jacket platforms under wave loading is Pile–Soil–Structure Interaction (PSSI); thereby, it must be expected that different PSSI models may impact the fatigue damage assessments in harsh environments. In this study, the sensitivity analyses of fatigue damage results of an offshore jacket platform to different PSSI models have been performed by modelling piles up to the actual penetration depth with computationally demanding Beam on Nonlinear Winkler Foundation (BNWF) as the Reference Model (RM). Also, two different models were applied by analysing RM under Center-of-Damage (CD) wave (M2 and M4) as well as conducting the linear analysis (M1 and M3) to develop stiffness matrix and independent springs models. It was concluded that the independent springs model obtained by linear analysis provides acceptable fatigue damage compared to other alternative linear models in the case of large CD wave and shallow weak soil layers.