• Earthquakes and Structures
• /
• v.5 no.6
• /
• pp.679-702
• /
• 2013

During an earthquake, soils filter and send out the shaking to the building and simultaneously it has the role of bearing the building vibrations and transmitting them back to the ground. In other words, the ground and the building interact with each other. Hence, soil-structure interaction (SSI) is a key parameter that affects the performance of buildings during the earthquakes and is worth to be taken into consideration. Columns are one of the most crucial elements in RC buildings that play an important role in stability of the building and must be able to dissipate energy under seismic loads. Recent earthquakes showed that formation of plastic hinges in columns is still possible as a result of strong ground motion, despite the application of strong column-weak beam concept, as recommended by various design codes. Energy is dissipated through the plastic deformation of specific zones at the end of a member without affecting the rest of the structure. The formation of a plastic hinge in an RC column in regions that experience inelastic actions depends on the column details as well as soil-structure interaction (SSI). In this paper, 854 different scenarios have been analyzed by inelastic time-history analyses to predict the nonlinear behavior of RC columns considering soil-structure interaction (SSI). The effects of axial load, height over depth ratio, main period of soil and structure as well as different characteristics of earthquakes, are evaluated analytically by finite element methods and the results are compared with corresponding experimental data. Findings from this study provide a simple expression to estimate plastic hinge length of RC columns including soil-structure interaction.

• Earthquakes and Structures
• /
• v.10 no.6
• /
• pp.1369-1389
• /
• 2016

The soil-structure interaction effect significantly influences the design of multi-storey buildings subjected to lateral seismic loads. The shear walls are often provided in such buildings to increase the lateral stability to resist seismic loads. In the present work, the nonlinear soil-structure analysis of a G+5 storey RC shear wall building frame having isolated column footings and founded on deformable soil is presented. The nonlinear seismic FE analysis is carried out using ANSYS software for the building with and without shear walls to investigate the effect of inclusion of shear wall on the moments in the footings due to differential settlement of soil mass. The frame is considered to behave in linear elastic manner, whereas, soil mass to behave in nonlinear manner. It is found that the interaction effect causes significant variation in the moments in the footings. The comparison of non-interaction and interaction analyses suggests that the presence of shear wall causes significant decrease in bending moments in most of the footings but the interaction effect causes restoration of the bending moments to a great extent. A comparison is made between linear and nonlinear analyses to draw some important conclusions.

• Structural Engineering and Mechanics
• /
• v.20 no.4
• /
• pp.421-434
• /
• 2005

In this paper, the finite element method is applied to investigate the effect of the lateral boundary in homogenous soil on the seismic response of a superstructure. Some influencing factors are presented and discussed, and several parameters are identified to be important for conducting soil-structure interaction experiments on shaking tables. Numerical results show that the cross-section width L, thickness H, wave propagation velocity and lateral boundaries of soil layer have certain influences on the computational accuracy. The dimensionless parameter L/H is the most significant one among the influencing factors. In other words, a greater depth of soil layer near the foundation should be considered in shaking table tests as the thickness of the soil layer increases, which can be regarded as a linear relationship approximately. It is also found that the wave propagation velocity in soil layer affects the numerical accuracy and it is suggested to consider a greater depth of the soil layer as the wave propagation velocity increases. A numerical study on a soil-structure experimental model with a rubber ring surrounding the soil on a shaking table is also conducted. It is found the rubber ring has great effect on the soil-structure interaction experiments on shaking table. The experimental precision can be improved by reasonably choosing the elastic parameter and width of the rubber ring.

• Earthquakes and Structures
• /
• v.17 no.5
• /
• pp.521-532
• /
• 2019

This paper describes the construction of a laminar box for simulating the earthquake response of soil and structures. The confinement of soil in the transverse direction does not rely on the laminar frame but is instead achieved by two acrylic glass walls. These walls allow the behaviour of soil during an earthquake to be directly observed in future study. The laminar box was used to study the response of soil with structure-footing-soil interaction (SFSI). A single degree-of-freedom (SDOF) structure and a rigid structure, both free standing on the soil, were utilised. The total mass and footing size of the SDOF and rigid structures were the same. The results show that SFSI considering the SDOF structure can affect the soil surface movements and acceleration of the soil at different depths. The acceleration developed at the footing of the SDOF structure is also different from the surface acceleration of free-field soil.

• Interaction and multiscale mechanics
• /
• v.5 no.4
• /
• pp.369-383
• /
• 2012

In this paper, soil-structure interaction analysis has been presented for beams resting on multilayered geosynthetic-reinforced granular fill-soft soil system. The soft soil and geosynthetic reinforcements are idealized as nonlinear springs and elastic membranes, respectively. The governing differential equations are solved by finite difference technique and the results are presented in non-dimensional form. It is observed from the study that use of geosynthetic reinforcement is not very effective for maximum settlement reduction in case of very rigid beam. Similarly the reinforcements are not effective for shear force reduction if the granular fill has very high shear modulus value. However, multilayered reinforced system is very effective for bending moment and differential settlement reduction.

• Geomechanics and Engineering
• /
• v.24 no.1
• /
• pp.15-28
• /
• 2021

Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. However, there is still a lack of knowledge of lateral behavior of digging well foundation considering the soil-foundation interaction. In this study, scaled models of bridge pier-digging well foundation system are constructed for quasi-static test to investigate their lateral behaviors. The failure mechanism and responses of the soil-foundation-pier interaction system are analyzed. The testing results indicate that the digging foundations tend to rotate as a rigid body under cyclic lateral load. Moreover, the depth-width ratio of digging well foundation has a significant influence on the failure mode of the interaction system, especially on the distribution of foundation displacement and the failure of pier. The energy dissipation capacity of the interaction system is discussed by using index of the equivalent viscous damping ratio. The damping varies with the depth-width ratio changing. The equivalent stiffness of soil-digging well foundation-pier interaction system decreases with the increase of loading displacement in a nonlinear manner. The absolute values of the interaction system stiffness are significantly influenced by the depth-width ratio of the foundation.

• Coupled systems mechanics
• /
• v.3 no.3
• /
• pp.267-289
• /
• 2014

A proper physical modeling of infilled building frame-foundation beam-soil mass interaction system is needed to predict more realistic and accurate structural behavior under static vertical loading. This is achieved via finite element method considering the superstructure, foundation and soil mass as a single integral compatible structural unit. The physical modelling is achieved via use of finite element method, which requires the use of variety of isoparametric elements with different degrees of freedom. The unbounded domain of the soil mass has been discretized with coupled finite-infinite elements to achieve computational economy. The nonlinearity of soil mass plays an important role in the redistribution of forces in the superstructure. The nonlinear behaviour of the soil mass is modeled using hyperbolic model. The incremental-iterative nonlinear solution algorithm has been adopted for carrying out the nonlinear elastic interaction analysis of a two-bay two-storey infilled building frame. The frame and the infill have been considered to behave in linear elastic manner, whereas the subsoil in nonlinear elastic manner. In this paper, the computational methodology adopted for nonlinear soil-structure interaction analysis of infilled frame-foundation-soil system has been presented.

• Structural Engineering and Mechanics
• /
• v.55 no.1
• /
• pp.161-189
• /
• 2015

Soil-pile raft-structure interaction is recognized as a significant phenomenon which influences the seismic behaviour of structures. Soil structure interaction (SSI) has been extensively used to analyze the response of superstructure and piled raft through various modelling and analysis techniques. Major drawback of previous study is that overall interaction among entire soil-pile raft-superstructure system considering highlighting the change in design forces of various components in structure has not been explicitly addressed. A recent study addressed this issue in a broad sense, exhibiting the possibility of increase in pile shear due to SSI. However, in this context, relative stiffness of raft and that of pile with respect to soil and length of pile plays an important role in regulating this effect. In this paper, effect of relative stiffness of piled raft and soil along with other parameters is studied using a simplified model incorporating pile-soil raft and superstructure interaction in very soft, soft and moderately stiff soil. It is observed that pile head shear may significantly increase if the relative stiffness of raft and pile increases and furthermore stiffer pile group has a stronger effect. Outcome of this study may provide insight towards the rational seismic design of piles.

• Coupled systems mechanics
• /
• v.1 no.4
• /
• pp.381-395
• /
• 2012

Dynamic response of Pile Supported Structures is highly depended on Soil Pile Structure Interaction. In this paper, by comparison of experimental and numerical dynamic responses of a prototype jacket offshore platform for both hinge based and pile supported boundary conditions, effect of soil-pile-structure interaction on dynamic characteristics of this platform is studied. Jacket and deck of a prototype platform is installed on a hinge-based case first and then platform is installed on eight skirt piles embedded on continuum monolayer sand. Dynamic characteristics of platform in term of natural frequencies, mode shapes and modal damping are compared for both cases. Effects of adding and removing vertical bracing members in top bay of jacket on dynamic characteristics of platform for both boundary conditions are also studied. Numerical simulation of responses for the studied platform is also performed for both mentioned cases using capability of ABAQUS and SACS software. The 3D model using ABAQUS software is created using solid elements for soil and beam elements for jacket, deck and pile members. Mohr-Coulomb failure criterion and pile-soil interface element are used for considering nonlinear pile soil structure interaction. Simplified modeling of soil-pile-structure interaction effect is also studied using SACS software. It is observed that dynamic characteristics of the system changes significantly due to soil-pile-structure interaction. Meanwhile, both of complex and simplified (ABAQUS and SACS, respectively) models can predict this effect accurately for such platforms subjected to dynamic loading in small range of deformation.

• Structural Engineering and Mechanics
• /
• v.41 no.6
• /
• pp.711-734
• /
• 2012

The foundation of a tall building frame resting on settable soil mass undergoes differential settlements which alter the forces in the structural members significantly. For tall buildings it is essential to consider seismic forces in analysis. The building frame, foundation and soil mass are considered to act as single integral compatible structural unit. The stress-strain characteristics of the supporting soil play a vital role in the interaction analysis. The resulting differential settlements of the soil mass are responsible for the redistribution of forces in the superstructure. In the present work, the nonlinear interaction analysis of a two-bay ten-storey plane building frame- layered soil system under seismic loading has been carried out using the coupled finite-infinite elements. The frame has been considered to act in linear elastic manner while the soil mass to act as nonlinear elastic manner. The subsoil in reality exists in layered formation and consists of various soil layers having different properties. Each individual soil layer in reality can be considered to behave in nonlinear manner. The nonlinear layered system as a whole will undergo differential settlements. Thus, it becomes essential to study the structural behaviour of a structure resting on such nonlinear composite layered soil system. The nonlinear constitutive hyperbolic soil model available in the literature is adopted to model the nonlinear behaviour of the soil mass. The structural behaviour of the interaction system is investigated as the shear forces and bending moments in superstructure get significantly altered due to differential settlements of the soil mass.