Showing papers on "Soil structure interaction published in 2018"

Seismic assessment of a benchmark based isolated ordinary building with soil structure interaction

Abstract: Base isolation (BI) has been applied all over the world as a well-known technique in order to reduce the destroying effects of earthquakes. Even if many researches have been published on this issue, few contributions have been focused on the effects that soil-structure interaction (SSI) can have on isolated buildings. In this regard, the paper aims at simulating the SSI effects on a residential structure by performing 3D numerical simulations. The soil is described with non-linear hysteretic materials and advanced plasticity models. The paper applies the open-source computational interface OpenSeesPL, implemented within the finite element code OpenSees. The interface performs the 3D spatial soil domain, boundary conditions and input seismic excitation with convenient post-processing and graphical visualization of results (including deformed ground response time histories). The proposed approach enables to drive the assessment of isolation technique with evaluation of soil non-linear response into a unique twist. Therefore, the paper aims at assessing the cases where BI becomes detrimental. In particular, the model of the structure allows us to assess the structural performance, calculating accelerations and displacements at various heights. Consequently, this study can be considered one of the few attempts to propose new design considerations for engineers and consultants.

A Centrifuge Study of Seismic Structure-Soil-Structure Interaction on Liquefiable Ground and Implications for Design in Dense Urban Areas

Abstract: Current practice in seismic design often assumes free-field conditions for the estimation of liquefaction-induced building settlement. This is inaccurate, as a structure places additional stresses ...

Earthquake soil-structure interaction of nuclear power plants, differences in response to 3-D, 3 × 1-D, and 1-D excitations

Abstract: Author(s): Abell, JA; Orbovic, N; McCallen, DB; Jeremic, B | Abstract: In soil-structure interaction modeling of systems subjected to earthquake motions, it is classically assumed that the incoming wave field, produced by an earthquake, is unidimensional and vertically propagating This work explores the validity of this assumption by performing earthquake soil-structure interaction modeling, including explicit modeling of sources, seismic wave propagation, site, and structure The domain reduction method is used to couple seismic (near-field) simulations with local soil-structure interaction response The response of a generic nuclear power plant model computed using full earthquake soil-structure interaction simulations is compared with the current state-of-the-art method of deconvolving in depth the (simulated) free-field motions, recorded at the site of interest, and assuming that the earthquake wave field is spatially unidimensional Results show that the 1-D wave-field assumption does not hold in general It is shown that the way in which full 3-D analysis results differ from those which assume a 1-D wave field is dependent on fault-to-site geometry and motion frequency content It is argued that this is especially important for certain classes of soil-structure systems of which nuclear power plants subjected to near-field earthquakes are an example

Seismic performance and failure mechanism of a subway station based on nonlinear finite element analysis

Abstract: A nonlinear three-dimensional finite element model is employed to investigate the seismic performance and failure mechanism of a subway station. The interaction between subway station and surrounding soil is considered and the nonlinear behavior of the station structure is taken into account. Structural concrete and steel bars are simulated separately. The results demonstrated that the carrying capacities of structural middle columns and wall-to-roof slab connections are vital in underground structure’s seismic design. During an earthquake, the structure’s plastic damage first appears at beam-to-roof slab connections; but the damage at beam-to-roof slab connections does not develop significantly as seismic going. The heaviest damage parts is columns’ bottom, and then is columns’ top. The damage of wall-to-slab connections can, firstly, let the load transfer to columns and, secondly, reduce the restraint to the roof slab. The relative displacement between the roof slab and bottom slab leads to additional moment on structural middle columns. Besides, the damage at the connections of walls-to-diagonal bracings and slabs-to-diagonal bracings is remarkable. The structure is failure as an italic “M” shape. The results are consistent with the phenomena observed in the collapse of Daikai subway station during 1995 Great Hanshin Earthquake.

Performance of Viscous Damping in Inelastic Seismic Analysis of Moment-Frame Buildings

Abstract: This report investigates the performance of several viscous damping formulations in the inelastic seismic response of moment-frame buildings. The evaluation employs a detailed model of a 20-story steel building. Damping schemes included in the study are Rayleigh, condensed Rayleigh, Wilson-Penzien, two versions of tangent Rayleigh and one implementation of capped damping. Caughey damping is found not to be computationally viable. Differences among the damping schemes, as quantified by amounts of plastic hinge rotations and story drifts, become noticeable once these quantities reach the 3% level. In order of least to greatest hinge rotations and drifts that occur under lateral response to horizontal ground motion, the damping schemes rank as Rayleigh (most damping action), condensed Rayleigh, Wilson-Penzien, the standard form of tangent Rayleigh and capped damping, which are about the same, and the elastic velocity version of tangent Rayleigh (least damping action). Performance of Rayleigh damping under vertical ground motion is discussed, including the effect of soil-structure interaction. The propensity of Rayleigh damping to generate excessive damping forces and moments during inelastic seismic analysis is explained, and a parameter is introduced that can predict the potential magnitude of the effect. A review of some literature on the role of viscous damping on the inelastic seismic response of moment frames is also presented.

Soil–structure interaction analysis in natural heterogeneous deposits using random field theory

Abstract: Inherent variability of soil properties induces inevitable sources of uncertainties in geotechnical analyses. Hence, deterministic evaluation of geostructure performance may lead to undesired unconservative outcomes which in turn may result in the system failure. In this study, a numerical simulation approach is employed to examine the influence of variation of different random soil properties on the soil–structure interaction phenomenon as well as the subgrade reaction coefficient within the shallow foundation analysis framework. Implementing Monte Carlo simulations along with the random field theory into the finite difference numerical iterations, several probabilistic analyses are performed in an undrained condition. The results of stochastic simulations illustrate the significant influence of incorporating the spatial variability of index soil properties on the response analysis of shallow foundations above heterogeneous soil strata. In particular, heterogeneity of soil layer is observed to bear a remarkable role in the evaluation of subgrade reaction coefficient. Adopting the results of numerical analysis, it is observed that as the coefficient of variation and as a result, heterogeneity of soil layers increases, the mean subgrade reaction coefficient decreases. The descending rate of mean subgrade reaction coefficient decreases as the scale of fluctuation increases and the soil behaviour tends towards the homogeneous state.

Considerations for the Mitigation of Earthquake-Induced Soil Liquefaction in Urban Environments

Abstract: In cities, seismic coupling between structures is known to influence ground motions, settlement patterns, and demand on superstructures. Yet the effects of interactions between soil and bui...

Influence of soil‐structure interaction on performance of a super tall building using a new eddy‐current tuned mass damper

Abstract: Author(s): Zhou, Z; Wei, X; Lu, Z; Jeremic, B | Abstract: Tuned mass dampers (TMDs) can be used as vibration control devices to improve the vibration performance of high-rise buildings. The Shanghai Tower (SHT) is a 632-m high landmark building in China, featuring a new eddy-current TMD. Special protective mechanisms have been adopted to prevent excessively large amplitude of the TMD under extreme wind or earthquake loading scenarios. This paper presents a methodology for simulating behavior of the new eddy-current TMD that features displacement-dependent damping behavior. The TMD model was built into the SHT finite element model to perform frequency analysis and detailed response analyses under wind and earthquake loads. Furthermore, soil-structure interaction (SSI) effects on wind and seismic load responses of the SHT model were investigated, as SSI has a significant impact on the vibration performance of high-rise buildings. It was found that SSI has more significant effects on acceleration response for wind loads with a short return period than for wind loads with a long return period. Some of the acceleration responses with SSI effects exceed design limits of human comfort for wind loads with shorter return periods. As to the seismic analyses, it was found that SSI slightly reduces the displacement amplitude, the damping force, and the impact force of the TMD.

Seismic Response of Adjacent Unequal Buildings Subjected to Double Pounding Considering Soil-Structure Interaction

Abstract: Various cases of two adjacent multi-story buildings with different numbers of floors and equal or unequal foundation levels under earthquake loading and considering soil-structure interaction (SSI) are investigated. A two-dimensional model for each case of the two adjacent unequal buildings without separation distance is used and a special arrangement of contact elements in the contact zone is employed to fulfil all possible deformation contact modes which take place under seismic loading. The soil is modelled by two-dimensional 4-node elements which are in contact with the foundations of the two adjacent buildings. This paper studies the earthquake-induced double pounding that takes place between the two adjacent unequal height buildings in some upper points at superstructure in the contact zone and also at foundation level, considering soil-structure interaction (SSI). The double pounding and the soil-structure interaction (SSI) effects should be taken into consideration in the seismic analysis of adjacent buildings especially those with different heights and different foundation levels.

Investigation of Soil–Structure Interaction Effects on Seismic Response of a 5 MW Wind Turbine

Abstract: This paper investigates the seismic behavior of a wind turbine, including soil–structure interaction (SSI). A full-system finite-element model is introduced for dynamic analysis, including SSI. The model is based on the NREL 5 MW reference wind turbine that consists of a rotor blade system with three rotating blades, nacelle, and tower connected to a soil–foundation system. The proposed model is validated using the full-system natural frequencies of the reference wind turbine. In the soil foundation system, the foundation is modeled as a rigid gravity-based foundation with two DOFs and the SSI effect is considered using a cone model. Dynamic analyses are developed in frequency and time domains, and the model is subjected to earthquake excitation and wind loading for different soil types for parked and operational conditions. Transfer functions are obtained, and the modal frequencies of the soil foundation structure system are estimated. Results show that SSI plays an important role in the response of the wind turbine. We can conclude that for a parked wind turbine, the effect of SSI is beneficial while considering that SSI has a detrimental effect in the operational conditions of wind turbine. The participation of different input loads in total response of an operational wind turbine is also presented.