Shaking table testing of hard layered soil-pile-structure interaction system

Heuristic-based multi-objective optimization design for viscous dampers in RC frame structures considering soil-structure interaction

ABSTRACTMetamaterials have been developed to control electromagnetic, acoustic, and elastic waves, and can also be employed to manage seismic waves. As building clusters can significantly affect ground vibrations, this study extends the concept of metamaterials to evaluate a periodic soil‐structure interaction (SSI) system capable of reducing the ground vibrations caused by seismic waves. Using the theory of SSI with Floquet–Bloch theorem, a governing equation for a unit cell in a periodic SSI system is derived with effective earthquake forces from exterior sources. The dispersion relations of the periodic SSI system are subsequently obtained, and its frequency band gaps (FBGs) for surface waves are identified. Furthermore, the dynamic stiffness of rigid foundation, on which periodic superstructures are installed, and corresponding input motion are calculated when Rayleigh surface waves are incident to the system. The results indicated that foundation input motion is significantly reduced resulting in a reduction of structural response, and the dynamic displacements of the soil surface are significantly reduced owing to the FBGs within the SSI system. Finally, a parametric study is conducted to examine the effects of clear spacing between buildings, building height, and shear wave velocity in the underlying half‐space on SSI system behavior. The results confirm that the dynamic characteristics of a periodic SSI system depend on these factors and it must be designed accordingly.

Tuned mass damper (TMD) has been widely used as a common vibration reduction device to provide effective protection for structures. Soil–structure interaction (SSI) effects are significant for accurately assessing seismic responses of structure and TMD performance. In the present research, the effectiveness of TMD is comprehensively investigated by simulating the seismic responses of a 20-story structure equipped with TMD with different features including SSI effects. This paper establishes a reliable numerical model that incorporates SSI effects, and the viscoelastic boundary is utilized to simulate the soil condition and impose seismic action. By comparison with the results of the theory and shake program, the rationality of the model is verified. The mitigating effects of TMDs with different frequencies, mass and damping ratios are investigated under rigid foundation and soil condition, and the effectiveness of multiple tuned mass dampers (MTMDs) using two different approaches is compared. The results show that the TMD tuned to SSI system provides better applicability and performance. Whether considering SSI effects or not, increases its mass can amplify its mitigation effects, but may amplify its negative effects at lower floors. The MTMDs installed at top floor of the structure can perform better than that equally distributed at different floors in SSI system. This paper provides some valuable reference for the seismic analysis of soil-structure-TMD system in practical engineering.

The Soil-Structure Interaction (SSI) Effect exists everywhere, but the existing researches on actual damping of SSI system are not so sufficient, and the analysis of its real dynamic response becomes unsuitable to engineering applications. In this paper, the possibility of regarding SSI system as classical damping system in linear elastic range is studied. The motion domains and the equation of the dynamic system in each domain are confirmed with respect to boundaries. The research on Shaking Table Test of SSI system is shown as an example of supporting the feasibility of regarding SSI system as classical damping system similarly.

Earthquake responses of a base-isolated structure on a multi-layered soft soil foundation by using shaking table tests

The present study is aimed at determining the effect of variability in soil type and structure height on soil-structure system responses. In order to explore this innovative idea, a wide range of soil types and structure heights are assumed, and the responses are analyzed with respect to changes in soil type and structure height. It is intended to address the three-fold problem of determining under what circumstances soil-structure interaction (SSI) exerts significant effects on the results, on what condition it could be ignored, and whether taking account of SSI leads to conservative results. To verify the numerical models, the results are compared with those derived from the NEHRP method. Five planar concrete frames are examined under the action of thirty earthquake records. Seven types of soil are considered. For modeling the soil-structure system, the direct method is employed. The plastic behavior of the soil is formulated based on the multi-surface (nested surfaces) concept; the yield surfaces of sand are of the Drucker-Prager type, and those of clay are of the Von Mises type. The exact Incremental Dynamic Analysis (IDA) is adopted for analyzing the soil-structure system. The results indicate that, for sandy soils, the SSI impact is greater for looser sub-soils. For clayey soils, the medium clay has the most powerful SSI effect. For low and medium rise buildings, the SSI effect is more profound as the structure becomes taller, but for high rise buildings, the SSI effect wears off with increasing height.

Linear soil–structure interaction of coupled wall–frame structures on pile foundations

In the traditional design method, structures are usually assumed as rigid base structures without considering soil-structure interaction (SSI). However, whether the effect of SSI on the seismic performance of structures is beneficial or detrimental is far from consensus among researchers. Moreover, previous literature mostly concentrated on the seismic behaviour of mid-rise buildings and moment-resisting frames. Therefore, it is in real need to comprehensively investigate the seismic response of tall buildings considering SSI. In this study, a soil-foundation-structure model developed in finite element software and verified by shaking table tests is used to critically explore the effects of SSI on high-rise buildings with a series of superstructure and substructure parameters. The beneficial and detrimental impacts of SSI are identified and discussed. Numerical simulation results indicate the rise in the stiffness of subsoil can dramatically amplify the base shear of structures. As the foundation rotation increases, inter-storey drifts are increased, and base shears are reduced. In general, SSI amplifies the inter-storey drifts showing detrimental effects of SSI. However, as for the base shear, SSI exerts detrimental effects on most piled foundation cases as well as classical compensated foundation structures resting on C e soil, whereas, for compensated foundation structures resting on soil types D e and E e , effects of SSI are beneficial since the base shear is reduced. Moreover, regarding buildings with different structural systems and foundation types, minimum base shear ratios considering the SSI reduction effect are presented.

A practical and efficient coupling method for large scale soil–structure interaction problems

Equivalent fixed-base models for soil-structure interaction systems

Boundary reaction method for nonlinear analysis of soil–structure interaction under earthquake loads

Real-time dynamic hybrid testing for soil–structure interaction analysis

Experimental study on soil-structure interaction of steel frame under seismic excitations

Fragility Analysis of Bridges with Liquefaction Effects33 8AbstractOver-crossing bridges inherited with a loss-span risk due to liquefaction-induced ground deformation. The objective of this study is to construct site-dependent fragility curves of over-crossing bridges with a ground failure. A simple supported PCI girder typical bridge in Taiwan adopted in this research is to perform an extensive nonlinear time history analysis. The soil-structure interaction is incorporated in the analytical model of the pile foundation. Bowels and Reese models account for compression only soil springs and the viscous boundary is simulated with Berge model. The acceleration son various site soil conditions in the 1999 Chi-Chi earthquakes serve as input ground excitations. Park-Ang damage index and loss-span ratios are employed to achieve the fragility curves of various liquefactions. The fragility curves of various damage states, site soil conditions, and liquefaction depths correlated with PGA provide a guideline to achieve an optimal retrofit scheme for existing bridges susceptible to the liquefaction risk.

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.