Showing papers on "Soil structure interaction published in 2019"

Transparent Synthetic Soil and Its Application in Modeling of Soil-Structure Interaction Using Optical System

Abstract: This article introduces the uses of transparent synthetic soil for geotechnical problems using optical system, including transparent materials, sample preparation, geotechnical properties, experimental methods, and applications in physical modeling. Four typical kinds of transparent synthetic soil are shown and compared. For amorphous silica powder, normally the consolidated amorphous silica has a higher normalized strength but a lower modulus than the natural clays. For amorphous silica gels, the stress-strain behaviors are consistent with the typical stress-strain behaviors of sand for both dense and loose conditions. For fused silica, it has a higher shearing strength and higher modulus than the natural sand does; the deviatoric stress increases with the confining pressure, but the stress-strain curves of fused silica and the natural sand are particularly similar. For glass sand, with increasing of the relative density, the strain-stress relationship varies from strain hardening to stress softening, while its failure form is essentially the same as that of standard sand. According to the geotechnical properties of four typical materials of transparent synthetic soil grain, they are used to simulate different conditions and analyze practical engineering problems in different physical model tests. The process included the generation of a speckle pattern created by the interaction of laser light with transparent particles. Using digital image processing technology, speckle patterns can be obtained and used to calculate the displacement field. By utilizing this optical system, transparent synthetic soil can be used to non-intrusively investigate internal soil deformation, flow problems, and ground movement in physical model tests. Finally, both the advantages and disadvantages of the transparent soil experimental technique are analyzed.

Influence of soil–structure interaction on seismic pounding between steel frame buildings considering the effect of infill panels

Abstract: The present research aims to study the influence of the soil–structure interaction (SSI) and existence or absence of masonry infill panels in steel frame structures on the earthquake-induced pounding-involved response of adjacent buildings. The study was further extended to compare the pounding-involved behavior versus the independent behavior of structures without collisions, focusing much on dynamic behavior of single frames. The effect of SSI was analyzed by assuming linear springs and dashpots at the foundation level. The infill panels were modeled using equivalent diagonal compression struts. The steel frames were assumed to have elastic–plastic behavior with 1% linear strain hardening. The dynamic contact approach was utilized to simulate pounding between the adjacent buildings. Nonlinear finite element analysis was performed for two adjacent multi-story structures with four different configurations representing cases that can exist in reality. The seismic response of the studied cases generally emphasized that ignoring the soil flexibility and/or the contribution of the infill panels may significantly alter the response of adjacent structures. This may result in a false expectation of the seismic behavior of buildings exposed to structural pounding under earthquake excitation.

Advanced computation methods for soil-structure interaction analysis of structures resting on soft soils

Abstract: Adopting the most accurate and realistic modelling technique and computation method for treatment of dynamic soil–structure interaction (SSI) effects in seismic analysis and design of structures re...

Seismic performance of outrigger–belt truss system considering soil–structure interaction

Abstract: The focus of this study is to investigate the seismic behavior of outrigger-braced building considering the soil–structure interaction based on finding the best location of outrigger and belt truss system. For this purpose, a central outrigger-braced frame of a steel tall building is considered. A layered soil deposit underlied this frame and the resulting soil–structure system is subjected to seismic excitation. To analyze this system, direct method is employed in OpenSees. Also, elastic and in-elastic analyses are both considered and a comparison is made between current results and the results related to the system with fixed base. The best location of outrigger–belt truss system is determined by considering the maximum roof displacement, base moment and base shear with and without soil–structure interaction. It is shown that considering SSI affects the location of outrigger–belt truss system. Elastic analysis of both systems, namely with fixed base and with soil–structure interaction, showed that locating the belt truss at higher stories caused lower amounts of roof displacement.

Structure‐soil‐structure interaction of adjacent buildings subjected to seismic loading

Abstract: The effects of soil-structure interaction (SSI) on the seismic response of different types of structures has been thoroughly investigated in the past 4 decades. Yet, the phenomenon of structure-soil-structure interaction (SSSI) was often overlooked. The present study aims at the rigorous investigation of the interacting effects of adjacent buildings in a two dimensional setting. The soil medium was assumed as a viscoelastic half-space modeled using plane strain finite elements. The aforementioned unbounded half-space is simulated utilizing the state-of-the-art perfectly matched layers implemented in the finite element method (FEM). The problem of the SSSI is solved in frequency domain. In order to fully model the stories below the ground level for the case of high-rise buildings, special modifications were considered for the interaction of the structure and the soil medium due to presence of spatially varying ground motion on the boundary of excavated region. The effect of different parameters such as foundation moduli and distance between adjacent buildings were investigated and the results were compared with models built using the conventional rigid foundation assumption. The results of the study showed that the interacting effects of adjacent building are prominent and need to be considered in the seismic design of buildings.

Response spectrum method for seismic soil–structure interaction analysis of underground structure

Abstract: The response spectrum method (RSM) has been incorporated into many codes for seismic design of aboveground structures since 1950s. However, no RSM is presented in details for the seismic design of underground structures due to the complexity of seismic soil–structure interaction (SSI). In this paper, the RSM is developed for the seismic analysis of the underground structures including SSI. First, the underground design response spectrum is derived using two different procedures from the ground design response spectrum that is commonly available in most seismic design codes. Second, the SSI analysis model consisting of the underground structure and its adjacent soil is established with the roller side boundaries and the bottom boundary subjected to the underground response spectrum. Third, the RSM is applied to the SSI analysis model to estimate the structural response under the underground response spectrum. Finally, the numerical examples are presented to demonstrate the feasibility of the RSM for the SSI analysis model of underground structure.

Optimum design of steel braced frames considering dynamic soil-structure interaction

Abstract: Recent studies on design optimization of steel frames considering soil-structure interaction have focused on static loading scenarios, and limited work has been conducted to address the design optimization under dynamic soil-structure interaction. In the present work, first, a platform is developed to perform optimization of steel frames under seismic loading considering dynamic soil-structure interaction (SSI) in order to quantify the effects of earthquake records on the optimum design. Next, verification of the adopted modeling technique is conducted using comparison of the results with the reference solution counterparts in frequency domain. For time history analyses, records from past events are selected and scaled to a target spectrum using simple scaling approach as well as spectrum matching technique. For sizing of the steel frames, a recently developed metaheuristic optimization algorithm, namely exponential big bang-big crunch optimization method, is employed. To alleviate the computational burden of the optimization process, the metaheuristic algorithm is integrated with the so-called upper bound strategy. Effects of factors such as the building height, presence of soil domain, and the utilized ground motion scaling technique are investigated and discussed. The numerical results obtained based on 5- and 10-story steel braced frame dual systems reveal that, although dynamic SSI reduced the seismic demands to some extent, given the final design pertains to different load combinations, the optimum weight difference is not considerable.

Analytical model to predict building deflections induced by ground movements

Abstract: The building relative deflection is a parameter used to assess the level of the damage of the building when influenced by ground movements due to tunnelling or subsidence. The goal of this paper is to improve an analytical model that can predict the building-relevant relative deflection, induced by ground movements, by considering the soil–structure interaction phenomena. The Pasternak model is investigated to take into account the influence of the shear strain in the ground. The building is modelled with a Euler–Bernoulli beam placed on an initially deflected ground equivalent to the free-field ground movements. The static and the cinematic equilibrium of both the ground and the building are calculated to assess the transmitted building deflection. Mechanical parameters of the soil of the analytical models are discussed, and a methodology is developed to determine their values. Final results are compared with numerical finite element models (CESAR-LCPC) with a good agreement. They show the importance of the shear deformation of the soil that must be taken into account for a more confident prediction of the transmitted building deflection. To facilitate the operational use of the results, an abacus, relating the deflection ratio to the relative stiffness, is plotted.

Optimization criteria for design of tuned mass dampers including soil–structure interaction effect

Abstract: Many researches have focused on the optimal design of tuned mass damper (TMD) system without the effect of soil–structure interaction (SSI), so that ignoring the effect of SSI may lead to an undesirable and unrealistic design of TMD. Furthermore, many optimization criteria have been proposed for the optinal design of the TMD system. Hence, the main aim of this study is to compare different optimization criteria for the optimal design of the TMD system considering the effects of SSI in a high–rise building. To acheive this purpose, the optimal TMD for a 40–storey shear building is firstly evaluated by expressing the objective functions in terms of the reduction of structural responses (including the displacement and acceleration) and the limitation of the scaled stroke of TMD. Then, the best optimization criterion is selected, which leads to the best performance for the vibration control of the structure. In this study, the whale optimization algorithm (WOA) is employed to optimize the parameters of the TMD system. The numerical results show that the soil type and selected objective function efficiently affect the optimal design of the TMD system.

Influence of prefabricated vertical drains on the seismic performance of similar neighbouring structures founded on liquefiable deposits

Abstract: Increasing the resilience of structures to seismically induced soil liquefaction is a major objective for the earthquake engineering community. Increasingly, soil drains are being used to mitigate ...

Modeling of Landslide–Tunnel Interaction: the Varco d’Izzo Case Study

Abstract: This paper reports a case study of the interaction between a slow-moving landslide in clay soil and a railway tunnel protected by sheet pile walls, that crosses the landslide accumulation. The earthflow, that develops in the Southern Apennines, Italy, has been long studied and monitored by different organizations, such as the national railway company and the University of Basilicata. Since the investigated landslide and construction typologies are quite diffused in mountainous areas, the case study can be considered representative of a large number of other similar cases. Differently from other approaches proposed in the literature, the role of the landslide slip surface depth, changing in the directions longitudinal and transversal to the tunnel, and of structural connections, affecting the pile–tunnel system response, are accounted for in detail. Several numerical models are used to simulate the interaction between the sliding soil and tunnel. Different 2D and 3D geotechnical and structural models are adopted to reproduce stress–strain scenarios compatible with the experimental evidence. The modeling results indicate that the interaction varies considerably along the tunnel length because of the 3D geometry of the landslide, and is conditioned by the residual shear strength available on the slip surface. The expansion joints in the tunnel lining only marginally influence the stress in the structure because of the presence of the adjacent sheet pile walls, which enable considerable collaboration between the tunnel sectors.

Experimental observation on laterally loaded pile in unsaturated silty soil

Abstract: An experimental study was carried out to investigate the effects of soil partial saturation on the behaviour of laterally loaded piles. The proposed study was conducted by means of centrifuge tests...

Investigation of seismic performances of unconnected pile foundations using dynamic centrifuge tests

Abstract: An unconnected pile foundation allows separation between the lower pile and the pile cap, and it has been proposed as an effective foundation type for reducing the seismic load during strong earthquakes. However, previous quantitative evaluations of unconnected piles with various foundation types and earthquake intensities are inadequate. In this study, the influence of base shaking level and the material of the interposed layer between pile and pile cap on the seismic behaviour of unconnected piles were evaluated using a centrifuge model test to reproduce the field stress conditions. A dynamic centrifuge model test was completed on an experimental model consisting of dry sandy soil, a foundation and a single degree-of-freedom structure. The acceleration of the structure and the settlement of the foundation system were measured during base shaking. For the unconnected pile system, the structural seismic load reduction effect due to rocking behaviour was confirmed, and the unconnected pile foundation with the interposed layer with large stiffness had less vertical settlement than the conventional shallow foundation. Finally, the rotational stiffness and damping ratio for the foundation system used in the centrifuge model tests were derived and discussed.

Non-linear soil–pile interaction induced by ground settlements: pile displacements and internal forces

Abstract: In urban areas, the construction of tunnels and deep excavations beneath and near pile foundations can be detrimental for the superstructure and the foundation. A two-stage continuum-based non-line...

Effect of soil–structure interaction on a masonry structure under train-induced vibrations

Abstract: This paper presents an experimental investigation to assess the influence of soil–structure interaction (SSI) on an unreinforced masonry structure under train-induced vibrations. For this purpose, ...

Study on Dynamic Structure-Soil-Structure Interaction of Three Adjacent Tall Buildings Subjected to Seismic Loading

Abstract: The dynamic structure-soil-structure interaction (SSSI) involving three adjacent structures with pile-raft foundations arranged along the east-west direction in a viscoelastic half-space is numerically studied under earthquake excitation. The direction of earthquake excitation is perpendicular to the direction of the structural arrangement. In the simulation, the Davidenkov model of the soil skeleton curve is assumed for soil behavior, and the viscous-spring artificial boundary is adopted. In order to investigate the effects of SSSI, the clear distance between structures, structure types, structure heights, and the first natural periods of structures are considered, and a series of numerical simulations are conducted. The peak floor displacement and the peak inter-story shear force of structures are examined to determine the SSSI effects. Results show that SSSI effects change significantly with these factors. Furthermore, the structural seismic response could be increased or reduced as a result of SSSI, depending mainly on the structural characteristics, rather than the location of the structures. These results are significant for studying the effects of SSSI and the sustainable development of cities, especially for the seismic design of dense urban buildings.

The effect of base isolation and tuned mass dampers on the seismic response of RC high-rise buildings considering soil-structure interaction

Abstract: The most effective passive vibration control and seismic resistance options in a reinforced concrete (RC) high-rise building (HRB) are the base isolation and the tuned mass damper (TMD) system. Many options, which may be suitable or not for different soil types, with different types of bearing systems, like rubber isolator, friction pendulum isolator and tension/compression isolator, are investigated to resist the base straining actions under five different earthquakes. TMD resists the seismic response, as a control system, by reducing top displacement or the total movement of the structure. Base isolation and TMDs work under seismic load in a different way, so the combination between base isolation and TMDs will reduce the harmful effect of the earthquakes in an effective and systematic way. In this paper, a comprehensive study of the combination of TMDs with three different base-isolator types for three different soil types and under five different earthquakes is conducted. The seismic response results under five different earthquakes of the studied nine RC HRB models (depicted by the top displacement, base shear force and base bending moment) are compared to show the most suitable hybrid passive vibration control system for three different soil types.