Soil-structure Interaction Effects Research Articles

Soil-structure interaction effects on the seismic performance of steel moment-resisting frames equipped with optimal rotational friction dampers

This study investigate the soil-structure interaction (SSI) effects on the seismic performance of steel moment-resisting frames (SMRF) equipped with optimal rotational friction dampers (RFDs). Firstly, a simultaneous optimal design based on the energy concepts is expanded to find the optimal placement and the corresponding optimal parameters of the RFDs for the seismic protection of a nonlinear six-story SMRF. Then, the direct method is adopted to simulate the nonlinear SSI effects on the optimal RFDs-equipped SMRF. The input, hysteretic, dissipated energies and the drift of stories of the controlled SMRF subjected to four real earthquake excitations indicate that SSI can considerably influence the seismic performance of the controlled SMRF. Nevertheless, the significant amount of the seismic input energy is dissipated by optimal RFDs and therefore its limited amount is dissipated by the structural. Moreover, the optimal RFDs can maintain the story drift ratios within the acceptable drift limits.

The generation of uniform hazard Floor Response Spectra

In the generation of Floor Response Spectra (FRS), there are significant uncertainties in the earthquake excitations and site conditions, which lead to uncertainty in the resultant FRS. A fully probabilistic method is developed to account for the uncertainties and to generate FRS with a desired return period (RP). The uncertainties in seismic inputs and geotechnical models from nuclear industry are considered in this research. A set of seismic inputs at the bedrock with different loading levels are used to represent the uncertainty in earthquake excitations. A large number of site profiles are developed by Monte Carlo simulation to account for the uncertainty in soil properties. Following site response analysis and soil-structure interaction (SSI) analysis, amplification factors are determined for each site under the excitations of different ground motions to address the effects of seismic wave propagation and SSI. The uncertainties are propagated from site response analysis to SSI analysis consistently. Based on these analyses and seismic hazard curves at the bedrock, uniform hazard FRS are obtained with a complete probabilistic description. In the numerical examples based on the uncertainty model in nuclear industry, the uniform hazard FRS generated by the proposed method can reduce the seismic demands significantly (up to 46% as compared to results obtained by the current practice when the RP is set to 10,000 years) to provide an economical solution for seismic design. Furthermore, it overcomes the underestimation of FRS in some frequency ranges by the current practice. Sensitivity study is performed to study the influence of the logarithmic standard deviation and the correlation coefficient between adjacent soil layers of shear-wave velocity.

Dynamic Soil–Structure Interaction Effects in Buildings Founded on Vertical Reinforcement Elements

Pile foundation is an effective technique to support buildings in the presence of soft soil and seismic areas. More recently, the rigid inclusions system has also been utilized for founding buildings. Both systems increase the bearing capacity of the soil and allow reducing the total and differential settlements in the structure. However, the study of these systems in a complete and accurate way implies the consideration of the soil–structure interaction (SSI). In order to investigate the impact of different pile toe conditions (including the placement on hard soil, an anchorage and floating piles) in the response of mid-rise buildings, numerical models with a 5-storey frame building founded on the inclusions system (soil–inclusion–platform–structure) are analyzed and compared with the pile system (soil–pile–structure). Fully coupled finite difference numerical models were developed using Flac 3D. The influence of the dynamic characteristics of the structure was considered analyzing buildings with different heights (3 storeys to 7 storeys). The linear elastic perfectly plastic model with a Mohr–Coulomb failure criterion is used to represent the behavior of the soil. Values of the maximum lateral displacements, of the inter-storey drifts and of the shear forces distribution in the buildings, as well as the rocking of the foundation, are presented. Concerning the foundations, efforts and displacements are compared for the different systems. The results show that the type of support condition influences the seismic response of the building and the efforts and displacements in the rigid elements, depending on the foundation system. The efforts at the toe level in the rigid elements are highly influenced by the support conditions, but there is only a slight influence from the head connection.

Effect of SSI and Fixed-base Concept on the Dynamic Responses of Masonry Bridge Structures, Dalal Bridge as a Case Study

Historical masonry structures are very important as they carry cultural heritage, so it is important to protect these structures from natural disasters such as earthquakes and transferred to the next generations. It is known that masonry structures are weak against earthquakes, therefore, a suitable analysis method for assessment and retrofitting purposes is a must. Generally, the fixed-base concept is used for analysis and design purposes, however, in reality, the structures are not fixed-base but they are resting on soils. The aim of this study is to make a comparison study between dynamic responses of fixed-base and soil-structure interaction (SSI) models for bridge masonry structures, the historical Dalal bridge was selected as the case study. First, the bridge was modeled as a fixed base model, and then three different soil profiles (hard, medium and soft soils) were added to the underneath of the structure. The numerical models were analyzed under Elcentro earthquake record. Results indicating a good agreement between the fixed base and the case of hard soil base. However, considerable differences were observed for medium and soft soil profiles.

Soil-Structure Interaction: Comparative Review of International Codes and Other Literature with Indian Seismic Code

Abstract Currently, structural engineers design structures as fixed bases, ignoring soil-structure interaction (SSI). Due to difficulties in the modelling of soil and the absence of procedure to incorporate effects of SSI in seismic design codes. Various researchers have shown the importance of considering SSI during earthquakes. This paper highlights the interaction effects of SSI, its seismic response, the general procedure for engineers to incorporate the impact of SSI. Various methods to solve SSI problems and their provisions are mentioned in different International Seismic Codes reviewed. However, there is an urgent need to incorporate detailed guidelines considering SSI effects in the Indian Seismic code. Thus, Indian engineers should reach for international Codes or other available literature to solve their SSI assignments.

Review on Analysis of Multi-Storey Framed Structure Using ETABS in various zones considering Soil Structure Interaction

Abstract: The objective of the paper is to present a review on analysis of Multi – Storey Framed Structure and to create a comparative study in effect of Soil Structure Interaction (SSI) for various zones. The RCC Framed Structure is subjected to various loading and the structure is then analysed using ETAB2016. Keywords: Soil Structure Interaction, Time History Analysis, Response Spectrum Analysis, Dynamic Analysis

Train-induced environmental vibrations by considering different building foundations along curved track

Comparing with the straight track, the curved track accounts for a large proportion with the rapid development of metro networks. The train-induced horizontal vibrations, which can’t be ignored, are close to the vertical vibrations. The residents and the service of building structures adjacent to the curved subway lines are greatly affected by the train-induced horizontal vibrations and vertical vibrations. Meanwhile, subway lines inevitably pass through the sensitive areas which have the requirements for vibration control, and the effect of soil-structure interaction on vibration propagation from the ground to upper building structures are not clear so far. Thus, this paper presents a numerical method to study the vibration propagation laws in the ground soil and the effect of soil-structure interactions on building vibrations along a curved subway segment. The method consists of a train-track coupled model and a finite-infinite model. The train-track coupled model could obtain both vertical and horizontal forces of inner and outer wheel-rail, and they are the dynamic loads applying at the finite-infinite numerical model. Then, the numerical method is verified by comparing with the situ measurements, which have been performed along a curved track of Guangzhou metro. Finally, building with pile, raft, or strip foundations was modeled to study the impact of soil-structure interactions. The numerical results show that the horizontal and vertical vibrations along the curved track are larger than the corresponding vibrations induced by train operation on the straight track. The soil-structure interaction has a significant effect on vibration propagation both in the ground soil and from the ground soil into the upper building. A building with a pile foundation can alleviate the vibration of the upper structure, especially in high-frequency band.

Dynamic analysis of 10 MW offshore wind turbines with different support structures subjected to earthquake loadings

This paper investigates the structural dynamics of 10 MW offshore wind turbines (OWTs) supported by different substructures (Monopile, Tripod and Jacket) under wind, wave, current and earthquake loadings. The support structures are modeled using ANSYS, a finite element models (FEM) software package, by considering the nonlinear soil structure interaction (SSI) effects and earthquake loadings. A spring-displacement method has been employed to model the earthquake excitations on the support structures. FAST and AQWA tools have been used to analyze wind and wave loads which are fed into ANSYS via a dynamic link library (DLL) as external loads for combination with the earthquake loads to predict the support structures’ responses. Earthquakes of different magnitudes have been simulated in the study. Under the earthquake with a magnitude of 7 measured on a Richter scale, the tower top displacements of the tripod, jacket and monopile are 1.42 m, 1.75 m and 1.80 m, respectively. The relative position of the displacement trajectory of the tripod OWT is nearest to the centroid of the yaw bearing. The maximum stresses of the jacket and tripod are respectively 5.7 times and 2.3 times that of the monopile. The average stress of the jacket and tripod are respectively 0.74 times and 0.56 times that of the monopile. This phenomenon shows that the tripod and jacket have a good stability, but with a high risk of local failure under earthquakes. The responses of the piles are mainly dominated by the seismic loads, rather than the wind and current loads. It was observed that the piles of the jacket and tripod OWT, which have small diameters and thin wall thickness, are more sensitive to earthquakes. Thus, the jacket and tripod OWTs may rely on the large stiffness offered by substructures to improve their stability. These phenomena can provide powerful insight into the seismic design of different substructures.

Shaking table test and numerical simulation of shallow foundation structures in seasonal frozen soil regions

Frozen soil layers can induce the formation of double or multilayers on the ground. Such formations change the dynamic characteristics and dominant period of soil, directly influencing the stability and safety of upper buildings. In this paper, the frozen soil-structure interaction system in cold region was taken as the research object. The frozen soil model was made artificially, and two kinds of structure models with different natural frequencies were designed. Through a series of shaking table tests and finite element numerical analysis, the influence of structural natural frequency, soil frozen depth and seismic load on the seismic response of structure were studied. The test results indicate that ground freezing could weaken the soil–structure interaction effect and the nonlinear development of the soil structure. The effect of peak acceleration amplification of the ground is significant close to the surface. The acceleration amplification coefficient of the ground surface decreased as the freezing depth increased, which indicates that the freezing of the ground suppressed the acceleration response of the ground surface. If the peak frequency of a seismic wave is close to the natural frequency of the structure, it can significantly amplify the seismic response of the structure. Owing to the interaction between the soil and the structure, the degree of liquefaction of the ground varied with different structures. Subsequently, a nonlinear finite element program was used to establish the dynamic calculation model of frozen soil-structure interaction system considering the gradient change of stiffness of frozen soil and the dependence of frozen soil on temperature. On the basis of validating the numerical model rationality, the seismic response of frozen soil-structure interaction system under horizontal seismic excitation was further explored. The analysis results show that the seismic response of the structure increased significantly with amplitude excitation; the greater was the freezing depth, the greater was the seismic response of the structure, The influence of the frozen ground on the seismic response of structures in the design of structures in frozen soil areas should be considered. In summary, the dominant period of the ground, the dynamic characteristics of a structure, the type of seismic wave, and the degree of liquefaction of the ground have a significant influence on the seismic response of the structure. Therefore, considerable attention should be paid to the influence of frozen soil on the dynamic characteristics of a structure in frozen soil regions.

Fuzzy probabilistic evaluation of soil-structure interaction effects on the soft-first-story structures

Even though the soil-structure interaction (SSI) has been investigated for long, less attention has been paid to the probabilistic framework. The present study used a fuzzy probabilistic approach to evaluate the effect of SSI on the nonlinear behavior of a soft-first-story structure with uncertain soil types. Sensitivity analysis was carried out to identify the relative importance of uncertainty parameters on the structural responses of the model structure. The analysis results showed that consideration of SSI in structures with relatively weak soil conditions could enhance the probability of irreparable damages in the structures. It was also observed that the variations in the weight density and shear wave velocity of soil were the most influential parameters in the structural responses.

STUDY ON SEISMIC RESPONSE OF A NEW STAGGERED STORY ISOLATED STRUCTURE CONSIDERING SSI EFFECT

The new staggered story isolated structure is a new type of seismic isolated structure developed from base isolated structure and inter-story isolated structure. In order to explore the seismic response of the new staggered story isolated structure considering the soil-structure interaction (SSI), the model of a new staggered story isolated structure considering SSI effect is established to analyze the nonlinear dynamic time-history response under rare earthquakes, and the comparison between hard soil and soft soil was carried out. Results show that the stiffness of the new staggered story isolated structure reduced, the modal period extended and the seismic response reduced by considering the SSI effect, the softer the site soil, the more obvious those changes are. Meanwhile, the shear force and the damage of the core tube decreases, while the shear force and the damage of the frame increases, the shear force transfers from the core tube to the frame. Additionally, the energy absorption of the seismic isolated bearings at the frame reduced, the energy absorption of the seismic isolated bearings at the core tube increased, the softer the site soil, the more obvious the trend is.

Seismic vulnerability assessment of RC high-rise building considering soil–structure interaction effects

Seismic vulnerability assessment of RC high-rise building considering soil–structure interaction effects

Interpretation of simultaneously optimized fuzzy controller and active tuned mass damper parameters under Pulse-type ground motions

All fuzzy logic controller specifications and active tuned mass damper (ATMD) parameters are simultaneously optimized under seven pulse-type near-fault earthquake records. The last story's peak displacement and the maximum inter-story drift are separate objective functions. The controller is installed on the roof of a 15-story building, and its characteristics are determined by a 3-dimensional finite element model of a real structure. Adopting a simple model, soil-structure interaction effects are investigated. Geotechnical tests of the site soil are used to determine soil characteristics. A general-purpose center of mass optimization algorithm is established to tackle the optimization problem. The algorithm results are compared with those of two popular optimization algorithms. An ensemble of twenty-four pulse-type ground motions is utilized to evaluate and validate the proposed controller. Optimal results are compared and discussed for the two objective functions, where interpreting numerical results may contain practical information about excitations and the structure.

Role of Subgrade Reaction Modulus in Soil-Foundation-Structure Interaction in Concrete Buildings

One of the key issues in structural and geotechnical engineering is that most parts of buildings are usually analysed separately and then the outputs are used in foundation designs. In this process, some effects are neglected. In this study, the soil–structure interaction (SSI) in foundations of concrete buildings was evaluated using the direct finite element method (DFEM). 3D models were developed and used to analyse concrete buildings with different stories constructed on soft soil. Foundation settlement, deformation of foundation, soil pressure diagram, and weight of reinforcement in the foundation were considered as the main parameters. Deformation of the foundation was analysed using the finite element method considering the effect of combined loadings (combinations of dead load, live load, and earthquake load). It is shown that by changing values of subgrade reaction modulus (Ks) in foundation design, the effects of SSI on tall buildings can be considered automatically. The results also show that the soil–structure interaction can cause changes in the pattern of foundation settlement, foundation deformation, and the weight of reinforcement used in foundation design. Furthermore, dishing deformation in foundation appeared in terms of SSI effects. An equation is provided to simplify considering SSI effects in foundation design. This method is practical for civil (especially structural) engineers, and they can conveniently consider these effects in foundation design without using DFEM.

Influence of Soil-Structure Interaction on the Seismic Response of a Continuous Bridge with Friction Pendulum System

A three-dimensional finite element analysis was carried out for the influence of soil-structure interaction (SSI) on the seismic response of an isolated continuous bridge with a friction pendulum system (FPS). SSI was modelled using the soil resistance vs deflection nonlinear springs (following p-y curves). The influence of SSI on the dynamic behaviour and the seismic response of isolated bridges with different friction coefficients of FPS were investigated using six measured ground motions. Results show that the effect of SSI is limited on the isolation period of the bridge, but significant on the response amplitude of the bridge structures, and particularly on the response amplitude at the pier top and bottom. The displacement and acceleration at the pier top are underestimated, while the shear force and bending moment at the pier bottom are overestimated if the SSI effects are ignored, which suggests that SSI should be considered in the seismic analyses of continuous bridges.

Study on the seismic control measure of the underground large-scale frame structure

The seismic control measures with isolation bearings (SMIB) on top column joints are widely employed in underground frame structures with small cross-sections. This paper reveals the seismic control mechanism of the SMIB, and verifies the applicability of the SMIB for the underground large-scale frame structure (ULSFS). It is found that: the stresses of middle columns in the ULSFS would be controlled to some extent, but the seismic responses of floor slabs and outside walls would increase due to the smaller lateral horizontal resistance after the SMIB. The SMIB can not aim at the failure mechanism of the ULSFS, and it has been demonstrated to be ineffective for the ULSFS. Therefore, an innovative separation seismic control measure (SSCM) is proposed for the ULSFS based on the structural seismic characteristics and failure mechanisms. The fixed beam-column joints in the frame structure are released to be hinged, and the energy dissipation devices are added between the internal frame structure with outside walls. The analysis results show that the SSCM would cut down the adverse effects of the considerable soil structure interaction and decrease the seismic responses of the whole ULSLS efficiently. The seismic reduction ratio also demonstrates the SSCM has highly reliable seismic control effects on both the entire structure and vulnerable positions.

Analyse the effect of Soil Structure Interaction on Seismic Response of Building Cluster by Variation in Soil and Building Properties

The seismic response of a building is dependent on the foundation flexibility, soil properties as well as the interaction between the soil and structure. The frequency and amplitude of the seismic response depends on the soil properties. For simpler calculations, the soil is usually assumed to be rigid which is unrealistic mostly. The buildings are designed on basis of idealized conditions taking fixed base or on Winkler foundations. Until recently, the efforts to ascertain the effect of Soil-Foundation-Structure Interaction (SFSI) on the response of structure have been limited. This study aims at investigating the nature of soil-structure interaction and investigate the effect on the response of building owing to variation in soil stiffness, depth of foundation and building mass ratio using numerical method. The analysis shows that the response of building cluster decreases with increase in soil stiffness. Heterogeneous cluster proved better during earthquake than homogenous cluster. The results indicated that the soil and building properties have major influence on the dynamic response of building cluster and thus may be given due consideration during design and seismic analysis.

Seismic Performance Assessment of Ordinary Moment Resisting Frame Equipped with Viscous Dampers under Pulse-Like Earthquakes

In conventional structures, the earthquake-resistant design is based on flexibility after yielding of structural members to provide a loss of earthquake input energy, while, using dampers, the input energy loss can be concentrated in predetermined points to prevent the nonlinear behavior of the main members that are also in the gravity bearing path. However, near-fault earthquakes might cause unexpected failure and severe structural damage, especially those with the pulse-like effect. A pulsed movement in the near field records in this system will, however, result in unusual behavior. Technology advances and the creation of vibration control systems have helped control this type of behavior since the earthquake forces are applied indirectly to the structure. For further investigation of this issue, in this study, some traditional two-dimensional frames were modeled for 3, 8, and 12 floors. Seven near-fault pulsed and seven far-fault nonpulsed accelerometers are applied. The structural behavior in four modes is examined: (1) without damper and soil-structure interaction effect, (2) without damper and considering soil-structure interaction effect, (3) with damper and considering soil-structure interaction, and (4) with damper without considering soil-structure interaction. Each model is analyzed in OpenSees software under incremental dynamic analysis. Then, the fragility curve is plotted based on the results. The results indicate that frame (4) reaches the failure level at a higher spectral acceleration, which means that the performance of the viscous damper in reducing drift between floors is one of the main criteria for predicting damages. It also shows the effect of soil-structure interaction on increasing the drift between floors and reaching failure at lower spectral acceleration in all models. Also, by comparing the fragility curves of the models under near-field and far-field records, it is found that the probability of failure under far-field documents (without pulse) is less than that under near-field documents (with a pulse).

Sensitivity of strength reduction factor for structures considering soil-structure interaction

The conventional perception of soil-structure interaction being ever-beneficial to seismic response of structures has been challenged by evidences of damages inflicted on built infrastructure by a number of earthquakes. Numerical studies by many researchers have also revealed the possible detrimental effects of soil-structure interaction. It has been recently established that this uncertainty stems from two conflicting phenomena, viz. reduction of elastic seismic demand owing to elongated natural period and enhanced damping, and lowering of strength reduction factor. While the first phenomenon lowers the seismic demand and is therefore beneficial, the second phenomenon is detrimental likely to increase the seismic demand. Over the last decade, a number of researchers have estimated strength reduction factor for structures considering soil-structure interaction effects. This paper attempts to assess sensitivity of strength reduction factor to variations in a number of non-dimensional parameters. These parameters are related to geometrical and material properties of structure, foundation and soil. It is found that lowering of strength reduction factor is most sensitive to stiffness contrast between structure and soil. It is also observed that structures with large expected inelasticity tend to afford a much-lowered strength reduction factor. The effect of other factors is found to be comparatively little or insignificant.

Seismic behavior of reinforced concrete frame substructure with cast-in-place slab on independent foundation

This paper aims to study the effect of soil-structure interaction (SSI) on the seismic performance of reinforced concrete (RC) structures. The rubber-wood composite block was used to substitute the foundation soil, and the low-cycle reciprocating loading experiment of the RC frame substructure was performed. The damage process, component strain, yield mechanism, load-displacement performance, stiffness degradation, energy dissipation and foundation response were analyzed. The effect of SSI on the seismic behavior of the structure was investigated by altering the foundation coefficient in the reasonable non-linear analysis model. Finally, parametric studies were carried out. The results show that the seismic performance of the specimen is general, and the final failure is consistent with the typical disaster performance. Under the peak load, the soil reaction under an independent foundation reacts linearly. The SSI has a great disturbance on the yield displacement and yield mechanism. The longitudinal reinforcement ratio of the column makes it possible to monitor this disturbance. The axial compression ratio can make the yield mechanism perfect but has little effect on yield displacement. The effective flange width of the cast-in-place slab is estimated to be nearly 6 times the thickness considering the SSI.