No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
A comparative study to determine seismic response of the box culvert wing wall under influence of soil-structure interaction considering different ground motions
Abstract
The present study deals with evaluation of the effects of different ground motions, backfill-structure interaction (BSI) and soil-structure interaction (SSI) on dynamic response of a box culvert wing wall. In obtaining numerical results, five different earthquake records with different frequency contents, five different backfill types and four different subsoil types are taken into account. Firstly, a finite element model (FEM) and three analytical models are proposed for analysis of the wing wall-backfill system under fixed-base case, and these fixed-base models are
compared with each other through both modal analysis and displacement time-history analysis under the assumption of linear-elasticity. After validating the ability of the FEM approach, by extending the fixed-base FEM to take account of elastoplastic behavior of soil and SSI, a three dimensional (3-D) model has been described, and 3-D nonlinear analyses have been carried out in time domain. The numerical results show that the seismic response of the wing walls are affected remarkably by the SSI, BSI and frequency content of the earthquake.
... The Mohr-Coulomb model is used for the soils, and the parameters are shown in Table 3. In this case, the earthquake record is selected according to China's Code for Seismic Design of Urban Railway Structures (GB 50909-2014), and nine natural earthquake records are selected for elastic time-range calculations [29][30][31][32][33], which comprise three low-frequency earthquake records (L-1~3), three medium-frequency earthquake records (I-1~3), and three high-frequency earthquake records (H-1~3) [34][35][36]; the information of the earthquake records is shown in Table 4. The time-range curves and Fourier spectra are shown in Figure 4. ...
... When the structure is subjected to elastic-dynamic analysis, the seismic propagation directions are all upward along the Z-axis and the vibration direction is the X-direction. [29][30][31][32][33], which comprise three low-frequency earthquake records (L-1~3), three medium-frequency earthquake records (I-1~3), and three high-frequency earthquake records (H-1~3) [34][35][36]; the information of the earthquake records is shown in Table 4. The time-range curves and Fourier spectra are shown in Figure 4. ...
With the development of the Chinese economy and society, the height and density of urban buildings are increasing, and large underground transportation hubs have been constructed in many places to alleviate the pressure of transportation. Commercial buildings are usually developed above the large underground transportation hubs, so the underground structures may have very shallow depths or no soil cover. The seismic response and damage mechanisms of such underground structures still need to be studied. In this paper, an example of a project in China is taken as an object to analyze the seismic response and damage mechanism of the structure after simplification. The spatial distribution of deformations and internal forces of such structures and the location of the maximum internal forces are obtained, and the effect of the frequency of seismic motions on the structural response is obtained. Finally, an elastoplastic analysis of such structures is carried out to assess the damage location and the damage evolution process.
... He [24] and Mao [25] studied the dynamic characteristics of a two-stage cantilever retaining wall under a horizontal earthquake, using a shaking table model test. Kasif [26] used the 3D FEM in time domain to investigate the effects of various configurations on seismic response of the cantilever retaining walls considering soil-structure interaction. Kasif [27] adopt the FEM to study the effects of different ground motions, backfill-structure interaction and soil-structure interaction on dynamic response of a box culvert wing wall. ...
A two-stage cantilever retaining wall is composed of two single-stage cantilever retaining walls, which are stacked up and down. The structure not only has the advantages of a single-stage retaining wall, but also compensates for the shortcomings of the height limit of the single-stage retaining wall; therefore, it has been gradually applied in projects. Based on the actual project of Zhongwei-Lanzhou Passenger Dedicated Line into Lanzhou Hub, this paper studies the influence of the construction of new cantilever retaining wall and the filling of subgrade on the deformation and earth pressure of the new cantilever wall and the existing cantilever wall by means of field test and numerical simulation. The results show that with an increase in the filling height after the new cantilever wall (upper wall), the horizontal displacement of the top of the upper and lower walls increased nonlinearly. The displacement direction of the upper wall was the filling direction, and that of the lower wall was the deviation from the filling direction. The higher the filling height, the greater is the displacement. With an increase in the filling height, the earth pressure behind the upper wall increases gradually along the wall height and decreases slightly to the bottom of the wall, which is approximately a linear distribution. The earth pressure behind the existing cantilever wall first increases along the wall height and gradually decreases after reaching a certain depth, but the earth pressure of the lower wall does not increase significantly with an increase in the filling height behind the upper wall. The slope failure mode is the overall sliding failure of the retaining wall together with the fill soil. The sliding surface passed through the lower edge of the lower wall heel and was similar to an arc shape. The stability of the two-stage cantilever retaining wall was better than that of a single-stage retaining wall. Finally, a calculation method for the overall stability and earth pressure of the existing two-stage cantilever retaining wall was proposed.
... With the rapid advancement of infrastructure development, prefabricated box culverts, as a novel type of precast concrete structure, have been widely applied in urban drainage systems, underground passages, and other engineering projects, owing to their high construction efficiency and easily controllable quality [1][2][3][4][5]. However, in practical engineering applications, these culvert structures often face complex thermal environments. ...
... The advent of rapid global economic progression has been accompanied by an expansive growth in large-scale infrastructure, leading to an extensive application of prefabricated box culverts in diverse underground traffic engineering projects [1][2][3][4]. These structures, subjected to high temperatures resulting from natural and man-made phenomena such as earthquakes and fires, may experience alterations in structural performance [5,6]. ...
... Structures constructed with different purposes may be subjected to lateral thrust due to static or dynamic factors (Greco 2014;Ozturk et al. 2022Ozturk et al. , 2023. Retaining walls designed to meet the lateral soil thrust are examined under various headings due to dynamic or static load. ...
This study was aimed to (1) investigate the failure surface mechanism occurring behind the wall supporting narrow backfill with experimental and numerical approaches; (2) determine the effect of internal friction angle (ϕ), friction (δ), heel length (β), foundation thickness (α), backfill inclination (ψ), and backfill width (θ) parameters on lateral earth thrust coefficients; and (3) derive finite-element analysis (FEM)-response surface method (RSM)-based lateral earth thrust coefficient equations for inverted T-type retaining walls supporting narrow backfill. The study was performed for granular backfill. A small-scale test was performed to investigate the failure surface mechanism in the narrow granular backfill. The particle image velocimetry method was employed to determine failure surface patterns for various heel lengths and backfill widths. Finite-element (FE) analyses were also performed to verify the experimental results. From the analyses, it was seen that two characteristic soil blocks formed behind the horizontally translated wall. Due to these soil blocks, the wall was divided into three characteristic regions. Lateral active earth thrust coefficients were derived for the regions. RSM was employed to derive FE-based lateral earth thrust coefficient estimation equations for each region. In this context, three design matrices were created, comprising 76 runs. In the design, parameters ϕ, δ, β, α, ψ, and θ were used as independent variables. A total of 76 FE analyses were performed for various parameter combinations. The results of the FE analyses were used as a response. From the statistical analyses, lateral active earth thrust estimation equations for narrow backfill were derived. The suggested equations were compared with the results of experimental, numerical, and analytical studies, and it was seen that the method gives reliable results. The effects of independent variables and their interactions on lateral earth pressure coefficients were examined.
... Some researchers experimentally examined the effect of earth pressure on box culverts and compared the results with existing theoretical models to offer design improvements [11,12]. Several academics have studied box culverts to understand the impact of soil-structure interaction on the performance of box culverts [13,14]. Gong et al. carried out experimental and numerical evaluations to study the failure mechanism of reinforced concrete box culverts [15]. ...
The culverts are used to safely convey water under railways, highways, and overpasses. They are utilized in drainage areas or water channels and in areas where the bearing capacity of soil is low. The design and construction of this crucial infrastructure need to be improved to meet contemporary demands of reliability and affordability. Precast reinforced box culverts are popular alternatives as they ensure strength, durability, rigidity, and economy. This research seeks to develop an effective and affordable design improvement procedure for a precast box culvert using modern numerical tools. The Finite Element Method (FEM) based approach is used in studying the effects of haunch geometry and additional steel reinforcement on the load-bearing capacity of box culverts. A conventional box culvert is analyzed to create the numerical models in the Abaqus FEM code and to investigate the load-bearing capacity of culverts with an expanded span. The outcomes of the study reveal the critical places for stress concentration as well as the location of maximum damage. It is found that haunch geometry and additional reinforcement at these critical places significantly affect the load-carrying capacity of a culvert. From the comparison of capacity curves of models with and without haunches and diagonal reinforcement, it is found that a 25% increase in load-carrying capacity is achievable with the recommended changes. The proposed design improvement technique can be employed for the cost-effective and safe design of a concrete box culvert with larger span lengths and high water-flowing capacities. The findings of this study are expected to assist practitioners in strength enhancement tasks of box culverts for increased structural stability and drainage efficiency.
... Although peak ground acceleration (PGA) and peak ground velocity (PGV) are very useful intensity measures for seismological studies, none of them can provide any information on the frequency content. Therefore, PGV and PGA have to be supplemented by additional information for the proper characterization of a ground motion [62,63]. As a result, the ratio of PGA to PGV is a ground motion parameter that provides information about the frequency content of the input motion. ...
This paper presents a methodology for the optimization of double tuned mass dampers (TMDs) positioned on the top floor of a multi-story building subjected to ground motions considering soil-structure interaction (SSI). In the optimization process, it is considered that double TMDs are connected both in series and in parallel. STMD and PTMD are used to denote the series TMDs and parallel TMDs, respectively. The equations of motion for an n-story shear building controlled by STMD and PTMD are derived by considering the SSI effect and the optimum parameters of both devices are obtained by minimizing the amplitude of the displacement transfer function for the top floor of the building in the frequency domain analysis. The effectiveness of the PTMD and STMD designed using the Jaya algorithm (JA) is verified by numerical examples of a ten-story shear building under twelve earthquake records with different frequency content and the comparison with the traditional TMD is also performed. In order to investigate the effect of earthquake frequency content on the control performance of the TMDs, earthquakes considered are divided into three different groups as low, intermediate, and high-frequency contents. In addition, the influence of the soil stiffness on the optimum parameters and effectiveness of the PTMD and STMD is discussed. Numerical results show that the optimally designed PTMD and STMD effectively suppressed the maximum floor displacements and accelerations of the building. It is also shown that SSI effects can be ignored when the building is built on stiff soil. In addition, it is concluded that the SSI and earthquake frequency content have a significant effect on the control performance of TMDs and the seismic response of the building.
Three-sided underpass culverts are structural systems used to provide passing vehicle or pedestrian. It is of great importance that such infrastructure systems remain useable, especially after disasters such as earthquakes that can cause great destruction, in order to ensure that infrastructure services can be maintained continuously. In this context, the aim of this study is to investigate using finite element method (FEM) the dynamic responses of three-sided underpass culvert system under near-fault ground motions with velocity pulse and far-fault ground motions. For this aim, the modal analysis of the soil-underpass culvert interaction system has been realized using proposed soil-structure interaction (SSI) model. The frequencies of the interaction system obtained from the finite element model developed using proposed approaches have been verified comparing with the results ob-tained from the literature and the site periods. After showing that the modes of the interaction system can be obtained with the help of the proposed numerical model, the full transient dynamic analyses have been per-formed in the time history using five near-fault and far-fault records, considering four different soil systems. The comparisons shows that the variations of the soil systems and the ground motion type can significantly affect the top peak relative displacements and the dynamic stresses of the three-sided underpass culvert.
In recent studies, it has been stated that tuned tandem mass dampers (TTMD) will be a practical mechanical solution to reduce the dynamic responses of structures under seismic excitations. However, since TTMD is tuned based on the dominant frequency of the superstructure, ignoring the soil-structure interaction (SSI), it may cause a notable deterioration in the control performance of the control devices. Thus, a methodology for the optimum design of TTMD positioned on the top story of a high-rise building due to near-fault pulse-like ground motions considering potential SSI effects has been investigated in this paper. Firstly, the TTMD is located on the top story of a well-known 40-story shear building, and the equations of motion for soil-structure-TTMD interaction are derived. Based on the sequential quadratic programming (SQP), the tuning parameters of TTMD are then found for different support conditions in the frequency domain. The efficiency of SQP is also compared with two meta-heuristic algorithms (i.e., simulated annealing and pattern search algorithms). The effectiveness of optimum TTMD is tested using 30 near-fault pulse-like ground motions using time-domain analyses. Numerical results showed that the optimum TTMD is more effective in suppressing the maximum displacement and inter-story drift of the building, considering SSI. It is also found that the frequency content of the earthquake, as well as the pulse period of the earthquake and soil type, has a significant effect on the control performance of the TTMD.
Particle tuned mass damper has received considerable attention on mitigating structural seismic responses recently. However, soil-structure interaction effects have not been considered for the optimization design of particle tuned mass damper in the previous studies yet, which may play significant roles in particle tuned mass damper’s effectiveness. This paper investigates the seismic control performance of particle tuned mass damper for tall buildings considering SSI effects. A 40-story benchmark structure is adopted as the primary structure, and different soil conditions including soft, medium, dense soil, and the fixed-base case are considered. Based on the Cuckoo Search algorithm, an optimum design approach for the particle tuned mass damper implemented in SSI system under earthquake excitations is proposed, and the optimum parameters of particle tuned mass damper are obtained from the optimum design process. The optimum results indicate that the optimized particle tuned mass damper can effectively decrease the displacement response without the increase of peak acceleration, and the reduction rates could exceed 30% in some cases. Compared with other soil type cases, under soft soil condition, the optimum parameters of particle tuned mass damper are especially different, and the mitigation effects of the optimized particle tuned mass damper on maximum displacement weaken. Hence, it is necessary to consider the SSI effects for particle tuned mass damper’s seismic design. Furthermore, the interaction effects between the primary structure and particle tuned mass damper in SSI system are also evaluated through energy analysis. The results show that considering SSI effects, the optimized particle tuned mass damper device dissipates the overwhelming majority of the input energy, and it greatly decreases the structural energy, displaying excellent energy dissipation performance on seismic vibration control of structure.
This paper deals with the optimization of the tuned mass damper (TMD) with different objective functions for high-rise building under earthquake motions considering soil–structure interaction (SSI). A study is conducted to search for the TMD that outperforms five objective functions (i.e., OF-1–OF-5) containing combinations of the structural responses and foundation responses. The main goal of the present study is to evaluate and compare the control performance of these five objective functions. The optimum parameters of TMD are obtained by particle swarm algorithm (PSA) to minimize the acceleration transfer function. To determine the dynamic response of a 40-story building under the influence of SSI, six different foundation soil conditions and eight different earthquake records are considered. The results show that the SSI effects on the dynamic response of the high-rise building resting on relatively soft soil types such as SD and SE are of critical importance. It is shown that the effectiveness of the optimum TMD designed by OF-1 is better than the others in suppressing the peak response values for all soil types. After OF-1, the best performances are obtained for OF-3 and OF-5 which yield approximately the same effectiveness. It is also found that different earthquake records, soil types and objective functions are very effective on the effectiveness of TMD.
For rational solutions against seismic excitations of masonry bridges, the capability of 3D soil–structure interaction (SSI) modeling with experimental evidence has been insufficiently researched up to now. This is also valid for the effects of near- and far-fault earthquakes. Hence, the spectral responses measured by microtremors have been compared with the ones of 3D SSI analysis under the effects of near- and far-fault earthquakes for a historical masonry arch bridge in this article. The 3D SSI modeling of bridge and substructure soil was built with elastic finite element model using solid element and viscous boundary. The SSI analysis has been performed by direct approach using time-history analysis. The earthquake motions (near fault, far fault) were selected in accordance with the tectonic setting of the bridge’s region. From the study, it is possible to confirm that microtremors are able to detect spectral responses of the bridge by the presence of SSI influences. By the evidence of amplifications and soil–structure resonance, the microtremor measurements experimentally promise that: (i) the bridge can be adequately identified by SSI analysis compared to fixed base, (ii) the elastic model can satisfactorily provide information about the bridge’s responses (amplitudes, spectral response, stress distribution) under earthquake effect, and (iii) the far-fault motion especially due to SSI modeling is significant for the seismic responses. The study indicates that regarding the SSI influences into seismic computation has become quite efficient for determination of a possibility of various adverse effects (high displacements, critical stresses, resonance). Moreover, diagnosing the historical bridge well as a result of microtremors together with SSI modeling strongly proposes protection of the bridge with an appropriate retrofitting.
The dynamic response of the cantilever retaining walls is affected by many factors such as the geometry of the wall, the earthquake frequency content, the wall flexibility, the backfill characteristics, and the soil structure interaction. Therefore, it may not be possible to analyse all aspects of the dynamic response of the cantilever retaining walls in spite of their simplicity. It is also well known that some unfavourable effects on the behaviour of the walls may impair the balance of the wall. In this context, the study aims to investigate the dynamic response of the T type cantilever retaining wall considering soil structure interaction. In line with this purpose, the soil structure interaction system is produced with a three dimensional finite element model. The seismic analyses are performed in time domain using C-OLC360 component of 1983 Coalinga earthquake, and four different foundation soil systems are used in these analyses. The elasto-plastic behaviour of the backfill and the foundation soil are represented with Drucker-Prager material model. In order to reflect the material damping of the system, Rayleigh damping is utilized considering mass and stiffness proportional dampings. In addition, the viscous boundary dashpot elements which consider the criteria of Lysmer and Kuhlemeyer for wave propagation, are placed around the boundaries of the numerical model. The results are examined in terms of both the stresses and displacements. The findings have revealed that the dynamic response of the T shaped cantilever retaining walls is considerably affected by the soil structure interaction.
The seismic motion response of a cantilever retaining wall with cohesive and cohesionless backfill materials was evaluated using fully dynamic analysis based on finite difference method. The dynamic analysis was validated based on experimental test results and then compared to analytical and empirical correlations based on Newmark sliding block method. Seven different earthquake events and the backfills with low to high levels of cohesion were considered. Nonlinear regression analyses were carried out to provide correlations between free-field peak ground acceleration (PGA) and maximum relative displacement of the retaining wall. These results were compared to results from empirical and analytical methods. Furthermore, fragility analyses were conducted to determine the probability of damage to the retaining wall for different free-field PGAs and backfill cohesions. It is demonstrated to what extent a small amount of cohesion in backfill material can influence displacement of the retaining wall and probability of damage in seismic conditions.
Pounding phenomena considering structure-soil-structure interaction (SSSI) under seismic loads are investigated in this paper. Based on a practical engineering project, this work presents a three-dimensional finite element numerical simulation method using ANSYS software. According to Chinese design code, the models of adjacent shear wall structures on Shanghai soft soil with the rigid foundation, box foundation and pile foundation are built respectively. In the simulation, the Davidenkov model of the soil skeleton curve is assumed for soil behavior, and the contact elements with Kelvin model are adopted to simulate pounding phenomena between adjacent structures. Finally, the dynamic responses of adjacent structures considering the pounding and SSSI effects are analyzed. The results show that pounding phenomena may occur, indicating that the seismic separation requirement for adjacent buildings of Chinese design code may not be enough to avoid pounding effect. Pounding and SSSI effects worsen the adjacent buildings' conditions because their acceleration and shear responses are amplified after pounding considering SSSI. These results are significant for studying the effect of pounding and SSSI phenomena on seismic responses of structures and national sustainable development, especially in earthquake prevention and disaster reduction.
Historical masonry arch bridges, which represent the richness of cultural heritage of the country (Anatolia, Turkey), should be protected against detrimental effects and transferred well to next generations with a thorough effort given for the accurate estimations under the seismic responses affected by the nonlinear soil and structural characteristics. In this viewpoint, a relatively comprehensive method, full 3D nonlinear time history analysis of soil–structure interaction (SSI) (using direct method of configuration), has been employed in this work through the understanding of SSI effect well specifically investigated for a historical masonry stone arch bridge (Mataracı Bridge, Trabzon). For this purpose, the SSI model of bridge–substructure soil was built with the finite elements in 3D using the solid element, and then figured out in detail based on the results of seismic responses due to earthquake excitation. It is found from the results that in comparison with the fixed base solution, the influence of SSI becomes relatively prominent on the responses of displacement, acceleration, rotation, frequency (at lower modes of vibration), modal shapes, base shear, and overturning moment, while the stresses almost remain unchanged. The effort given in this study could be beneficial for other historical structures in the country for accurate estimations of the responses when seismically considered.
The dynamic response of an elastic continuously nonhomogeneous soil layer over bedrock retained by a pair of rigid cantilever walls to a horizontal seismic motion and the associated seismic pressure acting on these walls are determined analytically-numerically. The soil non-homogeneity is described by a shear modulus increasing nonlinearly with depth. The problem is solved in the frequency domain under conditions of plane strain and its exact solution is obtained analytically. This is accomplished with the aid of Fourier series along the horizontal direction and solution of the resulting system of two ordinary differential equations with variable coefficients by the method of Frobenius in power series. Due to the complexity of the various analytical expressions, the final results are determined numerically. These results include seismic pressures, resultant horizontal forces and bending moments acting on the walls. The solution of the problem involving a single retaining wall can be obtained as a special case by assuming the distance between the two walls to be very large. Results are presented in terms of numerical values and graphs using suitable dimensionless quantities. The effect of soil non-homogeneity on the system response is assessed through comparisons for typical sets of the parameters involved.
Box culverts may be constructed in active seismic areas, where ground shaking or ground failures can impose considerable earth pressures on them. In this study, the seismic response of box culverts was investigated experimentally and numerically. A series of scaled centrifuge tests was performed and subjected to three different earthquake signals, with different amplitudes and frequencies. Two values of culvert wall thickness and two values of sand relative density were considered in the experimental program. Experimental results are presented in terms of comparisons of seismic bending moments. These results were used to calibrate and verify two-dimensional numerical models developed using the computer program FLAC. The verified models were then used to investigate the effect of earthquake intensity and frequency, height of soil cover, and culvert thickness on the seismic bending moments for the different culvert sections. Based on the analysis results, charts are presented to aid in the seismic design of box culverts. © 2015, National Research Council of Canada, All Rights Reserved.
The response of buried box culverts is a complex soil-structure interaction problem, where the relative stiffness between the soil and structure is a critical factor. In addition, soil arching is an important aspect of the soil-culvert interaction problem. A series of static scaled physical model centrifuge tests were performed to investigate soil-culvert interaction. Two different box culvert thicknesses and Nevada sand specimens with different relative densities were used to explore the interaction between the sand and box culverts under different conditions. The static loading consisted of the self-weight from the soil body. The responses of the box culvert were recorded for all loading conditions. The results were evaluated in terms of bending moment, soil pressure, and soil-culvert interaction factors. Soil pressures were evaluated using different experimental methods, which provided comparable results. The soil pressure observed on the culvert top slab showed parabolic distribution, i.e., higher values at the edges and lower at the centre than the theoretical vertical soil (overburden) pressure. The horizontal soil pressure on the side wall increased with depth. The soil-culvert interaction factors decreased at the centre and increased at the edges of the top slab, as the thickness and relative stiffness of the culvert decreased. © 2015, National Research Council of Canada, All Rights Reserved.
A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.
Numerous field tests indicate that the soil-structure interaction (SSI) has a significant impact on the dynamic characteristics of super-tall buildings, which may lead to unexpected structural seismic responses and/or failure. Taking the Shanghai Tower with a total height of 632 m as the research object, the substructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower. The refined finite element (FE) model of the superstructure of Shanghai Tower and the simplified analytical model of the foundation and adjacent soil are established. Subsequently, the collapse process of Shanghai Tower taking into account the SSI is predicted, as well as its final collapse mechanism. The influences of the SSI on the collapse resistance capacity and failure sequences are discussed. The results indicate that, when considering the SSI, the fundamental period of Shanghai Tower has been extended significantly, and the collapse margin ratio has been improved, with a corresponding decrease of the seismic demand. In addition, the SSI has some impact on the failure sequences of Shanghai Tower subjected to extreme earthquakes, but a negligible impact on the final failure modes.
In the present study, the numerical and experimental investigations were performed on the backfill- exterior wall-fluid interaction systems in case of empty and full tanks. For this, firstly, the non-linear three dimensional (3D) finite element models were developed considering both backfill-wall and fluid-wall interactions, and modal analyses for these systems were carried out in order to acquire modal frequencies and mode shapes by means of ANSYS finite element structural analysis program. Secondly, a series of field tests were fulfilled to define their modal characteristics and to compare the results from proposed approximation in the selected structures. Finally, comparing the theoretical predictions from the finite element models to results from experimental measurements, a close agreement was found between theory and experiment. Thus, it can be easily stated that experimental verifications provide strong support for the finite element models and the proposed procedures themselves are the meritorious approximations to the real problem, and this makes the models appealing for use in further investigations.
The aim of this paper is to investigate how the soil-structure interaction affects sloshing response of the elevated tanks. For this purpose, the elevated tanks with two different types of supporting systems which are built on six different soil profiles are analyzed for both embedded and surface foundation cases. Thus, considering these six different profiles described in well-known earthquake codes as supporting medium, a series of transient analysis have been performed to assess the effect of both fluid sloshing and soil-structure interaction (SSI). Fluid-Elevated Tank-Soil/Foundation systems are modeled with the finite element (FE) technique. In these models fluid-structure interaction is taken into account by implementing Lagrangian fluid FE approximation into the general purpose structural analysis computer code ANSYS. A 3-D FE model with viscous boundary is used in the analyses of elevated tanks-soil/foundation interaction. Formed models are analyzed for embedment and no embedment cases. Finally results from analyses showed that the soil-structure interaction and the structural properties of supporting system for the elevated tanks affected the sloshing response of the fluid inside the vessel.
This study aims to investigate the effects of structure-soil-structure interaction (SSSI), soil-structure interaction (SSI) and fixed-base (FB) assumptions on seismic behavior in mid-rise reinforced concrete (RC) buildings located on soft soil. Three–dimensional (3D) high ductility RC frames 5-, 8-, 10-, 13-, and 15-storey buildings are modeled as a fully nonlinear frame element. Five different structural cases were created: SSSI models with and without pounding, FB models with and without pounding, and SSI models. In the scope of this study, direct finite element modeling of 3D inelastic soil volume was considered. A detailed investigation has been carried out considering 65 different model combinations to reflect SSSI, SSI and FB modelling approaches. As a result, total of 1365 analyses using 21 different ground motion records, the lateral displacement demands and displacement profiles of the buildings were examined and presented. It is found that the seismic behavior of adjacent buildings located on soft soils is different from the fixed-base assumption. The buildings should not be evaluated alone, as neighboring buildings on soft soils affect each other. Neighboring building and soil effects should be considered for buildings up to 8-storey even no collision occurs. For buildings with higher than 8-storey, it may be reasonable to consider SSI only with neglecting neighboring building effects if there is no collision. If the seismic gap distance between adjacent buildings is insufficient and seismic pounding potential exists, neighboring building effects with soil-structure interaction should be taken into account independent from building height.
In this paper, the dynamic behavior of concrete rectangular tanks subjected to motions caused by an earthquake considering the effects of soil-structure-fluid interaction is studied. An analytical mechanical model for a rectangular tank with flexible walls, taking into consideration the effects of rigid-base rocking motion and lateral translation, is developed. The model with a lumped-parameters idealization of foundation soil is used to evaluate the system's response to ground earthquake motions. Using this model, the soil-structure-fluid interaction effect can be taken into account in the seismic analysis of flexible rectangular tanks in a fast and practical manner. To verify the mechanical model, the numerical results of the fixed-base case are compared with the experimental results. The results show that dynamic soil-tank interaction under horizontal seismic excitations, depending on the type of soil, can cause a profound effect on the amplification of hydrodynamic forces and moments exerted on the tank structure.
This paper is concerned with the response behaviour of a retaining wall in seismic conditions from a two-dimensional perspective. The backfill was levelled behind the wall for some distance. Both the wall and the backfill were found on a stiff elastic medium. The manner in which the backfill affected the response behaviour of the wall when subject to base excitations was of interest. The wall was idealised into a linear elastic element which responded mainly in flexural actions. The novelty of the paper is in the use of shaker table testing of a scaled down model of the retaining wall and backfill to validate the accuracies of results from numerical simulations. The comparison is mainly based on displacement time - histories at the top of the wall. The alignment with displacement-based approach for the seismic assessment of structures is distinguished from many other investigations which typically put the focus on the behaviour of the backfill pressure. Laboratory testings of backfill materials including triaxial tests have been conducted to determine the value of parameters for characterising the hysteresis properties of the backfill. Calibration of backfill material model has also been shown to simulate the pre yield, post yield and damping behaviour of backfill. The ultimate objective of the paper is to present a viable means of achieving realistic and accurate modelling of the seismic response behaviour of a retaining wall and to provide data for benchmarking simplified (macro) numerical models to be developed in the future for supporting seismic design and assessment.
Structural eccentricity plays an important role in the seismic design of buildings. According to various seismic design codes, it is one of the parameters which define whether a building may be considered as regular in plan. Structural eccentricity is defined as the distance between the center of mass and the center of rigidity. However, the center of rigidity is rigorously defined in single story buildings and in some special classes of multi-story buildings, e.g. isotropic ones, under the assumption of fixed based conditions. The present paper deals with single story and multistory asymmetric buildings that possess a real elastic axis under the assumption of fixed base condition and examines the existence or not of an elastic axis under soil structure interaction effects. The flexibility matrix and the loading vector are defined under flexible base assumption and the elastic axis is determined based on the notion of twist center. Mathematical formulas are derived which provide the coordinates of the elastic axis. Numerical examples are presented which investigate not only soil-structure interaction effects but the influence of various loading vectors as well. In general, soil-structure interaction extinct the real elastic axis; hence an optimum torsion axis must be defined. Moreover, soil-structure interaction decreases the structural eccentricity at each story level.
The Peak Ground Acceleration (PGA) is extensively used in earthquake engineering practice to describe the ground motion characteristics for establishing the seismic vulnerability curves. However, a single parameter is not enough to describe the seismic excitation and does not allow expressing the complex relationship between the structural damage and the ground movement. Motivated to overcome these shortcomings, several ANN-based models were proposed to predict the seismic structural damage using other parameters. Unfortunately, not all include soil structure interaction. This paper aims to explore the predictive power of an ANN-based approach to reproduce the nonlinear dynamic behavior taking into account the various ground motion intensities, the variability of soil, and SSI. The basic strategy is to train a neural network by a numerical database obtained from a FEM model. This numerical model is further validated by experimental results. An optimum prediction for a nonlinear dynamic response is achieved using Artificial Neural Networks. Finally, fragility curves were established considering SSI for three different soil classes. Results revealed the importance of considering SSI effects on the evaluation of seismic structural damage and risk assessment analysis.
A solution for the response of flexible retaining walls excited by vertically propagating shear waves in inhomogeneous elastic or viscoelastic soil is obtained using the weak form of the governing differential equation of motion associated with the Winkler representation of earth pressures as a function of relative displacement between the wall and the free-field soil. Inputs to the model include the soil shear wave velocity profile, the flexural stiffness of the wall, the elastic boundary conditions at the top and bottom of the wall, the motion at the surface of the retained soil, and the mass distribution along the wall. The proposed solution is first verified against an available closed-form Winkler solution for uniform soil, and then with elastodynamic solutions for a wall supporting an infinite uniform elastic soil. A validation exercise is then performed using centrifuge data from flexible underground structures embedded in sand, shaken by suites of ground motions. Seismic earth pressures and bending moments are also computed using limit-equilibrium procedures based on horizontal inertial forces acting within an active wedge. The proposed solution compares favorably with the experimental data, whereas limit equilibrium procedures produce biased predictions.
Seismic response of cable-stayed bridges is investigated with the main focus pertaining to the effects of near-field ground motions and soil-structure interaction on the dynamic response of the bridges. A 1/60 scale model of a typical cable-stayed bridge was designed and fabricated for the laboratory investigations. Three different types of ground motion records from the 1999 Chi-Chi earthquake, namely far-field, non-pulse near-field, and pulse-type near-field were employed in the experiments and the numerical analysis of the bridge. Laboratory simulation of the soil-structure interaction was accomplished by a box-spring system with interchangeable springs as foundations for the bridge towers. A three-dimensional numerical model of the bridge was developed, and its response was verified by the experimental results. Results from the numerical and experimental investigations indicated that the effects of foundation soil stiffness on the response of the bridge was influenced by the type of input ground motions. The bridge response was amplified when their foundation was in softer soils.
Validated numerical approaches are very important in dynamic studies of soil-structure interaction. Experimental outputs of physical models are required to validate the numerical approaches. Testing and analysis of an experimental scaled model is economical in comparison with investigating real size structures. However, a set of scale factors are required to model a full-scale structure accurately as a scaled model in a laboratory environment. In this paper, the scaling procedure and design of a scaled multi-storey concrete wall-frame structure with a scale factor of 1:50 are addressed. A specially selected dry sand with round shaped particles and specific grain size distribution was adopted in this study. A flexible soil container was designed and built to represent the soil boundary behaviour during time-history seismic excitations. The experimental investigations were divided into three different stages: fixed based structure without soil interaction; soil container without any structure; and, a structure with raft and pile foundations in the soil container. Finally, the same experimental stages were modelled numerically using a 3D finite element software. The results showed that the finite element simulations produced a good response when compared with the experimental results and these numerical models are suitable to be employed for further dynamic studies.
The seismic design of the structures is carried out by technical regulations and codes in free-field conditions (regardless of underground cavities). While with the availability of tunnels and the complex interaction between the tunnel and the aboveground structures, may be contemplated wrongly, which could be dangerous for over ground buildings and structures. Consequently, the examination of the underground tunnels and their impact on the land surface and adjacent buildings' seismic response seems to be significant. The present research focuses on formation of the plastic hinges in steel structures due to underground cavities and the soil-tunnel-structure interaction of underground structures. First an existing model was verified by finite element method and the results were compared with a sample specimen. Thus, several effective parameters were considered and studied such as soil type, multi-story structures (4, 8 and 12 stories) and dynamic load type. And then the models were evaluated under real earthquake records. as a result, the seismic response of the structures and plastic conditions of plastic hinge conditions were obtained. The results indicate that the underground cavities have affected the formation of plastic hinges in the structure. And they increased the input energy to the structure and had an impact on the total behavior of the structures. Also, the high-rise structures were much more vulnerable to underground tunnels. Therefore, the structures which are located above the underground cavities should be retrofitted and rehabilitated.
Noted for its practical, accessible approach to senior and graduate-level engineering mechanics, Plates and Shells: Theory and Analysis is a long-time bestselling text on the subjects of elasticity and stress analysis. Many new examples and applications are included to review and support key foundational concepts. Advanced methods are discussed and analyzed, accompanied by illustrations. Problems are carefully arranged from the basic to the more challenging level. Computer/numerical approaches (Finite Difference, Finite Element, MATLAB) are introduced, and MATLAB code for selectedillustrative problems and a case study is included.
The dynamic response of rigid walls retaining a cross-anisotropic poroelastic soil layer over bedrock to seismic horizontal excitation is determined analytically under conditions of plane strain. The problem is treated as a special case of that of a pair of rigid walls with a large separation distance. Use is made of Biot’s anisotropic poroelastodynamic theory. Assuming time harmonic excitation, one is able to achieve an exact u-p formulation of the problem in the frequency domain. Expansion of the displacements and the pore-water pressure in terms of
Fourier sine and cosine series along the horizontal direction, reduces the partial differential equations of motion in the frequency domain into a system of three ordinary differential equations, which can be easily solved analytically. Thus, closed form expressions for the seismic soil pressure, the distance from the base of the point of application of the resultant seismic pressure and the base shear force and bending moment are obtained. From the above cross-anisotropic poroelastic solution its special cases of isotropic poroelastic solution and crossanisotropic elastic solution are obtained and compared with the corresponding existing analytical solutions for validation purposes. Finally, parametric studies are performed in order to assess the effect of cross-anisotropy on the seismic response of the wall-soil system.
The purpose of the study is to determine the effects of multiple support excitations (MSE) and soil–structure interaction (SSI) on the dynamic characteristics of cable-stayed bridges founded on pile foundation groups. In the design of these structures, it is important to consider the effects of spatial variability of earthquake ground motions. To do this, the time histories of the ground motions are generated based on the spatially varying ground motion components of incoherence, wave-passage, and site-response. The effects of SSI on the response of a bridge subjected to the MSE are numerically illustrated using a three-dimensional model of Quincy Bayview cable-stayed bridge in the USA. The soil around the pile is linearly elastic, homogeneous isotropic half space represented by dynamic impedance functions based on the Winkler model of soil reaction. Structural responses obtained from the dynamic analysis of the bridge system show the importance of the SSI and the MSE effects on the dynamic responses of cable-stayed bridges.
Cantilever retaining wall movements generally depend on the intensity and duration of ground motion, the response of the soil underlying the wall, the response of the backfill, the structural rigidity, and soil-structure interaction (SSI). This paper investigates the effect of material properties on seismic response of backfill-cantilever retaining wall-soil/foundation interaction system considering SSI. The material properties varied include the modulus of elasticity, Poisson’s ratio, and mass density of the wall material. A series of nonlinear time history analyses with variation of material properties of the cantilever retaining wall are carried out by using the suggested finite element model (FEM). The backfill and foundation soil are modelled as an elastoplastic medium obeying the Drucker-Prager yield criterion, and the backfill-wall interface behavior is taken into consideration by using interface elements between the wall and soil to allow for de-bonding. The viscous boundary model is used in three dimensions to consider radiational effect of the seismic waves through the soil medium. In the seismic analyses, North-South component of the ground motion recorded during August 17, 1999 Kocaeli Earthquake in Yarimca station is used. Dynamic equations of motions are solved by using Newmark’s direct step-by-step integration method. The response quantities incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that while the modulus of elasticity has a considerable effect on seismic behavior of cantilever retaining wall, the Poisson’s ratio and mass density of the wall material have negligible effects on seismic response.
A comprehensive non-linear finite element (FE) model of integral abutment bridges (IABs) is presented to facilitate the analysis of such bridges using commercial software, especially under seismic loading. The presented model is capable of capturing non-linearity in both the structure and soil, in addition to considering far-field soil response. The model is simple enough to be used for practical purposes. On the other hand, many aspects of seismic behaviour of IABs are unclear, due to complicated soil–structure interaction. Using the presented model, a parametric study is performed to identify the effects of bridge length, abutment type and soil type on seismic behaviour of IABs. Non-linear direct integration FE analyses are performed on the IAB models. The results of the parametric analyses demonstrate the importance of non-linear modelling of soil and pile in capturing a realistic seismic response of IABs.
In the scope of this paper, it is aimed to compare the effects of near and far-fault earthquakes on the seismic responses (amplitude, spectrum effect, stress) of a relatively complex historical stone masonry mosque (125-years old Kurtulus Mosque, Gaziantep-Turkey) through soil-structure-interaction (SSI) analysis as well as fixed base solution. The SSI analysis (using direct approach) has also been performed for the effect of boundary types (viscous, elementary) of substructure. A 3D finite element modeling of mosque and substructure soil is built with solid elements, and then the seismic responses of mosque are evaluated by time-history analysis. The near and far-fault motions, which have approximately identical peak ground accelerations from same earthquake, are selected by representing their own characteristics (i.e., velocity, distance, etc.) from the strong ground motion records in previous earthquakes (1979 Imperial Valley, 1992 Erzincan, 1999 Chi-Chi, 1999 Kocaeli, 2010 Darfield). It is found from the results that both the near and far-fault earthquakes mostly lead to the responses similarly significant for both the fixed base and SSI considerations. However, regarding the resonance effect on the mosque, the far-fault motion appears more prominent in fixed base solution. Moreover, the far-fault motions mostly result in high amplitudes in the viscous boundary of SSI compared to the elementary boundary. When compared to the fixed base and SSI due to the near and far-fault effects, it is seen that the SSI increases amplitude and stresses. Overall from the comparisons, the study indicates that the far-fault motion could be employed together with the near-fault motions for assessment of such historical mosques for further considerations.
In this study, a comprehensive investigation of the stochastic analysis of a suspension bridge subjected to spatially varying ground motions is carried out for variable local soil cases and wave velocities. Bosphorus Suspension Bridge built in Turkey and connects Europe to Asia in Istanbul is selected as a numerical example. The spatial variability of the ground motion is considered with the incoherence, wave-passage and site-response effects. The incoherence effect is examined by taking into account Harichandran and Vanmarcke model, the site-response effect is outlined by using firm, medium and soft soil types, and the wave-passage effect is investigated by using 1000-2000, 500-1000, and 300-500 m/s wave velocities for the firm, medium and soft soils, respectively. Mean of maximum response values obtained from the spatially varying ground motions are compared with those of the specialized cases of the ground motion model. At the end of the study, it is seen that total displacements are dominated by dynamic component. The response values obtained for SMFF soil condition are generally the largest. When the varying local soil condition is considered, the variation of relative contributions of response components to the total response values for varying wave velocity cases is insignificant. Also, the variation of the wave velocity has important effect on the deck and towers total response values as compared with those of the constantly travelling wave velocity case. It is concluded that the site-response effect of ground motion on the response of suspension bridges is more important than that of the wave-passage, and the variation of the wave velocities depending on the local soil conditions, has important effects on the dynamic behavior of suspension bridge.
The main purpose of the current study is to develop the new coefficients for consideration of soil-structure interaction effects to find the elevated tank natural period. Most of the recommended relations to find the natural period just assumed the fixed base condition of elevated tank systems and the soil effects on the natural period are neglected. Two different analytical systems considering soil-structure- fluid interaction effects are recommended in the current study. Achieved results of natural impulsive and convective period, concluded from mentioned models are compared with the results of a numerical model. Two different sets of new coefficients for impulsive and convective periods are developed. The values of the developed coefficients directly depend to soil stiffness values. Additional results show that the soil stiffness not only has significant effects on natural period but also it is effective on liquid sloshing wave height. Both frequency content and soil stiffness have significant effects on the values of liquid wave height.
Structure-soil-structure interaction (SSSI) phenomena under earthquake excitations are investigated in this paper. Based on the results of the shaking table test, this work presents a 3-dimensional finite element numerical simulation method using ANSYS software. In the simulation, an equivalent linear model is assumed for soil behavior, and contact elements are adopted to consider the nonlinearity state of the interface between foundation and surrounding soil. In addition, constrained equations are added to manage the uncoordinated degrees of freedom. By comparing the results of the finite element analysis with data obtained from the shaking table test, the dynamic response of the shaking table test can be simulated properly. Finally, the dynamic response of adjacent structures considering the SSSI effect is analyzed. The results show that with increased excitation, contact pressure, strain amplitude, and pile slip increase, whereas the peak acceleration magnification coefficient decreases. These results are significant for studying the effect of SSSI on seismic responses of structures.
Simplified linear elastic analytical solutions are presented for the seismic pressures against rigid walls which agree closely with the exact solutions presented by Wood (1973). The finite element method is used to extend the analyses to nonhomogeneous elastic materials and to nonlinear soils. The finite element analyses give almost exact solutions for the elastic cases. Some practical guidelines are given for estimating the dynamic pressures for use in practice.
The dynamic response of a water-saturated linear poroelastic soil layer over bedrock retained by a pair of rigid cantilever walls to a horizontal seismic excitation is obtained analytically–numerically under plane strain conditions. Hysteretic damping in the soil skeleton may also be present. The problem is solved in the frequency domain and its exact solution is obtained analytically. This is accomplished with the aid of Fourier series along the horizontal direction and solution of the resulting system of ordinary differential equations to obtain the amplitudes of the soil skeleton displacements and the pore water pressure. Soil displacements and stresses, pore water pressure as well as wall pressures and resultant forces are explicitly presented. Their variation with frequency, hysteretic damping, porosity and permeability is numerically obtained and compared against an approximate solution, to assess the degree of validity of the assumptions.
A critical evaluation is made of the response to horizontal ground shaking of flexible cantilever retaining walls that are elastically constrained against rotation at their base. The retained medium is idealized as a uniform, linear, viscoelastic stratum of constant thickness and semi-infinite extent in the horizontal direction. The parameters varied include the flexibilities of the wall and its base, the properties of the retained medium, and the characteristics of the ground motion. In addition to long-period, effectively static excitations, both harmonic base motions and an actual earthquake record are considered. The response quantities examined include the displacements of the wall relative to the moving base, the wall pressures, and the associated shears and bending moments. The method of analysis used is described only briefly, emphasis being placed on the presentation and interpretation of the comprehensive numerical solutions. It is shown that, for realistic wall flexibilities, the maximum wall forces are significantly lower than those obtained for fixed-based rigid walls and potentially of the same order of magnitude as those computed by the Mononobe-Okabe method.
Numerical analysis was carried out on earthquake-induced displacement of anchored bulkheads. The permanent displacement of several meters experienced in liquefied areas during the Niigata earthquake was large enough to damage the functions of nearby structures. Since the conventional methods of predicting seismically-induced displacement could not deal with thin sheet-pile walls subject to liquefaction, they were modified and improved. The new method analyzed the limit equilibrium of a backfill soil wedge under the action of pseudostatic seismic force, and calculates the critical acceleration of an earthquake which is required for the sliding mechanism to be activated. By following Newmark's sliding block theory, the seismic acceleration in excess of the critical value is integrated twice with time so that permanent displacement may be obtained. Effects of pore water pressure development is taken into account by allowing the variation of critical acceleration with time. Finally parametric studies were carried out by using the method derived here, and their results are explained briefly.
The shaking table test of a soil-structure interaction system under hard soil conditions (with an average shear wave velocity of more than 153 m/s) is briefly presented in this paper, and the soil dynamic characteristics, including the shear moduli and damping ratio, are identified using the acceleration results of the test. Based on the identification results of the soil, a three-dimensional finite element analysis of the shaking table test was conducted using the ANSYS program. The surface-to-surface contact element was taken into consideration for the nonlinearity of the interface state of the soil-pile, and an equivalent linear model was used for the soil behavior. By comparing the results of the finite element analysis with the data obtained from the shaking table test, a computational model was validated.
Following a brief review of the inaccuracies that may result from the use of a popular model for evaluating the dynamic soil pressures and associated forces induced by ground shaking in a rigid wall retaining an elastic stratum, the sources of the inaccuracies are identified and a modification is proposed which, while retaining the attractiveness of the original model, defines correctly the action of the system. In the proposed modification, the soil stratum is modeled by a series of elastically supported, semiinfinite horizontal bars with distributed mass rather than by massless springs. The concepts involved are introduced by reference to a fixed‐based wall retaining a homogeneous elastic stratum, and are then applied to the analysis of more complex soil‐wall systems. Both harmonic and transient excitations are considered, and comprehensive numerical solutions are presented that elucidate the actions of the systems examined, and the effects and relative importance of the numerous parameters involved.
The seismic excitation experienced by structures is a function of the earthquake source, travel path effects, local site effects, and soil-structure interaction (SSI) influences. The result of the first three of these factors is referred to as free-field ground motion. The structural response to free-field motion is influenced by the SSI. In particular, accelerations within structures are affected by the flexibility of the foundation support and variations between the foundation and free-field motions. Consequently, an accurate assessment of inertial forces and displacements in structures can require a rational treatment of SSI effects. In the current study, to depict these effects on the seismic response of moment-resisting building frames, a 10-story moment-resisting building frame resting on a shallow foundation was selected in conjunction with three soil types with shear-wave velocities of less than 600 m/s, representing Soil Classes Ce, De, and Ee according to an existing Australian Standard. The structural sections were designed after applying dynamic nonlinear time-history analysis, based on both the elastic method, and inelastic procedure using the elastic-perfectly plastic behavior of the structural elements. The frame sections were modeled and analyzed using the finite-difference method andthe FLAC 2D software under two different boundary conditions: (1) fixed-base (no SSI) and (2) considering the SSI. Fully nonlinear dynamic analysis under the influence of various earthquake records was conducted and the results of the two different cases for elastic and inelastic behavior of the structural model were extracted, compared, and discussed. The results indicate that the performance level of the model resting on Soil Class Ce does not change substantially and remains in the life safe level while the performance level of the model resting on Soil Classes De and Ee substantially increase from the life safe level to near collapse for both elastic and inelastic cases. Thus, considering SSI effects in the elastic and inelastic seismic design of concrete moment-resisting building frames resting on Soil Classes De and Ee is essential. Generally, by decreasing the dynamic properties of the subsoil such as the shear-wave velocity and shear modulus, the base shear ratios decrease while interstory drifts of the moment-resisting building frames increase relatively. In brief, the conventional elastic and inelastic design procedure excluding the SSI is not adequate to guarantee structural safety for moment-resisting building frames resting on Soil Classes De and Ee.
The present study makes an attempt to investigate the soil-structure resonance effects on a structure based on dynamic soil-structure interaction (SSI) methodology by direct method configuration using 2D finite element method (FEM). The investigation has been focused on the numerical application for the four soil-structure models particularly adjusted to be in resonance. These models have been established by single homogenous soil layers with alternating thicknesses of 0, 25, 50, 75 m and shear wave velocities of 300, 600, 900 m/s-a midrise reinforced concrete structure with a six-story and a three-bay that rests on the ground surface with the corresponding width of 1,400 m. The substructure has been modeled by plane strain. A common strong ground motion record, 1940 El Centro Earthquake, has been used as the dynamic excitation of time history analysis, and the amplitudes, shear forces and moments affecting on the structure have been computed under resonance. The applicability and accuracy of the FEM modeling to the fundamental period of soils have been confirmed by the site response analysis of SHAKE. The results indicate that the resonance effect on the structure becomes prominent by soil amplification with the increased soil layer thickness. Even though the soil layer has good engineering characteristics, the ground story of the structure under resonance is found to suffer from the larger soil layer thicknesses. The rate of increment in shear forces is more pronounced on midstory of the structure, which may contribute to the explanation of the heavily damage on the midrise buildings subjected to earthquake. Presumably, the estimated moment ratios could represent the factor of safeties that are excessively high due to the resonance condition. The findings obtained in this study clearly demonstrate the importance of the resonance effect of SSI on the structure and can be beneficial for gaining an insight into code provisions against resonance.
The foundation on deformable soil, which, in general, radiates energy, can be represented in structural dynamics as a simple spring-dashpot-mass model with frequency-independent coefficients. For the two limiting cases of a site, the homogeneous half-space and the homogeneous layer fixed at its base, the coefficients are specified in tables for varying parameters such as ratios of dimensions and Poisson's ratio. Rigid foundations on the surface and with embedment are considered for all translational and rotational motions. In a practical analysis of soil–structure interaction this dynamic model of the foundation is coupled directly to that of the structure, whereby a standard dynamics program is used. © 1997 by John Wiley & Sons, Ltd.
During the past strong ground motions, chimneys constructed according to international standards are representative of similar structures at industrial areas throughout the world, including those collapsed or moderately damaged in earthquake-prone regions. This is due to the specialty of structural characteristics and the special loads acting on the structure such as earthquakes, wind and differences in the level of temperature, etc. In this context, the researchers and designers should focus on the dynamic behavior of chimneys especially under high temperature and seismic effects. For this purpose, the main focus of this study is to evaluate the dynamic response of a chimney under the above-mentioned effects considering soil-structure interaction (SSI). A 52 m steel chimney in Yeşilyurt township of Samsun City in Turkey was studied. The in-situ model testing and numerical models were compared. Before the commissioning of the chimney, a series of tests was realized to define its dynamic characteristics in case of no-heat and after the fabric got to work, the same tests were repeated for the same sensor locations to understand the heat effect on the dynamic response of the chimney. The ambient vibration tests are proven to be fast and practical procedures to identify the dynamic characteristics of those structures. The dynamic testing of the towers promises a widespread use, as the identification of seismic vulnerability of such structures becomes increasingly important. The data presented in this study are considered to be useful for the researchers and engineers, for whom the temperature and SSI effects on steel chimneys are a concern. Using the modal analysis techniques, presented finite element simulation for the soil/pile foundation-chimney interaction system is verified. The results of modal analyses using numerical solutions are shown to have acceptable accuracy compared with results obtained by in-situ test. The present study also aims to provide designers with material examples about the influence of these on the seismic performance of steel chimneys by means of reflecting the changes in the dynamic behavior.
An overview of past and recent developments on the subject of seismic earth pressures on yielding, gravity-type walls, retaining cohesionless backfill, is first presented, focusing on available data on the issue of phase difference that develops between the peak values of wall inertia and seismic earth thrust increment. The results of a FEM parametric study are next presented regarding the dependence on the resulting dynamic earth thrust reduction – acting on the time of peak wall inertia – on backfill rigidity, wall height, and shaking characteristics. The reliability of the numerical analyses was verified by modeling centrifuge tests reported by Nakamura [24] and successfully comparing measured vs. computed behavior. The results of the parametric analyses indicate that the seismic active earth thrust, acting on the wall at the time of maximum wall inertia, is significantly reduced (compared to its peak value) with increasing shaking intensity of backfill, increasing wall displacements, increasing wall height, and decreasing backfill rigidity. No systematic dependence on the ratio of input motion frequency to the natural frequency of the backfill (f/f1) was observed. The above findings: (1) verify earlier experimental and numerical results, (2) explain the reported lack of damage to retaining walls under strong ground shaking, and (3) indicate the need for revising the pertinent provisions of current seismic codes. Graphs summarizing the results of the numerical analyses are presented which may be used as a guide for selecting the magnitude of seismic active earth thrust that needs to be taken into account in the design of the examined type of earth retaining walls.