scholarly journals Dynamic Behaviour of Raft Foundation for Tall building with Variable Subsoil

2020 ◽  
Vol 10 (2) ◽  
pp. 230-235
Keyword(s):  
Dynamic Response ◽  
Soil Structure ◽  
Lateral Displacement ◽  
Specific Effect ◽  
Soil Structure Interaction ◽  
Structural Safety ◽  
Natural Period ◽  
Analysis And Design ◽  
Structure Interaction ◽  
Fixed Base

Structures are often constructed on layers of soil unless bedrock is very close to the ground surface. When the ground is stiff enough, the dynamic response of the structure will not be influenced significantly by the soil properties during the earthquake, and the structure can be analysed under the fixed base condition. When the structure is resting on a flexible medium, the dynamic response of the complete structure will be different from the fixed base condition, where the interaction between the soil and the structure has to be incorporate. This behavioural difference because of the phenomenon commonly referred to as Soil-Structure Interaction (SSI), which if not considered in analysis and design properly; the accuracy in assessing the structural safety, response for earthquake excitation could not be reliable solution. Hence evaluation of the site, specific effect of soil stiffness on structure becomes important to understand behaviour of structure. Flexibility of soil increases natural period of structure, which basically turn changes the seismic response of structure. The interaction among structure, their foundation and soil media below foundation alter the actual behaviour of structure. Here G+25 storey building is modelled and analysed, employing Finite Element Method adopting Commercial code SAP2000 V19 under fixed base (no soil-structure interaction) and flexible base considering soil-structure interaction. An attempt has been made to evaluate the effect of soil structure interaction of super structure by considering the systematic parameters like time period, lateral displacement, storey drift, bending moment in dual global structural axis i.e., X-X and Y-Y direction.

Effect of foundation flexibility on the across-wind response of reinforced concrete chimneys with free-standing liners

2000 ◽  
Vol 37 (3) ◽  
pp. 676-688 ◽  
Author(s):  
Jon K Galsworthy ◽  
M Hesham El Naggar
Keyword(s):  
Dynamic Response ◽  
Soil Structure ◽  
Soil Structure Interaction ◽  
Mode Shapes ◽  
Base Case ◽  
Free Standing ◽  
Structure Interaction ◽  
Fixed Base ◽  
Base Forces ◽  
Flexible Foundation

Chimneys with free-standing liners are often analyzed as fixed base cantilever beams, ignoring the effect of soil-structure interaction on their response. However, soil-structure interaction influences the dynamic response of chimneys in two ways: it alters the natural frequencies, damping ratios, and mode shapes, and it results in coupling of the response of the liner and the shell. In this analysis, the stack was modelled as a continuous cantilever beam with distributed stiffness and mass supported by a flexible foundation. It was found that the relative shell-liner deflection for the flexible foundation case was approximately 35% higher than that for the fixed base case. This increase in deflection may exceed design tolerances for a chimney cap and may lead to liner and (or) shell damage if combined with other adverse conditions such as aerodynamic interference effects with other chimneys. The base forces in the shell decrease significantly due to the foundation flexibility, with values as low as 50% of those of the fixed case. The base forces in the liner were approximately 35% of shell base forces for the fixed base case. These forces are not accounted for in the design of liners using the fixed base assumption. It was concluded that the effects of the foundation flexibility are significant and must be included in the analysis of chimneys with free-standing liners. This is especially true for chimneys in regions with low seismic activity, since the design of the liner would be based on minimal lateral forces.Key words: soil-structure interaction, chimneys, dynamic response, wind.

scholarly journals Soil Densification Effect on The Seismic Response of Structures Taking into Consideration Soil-Structure Interaction

2021 ◽  
Vol 2 (4) ◽  
pp. 13-17
Author(s):  
Radhwane Boulkhiout
Keyword(s):  
Dynamic Response ◽  
Seismic Response ◽  
Soil Structure ◽  
Lateral Displacement ◽  
Motion Vector ◽  
Stability Index ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Seismic Force ◽  
Soil Densification

Soil compaction is a considerable construction activity to ensure safety and durability, notably in the transportation industry. This technique of compaction increases soil bulk density and soil strength, while decreases porosity, aggregate stability index, soil hydraulic conductivity, and nutrient availability, thus reduces soil health. Consequently, it lowers crop performance via stunted aboveground growth coupled with reduced root growth. Therefore, if the characteristics of the soil are changed, it will affect the response of the structures. In this work, the effect of improving soil characteristics by compaction techniques on the dynamic response of foundations and structures, taking into consideration the effect of soil-structure interaction was determined. The dynamic response of foundations is presented by the impedances functions, which are determined numerically by the CONAN program, based on the cone method. In addition, the response of the structure will be presented according to the lateral displacement in each level of it. This motion vector is a function of the forces in each level; for this, the equivalent static method was applied, which allows to calculate the seismic force at the base and its distribution on the height of the structure. The results obtained show the efficiency of soil densification on the seismic response of MDOF frames.

Effect of Soil–Structure Interaction on Nonlinear Dynamic Response of Reinforced Concrete Structures

2020 ◽  
Vol 20 (13) ◽  
pp. 2041013
Author(s):  
Christos Mourlas ◽  
Neo Khabele ◽  
Hussein A. Bark ◽  
Dimitris Karamitros ◽  
Francesca Taddei ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Dynamic Loading ◽  
Nonlinear Dynamic ◽  
Soil Structure ◽  
Soil Structure Interaction ◽  
Nonlinear Dynamic Response ◽  
Rc Structures ◽  
Structure Interaction ◽  
Fixed Base ◽  
Dynamic Loading Conditions

Investigating the nonlinear dynamic response of reinforced concrete (RC) structures is of significant importance in understanding the expected behavior of these structures under dynamic loading. This becomes more crucial during the design of new or the assessment of the existing RC structures that are located in seismically active areas. The numerical simulation of this problem through the use of detailed 3D modeling is still a subject that has not been investigated thoroughly due to the significant challenges related to numerical instabilities and excessive computational demand, especially when the soil–structure interaction (SSI) phenomenon is accounted for. This study aims at presenting a nonlinear simulation tool to investigate this numerically cumbersome problem in order to provide further inside into the SSI effect on RC structures under nonlinear dynamic loading conditions. A detailed 3D numerical model of full-scale RC structures considering the SSI effect through modeling the nonlinear frame and soil domain is performed and discussed herein. The constructed models are subjected to dynamic loading conditions and an elaborate investigation is presented considering different type of structures, material properties of soil domains and depths. The RC structures and the soil domains are modeled through 8-noded hexahedral isoparametric elements, where the steel bar reinforcement of concrete is modeled as embedded beam and truss finite elements. The Ramberg–Osgood constitutive law was used for modeling the soil domain. It was shown that the SSI effect can significantly increase the flexibility of the system, altering the nonlinear dynamic response of the RC frames causing local damages that are not observed when the fixed-base model is analyzed. Furthermore, it was found that the structures founded on soft soil developed larger base-shear compared to the fixed-base model which is attributed to resonance phenomena connected to the SSI effect and the imposed accelerograms.

scholarly journals Dynamic Analysis of Partially Embedded Structures Considering Soil-Structure Interaction in Time Domain

2011 ◽  
Vol 2011 ◽  
pp. 1-23 ◽  
Author(s):  
Sanaz Mahmoudpour ◽  
Reza Attarnejad ◽  
Cambyse Behnia
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Response ◽  
Time Domain ◽  
Soil Structure ◽  
Soil Structure Interaction ◽  
Structure System ◽  
Structure Interaction ◽  
Scaled Boundary Finite Element ◽  
Element Method

Analysis and design of structures subjected to arbitrary dynamic loadings especially earthquakes have been studied during past decades. In practice, the effects of soil-structure interaction on the dynamic response of structures are usually neglected. In this study, the effect of soil-structure interaction on the dynamic response of structures has been examined. The substructure method using dynamic stiffness of soil is used to analyze soil-structure system. A coupled model based on finite element method and scaled boundary finite element method is applied. Finite element method is used to analyze the structure, and scaled boundary finite element method is applied in the analysis of unbounded soil region. Due to analytical solution in the radial direction, the radiation condition is satisfied exactly. The material behavior of soil and structure is assumed to be linear. The soil region is considered as a homogeneous half-space. The analysis is performed in time domain. A computer program is prepared to analyze the soil-structure system. Comparing the results with those in literature shows the exactness and competency of the proposed method.

Effects of Slenderness and Fundamental Frequency on the Dynamic Response of Adjacent Structures

2019 ◽  
Vol 19 (09) ◽  
pp. 1950105
Author(s):  
Gonzalo Barrios ◽  
Vinuka Nanayakkara ◽  
Pramodya De Alwis ◽  
Nawawi Chouw
Keyword(s):  
Dynamic Response ◽  
Fundamental Frequency ◽  
Soil Structure ◽  
Numerical Models ◽  
Ground Motions ◽  
Soil Structure Interaction ◽  
Reference Case ◽  
Maximum Acceleration ◽  
Structure Interaction ◽  
Adjacent Structures

In conventional seismic design, the structure is often assumed to be fixed at the base. However, this assumption does not reflect reality. Furthermore, if the structure has close neighbors, the adjacent structures will alter the response of the structure considered. Investigations on soil–structure interaction and structure–soil–structure interaction have been performed mainly using numerical models. The present work addresses the dynamic response of adjacent single-degree-of-freedom models on a laminar box filled with sand. Impulse loads and simulated ground motions were applied. The standalone condition was also studied as a reference case. Models with different fundamental frequencies and slenderness were considered. Results from the impulse tests showed that the top displacement of the models with an adjacent structure was reduced compared with that of the standalone case. Changes in the fundamental frequency of the models due to the presence of an adjacent model were also observed. Results from ground motions showed amplification of the maximum acceleration and the top displacement of the models when both structures have a similar fundamental frequency.

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