Effects of Soil-Structure Interaction, Damping and Higher Modes on the Response of a Mid-Story-Isolated Structure Founded on Multiple Soil Layers

2014 ◽  
Author(s):  
Chong-Shien Tsai ◽  
Hui-Chen Su
Keyword(s):  
Soil Structure ◽  
Mechanical Impedance ◽  
Soil Structure Interaction ◽  
Entire System ◽  
Soil Layers ◽  
Higher Modes ◽  
Closed Form Solutions ◽  
Structure Interaction ◽  
Fixed Base ◽  
Beam Type

This paper focuses on investigating the effects of soil-structure interaction (SSI), higher modes, and damping on the response of a mid-story-isolated structure founded on multiple soil layers overlying bedrock. Closed-form solutions were obtained for the entire system, which consists of a shear beam type superstructure, seismic isolator, and multiple soil layers overlying bedrock, while subjected to ground motion. The proposed formulations simplify the problem in terms of well-known frequency and mechanical impedance ratios that can take into account the effects of SSI, higher modes, and damping in the entire system, and be capable of explicitly interpreting the major dynamic behavior of a mid-story-isolated structure interacting with the multiple soil layers overlying bed rock. The SSI effects on the dynamic response of a mid-story-isolated structure as a result of multiple soil layers overlying bedrock were extensively investigated through a series of parametric studies and physically explained by virtue of derived formulations. In addition, the results of numerical exercises show that higher damping provided by the isolator may provoke higher mode response of the superstructure; that the lower structure below the isolator may have significantly larger deformations compared to those of the upper structure above the isolator; and that isolator displacements may be amplified by the SSI effects while compared to those of mid-story-isolated structures with fixed-base.

Investigation of Soil-Structure Interaction and Higher-Mode Effects on Dynamic Response of Base-Isolated Structure Founded on Half Space

2013 ◽  
Author(s):  
C. S. Tsai ◽  
H. C. Su
Keyword(s):  
Closed Form ◽  
Soil Structure ◽  
Dynamic Responses ◽  
Soil Structure Interaction ◽  
Entire System ◽  
Higher Mode Effects ◽  
Closed Form Solutions ◽  
Structure Interaction ◽  
Mode Effects ◽  
Isolated Structures

This paper attempts to investigate the effects of soil-structure interaction (SSI) and higher modes on the dynamic responses of base-isolated structures through closed-form solutions for a superstructure, seismic isolator, and soil system under various conditions, comprising the cases of rigid and half-space foundations. The proposed system considers continuum media for both the superstructure and soil foundation, which can take the effects of higher modes into account, along with a discontinuous layer with a governing equation that interprets the mechanical behavior of the base-isolation system. Then, the closed-form solutions in terms of well-known frequency and impedance ratios under various conditions of soil foundations were obtained through rigorous mathematical derivations and validations by collapsing the entire system to a single degree-of-freedom system in structural dynamics and well-known cases of wave propagation in elastic solids. The closed-form solutions derived in this study explicitly revealed the characteristics of the SSI and higher mode effects in influencing the seismic behavior of base-isolated structures. Furthermore, the SSI effects on the dynamic responses of the entire system were extensively evaluated. The conclusive results of this paper will be useful for understanding the SSI and higher mode effects on the dynamic responses of base-isolated structures.

Effects of Soil-Structure Interaction on the Response of a Structure With Tuned Mass Dampers

2015 ◽  
Author(s):  
Chong-Shien Tsai ◽  
Hui-Chen Chen
Keyword(s):  
Soil Structure ◽  
Damping Ratio ◽  
Excitation Frequency ◽  
Soil Structure Interaction ◽  
Entire System ◽  
Mass Ratio ◽  
Tuned Mass Dampers ◽  
Soil Layers ◽  
Structure Interaction ◽  
Multiple Tuned Mass Dampers

This paper aims at examining the effects of soil-structure interaction (SSI) on the response of a structure which is equipped with multiple tuned mass dampers (MTMD) and founded on multiple soil layers overlying bedrock. Closed-form solutions have been obtained for the entire system, which consists of a shear beam type superstructure, multiple tuned mass dampers, and multiple soil layers overlying bedrock, while subjected to ground motion. The proposed formulations simplify the problem in terms of well-known frequency ratios, mechanical impedance and mass ratio, which can take into account the effects of SSI, mass ratio of the MTMD at each excitation frequency and damping ratio in the entire system. These formulations are capable of explicitly interpreting the major dynamic behavior of a structure equipped with multiple tuned mass dampers and interacting with the multiple soil layers overlying bed rock. The SSI effects on the dynamic response of a tuned-mass-damped structure as a result of multiple soil layers overlying bedrock were extensively investigated through a series of parametric studies.

Study of Pushover Analysis on RC Framed Structure with Underground Structure Considering the Effects of Soil Structure Interaction

2020 ◽  
Vol 8 ◽  
pp. 22-29
Author(s):  
Nasala Dongol ◽  
Prachand Man Pradhan ◽  
Suman Manandhar
Keyword(s):  
Soil Structure ◽  
Response Spectrum ◽  
Underground Structure ◽  
Pushover Analysis ◽  
Standard Penetration Test ◽  
Soil Structure Interaction ◽  
Base System ◽  
Building Site ◽  
Structure Interaction ◽  
Fixed Base

This study states that the effects of soil structure interaction on the Reinforced Concrete (RC) framed structures is directly influenced by the soil properties of the site. Here, one preexisting structure is taken for the study. The building is a hospital building with two underground basements. Taking into account the actual soil condition of building site, this study provides idea on the soil structure interaction on the structure The properties of springs are calculated from different standard penetration test (SPT) values, Poisson’s ratio and elasticity of soil along the depth of the soil. Entire soil-foundation-structure system is modelled and analyzed using spring approach. Static analysis, response spectrum analysis and pushover analysis (PA) are done in order to find the variations in natural periods, base shears and deflections of the structures by incorporating soil flexibility as compared to structures with conventional fixed base. Pushover analysis is done to evaluate the performance of the structure when modelled in fixed base and spring base system.

scholarly journals Effect of Soil-Structure Interaction on the Seismic Response of Existing Low and Mid-Rise RC Buildings

2020 ◽  
Vol 10 (23) ◽  
pp. 8357
Author(s):  
Ibrahim Oz ◽  
Sevket Murat Senel ◽  
Mehmet Palanci ◽  
Ali Kalkan
Keyword(s):  
Seismic Response ◽  
Seismic Performance ◽  
Soil Structure ◽  
Soft Soil ◽  
Soil Structure Interaction ◽  
Soil Conditions ◽  
Existing Buildings ◽  
Structure Interaction ◽  
Fixed Base ◽  
New Buildings

Reconnaissance studies performed after destructive earthquakes have shown that seismic performance of existing buildings, especially constructed on weak soils, is significantly low. This situation implies the negative effects of soil-structure interaction on the seismic performance of buildings. In order to investigate these effects, 40 existing buildings from Turkey were selected and nonlinear models were constructed by considering fixed-base and stiff, moderate and soft soil conditions. Buildings designed before and after Turkish Earthquake code of 1998 were grouped as old and new buildings, respectively. Different soil conditions classified according to shear wave velocities were reflected by using substructure method. Inelastic deformation demands were obtained by using nonlinear time history analysis and 20 real acceleration records selected from major earthquakes were used. The results have shown that soil-structure interaction, especially in soft soil cases, significantly affects the seismic response of old buildings. The most significant increase in drift demands occurred in first stories and the results corresponding to fixed-base, stiff and moderate cases are closer to each other with respect to soft soil cases. Distribution of results has indicated that effect of soil-structure interaction on the seismic performance of new buildings is limited with respect to old buildings.

Seismic behavior of structures considering uplift and soil–structure interaction

2017 ◽  
Vol 20 (11) ◽  
pp. 1712-1726
Author(s):  
Farhad Behnamfar ◽  
Seyyed Mohammad Mirhosseini ◽  
Hossein Alibabaei
Keyword(s):  
Seismic Behavior ◽  
Soil Structure ◽  
Nonlinear Dynamic Analysis ◽  
Steel Structures ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Nonlinear Seismic Response ◽  
Tensile Forces ◽  
Fixed Base ◽  
Flexible Base

A common assumption when analyzing a structure for earthquake forces is that the building is positively attached to a rigid ground so that it can sustain possible tensile forces without being detached, or uplifted, from its bearing points. Considering the facts that almost no tension can be transferred between a surface foundation and soil and soft soils interact with the supported structure during earthquakes, in this research, the effects of uplift and soil–structure interaction on nonlinear seismic response of structures are evaluated. Several reinforced concrete and steel structures under different suits of consistent ground motions are considered. The base of the buildings is modeled with vertical no-tension springs being nonlinear in compression. The total soil–structure interaction system is modeled within OpenSees, and the seismic behavior is evaluated using a nonlinear dynamic analysis. The nonlinear responses of buildings are determined and compared between three cases: fixed base, flexible base without uplift, and flexible base with uplift. The cases for which uplift in conjunction with soil–structure interaction should be considered are identified.

Probabilistic Seismic Soil Structure Interaction Analysis of the Mu¨hleberg Nuclear Power Plant Reactor and SUSAN Buildings

2010 ◽  
Author(s):  
David K. Nakaki ◽  
Philip S. Hashimoto ◽  
James J. Johnson ◽  
Yahya Bayraktarli ◽  
Olivier Zuchuat
Keyword(s):  
Power Plant ◽  
Nuclear Power ◽  
Soil Structure ◽  
Response Spectra ◽  
Soil Structure Interaction ◽  
Response Analysis ◽  
Structure Interaction ◽  
Fixed Base ◽  
Plant Reactor ◽  
Stiffness And Damping

Probabilistic seismic soil-structure interaction (SSI) analysis was performed for the Mu¨hleberg Nuclear Power Plant Reactor and SUSAN Buildings in support of the seismic probabilistic saftety assessment of the plant. An efficient hybrid method, employing computer programs SASSI2000 and CLASSI presented in a companion paper, was used in this analysis. The method takes advantage of the capability of SASSI2000 to analyze embedded structures with irregular geometry and the computational efficiency of CLASSI to rapidly perform the SSI response analysis of large structure models. Fixed base finite element models of the buildings were first developed from which the structure geometry, nodal masses, natural frequencies, and mode shapes were extracted. The structure embedments were modeled using SASSI2000. Impedance functions and scattering vectors were calculated by imposing rigid body constraints to the embedded foundation. The fixed base structure dynamic properties and the foundation impedances and scattering functions were input to CLASSI to perform the response analysis. The probabilistic analysis was performed following the Latin Hypercube Simulation (LHS) approach documented in NUREG/CR-2015. Variables defined by probability distributions were sampled according to a stratified sampling approach. The combination of the parameters for each simulation was determined by Latin Hypercube experimental design. Variables in the LHS included the earthquake ground acceleration time histories, structure stiffness and damping, and soil stiffness and damping. Thirty response simulations were performed using CLASSI in which the variable values were randomly selected. The use of CLASSI has the advantage that the response analysis simulations can be executed in a fraction of the time that would be required with SASSI2000 alone. For each simulation, in-structure response spectra (ISRS) were calculated at selected locations in the buildings. Probabilistic distributions, described by the median and 84th percentile response spectra, were calculated from the thirty simulations. The probabilistic ISRS are subsequently used in the seismic fragility evaluations of selected essential equipment.

scholarly journals ON APPLICATION OF COMBINED PILE-RAFT FOUNDATIONS FOR ROAD STRUCTURES

2020 ◽  
Author(s):  
Steffen Leppla ◽  
Arnoldas Norkus
Keyword(s):  
Soil Structure ◽  
Soft Soil ◽  
Structure Design ◽  
Bridge Engineering ◽  
Soil Structure Interaction ◽  
Design Solution ◽  
Natural Soil ◽  
Soil Layers ◽  
Structure Interaction ◽  
Raft Foundations

Roads and road infrastructure systems are designed to satisfy ultimate and serviceability conditions under long-term actions caused by transport loadings and environmental effects. Selected design solutions must be safe and rational in terms of construction and maintenance costs. In cases when weak or soft soil layers of natural soil profiles are shallow and/or the traffic loads are very large, the Combined Pile-Raft Foundation (CPRF) is the economical road and railway structure design solution. Application of CPRF is cheaper geotechnical solution comparing with soil change or usual piled foundation alternatives. The development of this system is based on the analysis of relevant mechanical properties of soil layers and the evaluation of the soil-structure interaction. The soil-structure interaction is of highest importance allowing proper evaluation of load bearing resistance and deformation transmitted by raft and piles to soil layers. The soil and foundation system usually is subjected by loadings, resulting elastic-plastic resistance range. Therefore, relevant nonlinear physical laws due to the stress levels are used. The paper purpose is summarizing the experience of application of Combined Pile-Raft Foundations used in road and railway construction and bridge engineering.

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.

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