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.

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.

An Optimum Tuning Application of Mass Dampers Considering Soil-Structure Interaction

2018 ◽  
pp. 44-73
Author(s):  
Gebrail Bekdaş ◽  
Sinan Melih Nigdeli
Keyword(s):  
Optimum Design ◽  
Soil Structure ◽  
Damping Ratio ◽  
Harmony Search ◽  
Soil Structure Interaction ◽  
Tuned Mass Dampers ◽  
Maximum Displacement ◽  
Structure Interaction ◽  
High Rise ◽  
Design Variables

In order to obtain a significant reduction for seismic responses of structures using tuned mass dampers (TMDs), optimization is a mandatory process. A music-inspired metaheuristic algorithm called harmony search is employed in the proposed method for optimum design of TMDs implemented on structures considering soil-structure interaction (SSI). The present approach considers time domain analyses conducted for several earthquake excitations. The optimum design variables, such as mass, period, and damping ratio of TMD are searched for an optimization objective (the maximum displacement of structure) and a design constraint (the maximum scaled stroke capacity of TMD). The proposed method was investigated with a 40-storey high-rise structure for different soil characteristics and the optimum results were compared with a previously developed metaheuristic approach. Results show that the proposed method is feasible and more effective than the compared method.

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.

Seismic response of sands in centrifuge tests

2008 ◽  
Vol 45 (4) ◽  
pp. 470-483 ◽  
Author(s):  
Mohammad H.T. Rayhani ◽  
M. Hesham El Naggar
Keyword(s):  
Shear Modulus ◽  
Seismic Response ◽  
Soil Structure ◽  
Site Response ◽  
Damping Ratio ◽  
Soil Structure Interaction ◽  
Response Analysis ◽  
Structure Interaction ◽  
Centrifuge Tests ◽  
Seismic Site Response

Seismic site response of sandy soils and seismic soil–structure interaction are investigated using an electrohydraulic earthquake simulator mounted on a centrifuge container at an 80g field. The results of testing uniform and layered loose to medium-dense sand models subjected to 13 simulated earthquakes on the centrifuge are presented. The variation of shear modulus and damping ratio with shear strain amplitude and confining pressure was evaluated and their effects on site response were assessed. The evaluated shear modulus and damping ratio agreed reasonably with laboratory tests and empirical relationships. Site response analysis using the measured shear wave velocity and estimated modulus reduction and damping ratio as input parameters produced good agreement with the measured site response. The effect of soil–structure interaction for structures situated on dry sand is also investigated. These tests have revealed many important insights with regard to the characteristics of seismic site response and seismic soil–structure behaviour. The tests showed that the seismic response of soil deposits, input motions, and overall behaviour of the structure are affected by soil stratification. The results showed that the seismic kinematic soil–structure interaction is not very significant for structures situated on loose sand.

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.

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