Investigation of Soil Structure Interaction and Wall Flexibility Effects on Natural Sloshing Frequency of Vessels

The main purpose of this study is to establish the effects of vessel walls flexibility on its natural sloshing frequency considering soil-structure-fluid interaction theory. Furthermore, two new efficiently relations to find both of wall flexibility and soil-structure interaction effects on natural frequency are developed. Regarding the aim of current study three different conditions of elevated tanks are applied. Fixed base condition with an emphasis on recommendations of international code ACI-350, analytical FSSI regarding equivalent mass spring method, and the numerical direct method regarding theory of finite element are taken into consideration. Results indicate that there is no significant effect of walls flexibility on natural sloshing frequency regarding fixed base assumptions of vessels. On the contrary, significant effects of wall flexibility are achieved considering SSI theory. Results of international code ACI-350 show that, the international codes assumptions have imprecise estimations of natural sloshing frequency in the range of hard to very soft soil categories. On the other hand, it is observed that the wall flexibility has a more highlighted effect on natural frequency in soft soils rather than soil-structure interaction. The significance of wall flexibility effect on natural frequency is more than that of SSI considering soil softening.

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

Applied Sciences ◽

10.3390/app10238357 ◽

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.

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Seismic analysis of a highway bridge considering soil-structure interaction effects

Bulletin of the New Zealand Society for Earthquake Engineering ◽

10.5459/bnzsee.12.4.305-313 ◽

1979 ◽

Vol 12 (4) ◽

pp. 305-313

Author(s):

Toshio Iwasaki ◽

Kazuhiko Kawashima

Keyword(s):

Seismic Response ◽

Natural Frequency ◽

Soil Structure ◽

Soft Soil ◽

Ground Surface ◽

Highway Bridges ◽

Interaction Effects ◽

Soil Structure Interaction ◽

Structure Interaction ◽

Fundamental Natural Frequency

In analyzing seismic behaviour of highway bridges constructed on soft soil deposits, it is important to take account of soil-structure interaction effects. In this paper, seismic response of a bridge pier-foundation is investigated based on earthquake acceleration records measured simultaneously on the pier crest and on the ground surface near that bridge. Four motions were used in the analysis, i.e., two were induced by two earthquakes with magnitudes of 7.5 and 6.6, respectively; and two by their aftershocks. In the former two earthquakes, the maximum accelerations were 186 and 438 gals on the ground surface, and 310 and 230 gals on the pier top, respectively. Analyses of frequency characteristics of the motions showed that the predominant frequencies of pier-foundation were always approximately identical with the fundamental natural frequency of the subsoil. Analyses of micro-tremors measured at the sites revealed that the natural frequency of the pier-foundation system is higher than the fundamental natural frequency of the subsoil. Analytical models were formulated to calculate the seismic response of the pier-foundation assuming the subsoil and pier-foundation to be a shear column model with an equivalent linear shear modulus and an elastically supported beam on the subsoil, respectively. Bedrock motions were computed from the measured ground surface motions and then applied to the bedrock of the analytical model. The seismic responses of pier-foundation were thus calculated and compared with the measured records giving a good agreement.

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Assessment of Soil-Structure Interaction in Seismic Bridge Pier Analysis Using Force and Displacement Based Approaches

Selected Scientific Papers - Journal of Civil Engineering ◽

10.2478/sspjce-2015-0023 ◽

2015 ◽

Vol 10 (2) ◽

pp. 113-126

Author(s):

R N P Singh ◽

Hemant Kumar Vinayak

Keyword(s):

Soil Structure ◽

Seismic Analysis ◽

Soft Soil ◽

Bridge Pier ◽

Soil Structure Interaction ◽

Base Shear ◽

Structure Interaction ◽

Capacity Spectrum ◽

Fixed Base ◽

Displacement Based

Abstract The seismic analysis carried out assuming foundation to be perfectly rigid and bonded to the soil underneath is far from truth and therefore, the soil-structure interaction effect on the dynamic behavior of the bridge pier should be considered. The assessment of soil-structure effect on the design force generated has been estimated using Force based, Capacity Spectrum and Direct Displacement based methods considering fixed and flexible foundations. For this purpose a single cantilever bridge pier of constant diameter with varying heights has been considered for the analysis in different type of soils and earthquake zones. The study has revealed that soil-Structure Interaction index is negative in some cases, especially in soft soil, implying base shear demand being greater than that of fixed base contrary to the traditional views.

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Free Vibration Analysis of Building Considering Soil Structure Interaction

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.857.125 ◽

2016 ◽

Vol 857 ◽

pp. 125-130 ◽

Cited By ~ 1

Author(s):

Thaiba T. Beegam ◽

Tissa Sebastian

Keyword(s):

Soil Structure ◽

Interaction Analysis ◽

Soft Soil ◽

Free Vibration Analysis ◽

Soil Structure Interaction ◽

Soil Stiffness ◽

Structure Interaction ◽

Winkler Model ◽

Fixed Base ◽

Flexible Base

Modeling and design of foundation are always done without considering the effect of stiffness of the soil. In the conventional non-interaction analysis of building frame settlements are calculated without considering the influence of the structural stiffness. Therefore a modeling and interaction analysis of soil structure interaction will help to find soil stiffness and effects of soil structure interaction on structure. In this paper, soil structure interaction analysis of a symmetric space frame of 2 bays in both x and y direction are assessed with SAP 2000 software. The frame is modeled with different storey resting on raft foundation with fixed base and flexible base. Three types of soil, i.e. hard, medium, and soft soil are used for Soil Structure Interaction (SSI) study. MODAL analysis is carried out to illustrate the effects of soil-raft-structure interaction on the response of structures. The Soil is considered as Winkler model and elastic continuum model. The developed methodology is validated with results available in the literature. The effects of SSI on frequency of modal are studied. The comparison is carried out the frame with different base conditions.The frequency of the building was found to be decreased when SSI was considered.

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