Papers by Keyword: Soil-Structure Interaction (SSI)

Abstract: Following the nuclear power plant accident in Fukushima Japan, seismic capacity evaluation has become a crucial issue in combination building safety. Condensate storage tanks are designed to supplies water to the condensate transfer pumps, the control rod drive hydraulic system pumps, and the condenser makeup. A separate connection to the condensate storage tank is used to supply water for the high pressure coolant injection system, reactor core isolation cooling system, and core spray system pumps. A condensate storage tank is defined as a seismic class I structure, playing the important role of providing flow to the operational system and the required static head for the suction of the condensate transfer pumps and the normal supply pump. According to the latest nuclear safety requirements, soil structure interaction must be considered in all seismic analyses. This study aims to rebuild the computer model of condensate storage tanks in Taiwan using the SAP 2000 program in conjunction with the lumped mass stick model and to evaluate the soil structure interaction by employing the SASSI 2000 program. The differences between the results with the soil structure interaction and spring model are compared via natural frequency and response spectrum curves. This computer model enables engineers to rapidly evaluate the safety margin of condensate storage tank following the occurrence of earthquakes or tsunamis.

Abstract: This paper presents an auto-mesh generation technique using KIESSI (KAIST Infinite Elements for Soil-Structure Interaction) of near field zone for soil-structure interaction analysis (SSI). The working principle of KIESSI is based on coupled three dimensional finite element-infinite element methodology. Also, KIESSI is based on finite element method (FEM) for structure and near-field soil medium and infinite element method for layered half-space far-field. This study utilizes the auto mesh generation technique of near field zone on KIESSI package. The verification example for the effectiveness of automatically meshing technique may be shown through a compliance analysis of layered surface footing. For application example, seismic response analysis at a typical nuclear power plant is carried out in consideration of SSI. The obtained floor response spectrum results in good agreement as compared with the measured response data and the results from SSI analysis package such as SASSI (A System for Analysis of Soil-Structure Interaction).

Abstract: Two geotechnical centrifuge model tests of a soil-structure system with different burial depths are performed to investigate the interaction between soil and structure. The tests are performed at 50 gravitational centrifuge accelerations and the input motion is Kobe wave. This paper focuses on the accelerations and displacements in the soil-structures system. The peak accelerations and displacements along the axis of the structure and along the vertical line 17cm away from the axis are presented. The acceleration and displacement response due to the interaction between soil and structure are studied.

Abstract: An analytical approach based on branch mode method is formulated in this paper to study the dynamic response of eccentric structure considering soil-structure interaction The superstructure branch and foundation soil branch are coupled through mode aggregation procedure. The computational scale of system equations decreases to an acceptable level. Sample analysis indicate that the seismic response of eccentric structure increases first and then decreases with the decreasing of stiffness of soil-foundation system, which is affected by the inertia effect of foundation branch. For the soft soil case, the influence of SSI effect is more intensive that the trends of transfer function curves are fundamentally changed comparing to the results of other foundation conditions.

Abstract: To investigate the seismic response of long-span rigid frame bridges with high-pier, the shaking table test of a 1/10 scaled rigid frame bridge model is introduced in this paper. Details about test equipment, model design, test arrangement, input ground motion waves and test principle are provided. The response of bridge model under the seismic excitation included the uniform excitation and the multi-support excitation is observed. The influence of the soil-structure interaction on the bridge is considered through the real-time dynamic hybrid testing method. The impact effect for different ground motion input during the test is discussed. The influence of multi-support excitation, soil-structure interaction and impact effect on structural seismic responses are studied based on the test results. The isolation effectiveness and the damping effect are discussed as well.

Abstract: This paper presents an accurate analytical method to obtain the rocking impedance function of a surface-supported strip foundation. The Green’s functions of the elastic half-space under concentrated or uniform loads with infinite length are derived and an elaborate integration method is used to calculate the multi-value improper integral. The interface between the foundation and the supporting medium is divided into a number of strip units. The rocking impedance function is solved by adding the moments in every strip, based on the fact that the vertical displacement of each unit can be uniquely determined by the rotation amplitude of the rigid foundation. Excellent convergence has been observed. Comparing the numerical results to those obtained by the thin layer method, good agreements are achieved. Finally, the effect of the Poisson’s ratio on the rocking impedance function of the strip foundation is discussed in detail.

Abstract: Based on the theory of soil-structure interaction, the underground structure and surrounding soil as a system, and the finite element analysis model is established, and finite element dynamic analysis method is implemented, the three seismic acceleration time history of the different spectrum characteristics is inputted, the seismic effect on the surrounding ground of underground structure is analyzed. The results show that the effect on dynamic response is the limited range and not significant, when seismic design of structures on the surrounding sites is implemented, additional dynamic response on surrounding sites does not need to consider.

Abstract: A new analytical method for the analysis of interactions between the superstructure and foundation and foundation soil of a tall building is formulated. The computational model of a structural system and its foundation are simplified equivalently and continuously into a three-dimensional model, a combination of thin-walled tubes on a semi-infinite elastic subgrade. The various stiffness coefficients for evaluating elastic strain energy stored in foundation soil are as well derived by using the principle of energy equivalency. Some satisfying conclusions are obtained by the interaction analysis for the tube-in-tube structural system adopted by Guangdong Guomao Building.

Abstract: In this paper, the subway station structure seismic response of large-scale three-dimensional shaking table model test is analysis, the model system acceleration response time, the stress response of the model structure of the schedule and structure of the surface of the earth pressure time is obtained, which has been the subway underground structure seismic response of the general law, the conclusion can provide a reliable basis and guidance for the seismic design of the MTR underground structures in the general venue.

Abstract: A simple pseudo-dynamic method to predict the seismic rotational displacement of retaining wall is developed. The proposed method, which soil-structure interaction is considered, is a combination of the free-field seismic response of soil and pseudo-dynamic method. It is supposed that soil and structure is connected by a series of springs, the dynamic earth pressure is determined by the deformation of springs. So both active and passive conditions can be taken into account by means of different movement direction of retaining wall, no need to know whether active or passive earth pressure happens before analysis. A significant difference between this analysis and published method is that in the present analysis the time dependent process of earth pressure and displacement is obtained by iterative calculation. Although present analysis is limit to elastic state, comparisons with Mononobe-Okabe method show satisfactory agreement in the value of resultant forces acting on retaining wall. Moreover, it is revealed by numerical examples that the height of the resultant force from the base of the wall is underestimated by the Mononobe- Okabe method, this may cause unsafe factors. Furthermore, the effect of wide range of parameters like time, height of retaining wall, wall friction, horizontal and vertical seismic coefficients are taken into account to evaluate the seismic response of retaining wall. Apart from its intrinsic theoretical interest, the proposed analysis can be used for the assessment of the safety of retaining wall under seismic condition.