• Earthquakes and Structures
• /
• v.12 no.4
• /
• pp.469-478
• /
• 2017

This paper summarizes estimated seismic response results from three-dimensional nonlinear inelastic time-history analyses of some steel buckling-restrained braced (BRB) structures taking into account soil-structure interaction (SSI). The response results involve mean values for peak interstorey drift ratios, peak interstorey residual drift ratios and peak floor accelerations. Moreover, mean seismic demands in terms of axial force and rotation in columns, of axial and shear forces and bending moment in BRB beams and of axial displacement in BRBs are also discussed. For comparison purposes, three separate configurations of the BRBs have been considered and the aforementioned seismic response and demands results have been obtained firstly by considering SSI effects and then by neglecting them. It is concluded that SSI, when considered, may lead to larger interstorey and residual interstorey drifts than when not. These drifts did not cause failure of columns and of the BRBs. However, the BRB beam may fail due to flexure.

• Structural Engineering and Mechanics
• /
• v.69 no.6
• /
• pp.699-712
• /
• 2019

A cable-stayed bridge (CSB) is one of the most complicated structures, especially when subjected to earthquakes and taking into consideration the effect of soil-structure-interaction (SSI). A CSB of a 500 m mid-span was modeled by the SAP2000 software and was subjected to four different earthquakes. To mitigate the harmful effect of the vibration generated from each earthquake, four mitigation schemes were used and compared with the non-mitigation model to determine the effectiveness of each scheme, when applying on the SSI or fixed CSB models. For earthquake mitigation, tuned mass damper (TMD) systems and spring dampers with different placements were used to help reduce the seismic response of the CBS model. The pylons, the mid-span of the deck and the pylon-deck connections are the best TMDs and spring dampers placements to achieve an effective reduction of the earthquake response on such bridges.

• Earthquakes and Structures
• /
• v.25 no.2
• /
• pp.99-112
• /
• 2023

This paper investigates the influences of Soil-Structure Interaction (SSI) on the seismic behavior of two-dimensional reinforced concrete moment-resisting frames subjected to Far-Field Ground Motion (FFGM) and Near-Field Ground Motion (NFGM). For this purpose, the nonlinear modeling of 7, 10, and 15-story reinforced concrete moment resisting frames were developed in Open Systems for Earthquake Engineering Simulation (OpenSees) software. Effects of SSI were studied by simulating Beam on Nonlinear Winkler Foundation (BNWF) and the soil type as homogenous medium-dense. Generally, the building resistance to seismic loads can be explained in terms of Incremental Dynamic Analysis (IDA); therefore, IDA curves are presented in this study. For comparison, the fragility evaluation is subjected to NFGM and FFGM as proposed by Quantification of Building Seismic Performance Factors (FEMA P-695). The seismic performance of Reinforced Concrete (RC) buildings with fixed and flexible foundations was evaluated to assess the probability of collapse. The results of this paper demonstrate that SSI and NFGM have significantly influenced the probability of failure of the RC frames. In particular, the flexible-base RC buildings experience higher Spectral acceleration (Sa) compared to the fixed-base ones subjected to FFGM and NFGM.

• Geomechanics and Engineering
• /
• v.16 no.5
• /
• pp.527-538
• /
• 2018

The study on the performance of the nonlinear friction tuned mass dampers (FTMD) for the mitigation of the seismic responses of the structures is a topic that still inspires the efforts of researchers. The present paper aims to carry out a numerical study on the optimum tuning of TMD and FTMD parameters using a multi-objective particle swarm optimization (MOPSO) algorithm including soil-structure interaction (SSI) effects for seismic applications. Considering a 3-story structure, the performances of the optimized TMD and FTMD are compared with the uncontrolled structure for three types of soils and the fixed base state. The simulation results indicate that, unlike TMDs, optimum tuning of FTMD parameters for a large preselected mass ratio may not provide a best and optimum design. For low mass ratios, optimal selection of friction coefficient has an important key to enhance the performance of FTMDs. Consequently, a free parameter search of all FTMD parameters provides a better performance in comparison with considering a preselected mass ratio for FTMD in the optimum design stage of the FTMD. Furthermore, the SSI significant effects on the optimum design of the TMD and FTMD. The simulation results also show that the FTMD provides a better performance in reducing the maximum top floor displacement and acceleration of the building in different soil types. Moreover, the performance of the TMD and FTMD decrease with increasing soil softness, so that ignoring the SSI effects in the design process may give an incorrect and unrealistic estimation of their performance.

• Earthquakes and Structures
• /
• v.13 no.4
• /
• pp.353-363
• /
• 2017

The present study considers a multi-span continuous bridge, isolated by lead rubber bearing (LRB). Dynamic soilstructure interaction (SSI) is modelled with the help of a simplified, sway-rocking model for different types of soil. It is well understood from the literature that SSI influences the structural responses and the isolator performance. However, the abovementioned effect of SSI also depends on the earthquake ground motion properties. It is very important to understand how the interaction between soil and structure varies with the earthquake ground motion characteristics but, as far as the knowledge of the authors go, no study has been carried out to investigate this effect. Therefore, the objectives of the present study are to investigate the influence of earthquake ground motion characteristics on: (a) the responses of a multi span bridge (isolated and non-isolated), (b) the performance of the isolator and, most importantly, (c) the soil-structure interaction. Statistical analyses are conducted by considering 14 earthquakes which are selected in such a way that they can be categorized into three frequency content groups according to their peak ground acceleration to peak ground velocity (PGA/PGV) ratio. Lumped mass model of the bridge is developed and time history analyses are carried out by solving the governing equations of motion in the state space form. The performance of the isolator is studied by comparing the responses of the bridge with those of the corresponding uncontrolled bridge (i.e., non-isolated bridge). On studying the effect of earthquake motions, it is observed that the earthquake ground motion characteristics affect the interaction between soil and structure in such a way that the responses decrease with increase in frequency content of the earthquake for all the types of soil considered. The reverse phenomenon is observed in case of the isolator performance where the control efficiencies increase with frequency content of earthquake.

• Structural Engineering and Mechanics
• /
• v.55 no.1
• /
• pp.161-189
• /
• 2015

Soil-pile raft-structure interaction is recognized as a significant phenomenon which influences the seismic behaviour of structures. Soil structure interaction (SSI) has been extensively used to analyze the response of superstructure and piled raft through various modelling and analysis techniques. Major drawback of previous study is that overall interaction among entire soil-pile raft-superstructure system considering highlighting the change in design forces of various components in structure has not been explicitly addressed. A recent study addressed this issue in a broad sense, exhibiting the possibility of increase in pile shear due to SSI. However, in this context, relative stiffness of raft and that of pile with respect to soil and length of pile plays an important role in regulating this effect. In this paper, effect of relative stiffness of piled raft and soil along with other parameters is studied using a simplified model incorporating pile-soil raft and superstructure interaction in very soft, soft and moderately stiff soil. It is observed that pile head shear may significantly increase if the relative stiffness of raft and pile increases and furthermore stiffer pile group has a stronger effect. Outcome of this study may provide insight towards the rational seismic design of piles.

• Earthquakes and Structures
• /
• v.7 no.2
• /
• pp.233-250
• /
• 2014

In this paper, a three dimensional soil-structure interaction (SSI) is numerically simulated using finite element method in order to analyse the foundation moments in annular raft of tall slender chimney structures incorporating the effect of openings in the structure and the effect of soil flexibility, when the structure-soil system is subjected to El Centro (1940) ground motion in time domain. The transient dynamic analysis is carried out using LS-DYNA software. The linear ground response analysis program ProShake has been adopted for obtaining the ground level excitation for different soil conditions, given the rock level excitation. The radial and tangential bending moments of annular raft foundation obtained from this SSI analysis have been compared with those obtained from conventional method according to the Indian standard code of practice, IS 11089:1984. It is observed that tangential and radial moments increase with the increase in flexibility of soil. The analysis results show that the natural frequency of chimney decreases with increase in supporting soil flexibility. Structural responses increase when the openings in the structure are also considered. The purpose of this paper is to propose the need for an accurate evaluation of the soilstructure interaction forces which govern the structural response.

• Interaction and multiscale mechanics
• /
• v.6 no.4
• /
• pp.339-356
• /
• 2013

This paper investigates the optimized parameters of Tuned Mass Dampers (TMDs) for vibration control of high-rise structures including Soil Structure Interaction (SSI). The Artificial Bee Colony (ABC) method is employed for optimization. The TMD Mass, damping coefficient and spring stiffness are assumed as the design variables of the controller; and the objective is set as the reduction of both the maximum displacement and acceleration of the building. The time domain analysis based on Newmark method is employed to obtain the displacement, velocity and acceleration of different stories and TMD in response to 6 types of far field earthquakes. The optimized mass, frequency and damping ratio are then formulated for different soil types; and employed for the design of TMD for the 40 and 15 story buildings and 10 different earthquakes, and well results are achieved. This study leads the researchers to the better understanding and designing of TMDs as passive controllers for the mitigation of earthquake oscillations.

• Earthquakes and Structures
• /
• v.13 no.6
• /
• pp.573-588
• /
• 2017

The earthquake input is required when the soil-structure interaction (SSI) analysis is performed by the direct finite element method. In this paper, the earthquake is considered as the obliquely incident plane body wave arising from the truncated linearly elastic layered half space. An earthquake input method is developed for the time-domain three-dimensional SSI analysis. It consists of a new site response analysis method for free field and the viscous-spring artificial boundary condition for scattered field. The proposed earthquake input method can be implemented in the process of building finite element model of commercial software. It can result in the highly accurate solution by using a relatively small SSI model. The initial condition is considered for the nonlinear SSI analysis. The Daikai subway station is analyzed as an example. The effectiveness of the proposed earthquake input method is verified. The effect of the obliquely incident earthquake is studied.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.10a
• /
• pp.137-146
• /
• 1999

The SSI(Soil-Structure Interaction) analyses are being performed for the KNGR(Korean Next Generation Reactor) design because the KNGR is developed as a standard nuclear power plant concept enveloping various soil conditions. the SASSI program which adopts the flexible volume method is used for the SSI analyses. The soil curves used in the three dimensional SSI analyses of KNGR Nuclear Island(NI) structures are based on the upper bound shear modulus curve and lower bound damping degradation on SSI response the average shear modulus curve with average damping curve was used for two soil cases. This study presents the results of the variances by using different soil nonlinearity parameters based on the paametric SSI analyses. The results include the maximum member forces(shear and axial force) at the base of the NI structures and the 5% damping Floor Response Spectra (FRS) at some representative locations at the top of the NI superstructures. They are also compared together with the enveloped SSI results for eight soil cases and fixed-base analysis for rock case by using two control motions.