•Linear and nonlinear SSSI analyses of buildings using SASSI and LS-DYNA.•Subjectively compared results with observations from centrifuge experiments.•Simulations and experiments predict minimal SSSI ...effects in global response.•However, adjacent restraint can effect nonlinear footing response considerably.
The influence of structure-soil-structure interaction (SSSI) in low- to medium-rise buildings is investigated through numerical simulations, and observations are compared with those from previous studies that analyzed data from a set of centrifuge experiments of similar models. The buildings include a one-story moment-resisting frame building on spread footings and a two-story shear wall building on a basemat. The numerical simulations are performed using the industry-standard, frequency-domain, linear analysis code SASSI, and the time-domain nonlinear finite-element analysis code, LS-DYNA. In LS-DYNA the simulations are performed with and without geometric nonlinearities (gapping, sliding and uplift) to understand their effects on SSSI. Three plan arrangements of the buildings are considered to characterize the influence of relative location on SSSI: (1) an in-plane SSSI (iSSSI) arrangement, in which the two buildings are placed adjacent to each other along a line parallel to the direction of ground shaking, (2) an anti-plane arrangement (aSSSI), in which the two buildings are placed adjacent to each other along a line perpendicular to the direction of ground shaking, and (3) a combined in-plane-anti-plane (cSSSI) arrangement, in which two shear wall buildings are placed at two adjacent sides of the frame building on footings. Results from the numerical simulations in SASSI and LS-DYNA show that SSSI has negligible effect on the global spectral accelerations of the buildings in these arrangements. The numerical simulations agree with experimental observations in this regard. Numerical investigations into the SSSI response of the frame building on footings placed adjacent to a deep basement show that the presence of the deep basement reduces uplift in the footings and results in smaller peak spectral accelerations at the roof, underscoring the potential importance of geometric nonlinearities (gapping, sliding and uplift) in SSSI and foundation design.
•Cross-platform implementation of advanced models of elastomeric seismic isolation bearings in OpenSees, ABAQUS, and LS-DYNA.•Capabilities and limitations of user elements in three software ...platforms.•Implementation of a framework for verification and validation of numerical models for seismic isolators.•Discussion on the limitation of the isolator models and error quantification.•Estimation of the parameters of the mathematical model of elastomeric bearings in tension.
Stable inelastic response of seismic isolation bearings is key to the successful performance of base isolated nuclear structures, buildings and bridges. Since full-scale isolated nuclear structures (and buildings) cannot be tested for extreme earthquakes on simulators because their payload capacities are orders of magnitude smaller than weights of structures, confirmation of adequate performance must be provided by analysis of numerical models and testing of individual bearings. As the consequences of isolator failure are high, for example, core damage in a nuclear power plant and collapse for a building, the numerical models of the key nonlinear components, namely, the isolators, must be verified and validated (V + V). Herein, advanced models of elastomeric seismic isolation bearings are implemented as user elements in the open-source code OpenSees, and the commercial codes ABAQUS and LS-DYNA. These advanced models are verified and validated following ASME best practice to predict response under extreme loadings. Sources of error in the computational models are quantified, and where possible, eliminated. Those isolator characteristics crucial to robust estimates of performance are identified. Experiments are performed to obtain data for validation. The isolator models are validated using data from experiments and values of model parameters are recommended.
•ABAQUS models of SC walls can be developed to predict the nonlinear in-plane response.•Degradation of concrete and true steel stress-strain relationship should be included.•Shear strength of the SC ...walls increases with the increase of steel reinforcement ratio and the decrease of faceplate slenderness ratio.
This paper presents a numerical study of steel-plate concrete (SC) composite walls using the general-purpose finite element (FE) program ABAQUS. Predictions are compared to data from reversed cyclic, inelastic tests of four large-scale SC wall piers with an aspect ratio of 1.0. Each wall comprises two steel faceplates, infill concrete, steel studs and tie rods as connectors, and a steel baseplate that connects it to the reinforced concrete (RC) foundation. Key design variables are studied, including reinforcement ratio, connector type, and faceplate slenderness ratio. The predicted responses including global force-displacement relationships, damage to infill concrete and steel faceplates, shearing force contributions, and connector behavior, are in good agreement with the measured data. The steel faceplates are found to contribute between 20% and 70% of the total shearing resistance of the SC wall piers evaluated here, depending on the reinforcement ratio, faceplate slenderness ratio, story drift, and level of damage. Tie-rods are preferred to shear studs in the first few rows of connectors above the baseplate, where significant out-of-plane buckling of the steel faceplates and damage of the infill concrete are expected.
•Parametric study of the effects of design variables on the response of SC walls.•Finite element analysis of 98 SC wall piers using LS-DYNA.•Predictive equations for the monotonic response of SC ...walls up to peak strength.•Mechanics-based equations for the lateral load capacity of SC walls.•Verification of the equations using the results of analyses and test data.
This paper presents results of numerical studies on the in-plane monotonic response of steel-plate concrete (SC) composite shear wall piers. Results of finite element analysis of 98 SC wall piers are used to investigate the effects of wall aspect ratio, reinforcement ratio, slenderness ratio, axial load, yield strength of the steel faceplates, and uniaxial compressive strength of concrete on in-plane response, and to formulate (a) predictive equations to establish the trilinear lateral force versus lateral displacement response of SC wall piers up to peak strength, sufficient for seismic analysis of structures including SC wall piers and (b) a mechanics-based design equation for peak flexural strength, which addresses the interaction of co-existing shear and axial force. Design of Experiments is used to select the 98 piers. The baseline finite element model was formally validated using data from reversed cyclic, inelastic in-plane tests of four large-scale SC wall piers.
Soil-structure interaction (SSI) analysis is generally a required step in the calculation of seismic demands in nuclear structures, and is currently performed using linear methods in the frequency ...domain. Such methods should result in accurate predictions of response for low-intensity shaking, but their adequacy for extreme shaking that results in highly nonlinear soil, structure or foundation response is unproven. Nonlinear (time-domain) SSI analysis can be employed for these cases, but is rarely performed due to a lack of experience on the part of analysts, engineers and regulators. A nonlinear, time-domain SSI analysis procedure using a commercial finite-element code is described in the paper. It is benchmarked against the frequency-domain code, SASSI, for linear SSI analysis and low intensity earthquake shaking. Nonlinear analysis using the time-domain finite-element code, LS-DYNA, is described and results are compared with those from equivalent-linear analysis in SASSI for high intensity shaking. The equivalent-linear and nonlinear responses are significantly different. For intense shaking, the nonlinear effects, including gapping, sliding and uplift, are greatest in the immediate vicinity of the soil-structure boundary, and these cannot be captured using equivalent-linear techniques.
•Described a method of performing time-domain nonlinear SSI analysis.•Benchmarked this method against the established frequency-domain code, SASSI.•Performed fully nonlinear SSI analyses of two buildings using LS-DYNA.•Compared LS-DYNA results to those calculated using SASSI.•Observed significant differences for cases with highly nonlinear behavior.
•Development of a finite element model in LS-DYNA to simulate the response of RC walls.•Validation of the developed finite element model using data from 22 wall specimens.•Considering the effect of ...restrained shrinkage on the initial stiffness of RC walls.•Considering the effect of concrete crushing on the post-peak strength of RC walls.•Parametric study to investigate the effects of design parameters on monotonic response.
A finite element model is developed in LS-DYNA to simulate the in-plane cyclic behavior of lightly reinforced, low-aspect ratio reinforced concrete (RC) shear walls. Data from tests of 22 low-aspect ratio RC shear walls in three laboratories are used to validate the numerical model. The design variables in the testing programs included aspect ratio, day-of-test concrete compressive strength, vertical and horizontal web reinforcement ratio, reinforcement ratio in boundary elements, and yield and ultimate strengths of reinforcement, and these are addressed in the numerical model.
The finite element predictions and test results, including the force–displacement relationships and damage to the RC shear walls, are presented and contrasted. Numerical methods are proposed to model the effect of early stage cracking on the initial stiffness of RC walls and to capture post-peak strength degradation. The numerical simulations are in good agreement with the measured responses. The validated LS-DYNA model is used in a parametric study to investigate the effects of wall aspect ratio, reinforcement ratios in web and boundary elements, and compressive axial load on the monotonic response of RC walls. The accuracy of four equations used to predict the peak shear strength of low-aspect ratio walls is assessed using results of the numerical analyses.
The seismic design of an advanced nuclear reactor must consider the interaction of vessel internal components with the surrounding coolant: fluid–structure interaction (FSI). Available analytical ...solutions for FSI of submerged components do not accommodate multiple-component, intense seismic inputs and complex reactor and internal geometries. Physical testing of reactor vessels and internals to inform seismic design is impractical and cost-prohibitive, leaving the use of verified and validated, robust numerical models as the only plausible option for analysis and design. Physical data that could be used for validating such numerical models for multi-component shaking are not available. This article describes an experimental program performed on a 6-degree-of-freedom earthquake simulator to generate data that could support validation of seismic FSI numerical models for submerged components in commercial finite element codes. A scaled model of a base-supported reactor vessel with simplified representations of submerged internals was tested to generate submerged-component response histories for a range of seismic inputs. The generated data were used to validate numerical models in the finite element code LS-DYNA. Numerical models were validated for calculation of hydrodynamic pressure responses on internals, in-water frequencies of internals, and acceleration responses of internals. The generated data and the analysis recommendations could aid engineering analysts designing submerged components and systems for seismic effects.
•Lists implementations of seismic isolation of nuclear facilities in Europe.•Compiles and distils information on seismic isolation in the modern era.•Identifies recent developments and best practice ...in seismic protective systems.•Identifies future opportunities and technical needs.
Seismic isolation of nuclear power plants is in its infancy, with only a small number of applications worldwide. This outcome is due in part to the construction of only a small number of new build nuclear power plants since base-isolation technology became mainstream in the 1990s, perceived concerns regarding the long-term mechanical properties of isolation bearings, and a lack of guidance, codes and standards related to isolation of safety-related nuclear facilities. This paper charts the history of seismic isolation, identifies the research that led to the first implementation of isolation for buildings and bridges in the modern era, summarizes the first applications of the technology to nuclear facilities, and describes important research and developments, including the writing of nuclear standards, in the past 20 years. Future research and development needs are identified.
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