SIMPLIFIED APPROACH FOR SEISMIC ANALYSIS OF STRUCTURES

2002 ◽  
Vol 02 (02) ◽  
pp. 207-225 ◽  
Author(s):  
VETO VARMA ◽  
G. R. REDDY ◽  
K. K. VAZE ◽  
H. S. KUSHWAHA
Keyword(s):  
3D Model ◽  
Seismic Analysis ◽  
Computational Time ◽  
Beam Model ◽  
Structural Behaviour ◽  
Lumped Mass ◽  
Local Modes ◽  
Simplified Approach ◽  
Energy Equivalence ◽  
Mass Participation

The seismic analysis of a structure using continuum mechanics approach may yield good results. However, this approach is difficult to apply for complex geometrical problems such as nuclear reactor containment building. To incorporate the entire structural behaviour, a full 3D model is best suited. However, a large number of modes are required to achieve at least 90% mass participation or frequency content up to 33 Hz. This consumes a large computational time due to large number of local modes present. Therefore, an equivalent lumped mass beam model, which as compared to 3D model, is much simpler and produces conservative global responses, has been considered in analysis. The lumped mass equivalent beam model of the system can be prepared after carrying out static analysis of 3D model using static energy equivalence approach. Forces and moments obtained by the seismic analysis of this beam model can be applied on the 3D model in order to obtain stresses in each element. It was found that the results obtained by this approach gives higher results because of higher mass participation. Experimental investigation is also performed on one of the case study to support the analysis. Hence it is concluded that analysis using beam model based on strain energy equivalence, in combination with 3D model is much simpler, economic and gives conservative results.

scholarly journals An effective model for analysis of reinforced concrete members and structures under blast loading

2016 ◽  
Vol 19 (12) ◽  
pp. 1815-1831 ◽  
Author(s):  
Zhongxian Li ◽  
Bo Zhong ◽  
Yanchao Shi
Keyword(s):  
Reinforced Concrete ◽  
Seismic Analysis ◽  
Damage Effect ◽  
Computational Time ◽  
Isotropic Hardening ◽  
High Fidelity ◽  
Beam Model ◽  
Blast Loads ◽  
Concrete Members ◽  
Proposed Model

The traditional fiber beam model has been widely used in the seismic analysis of reinforced concrete members and structures. However, the inability to capture shear failure restricts its application to blast loadings. In this article, a numerical model that considers both rate-dependent shear behavior and damage effect is proposed based on the traditional fiber beam element. This is achieved using the modified compression-field theory with a concrete damage model and bilinear steel model in the principal directions. Meanwhile, a condensed three-dimensional stress–strain relation from the isotropic hardening plasticity model is implemented to simulate longitudinal reinforcement bars, as large shear strain would be produced under severe blast loads. The proposed model is validated by comparing the numerical and test results. The high-fidelity physics-based finite element model, validated by the same experiment, is also used in the study to prove the efficiency of the proposed model. Case studies of a reinforced concrete beam and a six-story reinforced concrete frame structure subjected to blast loads are then carried out. The results indicate that the proposed model is reliable compared with the high-fidelity physics-based model. In addition to the accuracy, comparisons of the computational time show an excellent performance with respect to the efficiency of the proposed model.

scholarly journals A computationally efficient hybrid 2D–3D subwoofer model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ahmad H. Bokhari ◽  
Martin Berggren ◽  
Daniel Noreland ◽  
Eddie Wadbro
Keyword(s):  
Hybrid Model ◽  
3D Model ◽  
Element Model ◽  
Acoustic Properties ◽  
Computational Time ◽  
Average Response ◽  
Frequency Range ◽  
Computationally Efficient ◽  
Lumped Element ◽  
Lumped Element Model

AbstractA subwoofer generates the lowest frequency range in loudspeaker systems. Subwoofers are used in audio systems for live concerts, movie theatres, home theatres, gaming consoles, cars, etc. During the last decades, numerical simulations have emerged as a cost- and time-efficient complement to traditional experiments in the design process of different products. The aim of this study is to reduce the computational time of simulating the average response for a given subwoofer design. To this end, we propose a hybrid 2D–3D model that reduces the computational time significantly compared to a full 3D model. The hybrid model describes the interaction between different subwoofer components as interacting modules whose acoustic properties can partly be pre-computed. This allows us to efficiently compute the performance of different subwoofer design layouts. The results of the hybrid model are validated against both a lumped element model and a full 3D model over a frequency band of interest. The hybrid model is found to be both accurate and computationally efficient.

scholarly journals History, observation and mathematical models in the seismic analysis of the Valadier abutment area in the Colosseum

1995 ◽  
Vol 38 (5-6) ◽  
Author(s):  
G. Croci ◽  
D. D'Ayala ◽  
R. Liburdi
Keyword(s):  
Mathematical Models ◽  
Seismic Analysis ◽  
Numerical Models ◽  
Time History ◽  
Historical Records ◽  
Direct Integration ◽  
Structural Behaviour ◽  
Seismic Behaviour ◽  
Before And After ◽  
Xix Century

The present work aimed to outline the need to investigate different fields of research to interpret the structural behaviour of a monument as complex as the Colosseum. It is shown how defining the numerical models first. then refining them, followed by interpretation of results. is strictly linked with the inforination gathered from historical records and observation of the ~nonumenta s it is today. The study is confined to the area of the Valadier abutment. analysing its state and its seismic behaviour before and after the XIX century restoration using different ilumerical tools, from the elastic modal analysis to the non linear step by step time history direct integration. The procedure comparati\ely evaluates the reliability in the interpretation of the results and identifies future lines or research.

Development of an Adjustable Frequency Device for a Test Vehicle Based on Curved Beam Theory

2021 ◽  
Vol 8 ◽  
pp. 5-8
Author(s):  
J. D. Yau ◽  
S. Urushadze
Keyword(s):  
Experimental Studies ◽  
Beam Theory ◽  
Frequency Measurement ◽  
Curved Beam ◽  
Beam Model ◽  
Lumped Mass ◽  
Test Beam ◽  
Test Vehicle ◽  
Instrumented Vehicle ◽  
Thin Beams

In this article, an adjustable frequency device based on curved beam theory is designed to control vertical stiffness of an instrumented vehicle that it can detect dynamic data when moving on a test beam for frequency measurement. The adjustable frequency device consists of a set of two-layer cantilever semi-circular thin-beams to support a lumped mass for vibrations, in which a rotatable U-frame is used to change its subtended angle for adjustment of the supporting stiffness and corresponding vertical frequencies of the vehicle. Based on curved beam theory, an analytical frequency equation of the single-degree-of-freedom test vehicle was derived and applied to mobile frequency measurement of a simple beam. To determine the sectional rigidity of the semi-circular thin-beams, both theoretical and experimental studies were be carried out in the ITAM laboratory of the Academy of Science in Czech. The analytical and experimental results indicated that the present semi-circular beam model with guided ends is applicable to prediction of natural frequencies of the test vehicle considering different supporting stiffness

scholarly journals Dam-Break Flows: Comparison between Flow-3D, MIKE 3 FM, and Analytical Solutions with Experimental Data

2018 ◽  
Vol 8 (12) ◽  
pp. 2456 ◽  
Author(s):  
Hui Hu ◽  
Jianfeng Zhang ◽  
Tao Li
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Analytical Solution ◽  
Water Depth ◽  
3D Model ◽  
Real Life ◽  
Surface Profile ◽  
Dam Break ◽  
Computational Time ◽  
Free Surface Profile

The objective of this study was to evaluate the applicability of a flow model with different numbers of spatial dimensions in a hydraulic features solution, with parameters such a free surface profile, water depth variations, and averaged velocity evolution in a dam-break under dry and wet bed conditions with different tailwater depths. Two similar three-dimensional (3D) hydrodynamic models (Flow-3D and MIKE 3 FM) were studied in a dam-break simulation by performing a comparison with published experimental data and the one-dimensional (1D) analytical solution. The results indicate that the Flow-3D model better captures the free surface profile of wavefronts for dry and wet beds than other methods. The MIKE 3 FM model also replicated the free surface profiles well, but it underestimated them during the initial stage under wet-bed conditions. However, it provided a better approach to the measurements over time. Measured and simulated water depth variations and velocity variations demonstrate that both of the 3D models predict the dam-break flow with a reasonable estimation and a root mean square error (RMSE) lower than 0.04, while the MIKE 3 FM had a small memory footprint and the computational time of this model was 24 times faster than that of the Flow-3D. Therefore, the MIKE 3 FM model is recommended for computations involving real-life dam-break problems in large domains, leaving the Flow-3D model for fine calculations in which knowledge of the 3D flow structure is required. The 1D analytical solution was only effective for the dam-break wave propagations along the initially dry bed, and its applicability was fairly limited.

Mathematical Models for Model-Based Control in Offshore Pipelay Operations

2009 ◽  
Author(s):  
Gullik A. Jensen ◽  
Thor I. Fossen
Keyword(s):  
Mathematical Models ◽  
Dynamic Models ◽  
Controller Design ◽  
Computational Time ◽  
Beam Model ◽  
Time Dynamic ◽  
Model Based ◽  
On Line ◽  
Stability And Accuracy ◽  
Control Application

This paper considers mathematical models for model-based controller design in offshore pipelay operations. Three classes of models for control design are discussed, real-world models suitable for controller design verification, controller and observer models which are used on-line in the control system implementation. The control application place requirements on the model with respect to the computational time, dynamic behavior, stability and accuracy. Models such as the beam model, two catenary models, as well as general finite element (FE) models obtained from computer programs were not able to meet all of the requirements, and two recent dynamic models designed for control are presented, which bridge the gap between the simple analytical and more complex FE models. For completeness, modeling of the pipelay vessel, stinger and roller interaction, soil and seabed interaction and environmental loads are discussed.

scholarly journals An Assessment of Simplified vs. Detailed Methodologies for SSI Analyses of Deeply Embedded Structures

2004 ◽  
Author(s):  
J. Xu ◽  
C. Miller ◽  
C. Hofmayer ◽  
H. Graves
Keyword(s):  
Performance Assessment ◽  
Nuclear Power ◽  
National Laboratory ◽  
Response Spectra ◽  
Nuclear Regulatory Commission ◽  
Brookhaven National Laboratory ◽  
Beam Model ◽  
Simplified Approach ◽  
Embedded Structures ◽  
Different Depths

Sponsored by the US Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) is carrying out a research program to develop a technical basis to support the safety evaluation of deeply embedded and/or buried (DEB) structures as proposed for advanced reactor designs. In this program, the methods and computer programs established for the assessment of soil-structure interaction (SSI) effects for the current generation of light water reactors are evaluated to determine their applicability and adequacy in capturing the seismic behavior of DEB structures. This paper presents an assessment of the simplified vs. detailed methodologies for seismic analyses of DEB structures. In this assessment, a lump-mass beam model is used for the simplified approach and a finite element representation is employed for the detailed method. A typical containment structure embedded in a soil profile representative of a typical nuclear power plant site was utilized, considering various embedment depths from shallow to full burial. BNL used the CARES program for the simplified model and the SASSI2000 program for the detailed analyses. The calculated response spectra at the key locations of the DEB structure are used for the performance assessment of the applied methods for different depths of burial. Included in the paper are: 1) the description of both the simplified and detailed models for the SSI analyses of the DEB structure, 2) the comparison of the analysis results for the different depths of burial between the two methods, and 3) the performance assessment of the analysis methodologies for SSI analyses of DEB structures. The resulting assessment from this study has indicated that simplified methods may be capable of capturing the seismic response for much deeper embedded structures than would be normally allowed by the standard practice.

An Empirical Formulation for the Damping Ratio of Shape Memory Alloy for Base-Isolated Structures

2019 ◽  
Vol 19 (07) ◽  
pp. 1950074
Author(s):  
Sharad Ghodke ◽  
R. S. Jangid
Keyword(s):  
Shape Memory ◽  
Empirical Equation ◽  
Seismic Analysis ◽  
Nonlinear Models ◽  
Damping Ratio ◽  
Computational Time ◽  
Traditional System ◽  
Linear Damping ◽  
Isolated Structures ◽  
Isolation Systems

Shape Memory Alloys (SMAs) are now widely used as a damping element into the isolation systems. The pre-stressed SMAs exhibit hysteretic damping through a nonlinear flag-shaped hysteresis loop. Many nonlinear models of the SMA are available to depict such behavior. The nonlinear models require a lot of effort and computational time for the analysis of base-isolated structures. Therefore, the codes recommend that a nonlinear model can be replaced by an equivalent linear model in the analysis. Linearization is a method to convert the nonlinearity of a system into a system with analogues linear parameters. This paper proposes an empirical equation for a damping ratio to get a linear damping coefficient of the SMAs which can be used in the seismic analysis of base-isolated structures. The evaluation of any damping ratio using the traditional system identification method does not give precise solutions due to variation in hysteretic parameters and the unpredictable nature of an earthquake. The empirical equation is proposed using a set of optimal statistical data obtained from the seismic analysis of a base isolated structure. Moreover, analysis of the base isolated structure using the newly modified equivalent elastic-viscous SMA model gives comparable and conservative results with a nonlinear SMA model as compared to the existing elastic-viscous SMA model. Since the hysteresis parameters are used to derive the empirical equation for the damping ratio, this equation is also applicable for any type of structure.

Improved modal convergence using the assumed modes method for rods carrying various lumped elements

2017 ◽  
Vol 46 (1) ◽  
pp. 3-30
Author(s):  
Philip D Cha ◽  
Tae Ha Park
Keyword(s):  
Piecewise Linear ◽  
Linear Functions ◽  
Mode Shapes ◽  
Computational Time ◽  
Piecewise Linear Functions ◽  
Lumped Mass ◽  
Modes Of Vibration ◽  
Geometric Boundary ◽  
Lumped Elements ◽  
Damped Oscillator

In this paper, the assumed modes method is used to determine the modes of vibration of an arbitrarily supported uniform and nonuniform rods carrying various lumped elements, including a lumped mass, a grounded spring, a grounded viscous damper, and an undamped and damped oscillator. In applying the assumed modes method, the set of trial functions used in the expansion can be arbitrary as long as they satisfy the geometric boundary conditions of the system. In practice, the trial functions are often selected to correspond to the eigenfunctions of the bare uniform rod. Numerical experiments show that while this set of trial functions converges to the exact results, the rate of convergence can be exceedingly slow. In order to expedite modal convergence, the eigenfunctions are augmented with piecewise linear functions that capture the slope discontinuities of the mode shapes at the attachment locations due to the presence of the lumped elements. The results obtained using the two sets of trial functions are compared with those obtained exactly. It is shown that including the piecewise linear functions significantly improves the accuracy of the modes of vibration of the system while drastically reducing the computational time and effort.

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