Effects of Uncertainties in Boundary Conditions on Dynamic Characteristics of Industrial Plant Components

2014 ◽  
Author(s):  
Oreste S. Bursi ◽  
Giuseppe Abbiati ◽  
Luca Caracoglia ◽  
Md Shahin Reza
Keyword(s):  
Boundary Conditions ◽  
Dynamic Characteristics ◽  
Seismic Risk ◽  
Dynamic Properties ◽  
Fragility Curves ◽  
Structural Safety ◽  
Industrial Plant ◽  
Piping System ◽  
Uncertain Boundary ◽  
Plant Components

Seismic risk assessment of industrial plants is of paramount importance to ensure adequate design against earthquake hazards. Seismic vulnerability of industrial plant components is often evaluated through a fragility analysis to conform to structural safety requirements. Fragility curves of single components are usually developed by neglecting the effect of actual boundary conditions. Thus, an incorrect evaluation of individual fragility curves can affect the overall fragility curve of a system. This may lead to “erroneous” seismic risk evaluation for a plant in comparison with its real state. Hence, it is important to study the effect of uncertainties, introduced at the boundaries when coupling effects are neglected, on the dynamic characteristics of a system. Along this line, this paper investigates the effects of uncertain boundary conditions on the probability distributions of the dynamic properties of a simple chain-like system with increasing number of degrees of freedom. In order to describe the uncertain boundary condition, a modified version of the well-known β distribution is proposed. Subsequently, the Analytical Moment Expansion (AME) method is employed to estimate the statistical moments of the output random variables as an alternative to more computationally-demanding Monte Carlo simulations. Finally, a preliminary extension of the proposed approach to a realistic piping system connected to a class of broad/slender tanks is discussed.

Dynamic Analysis of NPP Piping Systems and Components With Viscoelastic Dampers Subjected to Severe Earthquake Motions

2016 ◽  
Author(s):  
Ichiro Tamura ◽  
Masashi Kuramasu ◽  
Frank Barutzki ◽  
Daniel Fischer ◽  
Victor Kostarev ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Characteristics ◽  
Seismic Analysis ◽  
Dynamic Properties ◽  
Maxwell Model ◽  
Shaking Table ◽  
Nonlinear Dependence ◽  
Piping System ◽  
Frequency Dependent ◽  
Viscoelastic Dampers

In Shimane nuclear power plant of Chugoku Electric Power Co., a number of safety improvements are planned to be implemented aiming for the highest level of safety in the world to be achieved. One of the new safety measures is the application of viscoelastic dampers for seismic protection of safety related piping system and components. High performance of viscoelastic dampers has been confirmed by direct testing of the piping natural scale model at the shaking table subjected to severe seismic accelerations up to 20 m/s2. However, viscoelastic dampers as a dynamic protection device have frequency-dependent dynamic characteristics, which are difficult to reproduce in the frame of conventional seismic analysis based typically on the use of response spectrum method. For example, the dynamic properties of viscoelastic dampers exhibit nonlinear dependence on dissipation energy, shear rate of viscous fluid, and temperature. Method for Seismic analysis of systems with viscoelastic dampers (SAVD-Method) is one of the analytical approaches capable of considering the dynamic properties and nonlinear behavior of viscoelastic dampers. The SAVD-Method is a comparatively simple but reliable approach for dynamic analysis of a piping system and components with viscoelastic dampers. Frequency-dependent dynamic characteristics of the viscoelastic dampers are able to be modeled by a four-parameter Maxwell model. To consider the nonlinearity of the dynamic properties of viscoelastic dampers, the Maxwell model parameters were determined for different usage conditions in conjunction with the adjustment dependent on the energy dissipation criteria. Direct comparison of the shaking table measurements and analysis according to SAVD-method shows good matching of results for all controlled parameters and levels of seismic excitation.

Dynamic Response of Coupled Tanks and Piping Systems Under Seismic Loading

2015 ◽  
Author(s):  
Oreste S. Bursi ◽  
Giuseppe Abbiati ◽  
Luca Caracoglia ◽  
Vincenzo La Salandra ◽  
Rocco Di Filippo ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Boundary Conditions ◽  
Seismic Loading ◽  
Coupled System ◽  
Coupled Systems ◽  
Piping System ◽  
Axial Loads ◽  
Industrial Plants ◽  
Piping Systems ◽  
Uncertain Boundary

Dynamic analysis is an integral part of seismic risk assessment of industrial plants. Such analysis often neglects actual boundary conditions or proper coupling between structures of coupled systems, which introduces uncertainty into the system and may lead to erroneous results, e.g., an incorrect fragility curve, in comparison with the actual behaviour of the analyzed structure. Hence, it is important to study the effect of uncertainties on the dynamic characteristics of a system, when coupling effects are neglected. Along this line, this paper investigates the effects of uncertain boundary conditions on the dynamic response of coupled tank-piping systems subjected to seismic loading. In particular, to take into account the presence of the tank as boundary condition for the piping system, two sources of uncertainty were considered: the tank aspect ratio and the piping-to-tank attachment height ratio. Moreover, to model the seismic input, a Filtered White Noise (FWN) characterized by a Kanai-Tajimi spectrum was used. Finally, to study the dynamic interaction of a set of coupled tank-piping systems, the non-intrusive stochastic collocation (SC) technique was applied. It allowed for calculating surface responses of stresses and axial loads of a pair of components of the coupled system with a reduced number of deterministic numerical simulations.

SEISMIC RISK AND RESILIENCE ASSESSMENT OF INDUSTRIAL FACILITIES: CASE STUDY ON A BLACK CARBON PLANT

2020 ◽  
Author(s):  
George Karagiannakis
Keyword(s):  
Seismic Risk ◽  
Numerical Models ◽  
Fragility Curves ◽  
Human Life ◽  
Mitigation Strategies ◽  
Economic Losses ◽  
Risk And Resilience ◽  
Industrial Plants ◽  
Plant Equipment

This paper deals with state of the art risk and resilience calculations for industrial plants. Resilience is a top priority issue on the agenda of societies due to climate change and the all-time demand for human life safety and financial robustness. Industrial plants are highly complex systems containing a considerable number of equipment such as steel storage tanks, pipe rack-piping systems, and other installations. Loss Of Containment (LOC) scenarios triggered by past earthquakes due to failure on critical components were followed by severe repercussions on the community, long recovery times and great economic losses. Hence, facility planners and emergency managers should be aware of possible seismic damages and should have already established recovery plans to maximize the resilience and minimize the losses. Seismic risk assessment is the first step of resilience calculations, as it establishes possible damage scenarios. In order to have an accurate risk analysis, the plant equipment vulnerability must be assessed; this is made feasible either from fragility databases in the literature that refer to customized equipment or through numerical calculations. Two different approaches to fragility assessment will be discussed in this paper: (i) code-based Fragility Curves (FCs); and (ii) fragility curves based on numerical models. A carbon black process plant is used as a case study in order to display the influence of various fragility curve realizations taking their effects on risk and resilience calculations into account. Additionally, a new way of representing the total resilience of industrial installations is proposed. More precisely, all possible scenarios will be endowed with their weighted recovery curves (according to their probability of occurrence) and summed together. The result is a concise graph that can help stakeholders to identify critical plant equipment and make decisions on seismic mitigation strategies for plant safety and efficiency. Finally, possible mitigation strategies, like structural health monitoring and metamaterial-based seismic shields are addressed, in order to show how future developments may enhance plant resilience. The work presented hereafter represents a highly condensed application of the research done during the XP-RESILIENCE project, while more detailed information is available on the project website https://r.unitn.it/en/dicam/xp-resilience.

scholarly journals Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation

2021 ◽  
Vol 11 (10) ◽  
pp. 4589
Author(s):  
Ivan Duvnjak ◽  
Domagoj Damjanović ◽  
Marko Bartolac ◽  
Ana Skender
Keyword(s):  
Boundary Conditions ◽  
Damage Detection ◽  
Mode Shape ◽  
Experimental Validation ◽  
Detection Method ◽  
Dynamic Properties ◽  
Damage Index ◽  
Main Principle ◽  
The Difference ◽  
Different Levels

The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.

Seismic Risk Evaluation of Retrofitted Reinforced Concrete Buildings Utilizing Base Isolation and Considering Mainshock-Aftershock

2013 ◽  
Vol 671-674 ◽  
pp. 1372-1375
Author(s):  
Rui Long Han ◽  
Yue Li
Keyword(s):  
Seismic Risk ◽  
Risk Evaluation ◽  
Base Isolation ◽  
Seismic Hazards ◽  
Nonlinear Finite Element ◽  
Structural Safety ◽  
Seismic Fragility ◽  
Rc Frame ◽  
Actual Situation ◽  
Element Analysis

The insufficient consideration of seismic risk caused hidden danger for structural safety in many areas. A promising retrofit method for these structures is base isolation. In order to evaluate the effectiveness of this approach, a hypothetical RC frame based on actual situation is designed to be retrofitted using base isolation. Then, seismic fragilities for both un-retrofitted and isolated frames are analyzed, utilizing the results obtained from nonlinear finite-element analysis. The ground motion of the analysis contains 22 earthquake motions, and the results of considering mainshock-aftershock and those of considering only mainshock are compared. The study proves the well designed base isolation can reduce the seismic fragility of the RC frame effectively, and the exclusive consideration of mainshock will underestimate the seismic hazards for structures.

Experimental Validation and Numerical Simulation of Shape Memory Flat Wire Actuators

2014 ◽  
Author(s):  
Alexander Czechowicz ◽  
Sven Langbein
Keyword(s):  
Shape Memory Alloy ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Smart Materials ◽  
Empirical Data ◽  
Dynamic Properties ◽  
Fatigue Behavior ◽  
Different Boundary Conditions ◽  
Heating And Cooling ◽  
Actual Shape

Shape memory alloys (SMA) are thermally activated smart materials. Due to their ability to change into a previously imprinted actual shape through the means of thermal activation, they are suitable as actuators for mechatronical systems. Despite of the advantages shape memory alloy actuators provide, these elements are only seldom integrated by engineers into mechatronical systems. Reasons are the complex characteristics, especially at different boundary conditions and the missing simulation- and design tools. Also the lack of knowledge and empirical data are a reason why development projects with shape memory actuators often lead to failures. This paper deals with the dynamic properties of SMA-actuators (Shape Memory Alloy) — characterized by their rate of heating and cooling procedures — that today can only be described insufficiently for different boundary conditions. Based on an analysis of energy fluxes into and out of the actuator, a numerical model of flat-wire used in a bow-like structure, implemented in MATLAB/SIMULINK, is presented. Different actuation parameters, depending on the actuator-geometry and temperature are considered in the simulation in real time. Additionally this publication sums up the needed empirical data (e.g. fatigue behavior) in order to validate the numerical two dimensional model and presents empirical data on SMA flat wire material.

scholarly journals A comparative study on a complex URM building: part II—issues on modelling and seismic analysis through continuum and discrete-macroelement models

2021 ◽  
Author(s):  
G. Castellazzi ◽  
B. Pantò ◽  
G. Occhipinti ◽  
D. A. Talledo ◽  
L. Berto ◽  
...  
Keyword(s):  
Seismic Analysis ◽  
Dynamic Properties ◽  
Limit State ◽  
Central Italy ◽  
Nonlinear Static Analysis ◽  
Structural Safety ◽  
Masonry Building ◽  
Maximum Acceleration ◽  
Capacity Curves ◽  
Comparison Of The Results

AbstractThe paper presents the comparison of the results obtained on a masonry building by nonlinear static analysis using different software operating in the field of continuum and discrete-macroelement modeling. The structure is inspired by an actual building, the "P. Capuzi" school in Visso (Macerata, Italy), seriously damaged following the seismic events that affected Central Italy from August 2016 to January 2017. The activity described is part of a wider research program carried out by various units involved in the ReLUIS 2017/2108—Masonry Structures project and having as its object the analysis of benchmark structures for the evaluation of the reliability of software packages. The comparison of analysis was carried out in relation to: global parameters (concerning the dynamic properties, capacity curves and, equivalent bilinear curves), synthetic parameters of structural safety (such as, for example, the maximum acceleration compatible with the life safety limit state) and the response in terms of simulated damage. The results allow for some insights on the use of continuum and discrete-macroelement modeling, with respect to the dispersion of the results and on the potential repercussions in the professional field. This response was also analyzed considering different approaches for the application of loads.

The Dynamic Characteristics of Rigid Frame Single-Rib Arch Bridge

2013 ◽  
Vol 368-370 ◽  
pp. 1426-1430
Author(s):  
Li Xiong Gu ◽  
Rong Hui Wang
Keyword(s):  
Dynamic Characteristics ◽  
Bending Strength ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Bending Stiffness ◽  
Torsional Stiffness ◽  
Lateral Stiffness ◽  
Arch Bridge ◽  
Vertical Stiffness ◽  
Rigid Frame

In this paper, by establishing the finite element model to study the dynamic characteristics of rigid frame single-rib arch bridge. By respectively changing structural parameters of the span ratios, and the compressive stiffness of arch, and the bending stiffness of arch, and the bending stiffness of bridge girder, and the layout of boom to find out the regularity of the structure on lateral stiffness, and vertical stiffness, and torsional stiffness as well as dynamic properties, it come out the results of that lateral stiffness of the structure is weaker, and increasing the span ratios and the compressive strength of arch are conducive to the improvement of the overall stiffness, and improving the bending strength of arch and layout of boom are less effect on the overall stiffness and mode shape.

Correlation Study on Modal Frequency and Temperature Effects of a Cable-Stayed Bridge Model

2012 ◽  
Vol 446-449 ◽  
pp. 3264-3272 ◽  
Author(s):  
Li Min Sun ◽  
Yi Zhou ◽  
Xue Lian Li
Keyword(s):  
Experimental Study ◽  
Boundary Conditions ◽  
Dynamic Properties ◽  
Bridge Engineering ◽  
Fe Model ◽  
Steel Cable ◽  
Transverse Beam ◽  
Expansion Joints ◽  
Cable Stayed Bridge ◽  
Bridge Model

In recent years, structural health monitoring has been paid more and more attention in bridge engineering community. Previous researches showed that ambient temperature was one of principal factors affecting structural modal parameters in long-term. In this paper, an experimental study on correlation between dynamic properties of a cable-stayed bridge and its structural temperature was performed under temperature controlled laboratory environment. Using hammer impacting method, a dynamic testing was conducted based on a steel cable-stayed bridge model which had a span layout of 0.9+1.9+0.9m. During the experiment, the first six vertical bending modes under the environmental temperature of 0, 20 and 40°C were identified with the consideration of three kinds of boundary conditions at the deck’s ends as to two degrees of freedom, i.e. the longitudinal translation (UX) and the rotation about the transverse beam (RotZ). The above boundary conditions are UX & RotZ not constrained, UX constrained only and UX & RotZ constrained, attempting to simulate the different conditions of the bridge expansion joints. The efforts were paid to explain the physical mechanism of the results based on the updated FE model. This experimental study indicates a tendency that the frequency of the cable-stayed bridge model decreases with the increase of temperature. And furthermore, the relative difference of frequencies between 0 and 40 °C is affected by boundary conditions; in other words, when the deck is free to expand, the variation of model’s frequencies is smaller than that when the deck is restrained to expand, which is similar to the condition of the bridge’s expansion joints cannot work as normal. This experimental study can give some reference to the research of SHM and damage identification for cable-stayed bridges.

Dynamic Property Evaluation of a Long-Span Cable-Stayed Bridge (Sutong Bridge) by a Bayesian Method

2018 ◽  
Vol 19 (01) ◽  
pp. 1940010 ◽  
Author(s):  
Yan-Chun Ni ◽  
Qi-Wei Zhang ◽  
Jian-Feng Liu
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Structural Damage ◽  
Dynamic Properties ◽  
Modal Identification ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Sutong Bridge

Modal identification aims at identifying the dynamic properties including natural frequency, damping ratio, and mode shape, which is an important step in further structural damage detection, finite element model updating, and condition assessment. This paper presents the work on the investigation of the dynamic characteristics of a long-span cable-stayed bridge-Sutong Bridge by a Bayesian modal identification method. Sutong Bridge is the second longest cable-stayed bridge in the world, situated on the Yangtze River in Jiangsu Province, China, with a total length of 2 088[Formula: see text]m. A short-term nondestructive on-site vibration test was conducted to collect the structural response and determine the actual dynamic characteristics of the bridge before it was opened to traffic. Due to the limited number of sensors, multiple setups were designed to complete the whole measurement. Based on the data collected in the field tests, modal parameters were identified by a fast Bayesian FFT method. The first three modes in both vertical and transverse directions were identified and studied. In order to obtain modal parameter variation with temperature and vibration levels, long-term tests have also been performed in different seasons. The variation of natural frequency and damping ratios with temperature and vibration level were investigated. The future distribution of the modal parameters was also predicted using these data.

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