DEVELOPMENT OF A COMPUTER AIDED MODEL UPDATING SYSTEM (CAMUS (original) (raw)
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Model updating of real structures with ambient vibration data
Journal of Civil Structural Health Monitoring, 2016
It is important to develop reliable finite element models (FEMs) for real structures not only in the design phase but also for the structural health monitoring and life-cycle management purposes. To do so, model updating is often carried out to minimise the discrepancies between FEMs and real structures. Among existing model updating approaches, sensitivity based model updating methods which can be either manual or automated, have proven to be very effective in the application of real structures and have been widely used on flexible bridge structures. However, very few studies were reported on buildings especially those with medium-rise characteristics which are often associated with complicated initial modelling and different degrees of parameter uncertainties. In addition, even-though a handful of studies has been done on manual model updating for bridge structures, not much research has taken into account the influence of external structural components on manual model updating process. To address these issues, two case studies with real structures are established in this research. One is conducted with a 10 story concrete building to demonstrate the importance of having sufficiently detailed initial FEMs in automated model updating of medium-rise buildings and effective use of boundary limits and parameter groups to maintain the physical relevance of the updated FEMs. Other is an investigation with a single span inflexible foot bridge to highlight the necessity to consider external structural components in manual model updating of inflexible structures to develop reliable FEMs. Both case studies employ actual ambient vibration monitoring data obtained from the test structures for the model updating processes.
Finite element model updating of a RC building considering seismic response trends
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security 2013, 2013
This paper presents a study on the seismic response trends evaluation and finite element model updating of a reinforced concrete building monitored for a period of more than two years. The three story reinforced concrete building is instrumented with five tri-axial accelerometers and a free-field tri-axial accelerometer. The time domain N4SID system identification technique was used to obtain the frequencies and damping ratios considering flexible base models taking into account the soil-structure-interaction using 50 earthquakes. Trends of variation of seismic response were developed by correlating the peak response acceleration at the roof level with identified frequencies and damping ratios. A general trend of decreasing frequencies was observed with increased level of shaking. To simulate the varying behavior of the building with response levels, a series of three dimensional finite element models were calibrated considering several points on the developed frequency-response amplitude trend lines as targets for updating. To incorporate real in-situ conditions, soil underneath the foundation and around the building was modeled using spring elements and nonstructural components (claddings and partitions) were also included. Sensitivity based model updating technique was applied taking into account concrete, soil and cladding stiffness as updating parameters. It was concluded from the investigation that knowledge of the variation of seismic response of buildings is necessary to better understand their behavior during earthquakes, and also that the participation of soil and non-structural components is significant towards the seismic response of the building and these should be considered in models to simulate the real behavior.
FEM updating of tall buildings using ambient vibration data
Ambient vibration testing is the most economical non-destructive testing method to acquire vibration data from large civil engineering structures. The purpose of this paper is to demonstrate how ambient vibration Modal Identification techniques can be effectively used with Model Updating tools to develop reliable finite element models of large civil engineering structures. A fifteen story and a forty-eight story reinforced concrete buildings are used as case studies for this purpose. The dynamic characteristics of interest for this study were the first few lateral and torsional natural frequencies and the corresponding mode shapes. The degree of torsional coupling between the modes was also investigated. The modal identification results obtained from ambient vibration measurements of each building were used to update a finite element model of the structure. The starting model of each structure was developed from the information provided in the design documentation of the building. Different parameters of the model were then modified using an automated procedure to improve the correlation between measured and calculated modal parameters. Careful attention was placed to the selection of the parameters to be modified by the updating software in order to ensure that the necessary changes to the model were realistic and physically realisable and meaningful. The paper highlights the model updating process and provides an assessment of the usefulness of using an automatic model updating procedure combined with results from an ambient vibration modal identification.
Structural control & health monitoring, 2018
Uncertainties in finite element (FE) model updating arise from two main sources: measurement noise and modeling errors. The latter includes model parameter uncertainty and model uncertainty itself. Among these sources of uncertainty, model uncertainty has been proven to be the most influential source of error in FE model updating, which is particularly important when using the updated model for damage identification (DID) purposes. This paper investigates the effects of model uncertainty when updating mechanics-based nonlinear FE models of building structures subjected to earthquake excitation. To solve the parameter estimation problem, the unscented Kalman filter is used as parameter estimation tool. Numerically simulated response data of two state-of-the-art nonlinear FE models of building structures designed according to modern design codes are used as application examples. A twodimensional steel building and a three-dimensional reinforced concrete building, both subjected to seismic base excitation, are analyzed for different types and levels of model uncertainty. The results show that model uncertainty may have significant detrimental effects when using the updated FE model for DID, chiefly in the case of large modeling uncertainty. Although a good match between the measured (observed) and FE predicted responses is usually achieved, unobserved responses at global and local levels often show significant errors.
Model updating and seismic response of a super tall building in Shanghai
Computers & Structures, 2020
The Shanghai Tower is presently the tallest structure in China and one of the super tall buildings in the world. To get a quick and direct insight into the overall dynamic behavior of this complex structure, a lumped-mass finite element model based on macro beam theory was developed. Next, an in-depth sensitivity analysis was performed on this baseline model and model updating was conducted by using modal properties obtained from a full-scale field test of this building in its final stage of construction. The difference of the first nine frequencies was reduced from 27% to 4% after updating, and modal assurance criterion value was improved from 73% to 87%. Time history analyses under two severe seismic events were conducted on both the baseline and updated models. The maximum story drift from the updated model were 40% higher than that from the baseline model, demonstrating the significant influence of model updating on its seismic performance. The framework of model updating by simplified updated model for super tall buildings described in this study provides an efficient way to predict their seismic responses, and the outputs are reliable for wide range of applications in the area of long-term heath monitoring and seismic retrofit.
Sensitivity-Based Model Updating of Building Frames using Modal Test Data
KSCE Journal of Civil Engineering, 2018
Model updating is of significant importance in the actual analyses of real structures. The differences between experimental and numerical dynamic characteristics can be minimized by means of this procedure. This procedure can be carried out using two approaches, namely, the manual model updating and the global or local automated model updating. The local model updating is a convenient tool for all kind of structures capable of minimizing the differences mentioned previously nearly to zero and also of identifying the damage locations and monitoring structural integrity. In this way, current realistic behavior of structures can be represented by updated finite element models. This paper describes a Reinforced Concrete (RC) frame model, its ambient vibration testing, finite element modeling and sensitivity-based automated model updating. The RC frame is of ½ geometric scale with two floors and two bays in the longitudinal direction. It was built and then subjected to ambient vibration tests to determine experimentally their dynamic characteristics. Additionally, the finite element computer program ANSYS was used to determine its initial numerical dynamic characteristics. The experimental and numerical results were compared resulting in maximum differences of 38.38% between them. To minimize these differences, the finite element model was updated using the global and local automated approach using a sensitivity-based analyses with some uncertain parameters. The differences were finally reduced to 4.4% and 0.21% by the global and the local automated model updatings, respectively. It is concluded that sensitivity-based automated updating is a very effective procedure to obtain the updated finite element model which can reflect the current behavior of a structure.
Structural model updating using vibration measurements
ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN), 2009
A multi-objective optimization framework is presented for updating finite element models of structures based on vibration measurements. The method results in multiple Pareto optimal structural models that are consistent with the measured data and the residuals used to measure the discrepancies between the measured and the finite element model predicted characteristics. The relation between the multi-objective identification method and conventional single-objective weighted residuals methods for model updating is discussed. Computational algorithms for the fast, efficient and reliable solution of the resulting optimization problems are presented. The algorithms are classified to gradient-based, evolutionary strategies and hybrid techniques. In particular, efficient algorithms are introduced for reducing the computational cost involved in estimating the gradients and Hessians of the objective functions representing the modal residu-als. The computational cost for estimating the gradients and Hessian is shown to be independ-ent of the number of structural model parameters. The methodology is particularly efficient to system with several number of model parameters and large number of DOFs where repeated gradient and Hessian evaluations are computationally time consuming. Theoretical and com-putational developments are illustrated by updating finite element models of multi-span rein-forced concrete bridges using simulated modal data.
Incremental dynamic analysis of high‐rise towers
… Structural Design of …, 2010
The performance study of high-rise towers has been attracting attention recently. Powerful analysis methods are used to assess local and global behaviour of tall structures. Incremental Dynamic Analysis (IDA) is one the most powerful methods for accurate estimation of seismic performance of structures. In this paper, IDA is applied on high-rise towers, specifi cally Tehran telecommunication tower. Three different fi nite element models have been developed. The fi rst model is a two-dimensional fi bre beam element model on which IDA is applied. The other two models are fi nely meshed three-dimensional elastic and inelastic multiaxial-element-based models, which are used to investigate the validity of the two-dimensional model. Furthermore, the effi ciency of different Intensity Measures and Engineering Demand Parameters is investigated. The results show that there is a good agreement between the results of two-dimensional and three-dimensional models in linear and nonlinear domains. It is also observed that Sa(T1) is more effi cient than peak ground acceleration (PGA) as spectral acceleration is a structural specifi c intensity measure in comparison with, which is site-specifi c. Copyright © 2009 John Wiley & Sons, Ltd.
2018
This thesis research focusses on the development of a reliable and efficient 3D calculation model of an existing high-rise, reinforced concrete building in the Groningen area, in order to analyse the dynamic behaviour of the existing and subsequently retrofitted main bearing structure of this high-rise building. The assessment of the existing building is performed through a Non-Linear Time History analysis in Simulia Abaqus, in which cracking of concrete and yielding of reinforcement is taken into account. Multiple NLTH analyses are performed for optimisation of the 3D model in order to obtain correct results with a minimum amount of calculation costs. This optimisation process results in a clear understanding of the dynamic behaviour of the building and the main sensitivities of the model. The 3D model is verified by means of a simplified 1D beam type model, developed and analysed with the software package Matlab. This 1D model consists of three elements, corresponding to the three...
Structural Engineering International, 2018
The objective of this paper is to evaluate the acceptable differences limit between analytically and experimentally identified modal parameters and to assess its contribution to the success of finite element model updating. To achieve this aim, three one-story reinforced concrete buildings consisting of raft foundation, columns and beams were simultaneously constructed under laboratory conditions. Experimental measurements were taken for each building to determine the modal parameters using ambient vibration tests. All parameters, which could be expected to affect structural behavior, such as structural dimensions, concrete properties, reinforcement detailing, construction joints, concreting days, workmanship, temperature and humidity, were made the same, as far as possible, for each building to eliminate the influence of environmental effects on experimental measurements. At the end of the study, the differences in the experimentally identified natural frequencies were obtained between 3.14% and 11.83%, with all parameters the same for each building model. As a result of this paper, it is suggested that the maximum acceptable differences limit can be taken as 5%.