Manual model updating of highway bridges under operational condition

Ahmet C. Altunisik,Alemdar Bayraktar 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.1

Finite element model updating is very effective procedure to determine the uncertainty parameters in structural model and minimize the differences between experimentally and numerically identified dynamic characteristics. This procedure can be practiced with manual and automatic model updating procedures. The manual model updating involves manual changes of geometry and analyses parameters by trial and error, guided by engineering judgement. Besides, the automated updating is performed by constructing a series of loops based on optimization procedures. This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges using manual model updating procedure. Birecik Highway Bridge located on the 81stkm of Şanliurfa-Gaziantep state highway over Firat River in Turkey is selected as a case study. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the arch compartment is investigated. Three dimensional finite element model of the arch compartment of the bridge is constructed using SAP2000 software to determine the dynamic characteristics, numerically. Operational Modal Analysis method is used to extract dynamic characteristics using Enhanced Frequency Domain Decomposition method. Numerically and experimentally identified dynamic characteristics are compared with each other and finite element model of the arch compartment of the bridge is updated manually by changing some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the difference between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %49.1 to %0.6 by model updating. Also, a good harmony is found between mode shapes after finite element model updating.

Finite Element Model Updating of a Simply Supported Skewed PSC I-girder Bridge using Hybrid Genetic Algorithm

정대성,김철영 대한토목학회 2013 KSCE Journal of Civil Engineering Vol.17 No.3

Hybrid Genetic Algorithm (HGA) which combines the genetic algorithm as a global optimization and the simplex method as a local optimization is proposed for a finite element model updating of a real prestressed concrete bridge structure. In order to minimize the updating error between the measurement and the finite element model updating result, objective functions which are combinations of fitness functions based on the natural frequency, the mode shape and the static displacement are introduced. And an interface tool is also developed in order to utilize various element library and numerical analysis tools which are provided by commercial finite element and numerical analysis programs. A simply supported skewed PSC girder bridge which has 30 m span length is selected for the verification of the proposed FE model updating algorithm. Static vehicle loading test and forced vibration test by traveling vehicle as well as ambient vibration test were carried out to obtain the reference measurement data for numerical updating. A grillage model is used for the finite element analysis. Effect of the spring element to simulate the realistic support condition which is not perfectly free or restrained in real situation as well as that of the objective function on the updating accuracy are studied. From the result of parametric study, it is investigated that the use of spring element for support condition is effective to minimize the updating error for natural frequency and mode shape. Furthermore, including the static displacement fitness function together with those of dynamic properties may improve the global behavior of updated finite element model. It is concluded that the hybrid genetic algorithm proposed in this study is a very effective finite element model updating method to find an accurate result in updating real bridge structure based on measured data.

Vibration based damage detection in a scaled reinforced concrete building by FE model updating

Temel Türker,Alemdar Bayraktar 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.1

The traditional destructive tests in damage detection require high cost, long consuming time, repairing of damaged members, etc. In addition to these, powerful equipments with advanced technology have motivated development of global vibration based damage detection methods. These methods base on observation of the changes in the structural dynamic properties and updating finite element models. The existence, location, severity and effect on the structural behavior of the damages can be identified by using these methods. The main idea in these methods is to minimize the differences between analytical and experimental natural frequencies. In this study, an application of damage detection using model updating method was presented on a one storey reinforced concrete (RC) building model. The model was designed to be 1/2 scale of a real building. The measurements on the model were performed by using ten uni-axial seismic accelerometers which were placed to the floor level. The presented damage identification procedure mainly consists of five steps: initial finite element modeling, testing of the undamaged model, finite element model calibration, testing of the damaged model, and damage detection with model updating. The elasticity modulus was selected as variable parameter for model calibration, while the inertia moment of section was selected for model updating. The first three modes were taken into consideration. The possible damaged members were estimated by considering the change ratio in the inertia moment. It was concluded that the finite element model calibration was required for structures to later evaluations such as damage, fatigue, etc. The presented model updating based procedure was very effective and useful for RC structures in the damage identification.

Computational finite element model updating tool for modal testing of structures

Abdurrahman Şahin,Alemdar Bayraktar 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.2

In this paper, the development of a new optimization software for finite element model updating of engineering structures titled as FemUP is described. The program is used for computational FEM model updating of structures depending on modal testing results. This paper deals with the FE model updating procedure carried out in FemUP. The theoretical exposition on FE model updating and optimization techniques is presented. The related issues including the objective function, constraint function, different residuals and possible parameters for FE model updating are investigated. The issues of updating process adopted in FemUP are discussed. The ideas of optimization to be used in FE model updating application are explained. The algorithm of Sequential Quadratic Programming (SQP) is explored which will be used to solve the optimization problem. The possibilities of the program are demonstrated with athree dimensional steel frame model. As a result of this study, it can be said that SQP algorithm is very effective in model updating procedure.

가속도 및 각속도 데이터 융합 기반 유한요소모델 개선

김현준,조수진,심성한 한국구조물진단유지관리공학회 2015 한국구조물진단유지관리공학회 논문집 Vol.19 No.2

The finite element (FE) model updating is a commonly used approach in civil engineering, enabling damage detection, design verification, and load capacity identification. In the FE model updating, acceleration responses are generally employed to determine modal properties of a structure, which are subsequently used to update the initial FE model. While the acceleration-based model updating has been successful in finding better approximations of the physical systems including material and sectional properties, the boundary conditions have been considered yet to be difficult to accurately estimate as the acceleration responses only correspond to translational degree-of-freedoms (DOF). Recent advancement in the sensor technology has enabled low-cost, high-precision gyroscopes that can be adopted in the FE model updating to provide angular information of a structure. This study proposes a FE model updating strategy based on data fusion of acceleration and angular velocity. The usage of both acceleration and angular velocity gives richer information than the sole use of acceleration, allowing the enhanced performance particularly in determining the boundary conditions. A numerical simulation on a simply supported beam is presented to demonstrate the proposed FE model updating approach. 유한요소모델 개선은 구조물의 설계검증, 손상추적, 내하력 평가 등 다양하게 활용되고 있는 기법이다. 일반적인 유한요소모델 개선은구조물에서 계측된 가속도응답으로부터 구조물의 고유진동수와 모드형상을 구하고, 이를 바탕으로 모델을 개선하게 된다. 이와 같은 가속도응답기반 유한요소모델 개선은 구조물의 병진 자유도를 고려하기 때문에 물리적인 체계를 추정하는데 있어서 매우 적합하지만, 회전 자유도 상에서 변화하는 구조물의 경계조건을 판별하기에는 어려움이 있다. 최근 센서 기술의 개발로 인하여 저렴한 가격, 높은 정확성의 자이로센서들이 개발되고 있으며, 그에 따라 구조물의 회전 자유도에 관한 정보 획득이 용이해지고 있다. 본 연구에서는 이를 바탕으로 가속도와 각속도 응답을 함께 이용하는 데이터 융합 기반 유한요소모델 개선 기법을 제안하였다. 가속도와 각속도를 모두 활용한 데이터융합기법은, 가속도만 사용한 기존의 유한요소 모델 기법보다 구조물의 경계조건 판별에 정확한 정보를 제공한다. 본 논문에서는 단순보 모델을이용한 수치 시뮬레이션을 통해서, 제안한 가속도와 각속도 데이터 융합기반의 유한요소모델 개선 기법의 성능을 검증하였다.

Finite element model updating of jointed structure based on modal and strain frequency response function

Zhan Ming,Guo Qintao,Yue Lin,Zhang Baoqiang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

To acquire a reasonable model for structural dynamic strength analysis, a bottom-up finite element modeling and updating methodology based on multi responses is proposed. The fundamental principles of structural dynamics analysis and model updating were introduced, and the proposed strategy was applied to the case study of an L-shaped jointed structure. Components of the jointed structure were modeled sequentially, and inaccurate model parameters were updated based on the corresponding experimental modal results in the first stage. In the second stage, components were connected together by bolts. The joint interfaces were represented by thin-layer elements, and local joint parameters were updated based on strain frequency response function (FRF). Finally, the precision of finite element model (FEM) was validated by acceleration frequency response function. The results indicated that the proposed methodology is able to reduce model simulation errors in both components and the overall jointed structure. Not only can the updated model of a jointed structure reproduce the experimental results used in updating, but also predict responses that are not used in the process of model updating.

Computational finite element model updating tool for modal testing of structures

Sahin, Abdurrahman,Bayraktar, Alemdar Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.2

In this paper, the development of a new optimization software for finite element model updating of engineering structures titled as FemUP is described. The program is used for computational FEM model updating of structures depending on modal testing results. This paper deals with the FE model updating procedure carried out in FemUP. The theoretical exposition on FE model updating and optimization techniques is presented. The related issues including the objective function, constraint function, different residuals and possible parameters for FE model updating are investigated. The issues of updating process adopted in FemUP are discussed. The ideas of optimization to be used in FE model updating application are explained. The algorithm of Sequential Quadratic Programming (SQP) is explored which will be used to solve the optimization problem. The possibilities of the program are demonstrated with a three dimensional steel frame model. As a result of this study, it can be said that SQP algorithm is very effective in model updating procedure.

깊은 신경망을 이용한 구조물의 유한요소모델 업데이팅

공밍,박원석 대한토목학회 2019 대한토목학회논문집 Vol.39 No.1

The finite element model updating can be defined as the problem of finding the parameters of the finite element model which gives theclosest response to the actual response of the structure by measurement. In the previous researches, optimization based methods have been developed to minimize the error of the response of the actual structure and the analytical model. In this study, we propose an inverse eigenvalue problem that can directly obtain the parameters of the finite element model from the target mode information. Deep Neural Networks are constructed to solve the inverse eigenvalue problem quickly and accurately. As an application example of the developed method, the dynamic finite element model update of a suspension bridge is presented in which the deep neural network simulating the inverse eigenvalue function is utilized. The analysis results show that the proposed method can find the finite element model parameters corresponding to the target modes with very high accuracy. 유한요소모델 업데이팅은 계측에 의한 구조물의 실제 응답과 가장 가까운 응답을 내는 유한요소모델의 매개변수를 찾는 문제로 정의할 수 있다. 기존 연구에서는 실 구조물과 해석 모델의 응답의 오차를 최소화하는 최적화에 기반 한 방법이 개발되었다. 이 연구에서는 목표 모드 정보로부터 유한요소 모델의 매개변수를 직접 얻을 수 있는 역 고유치 문제를 구성하고 역 고유치 문제를 빠르고 정확하게 풀기 위한 깊은 신경망(Deep Neural Network)을 구성하는 방법을 제안한다. 개발한 방법의 적용 예로서 현수교의 역 고유치 함수를 모사하는 신경망을 이용한 동적 유한요소모델 업데이트를 보인다. 해석 결과 제시한 방법은 매우 높은 정확도로 목표 모드에 대응하는 매개변수를 찾아낼 수 있음을 보였다.

Finite element model updating effect on the structural behavior of long span concrete highway bridges

A.C. Altunisik,A. Bayraktar 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.6

In this paper, it is aimed to determine the finite element model updating effects on the structural behavior of long span concrete highway bridges. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. The bridge consist of fourteen spans, each of span has a nearly 26m. The total bridge length is 380m and width of bridge is 10m. Firstly, the analytical dynamic characteristics such as natural frequencies and mode shapes are attained from finite element analyses using SAP2000 program. After, experimental dynamic characteristics are specified from field investigations using Operational Modal Analysis method. Enhanced Frequency Domain Decomposition method in the frequency domain is used to extract the dynamic characteristics such as natural frequencies, mode shapes and damping ratios. Analytically and experimentally identified dynamic characteristics are compared with each other and finite element model of the bridge is updated to reduce the differences by changing of some uncertain parameters such as section properties, damages, boundary conditions and material properties. At the end of the study, structural performance of the highway bridge is determined under dead load, live load, and dynamic loads before and after model updating to specify the updating effect. Displacements, internal forces and stresses are used as comparison parameters. From the study, it is seen that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %46.7 to %2.39 by model updating. A good harmony is found between mode shapes after finite element model updating. It is demonstrated that finite element model updating has an important effect on the structural performance of the arch type long span highway bridge. Maximum displacements, shear forces, bending moments and compressive stresses are reduced %28.6, %21.0, %19.22, and %33.3-20.0, respectively.

FE 모델향상 기법을 이용한 세장한 아치구조의 경계조건 결정

조순호(Soon-Ho Cho) 한국소음진동공학회 2021 한국소음진동공학회 논문집 Vol.31 No.1

For a long time, finite element analysis was widely used as an analytical tool to predict the modal parameters of large civil structures such as frequencies and mode shapes. However, their predicted responses normally do not correlate well with those observed because of the physical uncertainties inherent in the boundary conditions, and material properties that are engaged during the mass and stiffness estimations in the FE model. A modal parameter- or an FRF-based finite element model updating procedure can effectively address the aforementioned issue by varying the structural parameters based on the optimization theory, resulting in a highly reliable FE model. This paper demonstrates how a numerical or mathematical model can be iteratively updated to closely match with the global responses of the physical model. In this study, a slender arch structure for green houses is considered as a test specimen. Using an impulse hammer, an input-output modal test is performed, and its natural frequencies and mode shapes are extracted using an advanced system identification, called PolyMAX. Additionally, the test specimen is numerically modeled using ANSYS and a common in-house program, which can be directly exported to a FE model updating tool. The modal parameters or FRFs extracted from a series of vibration records are used as the reference data for updating the initial finite element model by varying the stiffnesses of the members and base or connection springs in a 3-dofs. Finally, it is found that the updated finite element model shows sufficient improvement in the correlation between the test and analysis results in terms of the modal parameters or FRFs, while the latter case scatters more.