Conventional design of pier structures is based on the assumption of fully rigid joints. In practice, the real connections are semi-rigid that cause changes in dynamic characteristics. In this study, ...quality of the joints is investigated by considering changes in natural frequencies. For this purpose, numerical and experimental modal analyses are carried out on related physical model of a pier type structure. When numerical results are evaluated, natural frequencies generally do not match the expected experimental results. Uncertainties in different aspects of engineering problems are always a challenge for researchers. The numerical models which are constructed on the basis of highly idealized scheme may not be able to represent all of the physical aspects of the physical one. For this study, determination of percentage of semi-rigid joints is considered as an optimization problem based on the numerical and experimental frequencies. Probabilistic sensitivity analysis is also used to determine the search space. A new technique of optimization problem is solved by a combination of smart particle swarm optimization (PSO) and genetic algorithms, and a complicated and efficient system for model updating process is introduced. It is observed that the hybrid PSO-Genetic algorithm is applicable and appropriate in model updating process. It performs better than PSO algorithm, considering the good agreement between theoretical frequencies and experimental ones, before and after model updating.
•This work contributes to the exact and explicit sensitivity equation using time-domain data.•The proposed method allows one to update the Finite Element Model under small, moderate, and significant ...damage in the presence of noise and modeling error.•Damage detection can be identified by the measured time domain-response using the proposed sensitivity equation.•The advantages of the proposed method are explained than the derivation-based method and Direct Differentiation Method (DDM).
This paper presents an innovative explicit sensitivity equation for structural parameters estimation using the time domain data. The proposed exact sensitivity equation provides a linear relation between the time history response and variation of structural parameters. In order to achieve an accurate sensitivity equation, the incomplete measured responses of the damaged structure are incorporated into the mathematical formulation. The accuracy of the method is numerically examined in several damage scenarios. The crucial issues such as the weighting of the equation, measurement, and modeling errors are investigated. The proposed method is used to identify structural parameters subjected to impact and single harmonic excitation loads. The parameter estimation results show the robustness and accuracy of the proposed method. Moreover, the advantages of the proposed method are explained than the derivation-based method and the Direct Differentiation Method (DDM).
In this paper, a new sensitivity equation is formulated for structural parameter estimation based on the time-history response. There are three methods for calculating the structural response ...variation with respect to changes in structural parameters in the time domain: Finite Difference Method (FDM), Direct Differentiation Method (DDM), and Adjoint variable Method (AVM). These methods are gradient-based, and they cannot compute the actual sensitivity. The proposed sensitivity equation explicitly calculates the sensitivity (closed-form sensitivity) in an exact manner and provides a linear relationship between the time history response and the variation of structural parameters. The efficiency and accuracy of the proposed method are examined for the finite element model updating of a jacket-type platform. Moreover, the effectiveness of the proposed method is evaluated in the presence of measurement and environmental errors. The performance of the proposed sensitivity equation is compared with the mentioned direct differentiation method.
•The exact and explicit sensitivity equation is derived using time-domain data.•The proposed method linearly relates the variation of structural response to the measured time-domain data.•The proposed sensitivity relation is applied to the jacket type-platform under small, moderate, and significant damage.•The proposed method's advantages are explained than the other methods, such as the Direct Differentiation Method (DDM).
•A direct and straightforward relationship is proposed to calculate the acceleration response sensitivity to changes in structural parameters.•The proposed sensitivity equation simplifies sensitivity ...analysis in contrast to the finite difference method (FDM) and direct differentiation method (DDM).•By utilizing the measured responses in the computation of the sensitivity matrix, the introduced method exhibits precise performance compared to the current methods.•The suggested sensitivity approach is applicable for both damage identification and finite element model updating.
The utilization of time-domain data for structural damage diagnosis and finite element model updating has several benefits, such as direct implementation of the measured data with no requirement for domain changing and susceptibility to structural damages. This study introduces a straightforward sensitivity relation for the measured acceleration response, avoiding the requirement for computational techniques like direct differentiation methods. The proposed equation establishes a linear relationship between variations of the structural parameters and structural responses. The proposed sensitivity equation operates at the level of improved equations and exhibits greater accuracy compared to the current approaches. The numerical evaluation of the proposed sensitivity equation on two offshore jacket platforms reveals the accuracy of the proposed method. Additionally, an experimental case study to examine the efficacy and validation of the introduced sensitivity relation in real-world settings demonstrates the procedure’s viability. The numerical and experimental results reveal the accuracy of the proposed sensitivity equation.
•This work establishes a precise and linear correlation between structural parameters and variations in acceleration response in the time domain.•According to the proposed sensitivity relation, ...Finite Element Model (FEM) updating and sensitivity calculations can be done more quickly and efficiently than with current methods like FDM and DDM.•The sensitivity relation that has been developed is utilized for the purpose of damage identification on the jacket type platform.
One of the challenges of the finite element model updating using time domain data is the lack of a direct relationship between changes in structural parameters and structural responses. Computational techniques, such as the Finite Difference Method (FDM) and Direct Differentiation Method (DDM), are used to calculate the sensitivity of the structural response to variations of structural parameters in the time domain. The use of these methods is time-consuming for large and complex structure. In the present study, an exact sensitivity equation is presented that establishes a direct and linear relationship between changes of structural parameters and structural response variations. The proposed closed form equations, have high computational efficiency in calculating the sensitivity of time domain responses. The measured responses directly contribute to the calculation of the sensitivity matrix, so the finite element model updating procedure is improved in terms of accuracy and reliability. The proposed method updates the finite element model even using a single excitation frequency that distinguishes the presented sensitivity relationship from frequency response-based methods which use wide ranges of excitation frequencies for model updating. To evaluate the effectiveness of the proposed method, different damage scenarios with different intensities have been simulated on two offshore jacket platform models. The performance of the proposed method in identifying the location and severity of induced damages in the presence of measurement and modeling errors confirms the effectiveness of the proposed method.
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