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.
Numerous constructed jacket platforms in the Persian Gulf require continuous monitoring due to aging which poses a significant hazard to the environment. The main aim of this study is to sketch a ...health monitoring system to address the problem of limitations and shortcomings of sensor networks and also to solve the localization problem. In order to achieve this goal, experimental modal analysis (EMA) is performed on a physical model of an offshore jacket platform to develop a numerically updated finite element model. Both traditional and improved Cross-Model Cross-Mode (CMCM) iteration algorithms are employed for this purpose and different model order reduction methods are compared in terms of their effects on the structural dynamic behavior of the case-study (SPD8 jacket platform). A new formulation is also proposed for the first time to compare the results of damage scenarios using both iteration algorithms. The effectiveness of the methodology in practical cases is also assessed by considering various numbers of sensors. According to the results, the improved iteration technique eliminates the detrimental impacts of the model reduction procedure on the proposed methodology, and physical parameters such as length, type, and location of a member play significant roles in the success of a damage detection scenario.
•A monitoring approach is studied to address the problem of limitations of sensor networks.•The frame of proposed method adjusted considering the concept of reduced eigenvalue problem.•The research is an experimental study on a laboratory model of a jacket platform.•The improved technique eliminates the detrimental impacts of the model reduction procedure.•The method is more successful in diagnosing the lack of the bracing members.
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