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Nonlinear energy sink (NES) devices have recently been introduced in civil engineering for structural control. Because of the essential geometric nonlinearities governing these devices, identification must be performed in the time domain. Such methods can be challenging due to processing requirements, sensitivity to noise, and the presence of nonlinearity. Bayesian analysis methods have been shown to overcome these challenges, providing robust identification of nonlinear models. In this study we compare the unscented Kalman filter and the particle filter for the identification of a prototype NES device. Simulated responses developed using a device model and a sample set of parameters are used here to demonstrate and evaluate the identification process. Analysis of the identification results is conducted by varying the identification technique used and the selection of the prior distributions on the parameters. These preliminary numerical results will inform a later implementation on experimental response data.

Currently, construction tendencies tend to design flexible structures, such as footbridges, slabs and grandstands, due to the increased resistance of new materials and the regulation gap in building codes. These flexible structures are susceptible of excessive vibrations induced by human activities, producing serviceability failures and, sometimes, collapse. It is essential to improve the understanding of the effect of anthropic loads over the structures to mitigate serviceability problems and the risk of structural damage and, therefore, economic and human loses.

Scientific research has experienced a transformation over the last several decades. To tackle today’s grand challenges in science and engineering, researchers today must leverage and integrate the skills and knowledge of team members with computational resources and infrastructure that include data, computing, communications, and high performance computing resources.

Hybrid Simulation (HS) and Real Time Hybrid Simulation (RTHS) are recognized as powerful techniques for civil infrastructure assessment. Typically in HS/RTHS, a critical component is isolated as the physical component in the simulation, while the remainder of the structure is modeled numerically. This approach enables response evaluation on both local and global level. Broadening the applications that would like to use HS and RTHS requires that we examine more complex structural systems. When multiple components in the structural system have the same design and contribute roughly equally to the response, it may be difficult to select the most appropriate physical component. However, modeling errors in those structural components that reside in the numerical component can influence the accuracy of the global responses. Model updating based on the responses of the physical component for determining the model parameters will reduce the influence of the modeling errors. Advances in online system identification techniques and their application to more complex structural models, enables the option of incorporating online model updating into HS/RTHS. Through a simplified case study, we explore the feasibility of HS/RTHS with model updating (HSMU/RTHSMU). A two story steel frame equipped with two identical magnetic-rheological (MR) dampers. In RTHS, the first story MR damper is loaded as the physical component and the remainder of the structure, including the frame and the second MR damper, is numerically modeled. Simulation and conventional RTHS response are considered. In each case the second story MR damper model uses one initial parameter set, which is then updated online using identified parameters based on the physical component (RTHSMU). Online model updating is then investigated using a validation signal, and the fidelity and advantages of RTHSMU are discussed.

An increasing number of structures, such as pedestrian bridges, are affected by excessive vibration when they are dynamically excited. The development of new materials and improvements in guidelines have given rise to designs with longer spans and slender structural elements, which in turn cause such structures to be more susceptible to vibration problems. However, serviceability guidelines do not address the changes of the dynamic properties of pedestrian bridges nor do they accurately predict their dynamic response. In order to improve the structural analysis and design, a new computational tool is developed using an intercommunication platform between MATLAB and SAP2000 application programming interface (API) to consider different human walking models, including user-defined models, directly on the footbridge to take into account human-structure interaction effects. Details of the application are presented in this paper and results of the analysis for some walking models and their effects on the dynamic parameters of the bridge are given.

The study of vibrations in beams has been largely addressed by authors and researchers. However, relatively few researchers have considered the case of unknown boundary conditions, as usually it is reasonable to assume the classical cases such as simply supported, clamped or free. Indeed, there are a wide variety of boundary-condition configurations, each one representing a whole different problem with its own modal characteristics. A method for updating experimental beam models to specifically address the issue of unknown boundary conditions is proposed; this methodology takes advantage of vector comparison techniques such as the modal assurance criterion based on the Cauchy-Schwartz inequality to determine the degree of linear relationship between two mode shapes systematically and iteratively until an acceptable parametric match is found. This paper includes the phases of numerical study and experimental validation. A brief introduction with some relevant previous publications is presented, before explaining the methodology derivations and considerations in the numerical study section. A section devoted to demonstrate the methodology with an experimental example is presented in the Experimental validation section, and finally some conclusions and future work.