MS07.2: Nonlinear Phenomena in Mechanical and Structural Systems

The energy harvesting from mechanical vibrations using a Micro Fiber Composite (MFC) patch and its optimal placement are a main purposes of this paper. The plant consists of a pseudo-conical cantilever shell with opposite curvatures. After applying initial stresses at boundary conditions, the shell acquires four stable states in terms of a static configuration. The unique geometry of the shell and antisymmetric lamina sequence are analysed by finite element model simulations and a strain energy criterion is estimated to identify a suitable location for the piezoelectric element. The designed system is experimentally subjected to various external events such as a single jump between stable configurations, in-well or cross-well resonant forcing. The study does not only investigate the first natural frequencies corresponding to each stable configuration of the composite structure but also higher vibration mode shapes in terms of enhancing the energy recovery factor taking into account sources of mechanical energy as well as MFC structural limits.

O-type ball valves are widely used in various fields. The nonlinear vibration of O-type ball valves would cause damage on valve components and accessories, and flow-induced vibration is the major component of the whole vibration. During the use of valves, cavitation often occurs, accompanied by more severe vibrations. Therefore, it is crucial to investigate the effect of cavitation on valve vibration. In this paper, fluid solid interaction (FSI) method is used to study the vibration characteristics of an O-type ball valve with and without cavitation, the mechanism of cavitation leading to unbalanced intensification of vibrations in three axes is elucidated and it is concluded that cavitation increases the amplitude of the primary vibration frequency of the valve through the spectrogram comparison.

When designing a bridge subjected to seismic loading, the ductility capacity of the elements that are expected to enter the inelastic range must be defined. To achieve this, the engineer consults design recommendations or codes, but many times these recommendations vary from code to code or are insufficient because they only consider a few typologies. This paper analyzes the ductility capacity of piers and columns of a common urban bridge, composed of a superstructure of concrete slab and AASTHO-type beams, on a substructure of single or multiple reinforced concrete piers. From this type of bridge, different element heights and medium and high ductility behavior levels are analyzed using static and dynamic nonlinear methods. For this, it is also considered that the structures are located on three different types of soil (rigid, transition and soft) with soil characteristics of Mexico City and with the inclusion of the soil-structure interaction effect. The models made are designed according to local design requirements and push-over analyzes are carried out to define the capacity curve, through which the ductility capacity is determined. Additionally, step-by-step dynamic analyzes are carried out with a base of ten characteristic earthquakes of each type of soil, scaled to obtain the same level of seismic hazard as that considered in the design. From the results obtained, the average ductility demand of the elements is determined. Capacity and demand ductility values are compared. Results obtained in both analyzes are compared to verify if the elements can develop the proposed level of ductility. The obtained results are used to define design recommendations for the ductility capacity or seismic behavior factor of piers and columns of urban bridges.