Goian – Cerveira Footbridge over the Miño River. Spain - Portugal

<p>The Goián - Cerveira footbridge over the Miño river, result of an international competition held in 2017, will connect the Espazo Fortaleza park in Goián-Tomiño, Spain, and the Castelinho park in Vila Nova de Cerveira, Portugal.</p><p>The proposed footbridge saves a main span of 265m, and is a suspended structure, with two towers located on the riverbanks, avoiding intermediate supports on the riverbed, and only one suspension cable. The towers are located not centered with the axis of the footbridge deck, that adopts a curved layout both in plan and in elevation. The curved layout in plan fits better to the footbridge arrival in both riverbanks, and improves its structural behavior. Indeed, the eccentric location of the suspension cable within the deck generates important horizontal transverse forces, that are supported by the curved deck by behaving as an arch. This configuration is also very convenient for supporting and controlling wind loads. It is a classic bridge type -suspended bridge- but with a singular configuration due to the curved layout of the deck and its arc-like behavior.</p><p>The result is a very subtle and slender structure, a “line over the Miño river”, that highly preserves the environmental values of the river and the landscape.</p>

Modelisation of Thermally Induced Jitter in a Slender Structure

The thermomechanical interactions of onboard space vehicles is an interesting field of research and study. Since the pioneering paper by Bruno Boley, published in 1954, many authors have given their relevant contribution to the comprehension of phenomena not otherwise investigable if not with a cross-sectoral approach and a multidisciplinary methodology. The anomaly that occurred to the spacecraft Alouette 1, in 1962, marked the beginning of a long series of unexpected events due to unconceivable coupling between the mechanical and thermal behaviour of the system. This work aims to emphasise, by means of a simple model, the basic mechanism responsible for elastic vibrations induced by a thermal shock. This is a widespread event experienced by a spacecraft during the transitions shadow-sun and vice-versa or when a flexible appendage, previously shadowed by the spacecraft's main body, comes to the light as a consequence of an attitude manoeuvre [Ulysses, 1990]. For the investigation, a very slender structure has been considered in order to make the thermal and mechanical characteristic times comparable and realise the conditions of strong coupling. The accurate thermal analysis provides an equivalent thermal bending moment, depending on time, which appears as a boundary condition in the subsequent modal analysis of the structural element, where it plays the role of a trigger of elastic transverse vibrations.

Vibration Control of a High-Rise Slender Structure with a Spring Pendulum Pounding Tuned Mass Damper

High-rise structures are normally tall and slender with a large height-width ratio. Under the strong seismic action, such a structure may experience violent vibrations and large deformation. In this paper, a spring pendulum pounding tuned mass damper (SPPTMD) system is developed to reduce the seismic response of high-rise structures. This SPPTMD system consists of a barrel limiter with the built-in viscoelastic material and a spring pendulum (SP). This novel type of tuned mass damper (TMD) relies on the internal resonance feature of the spring pendulum and the collision between the added mass and barrel limiter to consume the energy of the main structure. Based on the Hertz-damper model, the motion equation of the structure-SPPTMD system is derived. Furthermore, a power transmission tower is selected to evaluate the vibration reduction performance of the SPPTMD system. Numerical results revealed that the SPPTMD system can effectively reduce structural vibrations; the reduction ratio is greater than that of the spring pendulum. Finally, the influence of the key parameters on the vibration control performance is conducted for future applications.

Fluid Drag With and Without Vortex-Induced Vibrations

Fluid drag is an integrated force that depends on the velocity of the fluid flow relative to the motion of a structure. In previous OMAE papers, we used nonlinear physics-based time-domain simulations to show how fluid drag evolves geometric changes in slender (long and thin) structures. We then showed how these changes physically determine the specific dynamic nature of the vibrations that the fluid can induce in the structure. Induced vibrations are four-dimensional oscillations in a marine riser, suspended pipe or other slender structure, whereby the maximum amplitude of deflection is generally perpendicular to the sustained action. The sustained action is often fluid drag. In this paper, we study the physical relationship between fluid drag and induced vibrations. By focusing on the nonlinear interaction between fluid and structure, we revisit a longstanding belief that vortex-induced vibrations amplify fluid drag. Using nonlinear physics-based simulations of a slender structure interacting with flowing fluid, we show how amplification depends on the type of vibration (imposed or free). In other words, drag amplification can occur when we impose a vibration on the structure, but does not occur when we allow sufficient geometric freedom so that the fluid merely induces the structure to vibrate. Using simple visual experiments, we confirm that Vortex-Induced Vibrations (VIV) do not amplify fluid drag. This result is consistent with basic energy conservation principles.