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To meet the need of constructing fixed cross strait links, super-long span bridge with a main span over 2 000m is considered as a candidate for their ability to cross deep and wide straits. To this end, some super-long span bridges with proper cable and girder systems were previously proposed and studied. The major design considerations are aimed at adopting new cable material, increasing the entire rigidity of the bridge, stabilizing the dynamic characteristics, strengthening the deck sections, etc. In this paper, a brief review of main cable and girder system is first given of the concepts previously proposed for the design of super-long span bridges. Then some typical examples are studied, focused on various issues related to the design of super-long span bridges, including composite cable, the unstressed length and tension force of the main cable, the stiffness and mass effects of the deck on critical wind speed, and the critical wind speed of various cable systems. The most challenges in super-long span bridges are to solve aerostatic and aerodynamic instability at required design wind speed. In this connection, the wind-induced aerostatic instability of super-long span bridges is studied by a two-stage geometric nonlinear analysis for dead loads and wind loads. The developed program adopted herein for geometric nonlinear analysis was verified and confirmed before. The proposed methods (i.e. composite cable, slotted girder, increasing deck stiffness and mass, cable layout, etc.) obtained for all the examples are in agreement with this study, which indicates applicability of the design approaches presented.

The torsional aerodynamic instability of single-axis solar trackers under strong wind seriously threatens the safety of solar trackers due to the occurrence of large torsional vibrations, and the corresponding mechanism is still unclear. In this study, the torque coefficient and torsional angle of a single-axis solar tracker are tested synchronously using an aeroelastic sectional model in a wind tunnel. The critical wind speed, torque coefficients, and interaction between the torsional angle and torque coefficients at different tilt angles are analyzed, and the following results can be obtained. Torsional aeroelastic instability occurs in a tilt angle range of -10° to 15°, and the critical wind speed decreases as the tilt angle increases. The standard deviation of dynamic torque coefficients is much larger than that of static torque coefficients, and torque coefficients showed a significant dominant frequency characteristic in the vibration state due to torsional vibration instead of wind load. The wind load in the windward area promotes vibration, while the wind load in the leeward area may promote vibration with the PV module tilt angle being slight and suppress vibration with the tilt angle being significant.

To apply silicon-based wind energy harvesters (WEHs) in natural environments, it is significant to decrease the onset critical wind speeds. A MEMS piezoelectric WEH with an aluminum nitride film was fabricated, and then characterized in a small wind tunnel. The onset critical wind speed region with the lower and upper limits was observed in the experiments. When wind speed was lower than the lower critical speed, the electrical output was low and the vibration of the harvester was mainly the turbulence-induced vibrations modulated by its natural frequency. When wind speed was between the lower critical speed and the upper critical speed, strong wind-induced vibration appeared sometimes but cannot be sustained. When the wind speed was higher than the upper critical speed, the wind-induced vibration with large and stable amplitudes can be sustained and the electrical output was relatively high. The onset critical wind speed region strongly depends on the attack angle of the harvester. The measured lower and upper onset critical wind speeds of the MEMS harvester were about 4.0 m s⁻¹ and 4.4 m s⁻¹, respectively, when the attack angle was about 15°. The measured maximum output power was about 0.14 μW for the case with the attack angle of 0° when wind speed was 7.3 m s⁻¹.