The Mode I and Mode II dynamic fracture toughness (DFT) values, KId and KIId for high
strength steels 40Cr and 30CrMnSiNi2A were evaluated using a combined experimental-numerical
method. The tests were performed on three point bend (3PB) and shear specimens with Hopkinson
pressure bar. The time of crack initiation was determined by a strain gauge. With the assistance of
3-D transient finite element analysis, the temporal evolution of the dynamic stress intensity factor
under different loading rates was obtained, and the DFT was determined by the fracture initiation
time. In Mode I tests, a brittle transgranular fracture was found in 40Cr, while evidence for ductile
fracture was observed on the failure surface of 30CrMnSiNi2A. In Mode II tests, both tensile cracks
and adiabatic shear bands were found for the two steels. The effect of ligament size on fracture
toughness was discussed. The correlations of KId and KIId with loading rate were also investigated.
The micromechanisms of loading rate effect on the DFT were discussed for both modes.
To investigate the wind-induced response and equivalent wind load of a super-tall building, an aeroelastic model of the building was designed to measure aerodynamic interference in wind tunnel tests. Experiments on pressure and vibration measurements were conducted in both uniform and turbulent wind fields, and the displacement response and surface wind pressure at different locations of the model were recorded. The displacement time-history response spectrum and aerodynamic spectrum in both fields were compared and analyzed. The research showed that the mean displacement responses of the model in the across-wind and along-wind directions gradually increased with velocity under different wind attack angles. The mean displacement response of torsion moment in a uniform wind field changed very little, and the mean and fluctuating wind pressures in each layer were significantly stratified, making it is easy to generate a coupled vortex-induced resonance. On the other hand, the mean displacement response of torsion moment in a turbulent field increased with wind velocity. Strong turbulence made the fluctuating wind pressure at the top and bottom of the model slightly more significant than in a uniform field. The resistance of super-tall buildings came from turbulence excitation in the along-wind direction and the self-excited resistance generated by the across-wind direction. The test methods and main research conclusions may provide a reference for glass curtain walls and the structural wind-resistant design of super-tall buildings.
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