How many Airbus planes have been destroyed in flight by severe turbulence?
The Aviation Safety database lists 91 accidents due to turbulence as of writing. None are on Airbus aircraft. The most recent in flight breakup of a transport aircraft listed was in 1993.

All of the aircraft in your examples are fairly old designs, dating back to the 60's or earlier. Your statement that the A350 has the exact same design requirements as an F-27 is inaccurate. While the load factors required for certification may have remained constant, the actual loads aircraft must be designed to survive have changed over time. As an example, for transport aircraft, the FAA regulation on gust and turbulence loads is 14 CFR 25.341, which has been updated 3 times since it was originally introduced in 1965. For the F-27 incident in Alaska, one of the factors noted was cracks in the wings from a lack of maintenance. Maintenance has been improved since then, as has the durability of aircraft designs. As accidents happen and the industry learns from experience, designs improve to better anticipate the conditions that aircraft will actually experience.

Other than the DC-8 in your last link, all of the occurrences happened in the 60's. Apart from the design of the aircraft, a lot has changed operationally since then. Weather radars have improved dramatically, both on the ground and on the aircraft. Modern radars have a much better ability to detect turbulence, even clear air turbulence to a degree. They have also become much less prone to operator error. Weather satellites now provide information on weather even in remote areas. Forecasts have improved as well, providing pilots and dispatchers a better idea of areas that should be avoided.

Below is an example of the kind of information that modern radar systems can provide to pilots about weather conditions in their path.


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