Complex sentence: On 29 December 2015 the Wharfe bridge partially collapsed, having been closed to traffic and pedestrians three days earlier, as a result of the heavy flooding which affected much of Yorkshire over the Christmas period.
Split into simpler sentences: On 29 December 2015 the Wharfe bridge partially collapsed. It had been closed to traffic and pedestrians three days earlier as a result of flooding which affected much of Yorkshire over the Christmas period.