What Andrews knew, or even suspected cannot be known. However, on page 93 of ANTR Walter Lord recalled the story of Andrews standing transfixed in the first class smoking room just before the end. This story has been discredited from time to time, and may be apocryphal. It is an eerie verisimilitude to this story, however. The alleged location would have been an excellent place to watch the ship come apart. The smoking room was directly in way of the breakup.
To passengers on deck, the ship gave no signs of impending breakup. However, events below foreshadowed what happened in the end. There was a cascade of events that Andrews should have known about that indicated the hull was in trouble. They included the flooding of the tunnel, the loss of bulkhead D, and the flooding upward through the bottom of boiler room #4. All of these were caused by loss of watertight integrity resulting from flooding and loss of buoyancy at one end of the hull girder. And, although there is no testimony about noises the hull was making, there must have been a lot of ugly sound coming from the hull as the unfair strain increased. So, Andrews had plenty of evidence that his creation was slowly coming apart as it sank. Whether he "connected the dots" or not is unknown.
Wilding correctly calculated that the hull should not have broken apart at the bow-down angles encountered throughout most of the night. In an undamaged and unflooded condition Titanic's hull was built to withstand those angles. But, he was not paid by H&W to tell the whole story.
It was not the angle of the hull, but the loss of buoyancy (or gain of weight) at one end of the hull girder that created the destruction. In effect, the dry and undamaged stern section was trying to cantilever the weight of the bow.
-- David G. Brown