In the Mystical City of God by Ven. Mary of Agreda it is said that Our Lord received something like 1115 scourges.

How can that possibly be correct? They were supposed to be limited to 40 or even 39 by law.

Similarly in Anne Catherine Emmerich's visions it is said the Scourging lasted like 45 minutes.

I wouldn't fret too much if Mary of Agreda got some details wrong.  There are times where she and Catherine Emmerick disagree on some things.  There's always a subjective filter in these kinds of things; in addition, who knows how many editors these texts have gone through.  It doesn't mean these weren't saintly women, but it doesn't guarantee 100% veracity of all the works attributed to them.  I'd look to the Shroud of Turin for evidence.  Roman flagrum, however, consisted of multiple strands, each of which could have several little ball-bearings or sharper metal scraps.  So, with 3 strands, the 40 lashes suddenly becomes 120.  And if each of the 3 strands had 10 ball bearings on it, now you're talking 1200, which approximates the 1145 number.  I think that there's some evidence from the Shroud that the flagrum used on Our Lord had 3 strands, each of which had 2 metal bearings, so 6 blows for each scouring, resulting in the number 240 (with 40 lashes), but, as depicted in The Passion, who knows if the soldiers got enraged at the docility with which Our Lord accepted the lashes; this seemed to bring out their wrath.  There's nothing to say they didn't exceed the 40 lashes.  I would be surprised if the law regarding the lash limit wasn't just for Roman citizens.