Costain and Yarm Road (formerly Kvaerner Cleveland Bridge) were fined £500,000 in December 2001 over the deaths in September 1999. The firms admitted health and safety breaches. The judge in the case, Mr Justice Owen, said the accident could have been prevented "by a number of simple measures".
Technitube did not admit any legal liability at the trial but did make a contribution to the overall compensation award.
Ronald Hill, 38, of Glasgow, Jeff Williams, 42, of Newport on the Isle of Wight, Andrew Rogers, 40, of Middlesbrough and Paul Stewart, 23, of Newcastle upon Tyne died when a gantry collapsed on the M5 motorway in Avonmouth, near Bristol.
The four men, who were removing and replacing beams in the bridge, were moving the gantry when the accident took place.