SIR,-with reference to the letter published in your September issue over the signature
“De Pontibus,” the total bending moment allowed for in each of the beams in question was 3,813,000 lbs. inches, giving an average stress in the tensile steel of about 15,000 lbs. per square inch. About 55 per cent. of this moment is in respect of the superimposed live load. I agree with your correspondent that the dead load alone would stress the rolled steel joists to approximately 10 tons per square inch and that the addition of the live load to this would reduce the factor of safety to approximately 2.