128 F. M. GUJMMOW. 



Referring now to the test of the structure and accepting 

 60 tons as the load when the cracks appeared on the under- 

 side of the beams, or 30 tons on each. The bending moment 

 caused by the deadload, and load of 30 tons on beam A at 

 point of crack = 2,560,000 inch lbs. The distance of the 

 centre of compression from the centre of tension = leverage 

 = 21 inches. The sectional area of the iron = 2*68 square 

 inches, and the tensile strain on the iron = 45,200 lbs. or 

 over 20 tons per square inch. The compression on the 

 concrete = 1,360 lbs. per square inch. On beam G, the 

 bending moment caused by the dead load, and loads of 30 

 tons at point of crack = 2,450,000 inch lbs. The distance 

 of the centre of compression from the centre of tension = 

 leverage = 20*5 inches. The sectional area of the iron 

 available = 2*65 square inches, and the tensile strain on 

 the iron = 42,400 lbs. per square inch, or over 19 tons. 

 The compression on the concrete = 1,330 lbs. per square 

 inch. 



Referring now to the beams, when loaded with the 142 

 tons, of which 120 tons may be taken as resting on the 

 beams, or 60 tons on each. The cracking of the beams 

 extended up to the underside of the plate, and consequently 

 the leverage, or distance between the centre of compres- 

 sion and centre of tension = 22f inches, and for beam A 

 the strain on the iron per square inch = 81,000 lbs. The 

 compression on the concrete = 3,510 lbs. per square inch. 

 On beam G the tensile strain on the iron is 78,900 lbs. 

 and the compression on the concrete is 3,400 lbs. per square 

 inch. 



As such abnormal strains could not have taken place it 

 must be inferred that the equally distributed loading arched 

 itself as the deflections increased, and the results obtained 

 by such loading can only be relied upon whilst the beam 

 showed only small deflections, viz., to the time when the 



