Revision of the Niagara Railway Arch Bridge . The recent discussions before various technical societies and inthe columns of the engineering journals indicate a strong preferencefor the retention of the straight line formula whenever a more logicalvalue can thus be determined, and a careful study of the question showsthat at least we should have a most careful review of all columntests made in the last thirty years, as the basis for a rational formula;and that it is preferable that more tests of columns of large size andcareful design be made in a most painstaking and thorough such
Revision of the Niagara Railway Arch Bridge . The recent discussions before various technical societies and inthe columns of the engineering journals indicate a strong preferencefor the retention of the straight line formula whenever a more logicalvalue can thus be determined, and a careful study of the question showsthat at least we should have a most careful review of all columntests made in the last thirty years, as the basis for a rational formula;and that it is preferable that more tests of columns of large size andcareful design be made in a most painstaking and thorough such checked data are available, then unit stresses for columnscan be tabulated once for all for safe end conditions, and no reasonlogically exists for caring what form the plotted line or curve maytake, except that for convenience in memorizing and for use wheji tablesare not at hand, some simple equation will still be desirable. PLATE XXXVII. TRANS. AM. SOC. CIV. ENGRS. VOL. LXXXIII, No. 1460. FOWLER ON REVISION OF NIAGARA RAILWAY ARCH 90 100 110 Length -f- Least Radius of Gyration REVISION OF NIAGARA RAILWAY ARCH BRIDGE 1961 Preliminary Methods of Calculation for 1918 following methods were applied in making calculations for the1918 revision of the Niagara Bridge. Arch Span. Dead Load.—The dead load shall be taken at the value for the centertop chord that will best assist the lowering of the stresses in the topchord, posts, and diagonals, and at the same time not overload thearch chord to an unsatisfactory degree. This will presumably be avalue between 200 000 and 300 000 lb. for U7 U8 (300 000 lb. wasfinally adopted). Live Load.—The live load shall be Coopers E-60 trains on bothtracks, and on account of the peculiar terminal nature of the serviceon this structure, they shall both be considered headed the same way. Impact.—The impact shall be taken at 50% of the live load stressimpact as determined by the old American Railway EngineeringAssociation fo
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