Lateral-Distribution Factors for Fatigue Design

by Charles G. Schilling, (M.ASCE), Assoc. Research Consultant; U.S. Steel Corp., Research Lab., Monroeville, Pa. 15146,

Serial Information: Journal of the Structural Division, 1982, Vol. 108, Issue 9, Pg. 2015-2033

Document Type: Journal Paper


An extensive finite-element parametric study developed a chart giving lateral-distribution factors for the fatigue design of steel highway bridges. The chart gives conservative upper-limit factors for interior and exterior beams. The factor for interior beams is 0.5. The factor for exterior beams varies with the distance from the beam to the outer traffic lane and reaches a value of 0.9 when the center of the lane is directly over the beam. These upper-limit values can be used to make an initial fatigue check. If this check is satisfactory, as it would be in many cases, no further check is required. Otherwise, a second check can be made by using a more precise criterion that depends on the beam span and moment of inertia. The factors from the chart are generally much less than the American Association of State Highway and Transportation Officials (AASHTO) factors. Lateral-distribution factors were calculated from field measurements on 21 steel bridges. The factors ranged from 0.20–0.52 and were in good agreement with factors from the lateral-distribution chart.

Subject Headings: Beams | Steel bridges | Fatigue (material) | Bridge design | Highway and road design | Highway bridges | Finite element method | Parameters (statistics)

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