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Title: Live Load on Concrete Bridge Decks

Author(s): Sylwia Stawska

Publication: Web Session

Volume: ws_F21_Stawska.pdf


Appears on pages(s):



Date: 10/17/2021

Live load specified in AASHTO is applicable for the design of bridges in all states. Extensive weigh-in-motion (WIM) data indicates that truck loads are strongly not only state-specific but also site-specific. The objective of this paper is to review the available recent WIM records, compare them and identify the differences and trends. For many WIM stations, the data is available for several years, so it is possible to observe the traffic changes over time. Bridges are affected by load effects rather than gross vehicle weight (GVW). Therefore, the recorded vehicles, axle loads, and axle spacings are used to calculate the bending moments and shear forces. The results are plotted in form of cumulative distribution functions (CDF) for easier comparison. The statistical parameters of live load can then be calculated and compared for different states, road categories, and also for different classes of vehicles. Also, the long-term effect of traffic-induced loads is considered. The fatigue damage is caused by a repeated number of passages of vehicles across a bridge, which may create one or more stress cycles in the structural components. It can result in the accumulation of fatigue consumption over time. The percentage of consumption depends on load magnitude and can be calculated using the available formulas. Knowing the statistical parameters of traffic from weigh-in-motion measurements, traffic volume (ADTT), the economic life of a bridge, and bridge-specific parameters, the total fatigue load spectrum is to be determined. A fatigue consumption formula was developed to calculate fatigue damage caused by the state-specific traffic loads.