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The safety of aging bridge inventory is one of the main concerns of the state and federal agencies. Therefore, there is a need to quantify the safety margin of existing infrastructure and new design bridges. The Serviceability Limit States, i.e. fatigue, requires additional statistical parameters and not only the maximum values but also load spectra, i.e. frequency of occurrence of loads. The maximum values are needed for shorter time periods, such as day, week, month or year. Load spectra as well as material resistance are random variables. To quantify the safety margin of existing and future bridges load and resistance models are needed. This dissertation provides documentation on the development of the statistical parameters of live load spectra for service limit states.
The analysis of load spectra includes consideration of the WIM data base from NCHRP 12-76 and Federal Highway Administration (FHWA). The obtained data included over 65 million vehicles from 32 different locations. For analysis three cases were considered: mid span of the simply supported bridges, negative moment over the support in continuous bridges and positive moment at 0.4 span length of continuous bridges. Calculations were carried out for span lengths from 30 ft to 200 ft.
Developed load models are for national loads. Statistical parameters were summarized and presented.
Adviser: Andrzej S. Nowak