Recently the American Association of State and highway Transportation Officials (AASHTO) adopted a Load and Resistance Factor Design (LRFD) code for the design of highway bridges. Based on structural reliability, the new code provides a rational basis for safe design of steel and concrete bridges. For these structures, load and resistance (safety) factors were determined by calibrating the new code to previous, non-LRFD versions of the code, so that a consistent level of reliability is achieved. However, the LRFD code was not calibrated for wood bridges. Therefore, there is a need to fill this gap. This paper is focused on the development of statistical models for wood bridge structures. Recent test results provided a considerable amount of new data for sawn wood and glued-laminated components. Statistical methods provide a good tool for the development of rational models for loads and resistance. Because of the random nature of load and resistance, reliability is a convenient measure of strutural performance that also provides a rational basis for comparison between wood and other structural materials. This paper presents the results of a recent projet leading to the development of rational desing criteria for wood bridges. In this first step, the structural reliability of selected wooden bridges deisgned by the AASHTO codes are determined, and inconsistencies in reliability are identified.
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