This paper presents a new approach for finding the moment distribution factors. In the current practice, The American Association of State Highway and Transportation Officials (AASHTO) specifications provide the distribution factor formulations for moment values as a function of span length, beam spacing, beam stiffness and slab thickness. The methodology presented in this study aims to investigate obtaining the live load distribution factors by using primarily the dynamic characteristics such as modal frequency, flexibility coefficient and also skew angle instead of using only the geometric properties. These dynamic characteristics can be easily obtained with simple field tests, and hence using the real data offers the researchers more reliable distribution factors. In this study, this approach is demonstrated on T-beam concrete bridges. First, 40 Finite Element (FE) modelsthat have different span lengths and skew angles are analyzed to find thenatural frequencies and flexibility coefficients. Second, moment values are collected under HS20 truck load for all models. Third, a multiple regression analysis is conducted to generate a fitting equation for moment distribution factors. After creating the equation, three extra FE models are used for the verification of the new equation. Finally, the new approach isverified by using experimental data coming from a real life bridge.
Abstract