عنوان مقاله [English]
With attention to the importance of the three-span continuous bridges and the complexity of analyzing structures with multi-degree of freedom, utilizing desirable numerical models to estimate the internal forces of this group of structures is highly effective. A new analyzing method is introduced in this study which can be used to the 3-span continuous bridges with constant section and heavy moment resistance in the transverse direction. The defined pattern is based on employing sinusoidal shape function both the bridge’s deflection shape and its corresponding applied forces. This model is developed by assuming a simple beam on the elastic constraints and thereby its results can be earned by minimizing the created potential function of the whole structure. Creating a desirable manual method in calculating the internal shear forces of columns in the three-span bridges is a good comparative idea over the complicated method proposed by Aashto needing 3-dimensional modeling in related software. By considering 5 different states of an example sample and analyzing those, the obtained results of the suggested way prove its high precision and efficiency on controlling the calculations manually because of having mostly the errors less than 3 percent related to the exact method.