Theoretical and experimental study on flexural behavior of prestressed steel plate girders

Applying prestressing techniques increases the load carrying capacity of girders, leading to substantial saving in construction material. In addition, prestressing a steel girder reduces its deflection under external loads, and thus, enhances its flexural behavior. The aim of this study is to use a finite-element formulation to verify the effectiveness of the prestressing technique with respect to the flexural behavior of a steel plate girder. The strength of two steel box girders is tested, one with prestressing (prestressed girder) and one without (control girder). Based on experimental results, a theoretical model is proposed for predicting the flexural resistance of a steel box girder with external tendons. To improve the calculation accuracy, finite-element formulation is applied to prestressing and external loading stages of the girder and external tendons, which are regarded as composite structures, and the interactions between them are fully considered. The friction between tendons and deviators is considerably small. Therefore, the friction resistance between the tendons can be neglected during the force analysis. The strain in the prestressed girder is distributed linearly along its height, indicating that the calculation performed using the plane section assumption is consistent with the actual situation for the same external load. The experimental and theoretically calculated values of strain in the bottom plate of a steel girder and tension force increment for deflections at mid-span and quarter span are in good agreement. This indicates that the finite-element formulation proposed in this study is correct and efficient.