How are stresses in the girder calculated with the resultant prestressing losses?

To calculate the stresses in the girder with the resultant prestressing losses, you can follow these steps:

1. Determine the initial prestressing force: This is the force applied to the girder during the prestressing process. It can be calculated based on the design requirements and the properties of the prestressing tendons.

2. Consider the prestressing losses: Prestressing losses occur due to various factors such as elastic shortening, creep, and relaxation of the prestressing tendons. These losses reduce the initial prestressing force over time.

3. Calculate the effective prestressing force: Subtract the prestressing losses from the initial prestressing force to obtain the effective prestressing force acting on the girder at a given time.

4. Determine the section properties: Obtain the cross-sectional properties of the girder, such as the area, moment of inertia, and modulus of elasticity. These properties are essential for calculating the stresses in the girder.

5. Apply equilibrium equations: Use the equilibrium equations to determine the internal forces and moments in the girder caused by the applied loads and the effective prestressing force.

6. Calculate the stresses: Divide the internal forces by the corresponding section properties to obtain the stresses in the girder. These stresses can be axial, bending, or shear stresses, depending on the loading conditions.

It is important to note that the calculation of stresses in prestressed girders is a complex process that requires consideration of various factors and assumptions. Therefore, it is recommended to consult relevant design codes and guidelines or seek assistance from a qualified engineer for accurate calculations.