Post-tensioning considerations in curved concrete bridges : Comparison of numerical simulation of friction losses against measurements

Combining non-standard design requirements in a bridge gives additionalconcerns on the accurate representation of its design calculations. A contractoris tasked to build a bridge that is part of a roundabout above a highway, with acertain slenderness which in turn requires the use of post-tensioning. Having thebridge in a horizontal curvature adds to the direct friction losses in the tendons.The aim of the thesis is to compare measurements of said bridge against differentcalculation methods, and identify discrepancies in the results. It is split into handcalculations from the European codes (EC2), a finite element model (FE model)focused on the friction interaction and the finite element model created by thedesign company of the bridge.Firstly only the calculation methods are compared. They show similar trendsacross different friction coefficients for all tendons of this bridge. But Differencescan be seen in actual values between the finite element model, and the methodbased on EC2. The former has on average about 1 cm longer expected elongationof the tendon. The results from the design company are evaluated and can beplaced in between the lower and upper limit of the EC2 results.The site measurements for each tendon represent the actual path of the tendonand the friction coefficient. Depending on which method is consulted, verydifferent friction coefficients need to be used in calculation to obtain themeasurement value. For one tendon the coefficient can very from μ = 0,15 toμ = 0,25. While a general trend can be seen for the relation of all calculations andthe measurements, one tendon varies greatly from this. An assumption is madethat the path built on site does not correspond to the designed path. Â