A Hole-Drilling Method For Evaluating The Permanent Prestress Of Existing Concrete Bridges

Permanent prestress is a key metric to measure the structure capability of existing prestressed concrete bridge. However, the problem of accurately estimating the permanent prestress poses a difficult challenge. This thesis addresses this challenge by proposing a hole-drilling method for estimation.Using the finite element (FE) method, this thesis analyzes the distribution of permanent prestress caused by prestressing of single-span girder. With other parameters fixed, this thesis analyzes the effect of aperture, hole depth, girder size, elastic modulus of concrete, reinforced concrete size, eccentric location, stress distribution at the edge of hole and its ratio factor, then the thesis finds the ratio factor is only related to hole depth, aperture and girder width. In particular, the ratio factor increases with the growth of hole depth. The increase becomes slowly when the hole depth is 1.2 times of aperture, where the strain release of hole edge can be measured.The thesis gets a regression equation which models the relationship of ratio factor with girder width and aperture, then the thesis uses the equation and method of strain release to predict the prestress of single-span girder. Furthermore, the thesis analyzes the structure of prestressed concrete bridge, and derives a closed formula to estimate the permanent prestress of prestressed concrete bridge.The contribution of this thesis is that we propose a novel method to evaluation prestress of existing concrete bridge, which gives a further study and reference on measuring the structure capability of existing prestressed concrete bridge.