Finite-element Simulation of the Releasing Process of Existing Stress in Concrete Structures by Drilling Hole Method
|Keywords||prestressed concrete drilling hole releasing method strain release rate|
The existing stress in concrete structures is one of the most important parameters to represent the force condition and the reliability of the structure. Therefore, the exact prediction of the existing prestressing force becomes crucial. The hole-drilling method is an effective method of measuring the stress inside concrete. And the method has theoretical significance and application value for researching the releasing process and the releasing rule.In this thesis, the releasing process of existing stress in prestressed concrete structure by the hole-drilling method is simulated by finite element method with the borehole diameter of 120mm, the inner diameter of 110mm, the maximum depth of 110mm. Strain releasing rate is used to describe the principle of releasing. Technique of element birth and death is used to simulate drilling process. The stress releasing rate under uniform load, gradient force, shear stress and pressure-shear stress state is studied. The strain releasing rate under every stress state is compared and analyzed the influence of the principle of releasing under different stress state. As well as the analysis under the different load (pressure and pure shear) and the component thickness, the strain changes and the discipline of strain release with the depth of drilling changes.The results indicate that the strain releasing value depends on the stress initial value and the stress condition. The strain releasing rate is related to the depth of hole, but not the stress state and load condition. The depth of the hole that stress has been completely released does not change with the stress condition and the initial stress. Strain release and the release rate values also depend on the size of component thickness direction; when larger than 150mm scantlings, the component size is no longer a factor in the impact of strain release.