The Crack Control Of Extra-long Concrete Structures By Unbonded Prestressing Technology

From the point of view to solve (control) the shrinkage and temperature crack of extra-long concrete structures, this paper, based on relevant engineer backgrounds, comprehensively and systematically discusses the crack-resistant questions of extra-long concrete structures with unbonded prestressed technology, including basic principle, qualitative analysis, quantification calculation, and so on, and solves the practical engineering problem in this regard aspect. The main points are as follow:1. The paper discusses the concept and cause of construction cracks, and the principle and method on the establishment of calculation temperature field.2. After narrating the basic concept of temperature stress, the calculation methods of temperature stress under various constraint conditions are presented in detail, and the relevant calculation formulae are derived.3. The paper studies the simplification calculation method of concrete shrinkage and the calculation of temperature and shrinkage stress that takes the effects of concrete creep into account.4. The paper probes into basic principles of extra-long problem using unbonded prestressed technology, and gives relevant formulae and standard of crack control, and researches in detail calculation methods of effective prestress under various constraint conditions, and derives relevant calculation formulae.5. The calculation method of overall bending effect on flexure extra-long construction is explored under prestress action, and the action mechanism and solution methods upon structural opening are discussed in detail. And other problems related to this thesis are discussed as well.6. The conclusion of finite element analysis of two representative engineering examples is given to illustrate the theory analysis above.