Experimental Research on Mechanical Behavior of Retard-bonded Partially Prestressed Concrete Beams
|School||Central South University of Forestry Science and Technology|
|Keywords||Retard-bonded Partially prestressed concrete Mechanical behavior Short-term stiffness Crack Finite element|
As one of the eminent structural forms, prestressed concrete structures are widely used in modern structure. But un-bonded and bonded traditional post prestressed concrete have the inextricability disadvantages. For instances, fatigue damage of the prestressed tendons and anchorages easily appears in un-bonded prestressed concrete structures. There are some complicated construction programs, such as the embedded ducts, prestressing installment, thick liquid pushing and so on, in bonded prestressed concrete structural form. In addition, it is hard to control construction quality. With the development of prestressed concrete and super retarder, there is a strongly need for finding a construction technique that can solve the problems. Retard-bonded prestressed concrete which is a new type prestressed system and has appeared in recent twenty years meets the requirements. At present, the research on retard-bonded prestressed concrete is very limit at home and abroad.For the further research on mechanical behavior and service property of retard-bonded prestressed concrete members, connected with the scientific and technological project of hunan province office of construction(2006468-28)—research on mechanical behavior and application of retard-bonded prestressed concrete, retard-bonded prestressed strands were made by manual work. And experimental research and theoretical analysis on mechanical behavior of three retard-bonded partially prestressed concrete T-beams were carried out under static loadings. In addition, the mechanical behavior of retard-bonded partially prestressed concrete beams was contrasted with that of traditional post prestressed concrete beams. The full-range experiment was conducted through concrete cracking and cracks development till the failure of beams under the action of one-third loading. The cracking load, load of cracks closure, sections strains distribution, development laws of deflection, cracks growth and distribution, as well as ultimate load-carrying capacity of beams were obtained by measurement. Based on the analysis of the experimental data and results, the main conclusions and achievements in the thesis are as follows:1. On the basis of the experimental research on the retard-bonded prestressed strands in three retard-bonded partially prestressed concrete beams, the deviation factorκ, friction resistance factorμand breakout friction were obtained.2.The development laws of deflection, cracks growth and distribution about test beams were studied comparatively. The results demonstrate that the mechanical behavior of retard-bonded partially prestressed concrete beams is very similar to that of bonded partially prestressed concrete beams.3. Based on experimental research of crack resistance and crack closure of retard-bonded partially prestressed concrete beams, the crack moment and moment of crack closure were studied. And compared with the retard-bonded partially prestressed concrete beams by traditional construction craft, the compressive stress of retard-bonded partially prestressed concrete beams is much larger, in order to close the cracks.4. The design formulas for the flexural ultimate load-carrying capacity, short-term stiffness and maximum crack width were proposed for retard-bonded partially prestressed concrete beams, and results calculated by them are identical with experimental results. Then the design formulas proposed could be offered to engineering designers for theoretical reference in the thesis.5. Through the numerical analysis and research on this thesis’s components with the software ABAQUS, the calculated results of deflection, moment of crack closure, flexural ultimate load-carrying capacity and so on are in reasonably close agreement with the experimental results. So it has further proved analytical theory reliable.