Aseismic Research On Unbonded Partially Prestressed Concrete Flat-Beam Frame Structure

Recently, the unbonded partially prestressed concrete flat-beam frame structures are widely being used due to reducing the floor height and total height of building efficiently, cutting down the internal forces of structures caused by seismic effects, economizing the costs. So, based on the previous research results, the aseismic design theory of this structure is analyzed, the low-cyclic reversed loading tests of two unbonded partially prestressed concrete flat-beam frame structures are conducted and the method of aseismic design is discussed in this dissertation. The contents include as follows:The influencing factors of the displacement ductility factor of the unbonded partially prestressed concrete frame structures, such as stirrup reinforcement characteristic value, nominal shear span ratio, axial compression ratio, the appearing order of plastic hinges and partial prestressing ralio(PPR) are discussed. The formula of displacement ductility factor of the unbonded partially prestressed concrete frame structures is suggested by regression analysis. With regard to the aseismic design and the request of ductility and energy dissipation, the restriction of the flat-beam/column sectional size and aseismic reinforced design are discussed. The calculated formula of the torsion in the terminal section of prestressed concrete flat-beam is improved by internal forces analysis.The low-cyclic reversed loading tests of two unbonded partially prestressed concrete frames with different PPR have been carried out. The aseismic behaviors are analyzed and compared, with emphases on failure mechanism, hysteretic property, displacement ductility, energy-dissipation capacity as well as stiffness degeneration, etc. The results show, when designed rationally, the unbonded partially prestressedconcrete frames can form beam hinge energy-dissipation machine and total destroy mechanism. The structural system has considerable energy-dissipation capacity, so can be generalized and used in medium seismic zones. Due to exerting prestress, the structure has satisfiable self-centering capability. According to hysteretic properties under low-cyclic loading and some other suggestions, the moment - curvature restoring force computation model of unbonded partially prestressed concrete section, which considering the PPR, is given.