Nonlinear Analysis Of Unbonded Partial Prestressed Concrete Beams Based On OpenSEES

The relative slip of the prestressed strand and concrete structure has been key issues of nonlinear analysis of the unbonded partial prestressed concrete structure under external loading. In the thesis, respectively based on the material constitutive model and the restoring force model of the section, nonlinear hysteresis analysis of unbonded partial prestressed concrete beams under low reversed cyclic loading, has been carried out by utilizing OpenSEES software. Among them, the nonlinear analysis programs based on the material constitutive model utilize that the finite element of concrete structure and prestressed strand are established separately, and then simulate the relative slip of the unbonded prestressed strand and concrete structure and changing prestressed size by the way of degree of freedom coupling. And in the nonlinear analysis programs based on the restoring force model of the section, the unbonded prestressed concrete beams directly are established whole as nonlinear beam element, and then the restoring force model of the section is used as the definition of section properties of the nonlinear beam element, where stress iterative calculation of the unbonded prestressed strand is not needed. In addition, seismic performance of unbonded partial prestressed concrete beam has been analyzed by utilizing OpenSEES software. And the main completed contents are as follow:(1)A brief overview of the status quo of experiment research and finite element analysis of unbonded prestressed concrete beam, and the thesis puts forward in the necessity of further research on application of the unbonded prestressed concrete structure in the earthquake zone.(2)The thesis systematacially illustrates nonlinear analysis theory of beam-column elements based on the flexibility method and fiber cross section, and introduces the finite element modeling method of OpenSEES software. On this basis, through selecting proper material constitutive model, the thesis implements the nonlinear numerical simulation of reinforced concrete beam-column members of Shen Jumin. Simulation results agree with experiment results reasonablely, which verifies applicability and reliability of nonlinear analysis theory of beam-column elements based on the flexibility method and fiber cross section.(3)Based on OpenSEES software, the thesis establishes finite element models of unbonded partial prestressed concrete beam, and carries out the nonlinear numerical simulation of experimental beams of the Tang Changhui, Liu Chexi, Su Jian. Simulation results agree with experiment results reasonablely, which verifies applicability and reliability of the nonlinear analysis programs of the unbonded partial prestressed concrete beam, and provides a new way for seismic analysis of unbonded partial prestressed concrete structure.(4)Based on the established finite element models of unbonded partial prestressed concrete beam, the thesis carries out seismic performance analysis of unbonded partial prestressed concrete beams by utilizing OpenSEES software. Analysis results show that the integrated reinforcement index is the main influence factor on the ultimate bearing capacity and displacement ductility, partial prestressing ratios is the main influence factor on the structural energy dissipation capacity. With increasing, the structural ultimate bearing capacity increases, the ductility decreases. And with increasing, the structural energy dissipation capacity decreases.(5)The thesis establishes bending moment- curvature hysteretic model of the section of symmetrical unbonded partial prestressed concrete beam, and which is planted into the secondary development platform of OpenSEES software. The thesis implements the nonlinear hysteresis analysis of symmetrical unbonded partial prestressed concrete beam, which obtains a method of researching the restoring force model of unbonded partial prestressed concrete structure based on the OpenSEES software.