Research Of Seismic Performance And Reinforcement Performance Of Precast Prestressed Concrete Connections With Unbonded Post-Tensioned Tendons

The unbonded precast prestressed structure is consisted of precast concrete beams and columns which formed as a whole frame in site via the prestress imposed by tendons. The beams are single-bay components and the columns are either single floor or are passing through 2-3 layer components. The style of the structure combines the advantages of the prestressed concrete structure and the precast structure. Based on the studies at home and abroad, there are carried out more experiments and theoretical studies for seismic performances and reinforcement performance of the precast prestressed concrete connections with unbonded post-tensioned tendons.Content can be summarized as follows1. Prestressed precast connections and hybrid precast connections are identified. By comparing and analyzing of existed connections the two ways of connections, precast prestressed connections and hybrid precast connections, are be used in this paper. The working mechanism, the characteristics of construction and the design and construction method are described respectively.2. Seismic performances of the prestressed precast connections are studied. This test researches one monolithic connection, four prestressed precast connections and three hybrid connection under reversed low cyclic loading. Based on the experiments the failure mode, hysteresis characteristics, skeleton curves, deforming capacity, displacement ductility, energy dissipation, tendon stress and gap of prestressed precast connections are studied. The results of the testing and analysis show that the prestressed connection has good seismic performance. The connections have such desirable seismic performances as self-centering capability and high bearing capacity.3. Reinforcement performances of connections are studied. Afte be strengthened the monolithic connection, four prestressed precast connections and three hybrid connection were tested under reversed low cyclic loading. Based on the experiments the failure mode, restore curves, energy dissipation, tendon stress, gap of connections and collaborative work of reinforcement materials are studied. The results of the test and analysis show that after strengthened the connections have the same seismic performance as good energy dissipation and self-centering capability under large displacement. The reinforcement materials and specimens can be worked together so the bearing capabilities of specimens decreased little.4. Nonlinear theoretical analysis of two precast prestressed connections. Using the method of moment-curvature to track the entire performance of specimens from the begining to failure the paper gained the ideal trilinear moment-rotation mode,ideal bilinear model of specimens and stress increment formula of tendons, and then drawed moment angle curves of connections. Results from the analysis showed that the moment-curvature analysis is a reasonable method for unbonded prestressed concrete structures and the three linear model put forwarded by author can be used to analyze the nonlinear properties better.5. The nonlinear static analysis and performance-based seismic design of precast prestressed frame structure. The deformation and failure mechanisms of traditional frame and precast prestressed frame are studied through Pushover nonlinear static analysis, which in favor of evaluating the design progress of precast prestressed in performance-based seismic design. The analyzed results show that the seismic performances of precast prestressed structure are reached or better than ordinary concrete frame structure.6. Some design suggestions for improving prestressed precast structure are proposed. The formulas of stress increment of prestressed tendons, bending strength and shear strength of beam-section in prestressed precast structures under the limit state are discussed. Finally some design requirements of construction are proposed.The precast prestressed structure studied in this dissertation has a potential of being widely used in seismic area. Its earthquake damage is light so its residual seismic capacity can meet the seismic design requirements. This structure can be widely used in seismic regions in China and has a broad application prospects.