What Are The Seismic Requirements Of Prestressed Anchor Concrete Structures

Pre-stressing is to improve the service performance of the structure. The compressive stress applied to the structure in advance during the construction period. The pre-compressive stress during the service period of the structure can fully or partially offset the tensile stress caused by the load to avoid structural damage. Prestressed anchors are often used in concrete structures. Before the concrete structure bears the load, pressure is applied to it in advance, so that the internal force of the concrete in the tension zone when the external load is acting produces a compressive stress, which is used to offset or reduce the tension caused by the external load. Stress prevents the structure from cracking or cracking late under normal use.

The prestressed concrete structure is to pre-apply pressure to the structure before the structure is subjected to the load, so that the internal force of the concrete in the tension zone when the external load acts to generate a compressive stress, which is used to offset or reduce the tensile stress generated by the external load, so that the structure is Under normal use, there will be no cracks or cracks relatively late.

The prestressed concrete structure has a larger deformation recovery capacity after the prestressed tendons are stretched. Therefore, the energy dissipation capacity of the prestressed concrete member is lower than that of the reinforced concrete member with the same strength. In the anti-expansion design, whether the plastic hinge section of the prestressed concrete member has sufficient energy dissipation capacity is a question of great concern. What are the seismic requirements for prestressed concrete structures? Let's take a look at the following prestressing machines.

The general requirements for the seismic design of prestressed concrete structures are: under moderate earthquakes, the obvious loss of prestressed anchors should be prevented and the normal use of the structure should be reduced; under strong earthquakes, collapse or serious damage should be avoided. The principle of the FIP Exhibition Committee on the seismic design of prestressed concrete structures is: the designed prestressed anchor structure can only withstand moderate-strength earthquakes in the elastic range, while the extra energy of strong earthquakes is absorbed by elasto-plastic deformation, although The structural damage is quite serious, but it should not collapse. The requirements of the my country Building Seismic Design Code (GBJ11-89) for seismic structural systems are: I) There should be a clear calculation diagram and a reasonable transmission path for seismic action; 2) There should be multiple seismic lines of defense, and the cause should be avoided. The damage of the structure or component leads to the loss of the seismic capacity or the bearing capacity of the entire system; 3) The anchor should have the necessary strength, good deformation capacity and energy dissipation capacity; 4) It should have a reasonable stiffness and strength distribution to avoid Because of local weakening or sudden changes in the formation of weak parts, measures should be taken to improve the seismic capacity.

The ductility of the cross-section of the component can indicate the deformability of the structure. A larger deformability can absorb and dissipate a larger amount of energy. Therefore, the reaction and acceleration of the structure can be suppressed, that is, the ground load can be suppressed. Because of the stress-strain of the prestressed steel used for the prestressed concrete upper member, there is no obvious stable yield section. When calculating the ductility coefficient, the load (bending moment)-deformation curve of the prestressed member is not elastoplastic and difficult to determine Yield displacement.