CN2784490Y - Prestress connection node for beam column of assembled concrete frame structure - Google Patents

Abstract

The utility model relates to a prestressing force connection node for beams and posts of assembled concrete frame structures, which belongs to the technical field of precast assembly type concrete structures in civil engineering. The utility model aims at overcoming the defects of a normal concrete structure that damage controlling design is difficult to realize, and cast-in-place connection nodes of precast units need cast-in-place concrete. The utility model is characterized in that beams (1) and posts (2) are all precast, gaps with the width no more than 10 mm are arranged between the beams and the posts, and the gaps are closed by mortar (3); a pore canal (4) is arranged in the position of upper and lower core points of the cross section of the beams (1) and on the posts (2) corresponding to the upper and the lower core points of the cross section of the beams, so that a non-adhesive prestressing force rib (5) can penetrate into the pore canal (4); the range between the upper and the lower parts at the end of the beams is respectively provided with two spiral steel reinforcement confined concrete (6) overlaping with each other, and the height of the range is no more than one half of the height of the posts to the surface of the posts. The utility model creates conditions for realizing the damage controlling design of the structure, and is favorable to the realization of strong nodes, or can reduce the configuration quantity of hoop reinforcements of nodes by adopting the identical design prestressing force.

Description

Prestressed Connection Nodes of Prefabricated Concrete Frame Structure Beam-column

technical field

The prestressed connection node of beam-column of prefabricated concrete frame structure is used for assembling prefabricated beam-column concrete components into a whole frame, and belongs to the technical field of prefabricated concrete structure in civil engineering.

Background technique

With the development of society, the functions of buildings are becoming more and more complex, and other losses caused by earthquakes may be much greater than those caused by the destruction of buildings themselves. At present, for strong earthquakes, the ultimate goal of structural design is to avoid the collapse of buildings to protect people's lives, and it is still difficult to achieve damage control design that controls the economic and functional losses caused by strong earthquakes. From a structural point of view, this difficulty mainly lies in the following three aspects: ordinary concrete structures rely on components to absorb and dissipate seismic energy, so it is inevitable that components suffer from cracking and crushing; the stress of steel bars exceeds the yield stress, which is difficult to calculate accurately; Large residual deformation. Therefore, how to solve these problems is of great significance to improve people's active control level of losses caused by earthquake disasters.

On the other hand, compared with the cast-in-place concrete structure, the prefabricated concrete structure has the advantages of reducing the amount of wet work on site, easy to ensure the quality of components, good durability, simplified support work, fast construction speed, saving materials, and is conducive to industrialization of construction. The social and environmental benefits are good, so the application of prefabricated concrete structures should be actively promoted. However, the seismic performance of prefabricated structures is determined by the connections between prefabricated components. Most areas in my country are in seismic fortification areas, so whether the connection is reliable or not directly affects the application of prefabricated structures. Initially, the prefabricated concrete structure was basically connected by welding. However, in the Tangshan earthquake in 1976, the prefabricated structure was seriously damaged and almost all collapsed. Since then, in order to improve the seismic performance of prefabricated structures, it is required that the connection nodes of prefabricated structures can be similar to cast-in-place nodes. For this reason, the assembly structure form of prefabricated components cast-in-place nodes is generally adopted. This connection node is to connect the steel bars protruding from the prefabricated beams and columns by welding or lap joints at the nodes, and re-cast the concrete at the nodes to form a cast-in-place reinforced concrete node. Although the integrity and seismic performance of this structural form are comparable to those of cast-in-place structures, the advantages of short construction period and good economic benefits of prefabricated concrete structures are greatly weakened because of the need for cast-in-place concrete for this connection node, which makes The development and application of prefabricated structures have been seriously affected. Therefore, it is necessary to eliminate cast-in-place concrete and give full play to the advantages of prefabricated concrete structures.

In view of the above reasons, we proposed the prestressed connection joints of beam-column of prefabricated concrete frame structure through research.

Utility model content

The utility model aims at the disadvantages that it is difficult to realize the damage control design of the common concrete structure, and that the prefabricated component cast-in-place connection nodes need cast-in-place concrete, and provides a new type of connection node to solve the above problems.

The structure of the prestressed connection node of the prefabricated concrete frame structure beam-column is shown in Figure 1: the beam 1 and the column 2 are both prefabricated, and there is a gap not greater than 10mm wide between the beam 1 and the column 2, which is closed by the mortar 3; Leave channels 4 at the upper and lower core points of the beam section and the corresponding upper and lower core points of the beam section on the column to penetrate the unbonded prestressed tendons 5; the upper and lower parts of the beam end are not less than 1/2 of the beam height from the column surface Two overlapping spiral steel bars 6 are respectively used to restrain the concrete.

The upper and lower core points of the cross-section of the beam 1, for a rectangular cross-section, are respectively 1/3 of the height of the cross-section from the upper and lower edges on the vertical central axis of the cross-section.

The spiral steel bars 6 are configured to prevent premature crushing of the concrete at the beam end when repeated large deformations are caused by earthquakes; The diameter should be between 1/2 beam width and 1/3 beam height; the minimum thickness of the concrete cover is the same as the stirrup requirements.

The design principle of the prestress size of unbonded prestressed tendons is: not only to ensure the frictional shear resistance of the connection, but also to keep the stress in the prestressed tendons within the yield limit.

The allocation amount of unbonded prestressed tendons in this connection node is determined according to the design bending capacity of the connection section. The inner diameter of the channel 4 should be 6-15mm larger than the diameter of the unbonded prestressed tendon.

In this connection joint, the beam-column is prestressed with the help of unbonded prestressed tendons to generate pressure and friction at the contact surface of the beam-column, and the beam-column components are assembled into a frame as a whole. The shear force of the beam is transmitted to the column through the friction force between the beam and the column, so there is no need to set corbels in the beam and the column. While the unbonded prestressed tendon provides the moment bearing capacity of the joint, it also builds up pressure between the contact surfaces of the beam and column, so that the joint has sufficient frictional shear resistance and transmits the shear force of the beam to the column. By properly designing the initial stress of the unbonded prestressed tendons, the stress in the unbonded prestressed tendons can be kept in the elastic range, and the precompressive stress between the beams and columns will be maintained even after the earthquake displacement of large intensity. This connection maintains rigidity under normal load and small earthquakes. When encountering a large-intensity earthquake, the beam-column contact surface becomes a hinge and rotates, thereby dissipating part of the energy. If necessary, an energy-consuming device is added to dissipate part of the seismic energy. Since the unbonded prestressed tendons remain elastic, the residual deformation of the structure after the earthquake is very small and can be ignored. This solves the aforementioned three problems of ordinary concrete structures, thus creating conditions for the realization of structural damage control design. In addition, due to the use of unbonded prestressed tendons, when the same amount of stirrups as ordinary reinforced concrete structures are arranged in the joint area and beams, the stress of the stirrups is reduced, which is conducive to the realization of strong joints; or when the same design stress is used The amount of stirrup configuration of nodes can be reduced.

Description of drawings

Fig. 1 is the front elevation view of the prestressed connection node of the beam-column of the prefabricated concrete frame structure;

Fig. 2 is a beam end sectional view (A-A section of Fig. 1);

Figure 3 is a sectional view of the middle part of the beam span (B-B section in Figure 1).

In the figure: 1 is a beam, 2 is a column, 3 is a mortar, 4 is a tunnel, 5 is an unbonded prestressed tendon, and 6 is a spiral steel bar.

Note: In order to make the drawing clear, other reinforcements of beams and columns are not drawn, and other reinforcements should be determined according to the design.

Detailed ways

In order to realize the prestressed connection joints of beams and columns of prefabricated concrete frame structures, first, beams 1 and columns 2 are prefabricated according to the cross-sectional size, reinforcement amount, and concrete strength grade determined in the design. The beams and columns are prefabricated reinforced concrete components, or they can be prefabricated Prestressed concrete elements. During prefabrication, the spiral reinforcement 6 is fixed at the end of the beam, and the holes 4 are reserved by pre-embedded bellows or steel pipes. Unpolished wooden templates should be used to make rough surfaces at the contact surfaces of beams and columns to increase friction. After the beam and column concrete is cured to the design strength, it can be transported and hoisted on site. The column is hoisted first, and then the beam is hoisted. The beam can be supported by installing temporary corbels on the column. After the columns and beams are in place, unbonded prestressed tendons 5 are penetrated into the reserved channels 4 . Unbonded prestressed tendons should be extruded plastic-coated unbonded steel strands (f _ptk = 1860N/mm ² ). After the unbonded prestressed tendon is penetrated, the mortar 3 is poured into the gap between the beams and columns, and the mortar of the channel 4 is poured. The mortar used for the gap between the beams and columns should be fiber mortar or epoxy mortar, and the fiber should be nylon fiber, the length of which can be 10-15mm, and the dosage can be 1.5-2kg per cubic meter of mortar. The tunnel can be poured with ordinary mortar. Mortar can be replaced by cement slurry, and the design compressive strength of mortar or cement slurry is required to be not lower than the design compressive strength of beam concrete. After the grout reaches the design strength, the unbonded prestressed tendons are stretched and anchored with anchors. Finally, the temporary support is removed to form the required connection node.

Claims (3)

1. The prestressed connection node of the prefabricated concrete frame structure beam and column is characterized in that: the beam (1) and the column (2) are prefabricated, and there is a gap not greater than 10mm wide between the beam and the column, and the mortar (3 ) is closed; holes (4) are reserved at the upper and lower core points of the beam (1) section, and the corresponding upper and lower core points of the beam section on the column (2) so as to penetrate the unbonded prestressed tendons (5); 1. The distance between the lower part and the column surface is not less than 1/2 of the beam height, and two overlapping spiral steel bars (6) are respectively used to restrain the concrete. 2. The prestressed connection node of beam-column prefabricated concrete frame structure according to claim 1, the upper and lower core points of the beam (1) section, for a rectangular section, are respectively the distance from the upper and lower edges on the vertical central axis of the section 1/3 section height. 3. The prestressed connection node of beam-column prefabricated concrete frame structure according to claim 1, the configuration amount of the spiral reinforcement (6) is not less than 2% of its bound concrete volume, and the pitch is not greater than the diameter of the spiral 1/4, the spiral diameter should be between 1/2 beam width and 1/3 beam height; the minimum thickness of the concrete cover is the same as the stirrup requirements.

Images