CN114809448B - A formwork-free assembled UHPC-recycled concrete composite column and its construction method - Google Patents

Abstract

The invention proposes a formwork-free prefabricated UHPC-recycled concrete composite column and a construction method, which belongs to the technical field of prefabricated concrete structures. It solves the problem of how to use recycled aggregates in prefabricated concrete structures to strengthen the node connections of prefabricated concrete structures and create a closed environment for recycled aggregates. Through the rational use of steel structures to strengthen the nodes of the prefabricated concrete structure, the connecting nodes meet the design requirements of "strong nodes". Through the prefabricated ultra-high performance concrete (UHPC) shell and the cast-in-place recycled concrete core, a closed environment is created for the recycled concrete. Reliable connections between steel bars and steel nodes, and steel nodes and steel nodes are achieved by rationally setting up the structure, and the bonding performance between concrete and steel nodes in the core area is improved by setting up circumferential ribs. The entire component does not require formwork and the connection is simple, which can effectively improve construction efficiency.

Description

A formwork-free assembled UHPC-recycled concrete composite column and its construction method

Technical field

The invention belongs to the technical field of prefabricated concrete structures, and in particular relates to a formwork-free prefabricated UHPC-recycled concrete composite column and a construction method.

Background technique

Prefabricated concrete structures are one of the important directions for the development of building structures in my country. They have the advantages of improving and ensuring project quality, increasing production efficiency, reducing construction costs, energy conservation and environmental protection, and have broad development space. Commonly used connection methods for prefabricated concrete structures include sleeve grouting connections, spiral stirrup grout anchor lap connections and corrugated pipe grout anchor lap connections. However, these connections are difficult to meet the design requirements of "strong node and strong anchorage", and have even become Structural weak points.

On the other hand, the renovation and demolition process of existing buildings generates a large amount of construction solid waste. According to statistics, my country's waste concrete output will exceed 3 billion tons in 2020, posing new challenges to the sustainable development of the construction industry. Recycled aggregates made from waste and industrial solid waste have emerged. Research has found that these recycled aggregates have high porosity and water absorption, absorb water during the concrete mixing process, and release water during the cement hydration process to replenish the moisture in the capillary pores in time, which is called the internal curing effect. The internal curing effect of recycled aggregates improves the self-drying, autogenous shrinkage, and basic creep of concrete. It is more scientific and reasonable to apply recycled aggregates in a closed environment.

In summary, applying recycled aggregates to prefabricated concrete structures can consume a large amount of construction solid waste and industrial solid waste. However, how to strengthen the node connections of prefabricated concrete structures and create a closed environment for recycled aggregates has become an urgent task. difficulty.

Contents of the invention

In view of this, the present invention aims to propose a formwork-free assembled UHPC-recycled concrete composite column and a construction method to solve the two problems mentioned in the above background technology. Through the rational use of steel structures to strengthen the nodes of the prefabricated concrete structure, the connecting nodes meet the design requirements of "strong nodes". Through the prefabricated ultra-high performance concrete (UHPC) shell and the cast-in-place recycled concrete core, a closed environment is created for the recycled concrete. Reliable connections between steel bars and steel nodes, and between steel nodes and steel nodes are achieved by rationally setting up the structure, and the bonding performance between concrete and steel nodes in the core area is improved by setting up circumferential ribs. The entire component does not require formwork, and the connection is simple, which can effectively improve construction efficiency.

In order to achieve the above purpose, the present invention adopts the following technical solution: a construction method of a template-free assembled UHPC-recycled concrete composite column, which specifically includes the following construction steps:

(1) Make steel nodes: design and make a number of short inner steel pipes, a number of long outer steel pipes, a number of long inner steel pipes, a number of short outer steel pipes and a number of circumferential ribs according to the size design, and weld the short inner steel pipes, long outer steel pipes and circumferential ribs into a For the upper part of the steel node, long inner steel pipes, short outer steel pipes and circumferential ribs are welded into the lower part of the steel node;

(2) Prefabricated UHPC shell: According to the design, several longitudinal steel bars and several stirrups are tied or spot welded into a steel cage. The upper part of the steel node and the lower part of the steel node are welded to both ends of the steel cage respectively. The ends of the longitudinal steel bars and the circumferential ribs Welding, the outer surface of the longitudinal steel bars is welded to the inner surface of the inner steel pipe, the upper surface of the stirrups is welded to the inner steel pipe section, the UHPC shell is poured at the position of the steel cage according to the design thickness, and maintained to the design strength;

(3) Connecting steel nodes: Transport several prefabricated stacked columns to the construction site, insert the upper part of the steel node of the stacked column into the lower part of the steel node, and adjust the angle to make the short inner steel pipe contact the long inner steel pipe, so that the long outer steel pipe The concave and convex shapes of the short outer steel pipe are interlocked with each other, and the concave and convex shapes are welded and connected;

(4) Pour the recycled concrete core: Pour the recycled concrete core densely inside the UHPC shell, wait for the recycled concrete core to reach the design strength, and then proceed to the next step.

A formwork-free assembled UHPC-recycled concrete composite column, including a short inner steel pipe, a long outer steel pipe, a long inner steel pipe, a short outer steel pipe, a number of circumferential ribs, a number of longitudinal steel bars, a number of stirrups, and a UHPC shell and recycled concrete core;

The outer surface of the short inner steel pipe is close to the inner surface of the long outer steel pipe, and the circumferential rib is located on the inner surface of the short inner steel pipe. The three are welded to form the upper part of the steel node; the outer surface of the long inner steel pipe is close to the inner surface of the short outer steel pipe, and the circumferential rib is located on the inner surface of the short inner steel pipe. On the inner surface of the long inner steel pipe, the three are welded to form the lower part of the steel node; several longitudinal steel bars and several stirrups are tied or spot welded into a steel cage. The upper part of the steel node and the lower part of the steel node are welded to both ends of the steel cage respectively. The UHPC shell is located at the position of the steel cage. , the recycled concrete core is located inside the UHPC shell, short inner steel tube and long inner steel tube.

Furthermore, the connection between the long outer steel pipe and the short outer steel pipe is in a concave and convex shape that interlocks with each other.

Furthermore, the steel strength grade of the short inner steel pipe, long outer steel pipe, long inner steel pipe, short outer steel pipe and circumferential ribs is not lower than Q355.

Furthermore, the thickness of the short inner steel pipe, long outer steel pipe, long inner steel pipe and short outer steel pipe is not less than 2/3 of the diameter of the longitudinal steel bar.

Furthermore, the thickness of the circumferential rib is not less than the diameter of the longitudinal steel bar, and the width of the circumferential rib is not less than 1.5 times the diameter of the longitudinal steel bar.

Furthermore, the distance between the circumferential rib and the edge of the short inner steel pipe is not less than the anchoring length of the longitudinal steel bar. The end of the longitudinal steel bar is welded to the circumferential rib, and the outer surface of the longitudinal steel bar is welded to the inner surface of the inner steel pipe.

Furthermore, the upper surface of the stirrups is welded to the edge of the short inner steel pipe.

Furthermore, the thickness of the UHPC shell is not less than the distance from the inner surface of the longitudinal steel bar to the outer surface of the superimposed column.

Furthermore, the recycled concrete core is recycled concrete mixed with recycled aggregate made from waste concrete or industrial tailings, or internal curing concrete mixed with highly absorbent resin materials or lightweight aggregates.

Compared with the existing technology, the present invention uses steel structure nodes to improve the connection method of traditional prefabricated concrete columns, and improves traditional reinforced concrete columns into superimposed columns of prefabricated UHPC shells and cast-in-situ recycled concrete cores. The structure strengthens the integrity of steel bars and steel nodes, steel nodes and steel nodes, and improves the bonding performance between concrete and steel nodes in the core area by setting up circumferential ribs. Taken together, this prefabricated composite column has the following advantages:

(1) Rational use of high-performance materials. The structural node is not only the intersection of the upper and lower frame columns, frame beams and floor slabs, but also the key point for the seismic fortification of the building structure. A steel structure is set at the node to enhance the stiffness and bearing capacity of the node; the outer frame column is in bending Under the action of moment, the stress is the largest on the outside of the section. The laminated column shell is made of ultra-high-strength UHPC to withstand tension or pressure, thereby giving full play to the performance of high-strength materials.

(2) The steel structure has good mechanical performance. The steel structure nodes are composed of short inner steel pipes, long outer steel pipes, long inner steel pipes, short outer steel pipes and circumferential ribs. The inner steel pipes are nested in the outer steel pipes to form good shear resistance, and the outer steel pipe connections are set to a concave and convex type. The bite mouth, on the one hand, enhances the torsion resistance, and on the other hand, lengthens the weld length to increase the tensile or bending resistance.

(3) Effectively improve the long-term deformation and durability of components. The UHPC shell on the outside of the laminated column is prefabricated in the factory, which has basically completed the early shrinkage deformation of the concrete and formed a dense and crack-free UHPC shell, thereby improving the service life and durability of the structure and also providing a seal for the recycled concrete. The environment and the internal curing effect of recycled aggregates effectively improve long-term deformations such as autogenous shrinkage and basic creep of components.

(4) The connection is reliable and the components have good integrity. The ends of the longitudinal steel bars are welded to the circumferential ribs, the sides of the longitudinal steel bars are welded to the inner surface of the inner steel pipe, and the stirrup surface is welded to the inner steel pipe section to achieve a reliable connection between the steel node and the steel cage; the outer steel pipe of the steel node is welded to achieve a reliable connection between the steel node and the steel cage. Reliable connection of steel nodes; by setting hoop ribs to improve the bonding performance between concrete and steel nodes in the core area, effective transmission of shear force at the nodes is achieved.

(5) Convenient connection and high construction efficiency. The steel nodes and UHPC shell of the composite columns are prefabricated in the factory, transported to the construction site, and the rigid nodes are nested and welded to complete the node connection. Finally, the recycled concrete core is poured to complete the construction. Compared with traditional connection methods, it is more efficient and faster, and will greatly improve construction efficiency.

Description of drawings

The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached picture:

Figure 1 is a schematic three-dimensional view of the internal structure of the formwork-free assembled UHPC-recycled concrete composite column according to the present invention;

Figure 2 is a three-dimensional schematic diagram of the prefabricated UHPC-recycled concrete composite column;

Description of the drawing codes: 1-short inner steel pipe; 2-long outer steel pipe; 3-long inner steel pipe; 4-short outer steel pipe; 5-circular rib; 6-longitudinal steel bar; 7-stirrups; 8-UHPC shell; 9-Recycled concrete core.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely explained below with reference to the accompanying drawings in the embodiments of the present invention. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The described embodiments are only some, not all, of the embodiments of the present invention.

1. Specific Embodiment 1. Refer to Figures 1-2 to illustrate this embodiment, a formwork-free assembled UHPC-recycled concrete composite column, including a short inner steel pipe 1, a long outer steel pipe 2, a long inner steel pipe 3, a short outer Steel pipe 4, several circumferential ribs 5, several longitudinal steel bars 6, several stirrups 7, UHPC shell 8 and recycled concrete core 9;

The outer surface of the short inner steel pipe 1 is close to the inner surface of the long outer steel pipe 2, and the circumferential rib 5 is located on the inner surface of the short inner steel pipe 1. The three are welded to form the upper part of the steel node; the outer surface of the long inner steel pipe 3 is close to the inner surface of the short outer steel pipe 4. On the surface, the circumferential ribs 5 are located on the inner surface of the long inner steel pipe 3, and the three are welded to form the lower part of the steel node; a number of longitudinal steel bars 6 and a number of stirrups 7 are tied or spot welded into a steel cage, and the upper part of the steel node and the lower part of the steel node are welded to the steel bars respectively. At both ends of the cage, the UHPC shell 8 is located at the position of the steel cage, and the recycled concrete core 9 is located inside the UHPC shell 8, the short inner steel pipe 1 and the long inner steel pipe 3.

The present invention designs the upper part of the steel node and the lower part of the steel node. The structural node is not only the intersection point of the upper and lower frame columns, frame beams and floor slabs, but also the key point of the seismic fortification of the building structure. The node is set as a steel structure to enhance the structure. The stiffness and bearing capacity of each point; under the action of bending moment, the outer frame column has the largest stress on the outside of the section. The laminated column shell is made of ultra-high-strength UHPC to withstand tension or pressure, thereby giving full play to the performance of high-strength materials.

The steel structure node is composed of a short inner steel pipe 1, a long outer steel pipe 2, a long inner steel pipe 3, a short outer steel pipe 4 and a circumferential rib 5. The short inner steel pipe 1 and the long inner steel pipe 3 form an inner steel pipe, and the long outer steel pipe 2 and The short outer steel pipe 4 forms an outer steel pipe, and the inner steel pipe is nested in the outer steel pipe to form a good shear resistance. The connection of the outer steel pipe is set as a concave and convex bite, on the one hand, it enhances the torsion resistance, and on the other hand, it lengthens the weld length. To increase tensile or bending resistance.

The steel strength grade of the short inner steel pipe 1, long outer steel pipe 2, long inner steel pipe 3, short outer steel pipe 4 and circumferential rib 5 is not lower than Q355. The strength of the longitudinal steel bars 6 needs to be taken into consideration to achieve strength matching, so the strength is generally not lower than Q355.

The thickness of the short inner steel pipe 1, the long outer steel pipe 2, the long inner steel pipe 3 and the short outer steel pipe 4 is not less than 2/3 of the diameter of the longitudinal steel bar 6. As the main force-transmitting components at the node, the thickness of the short inner steel pipe 1, long outer steel pipe 2, long inner steel pipe 3 and short outer steel pipe 4 is directly related to the safety of the node. First, it is necessary to ensure the reliable connection of the longitudinal steel bars 6 of the upper and lower columns of the node. Considering that the longitudinal steel bar 6 may suffer from local tension and compression in the anchorage area, the thickness of the short inner steel pipe 1, the long outer steel pipe 2, the long inner steel pipe 3 and the short outer steel pipe 4 is strengthened to 2/3 of the diameter of the longitudinal steel bar 6. Fully guarantee the node's stress-bearing capacity, seismic performance and support during construction.

The thickness of the circumferential rib 5 is not less than the diameter of the longitudinal steel bar 6, and the width of the circumferential rib 5 is not less than 1.5 times the diameter of the longitudinal steel bar 6. Thicker circumferential ribs 5 have greater stiffness and stronger shear resistance. The thickness of the circumferential ribs 5 is designed to withstand the concentrated force from the longitudinal steel bars 6, and can reliably transmit the concentrated force to the steel nodes. The design of the width of the rib 5 can facilitate the welding construction of the connection with the longitudinal steel bar 6, and can also enhance its bonding performance with the recycled concrete core.

The position of the circumferential rib 5 is not less than the anchoring length of the longitudinal steel bar 6 from the edge of the short inner steel pipe 1. The end of the longitudinal steel bar 6 is welded to the circumferential rib 5, and the outer surface of the longitudinal steel bar 6 is welded to the inner surface of the inner steel pipe. The reliable anchoring of the longitudinal steel bars 6 is fully guaranteed.

The upper surface of the stirrup 7 is welded to the edge of the short inner steel pipe 1. The end of the longitudinal steel bar 6 is welded to the circumferential rib 5, the side of the longitudinal steel bar 6 is welded to the inner surface of the inner steel pipe, and the surface of the stirrup 7 is welded to the inner steel pipe section to achieve a reliable connection between the steel node and the steel cage; the outer steel pipe of the steel node is welded Achieve reliable connection between steel nodes; improve the bonding performance between concrete and steel nodes in the core area by setting circumferential ribs 5 to achieve effective transmission of shear force at the nodes.

The thickness of the UHPC shell 8 is no less than the distance from the inner surface of the longitudinal steel bar 6 to the outer surface of the superimposed column. On the one hand, the outer surface of the UHPC shell 8 is flush with the surface of the outer steel pipe of the node, so as to achieve a neat and beautiful connection between components and nodes without affecting the construction of subsequent decoration projects; on the other hand, the inner surface of the UHPC shell 8 should at least reach the longitudinal steel bars 6 The inner surface realizes a reliable connection between the UHPC shell 8 and the steel cage, and can achieve good stress-bearing capacity and integrity after pouring is completed.

The recycled concrete core 9 is recycled concrete mixed with recycled aggregate made from waste concrete or industrial tailings, or internal curing concrete mixed with highly absorbent resin materials or lightweight aggregates. In an externally sealed environment, the internal curing effect of recycled concrete or internal curing concrete can be fully utilized to achieve the purpose of increasing the hydration degree of cement and reducing shrinkage and creep deformation.

This invention strengthens the nodes of the prefabricated concrete structure by rationally designing the steel structure, so that the connecting nodes meet the design requirements of "strong nodes", and improves the traditional reinforced concrete columns into superimposed columns of prefabricated UHPC shells and cast-in-place recycled concrete cores. The integrity of steel bars and steel nodes, steel nodes and steel nodes is strengthened through reasonable construction, and the bonding performance of concrete and steel nodes in the core area is improved by setting up circumferential ribs. The entire component does not require formwork and the connection is simple, which can effectively improve construction efficiency. This prefabricated composite column gives full play to the performance of high-strength materials, which can effectively improve the long-term deformation and durability of components and enhance integrity.

The construction method of a formwork-free assembled UHPC-recycled concrete composite column specifically includes the following construction steps:

(1) Make steel nodes: According to the size design, make a number of short inner steel pipes 1, a number of long outer steel pipes 2, a number of long inner steel pipes 3, a number of short outer steel pipes 4 and a number of circumferential ribs 5. Place the short inner steel pipe 1 and the long outer steel pipe Weld one piece each of 2 and circumferential rib 5 to form the upper part of the steel node, and weld one piece each of long inner steel pipe 3, short outer steel pipe 4 and circumferential rib 5 to form the lower part of the steel node;

(2) Prefabricated UHPC shell: According to the design, several longitudinal steel bars 6 and several stirrups 7 are tied or spot welded into a steel cage. The upper part of the steel node and the lower part of the steel node are welded to both ends of the steel cage respectively. The ends of the longitudinal steel bars 6 and The circumferential rib 5 is welded, the outer surface of the longitudinal steel bar 6 is welded to the inner surface of the inner steel pipe, the upper surface of the stirrup 7 is welded to the inner steel pipe section, the UHPC shell 8 is poured at the steel cage position according to the design thickness, and maintained to the design strength;

(3) Connecting steel nodes: Transport several prefabricated stacked columns to the construction site, insert the upper part of the steel node of the stacked column into the lower part of the steel node, and adjust the angle so that the short inner steel pipe 1 and the long inner steel pipe 3 are in contact, so that the long inner steel pipe 1 is in contact with the long inner steel pipe 3. The concave and convex shapes of the outer steel pipe 2 and the short outer steel pipe 4 mesh with each other, and are welded and connected at the concave and convex shapes;

(4) Pour the recycled concrete core: Pour the recycled concrete core 9 densely inside the UHPC shell, wait for the recycled concrete core 9 to reach the design strength, and then proceed to the next step.

The UHPC shell on the outside of the laminated column is prefabricated in the factory, which has basically completed the early shrinkage deformation of the concrete and formed a dense and crack-free UHPC shell, thereby improving the service life and durability of the structure and also providing a seal for the recycled concrete. The environment and the internal curing effect of recycled aggregates effectively improve long-term deformations such as autogenous shrinkage and basic creep of components.

The present invention improves the traditional connection method of prefabricated concrete columns by using steel structure nodes. The steel structure nodes are composed of short inner steel pipes 1, long outer steel pipes 2, long inner steel pipes 3, short outer steel pipes 4 and circumferential ribs 5, and have good force performance. The traditional reinforced concrete columns are improved into composite columns with prefabricated UHPC shells and cast-in-place recycled concrete cores, which effectively improves the long-term deformation and durability of the components. Strengthen the connection between steel bars and steel nodes and steel nodes and steel nodes through reasonable construction, improve the bonding performance between concrete and steel nodes in the core area by setting up circumferential ribs, and improve the integrity of the components. Steel structure nodes are more efficient and faster than traditional connection methods, which will greatly improve construction efficiency.

The embodiments of the present invention disclosed above are only used to help explain the present invention. The embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and changes may be made based on the contents of this manual. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can better understand and utilize the present invention.

Claims (9)

1. The construction method of the template-free assembled UHPC-recycled concrete superposed column is characterized by comprising the following construction steps of:

(1) Manufacturing a steel node: manufacturing a plurality of short inner steel pipes (1), a plurality of long outer steel pipes (2), a plurality of long inner steel pipes (3), a plurality of short outer steel pipes (4) and a plurality of circumferential ribs (5) according to the size design, welding the short inner steel pipes (1), the long outer steel pipes (2) and the circumferential ribs (5) to form upper parts of steel nodes, and welding the long inner steel pipes (3), the short outer steel pipes (4) and the circumferential ribs (5) to form lower parts of the steel nodes;

(2) Prefabricated UHPC shell: binding or spot welding a plurality of longitudinal steel bars (6) and a plurality of stirrups (7) into a steel bar cage according to the design, respectively welding the upper part and the lower part of a steel node at two ends of the steel bar cage, wherein the end parts of the longitudinal steel bars (6) are welded with the circumferential ribs (5), the outer surfaces of the longitudinal steel bars (6) are welded with the inner surfaces of the inner steel pipes, the upper surfaces of the stirrups (7) are welded with the sections of the inner steel pipes, casting a UHPC shell (8) at the positions of the steel bar cage according to the design thickness, and curing to the design strength;

(3) Connecting steel nodes: transporting the prefabricated overlapped columns to a construction site, inserting the upper parts of steel nodes of the overlapped columns into the lower parts of the steel nodes, enabling the short inner steel pipes (1) to be in contact with the long inner steel pipes (3) through adjusting angles, enabling the long outer steel pipes (2) to be meshed with the concave-convex shapes of the short outer steel pipes (4), and welding and connecting the concave-convex shapes at the meshed positions;

(4) Pouring a recycled concrete core: densely pouring a recycled concrete core (9) in the UHPC shell, and continuing the next procedure after the recycled concrete core (9) reaches the design strength;

the template-free assembled UHPC-recycled concrete superposed column comprises a short inner steel pipe (1), a long outer steel pipe (2), a long inner steel pipe (3), a short outer steel pipe (4), a plurality of circumferential ribs (5), a plurality of longitudinal steel bars (6), a plurality of stirrups (7), a UHPC shell (8) and a recycled concrete core (9);

the outer surface of the short inner steel pipe (1) is tightly attached to the inner surface of the long outer steel pipe (2), the circumferential rib (5) is positioned on the inner surface of the short inner steel pipe (1), and the short inner steel pipe, the long outer steel pipe and the long outer steel pipe are welded to form the upper part of a steel node; the outer surface of the long inner steel pipe (3) is tightly attached to the inner surface of the short outer steel pipe (4), the circumferential rib (5) is positioned on the inner surface of the long inner steel pipe (3), and the long inner steel pipe, the short outer steel pipe and the circumferential rib are welded to form the lower part of a steel node; a plurality of longitudinal steel bars (6) and a plurality of stirrups (7) are bound or spot welded into a steel reinforcement cage, the upper part of a steel node and the lower part of the steel node are respectively welded at two ends of the steel reinforcement cage, the UHPC shell (8) is positioned at the position of the steel reinforcement cage, and the recycled concrete core (9) is positioned inside the UHPC shell (8), the short inner steel tube (1) and the long inner steel tube (3).

2. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1, which is characterized by comprising the following steps: the joint of the long outer steel pipe (2) and the short outer steel pipe (4) is in a concave-convex shape which is meshed with each other.

3. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1 or 2, which is characterized by comprising the following steps: the steel strength grades of the short inner steel pipe (1), the long outer steel pipe (2), the long inner steel pipe (3), the short outer steel pipe (4) and the annular rib (5) are not lower than Q355.

4. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1 or 2, which is characterized by comprising the following steps: the thicknesses of the short inner steel pipe (1), the long outer steel pipe (2), the long inner steel pipe (3) and the short outer steel pipe (4) are not smaller than 2/3 of the diameter of the longitudinal steel bar (6).

5. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1, which is characterized by comprising the following steps: the thickness of the circumferential rib (5) is not smaller than the diameter of the longitudinal steel bar (6), and the width of the circumferential rib (5) is not smaller than 1.5 times of the diameter of the longitudinal steel bar (6).

6. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1, 2 or 5, wherein the construction method comprises the following steps: the position distance of the circumferential rib (5) is not less than the anchoring length of the longitudinal steel bars (6) at the edge of the short inner steel tube (1), the end parts of the longitudinal steel bars (6) are welded with the circumferential rib (5), and the outer surfaces of the longitudinal steel bars (6) are welded with the inner surface of the inner steel tube.

7. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1, 2 or 5, wherein the construction method comprises the following steps: the upper surface of the stirrup (7) is welded with the edge of the short inner steel pipe (1).

8. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1, 2 or 5, wherein the construction method comprises the following steps: the thickness of the UHPC shell (8) is not less than the distance from the inner side surface of the longitudinal steel bar (6) to the outer surface of the superposed column.

9. The construction method of the template-free assembled UHPC-recycled concrete composite column according to claim 1, 2 or 5, wherein the construction method comprises the following steps: the recycled concrete core (9) is recycled concrete doped with recycled aggregate prepared from waste concrete or industrial tailings, or internally cured concrete doped with super absorbent resin material or lightweight aggregate.