A multi-stage energy-consuming post-tensioned self-centering joint and its assembling method

Abstract

The present invention discloses a post-tensioned self-centering joint with multi-stage energy dissipation and its assembly method. The joint of the present invention can slide relatively, and energy dissipation is provided by the unilateral friction between the T-shaped member and the beam flange under small deformations. As the opening deformation of the joint increases, the SMA damper connected to the T-shaped plate begins to enter the phase change energy dissipation stage, and the introduced metal damper will not increase the residual deformation of the joint under the same prestress level. In order to avoid the low redundancy characteristics of the post-tensioned joint, the long circular hole allows the bolt rod connecting the T-shaped member and the beam flange to contact and bear pressure against the wall of the long circular hole of the beam flange, and can still effectively resist collapse in extreme cases. The present invention uses friction damping for energy consumption under small to medium earthquakes, and realizes combined energy dissipation mode energy consumption by coordinating with SMA phase change under medium to large earthquakes, and achieves complete reset by virtue of the post-tensioned prestressing tendons; in extreme cases, the force transfer of the joint is transformed into the hole wall bearing pressure mode to resist collapse, realizing the properties of multi-stage energy dissipation and multi-redundancy.

Description

Technical Field

[0001] The present invention belongs to the field of structural engineering, and in particular relates to a post-tensioning self-resetting node with multi-stage energy dissipation based on SMA damping and friction mechanism and an assembly method thereof. Background Art

[0002] Steel has the characteristics of light weight, high strength, high elastic modulus and high toughness. It is widely used in the field of structural engineering, especially complex long-span structures such as bridges and gymnasiums. Compared with steel structural components, the connection parts of the components are complex and have poor reliability due to sudden changes in stiffness and uneven construction quality. They are usually the weak areas of the structure. At present, there are mainly the following forms of steel structure node connections: full welding connection, bolt connection and bolt-weld hybrid connection. Considering labor costs and assembly requirements, the latter two are now widely used in most countries, especially bolt-weld hybrid connection. However, the earthquake damage survey of the 1994 Northridge earthquake showed that the bolt-weld hybrid connection steel node, which theoretically has good ductility, did not show the expected ductile failure performance, but mostly occurred in the flange weld where the quality is difficult to guarantee. The brittle fracture mode caused by cracks caused great difficulty in repair. This is one of the reasons why structural researchers developed new nodes. On the other hand, earthquake damage investigations found that although some steel nodes have the advantage of ductile energy dissipation, they still retain large permanent deformations due to accumulated plastic deformation after the earthquake, which greatly increases the period and difficulty of structural repair. Sometimes they even face the possibility of demolition, causing huge economic losses.

[0003] In order to improve the seismic performance of the node and ensure the ductility and energy dissipation of the node, engineers will strengthen the connection parts of the node, such as adding axillary plates, or weakening the beam flanges in the adjacent areas, so that the plastic deformation of the structure is concentrated on the target part, thereby ensuring the "strong node" requirement. In fact, the above-mentioned strengthening or weakening methods are a relative strength balance, and do not change the force transmission mechanism at the structural node (the upper and lower flanges of the beam form a couple that contributes most of the bending resistance, and the web transmits most of the shear force). Although this is conducive to achieving the seismic requirements based on life safety, from the perspective of the entire life cycle of the building structure, excessive residual deformation under moderate and strong earthquakes will inevitably make this node unattractive.

[0004] Furthermore, along with the methods of strengthening and weakening the strength of nodes, another new type of node came into being, that is, the node with recoverable performance. The node with recoverable function is also called the self-resetting node. It not only meets the design requirements of structural strength, stiffness and ductility energy dissipation, but also can reset itself after unloading, greatly reducing or even eliminating the residual deformation of the structure. In essence, this node is to separate the energy dissipation behavior of the structure from the main components of the structure by changing the above-mentioned node force transmission mechanism, and to be undertaken by a specific energy dissipator that is easy to replace or does not need to be replaced, and to be reset with the help of a reset element. This self-resetting node replaces the structural plastic hinge energy dissipation with an additional energy dissipation element, which reduces the energy dissipation capacity of the structure to a certain extent, but can greatly improve the recoverable performance of the structure. After reasonable design, it can achieve the organic unity of energy dissipation and reset. Nowadays, there are two main methods to realize this recoverable node, using the PT type node with the pre-tension mechanism of post-tensioned prestressed tendons (PT for short) and using smart materials with self-resetting performance at the node. The prestress level of the high-strength steel rod in the PT node needs to be combined with the auxiliary energy dissipator according to the performance target requirements, but the initial higher prestress level will increase the demand for anchoring, and also increase the possibility of node failure under strong earthquakes, and this failure is often fatal in extremely rare cases. With the innovation of metallurgical technology, the cost of ultra-high performance alloys has been greatly reduced, and more smart materials have begun to expand into the field of structural engineering, such as shape memory alloy (Shape Memory Alloy, referred to as SMA). It has good shape memory effect and superelastic properties. The former means that the smart material can restore its original shape by heating when unloading after being deformed by load, and the latter means that the material can automatically restore to its original shape after being unloaded after being deformed by load. This gives this smart material the potential for self-reset in the structure. At the same time, because this material can reset itself, a lot of elastic energy is released during the unloading process, and the energy actually dissipated is much smaller than that of steel. Therefore, although the deformation can be restored after the earthquake, there is also a disadvantage of insufficient energy dissipation, which may further increase the acceleration response of the structure under earthquake.

[0005] In addition, although this smart material has good recoverability, its austenite elastic modulus (taking NITI memory alloy as an example) is about one-third of that of steel. Therefore, when only SMA bar is used as the reset and energy dissipation element of the node, the strength, stiffness and energy dissipation of the node are limited. If other energy dissipation mechanisms (such as friction and angle steel) are introduced to improve the behavior of the node, it is necessary to strictly examine whether the restoring force stored in the node itself can effectively reset the node. Summary of the invention

[0006] The purpose of the present invention is to effectively give play to the advantages of various materials through technological innovation, thereby achieving the purpose of improving the shortcomings and defects of existing nodes, and finally proposing a feasible post-tensioning self-resetting node based on SMA damping and friction mechanism by controlling the energy consumption sequence of multi-stage energy consumption.

[0007] In view of the respective advantages and disadvantages of the above two types of self-resetting nodes, the node technologies of the two are combined to complement each other and achieve higher node performance (such as energy consumption and stiffness). The post-tensioned self-resetting node based on SMA damping and multi-stage energy dissipation of friction mechanism solves the problem of anchoring difficulty and sharp drop in node rotation stiffness after unloading caused by the high initial prestress level of post-tensioned nodes due to ensuring recoverability; it solves the problem that the SMA node has a large demand for inter-layer displacement and inter-layer acceleration under earthquakes due to low initial stiffness and insufficient energy consumption. The new node is based on performance-based design to make the node design concept clearer. The friction between low prestressed steel bars and T-shaped webs and steel beam end reinforcement plates (filler plates) is used to resist loads (such as wind loads) under normal use and stably dissipate the energy input into the system within the range of small and medium earthquakes. At the same time, the SMA bar damping within the austenite working range will optimize the sharp drop in stiffness after the PT node is disconnected, thereby controlling the deformation of the node. When the node is under moderate to large earthquakes, the SMA bar enters the phase transformation process from austenite to martensite, and the stiffness of the node decreases again, which helps to reduce local damage to the main components (ensuring that the main components remain in an elastic state). As the SMA bar damper starts to work, the node enters a combined energy dissipation mode, which strengthens the energy dissipation behavior of the node under large earthquakes. In addition, after unloading, the node can recover by itself without replacing any components, thereby achieving a repair-free function. In terms of node design, in order to resist extremely rare working conditions, the size of the oblong hole of the steel beam is reasonably designed, so that the high-strength bolt rod can squeeze the hole wall under this working condition and exert the bearing capacity of the steel beam, thereby overcoming the deficiency of the traditional PT node in extremely rare working conditions due to the failure of the prestressed steel rod and the subsequent complete failure of the node, and increasing the redundancy of the node.

[0008] A multi-stage energy-consuming post-tensioned self-resetting node, comprising a steel column 1, a T-type connector 4, an SMA bar damper 6, a post-tensioned prestressed steel rod 9 and a steel beam 8, characterized in that a steel beam 8 is installed on one side of the flange of the steel column 1, an oblong bolt hole 8-1 is formed at the end of the steel beam 8, and a T-type connector 4 is installed on the upper and lower sides of the end of the steel beam 8; a high-strength first bolt 5-1 passes through the oblong bolt hole 8-1 to fix the T-type connector 4 to the steel beam 8; the T-type connector 4 is connected to the flange of the steel column 1; an anchor device 7 is also fixed on the steel beam 8; one end of the SMA bar damper 6 is connected to the T-type connector 4, and the other end is connected to the anchor device 7; the post-tensioned prestressed steel rod 9 passes through the steel column 1 and the steel beam 8, is symmetrically arranged on both sides of the axis of the steel beam 8, and is anchored at the outer flange of the steel column 1 and the stiffening rib 13 at the end of the steel beam 8 through an anchor 11.

[0009] As a further improvement, the upper and lower protrusions at the middle web end of the T-shaped connector 4 form a T-shaped enlarged end 4-2, and the T-shaped enlarged end 4-2 is embedded with a tapping screw hole 4-3; the anchoring device 7 includes a main body and a cover plate part 7-2; the main body is fixedly connected to the steel beam 8; the main body and the cover plate part 7-2 are covered to form a conical hole 7-3, and the main body and the cover plate part 7-2 are fixed by screws 7-1; one end of the SMA bar damper 6 is threadedly fixed to the tapping screw hole 4-3, and the other end is fixed to the conical hole 7-3.

[0010] As a further improvement, the SMA bar damper 6 comprises a working section 6-1, and two ends of the working section 6-1 are respectively connected with a threaded enlarged end 6-2 matched with the tapping screw hole 4-3 and a frustum-type enlarged end 6-3 matched with the frustum-type hole 7-3 through a transition section 6-4.

[0011] As a further improvement, a circular hole 8 - 2 is formed on the steel beam 8 , and the third bolt 5 - 3 passes through the circular hole 8 - 2 to connect the anchor device 7 to the steel beam 8 .

[0012] As a further improvement, transverse short ribs 10 are welded to the stiffening ribs 13 at the ends of the steel beams 8 .

[0013] As a further improvement, a filler plate 12 is installed between the web of the T-shaped connector 4 and the steel beam 8; the contact surfaces of the web of the T-shaped connector 4 and the filler plate 12 are both formed with a rough layer.

[0014] As a further improvement, the steel column 1 is an I-shaped steel column; the steel beam 8 is an I-shaped steel beam; the T-shaped piece is composed of a flange, a web 4-1 and an enlarged end 4-2 of the T-shaped piece; the first bolt 5-1, the second bolt 5-2 and the third bolt 5-3 are all friction high-strength bolts; the steel column is provided with transverse stiffening ribs 2 and a reinforcing plate 3 for anchoring prestressed steel rods.

[0015] As a further improvement, when the node rotation angle is 5%, the first bolt 5-1 contacts the hole wall of the oblong bolt hole 8-1, that is, the radial distance between the center of the high-strength first bolt 5-1 and the hole wall of the oblong bolt hole 8-1 is the product of the beam height h multiplied by 5% plus the radius of the first bolt 5-1.

[0016] A method for assembling a multi-stage energy-consuming post-tensioning self-resetting node comprises the following steps:

[0017] Step 1: Standardize the production of steel columns 1, steel beams 8, T-shaped connectors 4 with T-shaped enlarged ends 4-2, SMAbar dampers 6, anchoring devices 7, post-tensioned prestressed steel rods 9 and corresponding beam-column stiffening ribs and anchoring plates in the factory; open bolt holes in the corresponding parts of the steel beams 8, steel columns 1, T-shaped connectors 4, anchoring devices 7 and filler plates 12; weld stiffening ribs 13 and reinforcing plates 3 to the corresponding parts of the steel columns 1 and steel beams 8;

[0018] Step 2: Install and position the steel beam 8, the steel column 1 and the T-shaped connector 4 with the T-shaped enlarged end 4-2 by bolts, and tighten the bolts;

[0019] Step 3: Install and tighten one end of the SMA bar damper 6 on the enlarged end 4-2 of the T-shaped piece, and the other end of the SMA bar damper 6 is connected to the anchor device 7, and the anchor device 7 is fixed to the preset position of the steel beam 8 by bolts. The second bolt 5-2 for fixing the steel beam 8 and the T-shaped connector 4 and the third bolt 5-3 for fixing the anchor device 7 and the steel beam 8 first apply half of the target preload force to compress the web (4-1) of the T-shaped connector 4 and the steel beam 8 and the anchor device 7. In addition, the first bolt 5-1 is manually tightened to position; then, the post-tensioning prestressing steel rod 9 is prestressed by a hydraulic jack to compress the flange of the steel column 1 and the steel beam 8; finally, the first bolt 5-1, the second bolt 5-2 and the third bolt 5-3 are applied to the target preload force, and the assembly is completed.

[0020] 1. The present invention combines the advantages of PT nodes and SMA nodes to achieve higher node performance (such as energy consumption and stiffness). The post-tensioned self-reset node based on SMA damping and friction mechanism multi-stage energy consumption solves the problem of anchoring difficulty and sharp reduction of rotational stiffness after node disengagement caused by the high initial prestress level of post-tensioned nodes due to ensuring recoverability; solves the problem that SMA nodes have low initial stiffness and insufficient energy consumption, resulting in large inter-layer displacement and inter-layer acceleration requirements under earthquakes; and realizes the function of self-reset and repair-free nodes under large earthquakes.

[0021] 2. The present invention is based on performance-based design and reasonably arranges the working sequence of the two types of damping mechanisms, making the node performance more flexible and adjustable. Due to the introduction of SMA dampers and medium and low levels of friction damping, the initial stress level of the prestressed steel rod (applied initial strength / steel rod yield strength) can be reduced to 0.1, thereby greatly reducing the difficulty of anchoring the prestressed steel rod and improving the anchoring reliability. The slightly tensioned PT node cooperates with medium and low friction damping to resist the loads (such as wind loads) under normal use and dissipate the energy within the range of small and medium earthquakes. In this process, the SMA damper only contributes a certain amount of node rotation stiffness, optimizing the unfavorable situation of sharp reduction in stiffness after the node is disengaged, and almost no energy consumption is provided. As the ground motion increases, the SMA damping enters the phase change stage, and the node immediately enters the combined energy consumption mode. At the same time, the node rotation stiffness is further reduced to reduce the damage to the main component beams and columns, and the node can be completely reset after the earthquake.

[0022] 3. The present invention is easy to install, and its performance can be adjusted to suit different earthquake-resistant areas and owner requirements by changing the preload of the high-strength bolts and the size of the SMA bar.

[0023] 4. The node proposed in the patent of the present invention is completely symmetrical about the neutral axis, so the performance of the node under the action of positive and negative bending moments is consistent. Taking the positive bending moment as an example, under the action of the positive bending moment, the lower flange of the beam in contact with the T-shaped piece gradually "de-compresses" and the upper flange of the beam gradually "increases pressure". This force transmission mode provides the node with bending resistance until the lower flange of the beam is completely "de-compressed". Then the lower flange of the beam enters the stage of overcoming the static friction between the T-shaped piece. Further, the beam and the T-shaped piece rotate relative to each other, and the SMA bar damping undergoes elastic elongation and deformation. As the loading continues, the SMA bar damping enters phase change energy consumption. At this time, after the node is unloaded, it can be completely reset and the main components of the beam and column are in the elastic working range. The friction and SMA damping do not need to be replaced, so no repair work is required.

[0024] 5. The NITI smart alloy with moderate elastic modulus used in this node has two-stage benefits: first, under small and medium earthquakes, it can improve the mechanical properties of the node after disconnection (increase the node rotation stiffness, relying on its elastic deformation), thereby controlling the lateral deformation of the structure, and protecting non-structural components that are sensitive to interlayer lateral displacement; second, under medium and large earthquakes, it activates its phase change energy dissipation behavior, acts as a supplementary damping and friction damping to form a composite damping to achieve the purpose of fully dissipating the energy of the system, and at the same time, with the reduction of node stiffness, it is beneficial for the main components (beams and columns) to maintain an elastic state and reduce the local damage of the components under pressure. In addition, after suffering from medium and large earthquakes, the SMA damping automatically resets, that is, the additional damping will not increase the demand for steel strands, and the node can be restored to a lossless state without repair.

[0025] 6. This design reasonably designs the size of the oblong hole and allows the hole wall and the bolt rod to bear pressure when the node rotation angle exceeds 5%, that is, the node is transformed into a pressure-bearing node (the ultimate bearing capacity of the beam is exerted, which is consistent with the force of the traditional node), preventing the structure from completely failing and presenting a multi-redundancy feature. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the position of the present invention in the structure;

[0027] Figure 2-1 It is a schematic diagram of the overall three-dimensional structure of the node of the present invention;

[0028] Figure 2-2 It is a three-dimensional structural schematic diagram of a T-type connector;

[0029] Figure 2-3 is a schematic diagram of the three-dimensional structure of the anchoring device;

[0030] Figure 3 Schematic diagram of node disassembly;

[0031] Figure 4 It is a front view of the present invention;

[0032] Figure 5 It is a side view of the present invention;

[0033] Figure 6 A top view of the present invention;

[0034] Figure 7 It is a schematic diagram of an I-shaped steel beam with bolt holes;

[0035] Figure 8 This is a schematic diagram of the SMA bar.

[0036] Fig. 9 Schematic diagram of prestressed steel rod and cylindrical anchor

[0037] Among them, the parts are numbered as follows: 1. Steel column; 2. Column transverse stiffening rib; 3. Reinforcement plate; 4. T-type connector; 4-1. T-type web; 4-2. T-type enlarged end; 4-3. Tapped screw hole; 5-1. First bolt; 5-2. Second bolt; 5-3. Third bolt; 6. SMA bar damper; 6-1. Working section; 6-2. Threaded enlarged end; 6-3. Conical enlarged end; 6-4. Transition section; 7. Anchor device; 7-1. Screw; 7-2. Cover plate part; 7-3. Conical hole; 7-4. SMA installation device mounting screw hole; 8. Steel beam; 9. Post-tensioned prestressed steel rod; 10. Transverse short rib; 11. Anchor; 12. Filling plate; 13. Stiffening rib. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description is given below with reference to the accompanying drawings and specific implementation cases.

[0039] The present invention proposes a post-tensioned self-resetting node based on an SMA damping device and friction multi-stage energy dissipation, comprising: 1. an I-shaped steel column, 2. an I-shaped steel beam, 3. a T-shaped connector with an enlarged end, 4. an SMA bar damper, 5. a prestressed steel rod, 6. an anchor, 7. a reinforcement plate at the anchorage of the outer flange of the column, 8. a column transverse stiffening rib, 9. a beam anchoring end plate and end stiffening ribs, 10. a beam flange end plate reinforcement plate, and 11. friction high-strength bolts.

[0040] This self-resetting node is taken from the beam-column node selected in the structure, which includes the structural components described above. The column anchor reinforcement plate is welded on four sides at the outer flange of the column, the column transverse stiffening rib is welded on three sides at the I-shaped steel column node area, and the beam end anchor end plate, short rib and beam end flange reinforcement plate are welded at the preset position in the form of angle welds.

[0041] The flange of the I-shaped steel beam and the flange of the steel column are positioned with the T-piece and bolted. The SMA bar damper is further installed. All bolts are initially tightened. At this time, the prestressed steel rod is installed and applied with a preload exceeding the target value. After a period of time, the oil is returned and the rebound of the prestressed anchor is observed. After several iterations to the prestress target value, all friction-type high-strength bolts are finally tightened to the preset value. Among them, the web of the T-piece acts as a friction plate and transmits the node shear force. During the stress process of the node, the main components of the beam and column are in the elastic range, and friction and SMA damping dissipate energy, but these energy dissipation mechanisms can be reused, so no repair is required within the preset performance.

[0042] Assembly method of post-tensioned self-resetting node based on SMA damping device and friction multi-stage energy dissipation:

[0043] After the above-mentioned components are standardized and produced in the corresponding factories, they are pre-positioned on the factory assembly line. Holes are drilled in the I-shaped steel columns, steel beams, T-pieces, various anchors and reinforcement plates, and the stiffening ribs and reinforcement plates are welded to the preset positions of the steel columns and steel beams; the SMA bar needs to be heat treated after forming and then threaded; the enlarged end of the T-piece needs to be drilled and tapped to connect the SMA bar damping; the SMA damping anchor installation device needs to be drilled and cut.

[0044] The flange of the T-shaped piece is connected to the preset position of the column flange by bolts. After the connection is completed, it is transported to the site to complete the connection of each component, and all bolts are initially tightened.

[0045] Tension the prestressed steel rods, and after tensioning, tighten all bolts to the target torque.

[0046] Compared with the traditional joint, this joint has the following innovations: (1) SMA bar damping is separated from the joint shear mechanism to improve the rotational stiffness of the joint after detachment under small and medium earthquakes, and to enhance the energy dissipation behavior of the structure under medium and large earthquakes, and its function is more clear. (2) Because of the above-mentioned SMA bar damping, its improvement of the node energy dissipation behavior does not increase the node reset burden, and improves the stiffness after the node is detached, so the initial prestress level of the high-strength steel rod can be greatly reduced, thereby improving the reliability of anchoring and reducing the difficulty of anchoring. (3) This node separates the energy dissipation behavior from the main components, and friction and SMA phase change are responsible for it. These mechanisms can be used an unlimited number of times without replacement and repair, and are almost completely reset under the restoring force of the prestressed steel rod. (4) Compared with the PT node, this new node achieves the same initial stiffness with a smaller prestress level, and greatly improves the node unloading stiffness after the node is detached, which is beneficial to the control of interlayer deformation of the structure under small and medium earthquakes. (5) Compared with the SMA bar self-resetting node, the initial stiffness of the node is greatly improved, avoiding the unfavorable situation of the SMA bar being in shear. (6) The new node realizes multi-stage energy consumption by reasonably arranging the energy consumption sequence of the two energy consumption mechanisms, thereby optimizing the node performance. (7) All the above installation operations can be assembled, which speeds up the construction period.

[0047] The node of the present invention is essentially an effective combination of two self-resetting nodes, and adjusts the working sequence of the energy consumption mechanism to achieve the seismic requirements at different stages. For example, in order to avoid damage to non-structural components under small and medium earthquakes, the node needs to strictly control the interlayer deformation. Therefore, the rotational stiffness of the node cannot be reduced too much after unloading, but it cannot be too soft. The SMA bar damper can flexibly adjust the stiffness of the node at this stage. When the structure is subjected to a strong earthquake, ensuring that the main components are not damaged is the key to reducing the difficulty and cycle of post-earthquake repair. Therefore, the main structure must be weakened, corresponding to the SMA damping entering the phase change energy consumption stage. After the earthquake, it can also be reset by the reset element without repair. Therefore, from the perspective of the entire life cycle of the structure, the present invention has a high comprehensive economic benefit.

[0048] The above is only a specific example of the present invention. If only simple improvements and replacements are made to this patent, they are all within the protection scope of the present invention.

Claims

1. A multi-stage energy-dissipating post-tensioned self-centering joint, comprising a steel column (1), a T-shaped connector (4), an SMA bar damper (6), a post-tensioned prestressed steel bar (9), and a steel beam (8). Characterized in that, One side of the flange of the steel column (1) is provided with a steel beam (8). An oblong bolt hole (8-1) is formed at the end of the steel beam (8). T-shaped connectors (4) are installed on both the upper and lower sides of the end of the steel beam (8). A high-strength first bolt (5-1) passes through the oblong bolt hole (8-1) to fix the T-shaped connector (4) to the steel beam (8). The T-shaped connector (4) is connected to the flange of the steel column (1). An anchoring device (7) is also fixed on the steel beam (8). One end of the SMA bar damper (6) is connected to the T-shaped connector (4), and the other end is connected to the anchoring device (7). The post-tensioned prestressed steel bar (9) passes through the steel column (1) and the steel beam (8), is symmetrically arranged on both sides of the axis of the steel beam (8), and is anchored at the outer flange of the steel column (1) and the stiffener (13) at the end of the steel beam (8) through an anchor (11).

2. The multi-stage energy-dissipating post-tensioned self-centering joint according to claim 1, Characterized in that, At the upper and lower ends of the middle web of the T-shaped connector (4), T-shaped enlarged ends (4-2) are formed by bulging. Threaded holes (4-3) are embedded in the T-shaped enlarged ends (4-2). The anchoring device (7) includes a main body part and a cover part (7-2). The main body part is fixedly connected to the steel beam (8). After the main body part and the cover part (7-2) are covered, a truncated cone-shaped hole (7-3) is formed. The main body part and the cover part (7-2) are fixed by screws (7-1). One end of the SMA bar damper (6) is fixedly connected to the threaded hole (4-3) by threads, and the other end is fixed to the truncated cone-shaped hole (7-3).

3. The multi-stage energy-dissipating post-tensioned self-centering joint according to claim 2, Characterized in that, The SMA bar damper (6) includes a working section (6-1). At both ends of the working section (6-1), a threaded enlarged end (6-2) cooperating with the threaded hole (4-3) and a truncated cone-shaped enlarged end (6-3) cooperating with the truncated cone-shaped hole (7-3) are respectively connected through transition sections (6-4).

4. The multi-stage energy-dissipating post-tensioned self-centering joint according to claim 2, Characterized in that, A round hole (8-2) is formed on the steel beam (8). A third bolt (5-3) passes through the round hole (8-2) to connect the anchoring device (7) to the steel beam (8).

5. The multi-stage energy-dissipating post-tensioned self-centering joint according to claim 1, Characterized in that, A transverse short rib (10) is welded at the stiffener (13) at the end of the steel beam (8).

6. The multi-stage energy-dissipating post-tensioned self-centering joint according to claim 1, characterized in that a packing plate (12) is installed between the web of the T-shaped connector (4) and the steel beam (8). Rough layers are formed on the contact surfaces of the web of the T-shaped connector (4) and the packing plate (12).

7. The post-tensioned self-centering joint with multi-stage energy dissipation according to claim 1, characterized in that the steel column (1) is an I-shaped steel column; the steel beam (8) is an I-shaped steel beam; the T-shaped member consists of a flange, a web (4-1) and a T-shaped member enlarged end (4-2); the first bolt (5-1), the second bolt (5-2) and the third bolt (5-3) are all friction-type high-strength bolts; transverse stiffeners (2) and reinforcing plates (3) for anchoring prestressed steel bars are provided on the steel column.

8. The post-tensioned self-centering joint with multi-stage energy dissipation according to claim 1, characterized in that when the joint rotation angle is 5%, the first bolt (5-1) contacts the hole wall of the oblong bolt hole (8-1), that is, the radial distance between the center of the high-strength first bolt (5-1) and the hole wall of the oblong bolt hole (8-1) is the product of the beam height h multiplied by 5% plus the radius of the first bolt (5-1).

9. An assembly method for a post-tensioned self-centering joint with multi-stage energy dissipation Characterized in that It includes the following steps: Step 1: Standardize the production of the steel column (1), the steel beam (8), the T-shaped connecting member (4) with a T-shaped member enlarged end (4-2), the SMA bar damper (6), the anchoring device (7), the post-tensioned prestressed steel bar (9) and the corresponding beam-column clamping ribs and anchoring plates in the factory; drill bolt holes in the corresponding parts of the steel beam (8), the steel column (1), the T-shaped connecting member (4), the anchoring device (7) and the filler plate (12); weld stiffeners (13) and reinforcing plates (3) to the corresponding parts of the steel column (1) and the steel beam (8). Step 2: Install and position the steel beam (8), the steel column (1) and the T-shaped connecting member (4) with a T-shaped member enlarged end (4-2) by bolts and tighten the bolts. Step 3: Install and tighten one end of the SMA bar damper (6) at the T-shaped member enlarged end (4-2), connect the other end of the SMA bar damper (6) to the anchoring device (7), and fix the anchoring device (7) to the preset position on the steel beam (8) by bolts. First, apply half of the target pre-tightening force to the second bolt (5-2) for fixing the steel beam (8) and the T-shaped connecting member (4) and the third bolt (5-3) for fixing the anchoring device (7) and the steel beam (8) to press the web (4-1) of the T-shaped connecting member (4) and the steel beam (8) and the anchoring device (7). In addition, manually tighten and position the first bolt (5-1); then, apply prestress to the post-tensioned prestressed steel bar (9) through a hydraulic jack to press the flange of the steel column (1) and the steel beam (8); finally, apply the first bolt (5-1), the second bolt (5-2) and the third bolt (5-3) to the target pre-tightening force to complete the assembly.

Images