Node for reinforcing old reinforced concrete frame structure through BRB, design method and earthquake toughness improvement rapid evaluation method of node

Abstract

The invention belongs to the technical field of earthquake toughness improvement of old buildings and earthquake response rapid calculation based on an artificial intelligence technology, and discloses a node for a BRB reinforced old reinforced concrete frame structure, a design method and an earthquake toughness improvement rapid evaluation method of the BRB reinforced old reinforced concrete frame structure. The joint comprises a frame structure beam column joint composed of a reinforced concrete beam component, a column component and a plate component, a buckling restrained brace, a high-strength bolt, a connecting plate, a cladding plate, a bottom plate and stiffening ribs. According to the connection node structure provided by the invention, the damage to the opening positions of the plate components is easier to control through the structure design compared with the damage to the opening positions of the beam and column components in the conventional connection node structure, and the integrity and the bearing capacity of the beam and column components serving as main bearing components of the structure are better protected. According to the probability-based earthquake toughness improvement evaluation method, the structural vulnerability is adopted as a comparison parameter, and the reinforcing effect of the buckling restrained brace on the structure is displayed more visually and more comprehensively through vulnerability control rate analysis.

Description

Technical Field

[0001] This invention belongs to the field of seismic toughness improvement of old buildings and rapid calculation of seismic response based on artificial intelligence technology. It relates to a node design method for BRB-reinforced old reinforced concrete frame structures and a rapid assessment method for improving seismic toughness. Background Technology

[0002] As building materials age, their performance inevitably deteriorates. Furthermore, societal progress and increasing demands from the public mean that older buildings no longer meet current requirements. While demolishing and rebuilding older buildings can effectively address these issues, it incurs significant economic losses and contradicts the principles of low-carbon and environmentally friendly development. Therefore, it is necessary to develop effective technologies to enhance the seismic resilience of older buildings in earthquake-prone areas. Buckling-restrained braces (BRBs) are a common method for improving the seismic resilience of older buildings. The connection between BRBs and reinforced concrete (RC) frame structures is often anchored to the reinforced concrete members. During construction, holes need to be drilled in the main load-bearing members such as beams and columns, and these holes are often quite deep to ensure sufficient anchorage length. However, the beam and column sections of existing older RC frame structures are often small, making it easy to compromise the integrity of the existing structural members and potentially cause irreversible damage. Furthermore, the opening needs to withstand tensile stress, while concrete has relatively low tensile strength. Stress concentration caused by tensile stress can easily lead to localized damage at the opening, resulting in anchorage failure. These shortcomings limit the use of BRB in the reinforcement and renovation of RC frame structures. Therefore, it is necessary to develop more reasonable BRB reinforcement methods for RC frame structure connection nodes.

[0003] Assessing the improvement in seismic toughness of a reinforced structure is crucial for adjusting its functional use and evaluating the effectiveness of reinforcement measures. The method for measuring the improvement in seismic toughness in the prefabricated self-resetting variable stiffness energy-dissipating connection structure with sleeve bolts and its installation method (CN110093993A) uses deterministic control rates based on macroscopic responses such as floor lateral displacement and acceleration, lacking a probabilistic method for measuring seismic toughness improvement. Structural vulnerability is the conditional probability that a structure's response will exceed a set limit state under given conditions. However, traditional methods for assessing structural seismic vulnerability neglect the impact of uncertainties in unknown parameters of demand and capacity models, i.e., they fail to consider the cognitive uncertainties of various models.

[0004] Therefore, it is necessary to develop a quantitative method for assessing the improvement in seismic toughness by quantifying the effects of various uncertainties. Furthermore, the aforementioned toughness assessment methods first require extensive finite element analysis to obtain the dynamic response of the structure before and after reinforcement, wasting significant computational resources and hindering widespread application. Therefore, it is essential to develop a method that can rapidly obtain the structural dynamic response. Summary of the Invention

[0005] To address the shortcomings of the aforementioned connection nodes, this invention designs and provides a node design method and a seismic toughness improvement assessment method for BRB-reinforced old reinforced concrete frame structures. By designing a novel node structure to avoid openings in beam and column members and achieve superior force transmission performance, a rapid calculation method for the dynamic response of building structures based on a time-series predictive neural network is established. Furthermore, a rapid assessment method for seismic toughness improvement that can quantify the effects of various uncertainties is proposed.

[0006] The technical solution of the present invention:

[0007] A joint for BRB reinforcement of old reinforced concrete frame structures includes a frame structure beam-column joint composed of reinforced concrete beam members, column members, and slab members, buckling restraint braces, high-strength bolts, connecting plates, cladding plates, bottom plates, and stiffening ribs.

[0008] Several bolt holes are arranged in an array on the connecting plate and the base plate;

[0009] Several connection holes are opened on the plate members of the beam-column joint of the frame structure. The size and position of the connection holes correspond to the bolt holes on the bottom plate to realize the connection. The cladding plate covers the column members of the beam-column joint of the frame structure. The connection plate is vertically connected to the cladding plate. There are stiffening ribs connecting the connection plate and the cladding plate. The connection plate, cladding plate, bottom plate and stiffening ribs are welded to form the connection node assembly.

[0010] The diameter and spacing of the bolt holes on the connecting plate and the base plate shall be selected and calculated in accordance with the Technical Specification for High Strength Bolt Connection of Steel Structure (JGJ82-2011); the size of the connecting hole on the plate member of the beam-column node of the frame structure shall be larger than the size of the bolt hole on the base plate to ensure that the high strength bolt passes through the beam-column node of the frame structure and the connecting node component does not have a large displacement due to the excessively large opening.

[0011] The buckling-restrained brace is an energy-dissipating buckling-restrained brace connected to the connecting plate, and consists of an energy-dissipating section and a connecting section;

[0012] The steel strength grade of the connecting plate shall not be lower than that of the steel strength grade of the connecting section of the buckling-restrained brace;

[0013] The bearing capacity and diameter of high-strength bolts are calculated according to the high-strength bolt friction type connection specified in the "Technical Specification for High-Strength Bolt Connection of Steel Structure" (JGJ82-2011) to bear the dynamic load under earthquake;

[0014] The specific design of the connecting plate, the covering plate, the bottom plate and the stiffening ribs is determined by finite element analysis. The connecting plate, the covering plate and the bottom plate have the same thickness.

[0015] Stiffening ribs are arranged on the connecting plate and the bottom plate to limit the deformation of the connecting plate and the bottom plate, and the arrangement position is adapted to the bolt holes on the connecting plate and the bottom plate.

[0016] The connection node assembly consists of four pieces, divided into two groups: an upper assembly and a lower assembly. The two connection node assemblies in each group are connected to each other by high-strength bolts. The connection between the two connection node assemblies in each group encloses the column members of the beam-column joint of the frame structure. The connection between the upper and lower assemblies encloses the beam and slab members of the beam-column joint of the frame structure, so that the connection node assembly forms an overall enclosure of the beam-column joint of the frame structure. The connection section of the buckling-restrained brace is connected to the connection plate of the connection node assembly by high-strength bolts.

[0017] The angle between the buckling-restrained brace and the column member of the beam-column joint in the frame structure is 35° to 55°.

[0018] The contact surfaces of beam-column joints and connecting joint components in the frame structure are made smooth to avoid local stress concentration under bolt preload.

[0019] A joint design method for BRB-reinforced old reinforced concrete frame structures includes the following steps:

[0020] Step 1: Collect the number of floors, structural cross-section, and structural plan of the building structure to be reinforced, and select the floors of the building structure to be reinforced; arrange the buckling restraint braces using a single diagonal brace arrangement method, and determine the positions of the two ends of the buckling restraint braces at the beam-column joints of the frame structure; based on the dimensions of the beam, column, and slab members of the beam-column joints of the frame structure, the reinforcement drawings of the beam, column, and slab members, and the strength grade of the steel used for the connection section of the buckling restraint braces, preliminarily design the connection node components, including the dimensions of the base plate and the arrangement of high-strength bolts;

[0021] Step 2: Perform finite element analysis on the preliminary design nodes, and modify and optimize the stiffening ribs, bolt hole openings and positions, and high-strength bolt parameters on the connection node components based on the results; when the concrete strength grade of the plate members of the beam-column joint of the frame structure is not higher than C30, consider arranging metal sleeves at the connection holes on the plate members of the beam-column joint of the frame structure and arranging steel plates on the contact surface of the plate members of the beam-column joint of the frame structure. The diameter of the metal sleeve and the size of the steel plate are obtained by optimization through finite element analysis;

[0022] Step 3: Manufacture the connection node assembly according to the modified and optimized parameters in Step 2 and make holes in the plate members of the beam-column joint of the frame structure; pre-connect the connection node assembly and the beam-column joint of the frame structure without applying pre-tightening force using high-strength bolts.

[0023] Step 4: Pre-connect the connecting segment of the buckling-restrained brace to the connecting node assembly, and adjust the angle of the buckling-restrained brace to the design value;

[0024] Step 5: Tighten all bolts on the node and apply preload.

[0025] A rapid assessment method for earthquake toughness enhancement capable of quantifying the effects of multiple uncertainties is proposed, comprising the following steps:

[0026] Step 1: Collect basic data of the building structure, including the column grid layout, reinforcement details and material properties of each component of the building structure to be reinforced. This basic data will be used to train a fast calculation model for the dynamic response of the building structure. Based on the target spectrum given by the seismic code of my country (GB50011-2010), download the measured ground motion records from the Pacific Earthquake Engineering Center of the United States for subsequent finite element analysis of the building structure.

[0027] Step 2: Based on the basic data of the building structure collected in Step 1, establish finite element models of the building structure before and after reinforcement using a finite element platform.

[0028] Furthermore, in the established finite element model of the reinforced building structure, the buckling restraint brace is constructed with energy dissipation segment and connection segment according to the actual buckling restraint brace.

[0029] Furthermore, the materials used for beam-column joints in the frame structure in the established finite element model are reduced in strength based on the actual material strength of the building structure to be reinforced or the steel corrosion model.

[0030] Step 3: Using the measured ground motion records downloaded in Step 1, perform nonlinear dynamic time history calculations on the building structure before and after reinforcement using finite element software, and record the dynamic response data of the building structure output by the finite element calculation. This dynamic response data of the building structure will be used to train a fast calculation model for the dynamic response of the building structure.

[0031] Step 4: Construct a fast calculation model for the dynamic response of building structures based on a Long Short-Term Memory (LSTM) network. This model replaces traditional finite element analysis and obtains dynamic response data of building structures under seismic loading. The input features of this LSTM network include seismic intensity, the basic data of the building structure collected in Step 1 (including building height, width, number of floors, usage function, and natural period), and the dynamic response data of the building structure obtained in Step 3 (i.e., the dynamic response data obtained through finite element analysis). The output feature of this LSTM network is the dynamic response data of the building structure. The number of convolutional layers, feature dimensions, number of hidden layer neurons, number of neural network layers, number of samples, number of training iterations, sliding window width, update step size, and inter-layer random deactivation ratio in this LSTM network are determined based on actual conditions.

[0032] Step 5: Based on the predicted dynamic response data of the building structure in Step 4 and Bayesian theory, establish the seismic response demand model (Engineering Demand Parameter, EDP) for the building structure before and after reinforcement:

[0033] ln(EDP)=θ1+θ2ln(IM)+σε (1)

[0034] In the formula, θ1 and θ2 represent the parameters of the seismic response demand model, ε represents the residual of the seismic response demand model, which follows a standard normal distribution with parameters (0, 1), σ is the standard deviation of the residual, and IM represents the intensity quantification index of the ground motion.

[0035] Step 6: Based on push-over analysis or existing literature, determine the capacity model (C) of the building structure under different limit states, and establish the limit state equations of the building structure:

[0036] g(IM|Θ)=ln(C)-ln(EDP) (2)

[0037] Step 7, according to the definition of seismic vulnerability of building structures, is written as follows:

[0038]

[0039] In the formula, Φ(·) represents the standard normal distribution function, and β C β represents the uncertainty of structural capability. EDP|IM,Θ Let θ be the logarithmic standard deviation of the structural requirements given the seismic intensity and unknown parameters; the unknown parameters Θ = (θ1, θ2, σ), and the posterior probability density function f(Θ) of Θ is:

[0040] f(Θ)=cL(Θ)p(Θ) (4)

[0041] In the formula, c=[∫L(Θ)p(Θ)dΘ] -1 is the normalization coefficient, used to ensure that the integral of f(Θ) is 1.0; L(Θ)=∏f(D|Θ) is the likelihood function, f(D|Θ) represents the probability density function of the observed value given the model parameters; p(Θ) is the prior probability density function of Θ, and its uninformative prior probability density function is p(Θ)=1 / σ;

[0042] Step 8: Based on the total probability theory, the impact of the uncertainty of unknown parameters in the model on seismic vulnerability can be quantified, i.e.

[0043] P f [g(IM)<0]=∫P f [g(IM|Θ)<0]f(Θ)dΘ (5).

[0044] The beneficial effects of this invention are:

[0045] 1. The connection node assembly is integrated with the beam-column joint of the frame structure using high-strength bolts, and the openings in the beam-column joints are located on the slab members. The reinforcement spacing of the slab members is relatively large, allowing for more flexible selection of the opening location and bolt diameter. The openings on the slab members avoid the weakening of the beam and column cross-sectional load-bearing capacity caused by the previous connection node openings on the beam and column members. The opening location is a local stress concentration point, which is prone to crack development or local concrete crushing under dynamic loads. In the connection node structure provided by this invention, the failure at the opening location of the slab member is easier to control through structural design compared to the failure at the opening location of the beam and column members in the previous connection node structure, and it better protects the integrity and load-bearing capacity of the beam and column members as the main load-bearing components of the structure.

[0046] 2. All connection node components are installed using high-strength bolts, eliminating the need for grouting and welding, which are difficult to replace during installation. The connection node components encapsulate the beam-column joints of the frame structure, and each component is positioned and installed using the geometry of the beam-column joints and bolt holes, facilitating construction. By encapsulating the beam-column joints, the connection nodes transfer the lateral forces acting on the beam-column joints in all directions to the BRB, reducing the load-bearing capacity requirements of the components and improving post-earthquake structural integrity. If any connection node component suffers irreversible damage such as corrosion or deformation, the connecting bolts can be removed and the damaged component replaced according to the installation procedure for repair, facilitating the restoration of the building's structural function and the repair of the BRB layout after an earthquake.

[0047] 3. The probabilistic seismic toughness enhancement assessment method uses structural vulnerability as a comparison parameter. Through vulnerability control rate analysis, it more intuitively and comprehensively demonstrates the strengthening effect of buckling-restrained bracing on the structure. The deep learning-based structural macroscopic response prediction method employs long and short time-series prediction neural networks. By comparing the predicted differences in input features before and after strengthening, it objectively assesses the effectiveness of seismic strengthening measures. These prediction methods can complete the structural damage risk simulation under unknown seismic loading within seconds, significantly saving computation time. Attached Figure Description

[0048] Figure 1 A schematic diagram of the buckling restraint bracing arrangement for a frame structure constructed using nodes;

[0049] Figure 2 A schematic diagram of a joint construction design for BRB reinforcement of old reinforced concrete frame structures;

[0050] Figure 3 A top-view diagram of the node construction design;

[0051] Figure 4 A side view diagram of the node construction design;

[0052] Figure 5 A schematic diagram of the buckling restraint bracing arrangement of the frame structure in the implementation case.

[0053] Figure 6 To implement the stress-time curve of a stress concentration point on a beam-column joint in the finite element analysis results of the case study;

[0054] Figure 7 This is an application example of a fast structural response calculation model;

[0055] Figure 8 The vulnerability curve was actually calculated in the implementation case.

[0056] In the diagram: 1. Connection node; 2. Buckling-restrained brace; 3. Connection plate; 4. Stiffening rib; 5. Covering plate; 6. Base plate; 7. Beam-column node of frame structure; 8. First bolt hole; 9. Second bolt hole; 10. High-strength bolt; 11. Upper left half of the connection node assembly; 12. Upper right half of the connection node assembly; 13. Connection node assembly of the upper assembly; 14. Connection node assembly of the lower assembly; 15. Frame structure. Detailed Implementation

[0057] The invention will now be described in further detail with reference to the accompanying drawings and specific framework examples.

[0058] A node for reinforcing an old reinforced concrete frame structure using BRB (Buckling Restraint Brake) includes a buckling restraint brace 2, a frame structure 15, and a connection node 1. The connection node assembly consists of four pieces, divided into two groups: an upper component connection node assembly 13 and a lower component connection node assembly 14, with two pieces in each group. The connection node assemblies are interconnected by high-strength bolts. The connection between the two connection node assemblies in each group encloses the column members of the frame structure beam-column node 7. The connection between the upper component connection node assembly 13 and the lower component connection node assembly 14 encloses the beam and slab members of the frame structure beam-column node 7, thus forming a covering of the frame structure beam-column node. The buckling restraint brace 2 is connected to the connection plate 3 of the upper component connection node assembly 13 and the lower component connection node assembly 14 via high-strength bolts.

[0059] Stiffening ribs 4 are arranged at the connection between the connecting plate 3 and the covering plate 5 and at the connection between the connecting plate 3 and the bottom plate 6 to limit the deformation of the connecting plate 3 and the bottom plate 6; the first bolt hole 8 and the second bolt hole 9 are arranged according to the actual needs of the node, and the stiffening ribs 4 are arranged at equal intervals between the first bolt hole 8 and the second bolt hole 9.

[0060] A joint design method for BRB-reinforced old reinforced concrete frame structures includes the following steps:

[0061] Step 1: The building to be reinforced is a five-story frame structure. The column height of the first to fourth floors is 4200mm, and the column height of the fifth floor is 2800mm. The fifth floor is a stairwell leading to the roof. The first floor has a height of 3450mm and has relatively high stiffness. The second, third, and fourth floors are selected as reinforcement layers. The buckling restraint brace 2 of the frame is arranged in a single-oblique arrangement as follows: Figure 5 As shown; the beam-column node 7, which requires connection nodes, has a column size of 600mm×600mm, a beam size of 500mm×250mm, and a floor slab thickness of 150mm. The buckling restraint brace 2 used has a connection section with a steel strength grade of Q235. The initial selection of the node structure has a steel plate thickness of 25mm, a strength grade of Q235, and a connection plate length and width of 500mm. The node is then preliminarily designed.

[0062] Step 2: Use the CAE software ABAQUS to establish a finite element model of the node structure based on the preliminary design. Test the performance of the node structure by applying a low-cycle reciprocating load on the cross section of the buckling-restrained brace connection section and optimize the design based on the results. The load value is the ultimate bearing capacity of buckling-restrained brace 2.

[0063] Step 3, based on the parameters obtained from the optimization design, such as... Figure 6Manufacture the upper component connection node assembly 13 and the upper component connection node assembly 14 and make holes in the plate member of the beam-column node 7; pre-connect the upper component connection node assembly 13, the upper component connection node assembly 14 and the beam-column node 7 without applying pre-tightening force by using high-strength bolts.

[0064] Step 4: Pre-connect the buckling restraint brace 2 connecting segment to the connecting node assembly, and adjust the angle and other parameters of the buckling restraint brace 2 to the design value;

[0065] Step 5: Tighten all high-strength bolts on the node and apply preload.

[0066] A rapid assessment method for earthquake toughness enhancement capable of quantifying the effects of multiple uncertainties is proposed, comprising the following steps:

[0067] Step 1: Collect parameters such as column grid layout and reinforcement details of the building to be reinforced as mentioned above. Select Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP) as the three limit states of the building structure, and take β for each. c The values ​​are 0.1, 0.2, and 0.4. Download 46 sets of measured ground motion parameters and ground acceleration time history records for finite element analysis, including three categories: near-end without pulse, near-end with pulse, and far-end.

[0068] Step 2: Based on the collected building parameters, establish finite element models of the building before and after reinforcement, and convert them into code readable by the open-source platform Opensees. In the established finite element model of the reinforced structure, the buckling restraint brace part is constructed according to the actual buckling restraint brace structure, and the energy dissipation section and connection section are established and the section moment of inertia is modified. In the established structural finite element model, the steel bars used in the beam-column joints are superimposed with constitutive relations according to the actual corrosion situation.

[0069] Step 3: Incorporate the obtained seismic motion parameter file into the code and use Opensees to perform finite element analysis and record the structural response.

[0070] Step 4: Train a fast structural response calculation model based on a Long Short-Term Memory (LSTM) network. The input features are 3, the sliding window is 1, the number of hidden layer neurons is 128, and the inter-layer random deactivation ratio is 0.3. Use the trained model to predict the structural response. The comparison between the predicted values ​​and the finite element method (FEM) calculations is plotted on [the graph]. Figure 7 .

[0071] Step 5: Take the maximum inter-story drift angle calculated under the seismic motion as EDP. Use the EDP calculated from multiple sets of seismic motions and the PGA corresponding to the seismic motion as two coordinate axes for fitting analysis. Based on the obtained data, establish a seismic response demand model of the structure before and after reinforcement using structural dynamic response data and Bayesian theory.

[0072] Step 6: Based on the seismic vulnerability analysis of corroded reinforced concrete structures by Dai Kuangyu et al., the C values ​​for life safety (LS) and collapse prevention (CP) are taken as 0.59, 1.02, and 3.21, respectively. The limit state equation of the structure is established using the obtained structural parameters and the limit state values.

[0073] Step 7: Based on the data obtained from the Opensees finite element analysis, use the Bayesian criterion to calculate the posterior distribution of the unknown parameter Θ and determine the posterior probability density function of the demand model parameters.

[0074] Step 8: Quantify the impact of multiple uncertainties on seismic vulnerability using the theory of total probability, and obtain the following results: Figure 8 As shown in Table 1, the structural vulnerability control rate for each PGA value is calculated based on the data.

[0075] Table 1. Structural fragility control rate under several representative PGA values.

[0076]

[0077]

Claims

1. A joint for reinforcing old reinforced concrete frame structures using BRB (Brake Reinforced Rubber), characterized in that, The node includes a frame structure beam-column node composed of reinforced concrete beam members, column members, and slab members, buckling restraint braces, high-strength bolts, connecting plates, cladding plates, bottom plates, and stiffening ribs; Several bolt holes are arranged in an array on the connecting plate and the base plate; Several connection holes are opened on the plate members of the beam-column joint of the frame structure. The size and position of the connection holes correspond to the bolt holes on the bottom plate to realize the connection. The cladding plate covers the column members of the beam-column joint of the frame structure, and the connecting plate is vertically connected to the cladding plate. There are stiffening ribs connecting the connecting plate and the cladding plate. The connecting plate, the covering plate, the base plate, and the stiffening ribs are welded together to form the connecting node assembly; The buckling restraint brace is an energy-dissipating buckling restraint brace connected to the connecting plate, and consists of an energy-dissipating section and a connecting section.

2. The node according to claim 1, characterized in that, The diameter and spacing of the bolt holes on the connecting plate and the base plate are selected and calculated in accordance with the "Technical Specification for High Strength Bolt Connection of Steel Structure"; the size of the connecting holes on the plate members of the beam-column joint of the frame structure is larger than the size of the bolt holes on the base plate. The bearing capacity and diameter of high-strength bolts are calculated according to the high-strength bolt friction connection specified in the "Technical Specification for High-Strength Bolt Connection of Steel Structure" to bear the dynamic load under earthquake.

3. The node according to claim 1, characterized in that, The steel strength grade of the connecting plate is not lower than that of the steel strength grade of the connecting section of the buckling restraint brace.

4. The node according to claim 1, characterized in that, The specific design of the connecting plate, the covering plate, the bottom plate and the stiffening ribs is determined by finite element analysis, and the connecting plate, the covering plate and the bottom plate have the same thickness.

5. The node according to claim 1, characterized in that, The stiffening ribs are arranged on the connecting plate and the bottom plate to limit the deformation of the connecting plate and the bottom plate, and the arrangement position is adapted to the bolt holes on the connecting plate and the bottom plate.

6. The node according to claim 1, characterized in that, The connecting node assembly consists of four parts, divided into two groups: an upper assembly and a lower assembly. The two connecting node assemblies in each group are connected to each other by high-strength bolts. The connection between the two connecting node assemblies in each group encloses the column members of the beam-column joint of the frame structure. The connection between the upper and lower assemblies encloses the beam members and slab members of the beam-column joint of the frame structure, so that the connecting node assembly forms an overall enclosure of the beam-column joint of the frame structure. The connecting section of the buckling restraint brace is connected to the connecting plate of the connecting node assembly by high-strength bolts.

7. The node according to claim 1, characterized in that, The angle between the buckling restraint brace and the column member of the beam-column joint of the frame structure is 35° to 55°.

8. The node according to claim 1, characterized in that, The contact surfaces of the beam-column joints and connecting node components in the frame structure are made flat to avoid local stress concentration under bolt preload.

9. A node design method for BRB-reinforced old reinforced concrete frame structures, characterized in that, It includes the following steps: Step 1: Collect the number of floors, structural cross-section, and structural plan of the building structure to be reinforced, and select the floors of the building structure to be reinforced; The buckling-restrained braces are arranged using a single diagonal brace method. The positions of the two ends of the buckling-restrained braces at the beam-column joints of the frame structure are determined. Based on the dimensions of the beam, column, and slab members of the beam-column joints of the frame structure, the reinforcement drawings of the beam, column, and slab members, and the strength grade of the steel used for the connection section of the buckling-restrained braces, the connection node components are preliminarily designed, including the dimensions of the base plate and the arrangement of high-strength bolts. Step 2: Perform finite element analysis on the preliminary design nodes, and modify and optimize the stiffening ribs, bolt hole openings and positions, and high-strength bolt parameters on the connection node components based on the results; when the concrete strength grade of the plate members of the beam-column joint of the frame structure is not higher than C30, consider arranging metal sleeves at the connection holes on the plate members of the beam-column joint of the frame structure and arranging steel plates on the contact surface of the plate members of the beam-column joint of the frame structure. The diameter of the metal sleeve and the size of the steel plate are obtained by optimization through finite element analysis; Step 3: Manufacture the connection node components according to the modified and optimized parameters from Step 2, and make openings in the plate components of the beam-column joints of the frame structure. High-strength bolts are used to pre-connect the connection node components and the beam-column nodes of the frame structure without applying pre-tightening force. Step 4: Pre-connect the connecting segment of the buckling-restrained brace to the connecting node assembly, and adjust the angle of the buckling-restrained brace to the design value; Step 5: Tighten all bolts on the node and apply preload.

10. A rapid assessment method for seismic toughness enhancement capable of quantifying the effects of multiple uncertainties, characterized in that, The steps are as follows: Step 1: Collect basic data of the building structure, including the column grid layout, reinforcement details and material properties of each component of the building structure to be reinforced. This basic data will be used to train a fast calculation model for the dynamic response of the building structure. Based on the target spectrum given by my country's seismic code GB50011-2010, download measured ground motion records from the Pacific Earthquake Engineering Center in the United States for subsequent finite element analysis of the building structure. Step 2: Based on the basic data of the building structure collected in Step 1, establish finite element models of the building structure before and after reinforcement using a finite element platform. Furthermore, in the established finite element model of the reinforced building structure, the buckling restraint brace is constructed with energy dissipation segment and connection segment according to the actual buckling restraint brace. Furthermore, the materials used for beam-column joints in the frame structure in the established finite element model are reduced in strength based on the actual material strength of the building structure to be reinforced or the steel corrosion model. Step 3: Using the measured ground motion records downloaded in Step 1, perform nonlinear dynamic time history calculations on the building structure before and after reinforcement using finite element software, and record the dynamic response data of the building structure output by the finite element calculation. This dynamic response data of the building structure will be used to train a fast calculation model for the dynamic response of the building structure. Step 4: Construct a fast calculation model for the dynamic response of building structures based on a Long Short-Term Memory (LSTM) network. This model replaces traditional finite element analysis and obtains dynamic response data of building structures under seismic loading. The input features of the LSTM network include seismic intensity, the basic data of the building structure collected in Step 1 (including building height, width, number of floors, usage function, and natural period), and the dynamic response data of the building structure obtained in Step 3 (i.e., the dynamic response data obtained through finite element analysis). The output feature of the LSTM network is the dynamic response data of the building structures. The number of convolutional layers, feature dimensions, number of hidden layer neurons, number of neural network layers, number of samples, number of training iterations, sliding window width, update step size, and inter-layer random deactivation ratio in the LSTM network are determined based on actual conditions. Step 5: Based on the predicted dynamic response data of the building structure in Step 4 and Bayesian theory, establish the seismic response demand model (EDP) for the building structure before and after reinforcement. ln(EDP)=θ1+θ2 ln(IM)+σε (1) In the formula, θ1 and θ2 represent the parameters of the seismic response demand model, ε represents the residual of the seismic response demand model, which follows a standard normal distribution with parameters (0, 1), σ is the standard deviation of the residual, and IM represents the intensity quantification index of the ground motion. Step 6: Based on the push-over analysis of the building structure or existing literature, determine the capacity model C of the building structure under different limit states, and establish the limit state equations of the building structure: g(IM|Θ)=ln(C)-ln(EDP) (2) Step 7, according to the definition of seismic vulnerability of building structures, is written as follows: In the formula, Φ(·) represents the standard normal distribution function, and β C β represents the uncertainty of structural capability. EDP|IM,Θ Let θ be the logarithmic standard deviation of the structural requirements given the seismic intensity and unknown parameters; the unknown parameters Θ = (θ1, θ2, σ), and the posterior probability density function f(Θ) of Θ is: f(Θ)=cL(Θ)p(Θ) (4) In the formula, c=[∫L(Θ)p(Θ)dΘ] -1 is the normalization coefficient, used to ensure that the integral of f(Θ) is 1.0; L(Θ)=∏f(D|Θ) is the likelihood function, f(D|Θ) represents the probability density function of the observed value given the model parameters; p(Θ) is the prior probability density function of Θ, and its uninformative prior probability density function is p(Θ)=1 / σ; Step 8: Based on the total probability theory, the impact of the uncertainty of unknown parameters in the model on seismic vulnerability can be quantified, i.e. P f [g(IM)<0]=∫P f [g(IM|Θ)<0]f(Θ)dΘ (5)。

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