A method for improving the structural performance of masonry cultural relics buildings

Abstract

The present invention discloses a method for improving the structural performance of masonry cultural relic buildings, comprising the following steps: Step 1, seismic performance assessment, predicting the maximum inter-story displacement value D generated; Step 2, preliminary construction of the seismic structure, arranging the installation positions of the internal support frame and the external cable; Step 3, design of the internal support frame, performing design calculations on the cross-section; Step 4, verification calculation of the internal support frame, calculating the stress ratio limit R lim it ; Step 5, design of the external cable, two external cables are provided, and the diameter d does not exceed 20 mm; Step 6, simulation analysis calculation of the seismic structure, building a finite element model; Step 7, post-processing of the simulation analysis calculation results, comparing the maximum inter-story displacement d max with the maximum inter-story displacement value D. This method improves the seismic capacity of the original cultural relic building without damage, effectively reduces the displacement of the structure under earthquake action, does not change the force transmission path of the original structure, enhances the stability of the structure, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of the repair and reinforcement of ancient buildings, and particularly relates to a method for improving the structural performance of masonry cultural relic buildings. Background Art

[0002] Masonry cultural relic buildings generally have a long history. Long-term wind and rain have caused the material strength to degenerate severely, especially the strength of mortar joints has deteriorated the most severely. There is generally a problem of insufficient compressive bearing capacity under the basic combination of normal service loads, and most of them lack seismic design or construction measures, and there is a risk of overturning under earthquake action. At present, for the method of improving the structural performance of masonry cultural relic buildings, the reinforced concrete surface layer reinforcement scheme is mostly adopted, which deviates from the principles of not changing the original state of cultural relics, minimizing intervention, and the measures being reversible in the principles of cultural relic protection and repair. For the method of improving the structural performance of masonry cultural relic buildings, how to meet both the structural safety of cultural relics and the principles of cultural relic protection and repair, there is an urgent need for a new solution. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for improving the structural performance of masonry cultural relic buildings. This method improves its seismic capacity without damaging the original cultural relic building, effectively reduces the displacement of the structure under earthquake action, does not change the force transmission path of the original structure, enhances the stability of the structure, and has a wide application prospect.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for improving the structural performance of masonry cultural relic buildings, characterized by comprising the following steps:

[0006] Step 1, seismic performance assessment, evaluate the strength of the masonry building walls in the existing masonry cultural relic buildings, and estimate the maximum inter-story displacement value D generated by the masonry cultural relic buildings under earthquake conditions;

[0007] The masonry cultural relic buildings include masonry building walls and roofs arranged on the masonry building walls. The masonry building walls include building exterior walls and floors arranged inside the building exterior walls. The floors divide the masonry building walls into at least two layers, and a plurality of doors and windows are arranged on the masonry building walls;

[0008] Step 2, preliminary construction of the seismic structure, arrange the installation positions of the internal support frames and external cables according to the force transmission path of the masonry cultural relic buildings, wherein the internal support frames are arranged inside the masonry cultural relic buildings, and the external cables are correspondingly tied to the outside of the masonry cultural relic buildings in relation to the internal support frames;

[0009] The internal support frame includes vertical steel columns, a first transverse steel beam, and a second transverse steel beam. The vertical steel columns are attached to the inner surface of the building exterior wall. One end of the first transverse steel beam is fixedly installed on the vertical steel column. The first transverse steel beam is attached to the bottom of the floor slab, and a support column is provided at the bottom of the other end of the first transverse steel beam. The second transverse steel beam is attached to the bottom of the roof, and both ends of the second transverse steel beam are fixedly provided on the vertical steel columns. A longitudinal steel beam is provided between adjacent vertical steel columns. The top surface of the longitudinal steel beam is attached to the bottom of the floor slab or the roof, and the side surface of the longitudinal steel beam is attached to the inner wall of the building exterior wall.

[0010] Step 3: Design of the internal support frame. Estimate the vertical load and horizontal load of the internal support frame according to the mortar strength degradation degree of the masonry building wall. Design and calculate the cross-sections of the vertical steel columns, the first transverse steel beam, and the second transverse steel beam based on the vertical load and horizontal load borne by the internal support frame.

[0011] Step 4: Verification calculation of the internal support frame. Calculate the stress ratio limits of the vertical steel columns, the first transverse steel beam, and the second transverse steel beam respectively. R lim it ; When R lim it is within the range of 0.7 to 0.9, it indicates that the cross-section design of the vertical steel column, the first transverse steel beam, or the second transverse steel beam meets the design requirements. When R lim it > 0.9, it indicates that the selected cross-section size of the vertical steel column, the first transverse steel beam, or the second transverse steel beam is relatively small, and its cross-section size needs to be increased. When R lim it <0.7, it indicates that the selected cross-section size of the vertical steel column, the first transverse steel beam, or the second transverse steel beam is relatively large, and its cross-section size needs to be reduced.

[0012] Step 5: Design of the external cable. Two cables are provided. The diameter of the cable d does not exceed 20 mm, and the selected value of the cable prestress T does not exceed 40% of the cable breaking force.

[0013] The external cable includes multiple steel tie rods, multiple fasteners, and two cables. The two cables are attached to the outer surface of the masonry building wall and are arranged in parallel at intervals through multiple fasteners. The fasteners are connected to the vertical steel columns through tie rods penetrating the building exterior wall. The two cables are respectively arranged at the bottom of the roof and under the eaves. The external cable and the internal support frame form a hoop effect on the masonry cultural relic building to achieve the fastening effect of internal support and external pressure.

[0014] Step 6: Simulation analysis and calculation of earthquake-resistant structure. According to the structure of masonry cultural relic building and earthquake-resistant structure, a finite element model is built. The blocks constituting the walls of masonry buildings are set to friction contact. The vertical steel pillars and the building exterior walls, the first transverse steel beam and the floor slab, and the second transverse steel beam and the roof are all set to friction contact. Three seismic waves are applied to the constructed finite element model to perform response calculation and raise the maximum inter-layer displacement of the earthquake-resistant structure. d max ;

[0015] Step 7: Post-processing of simulation analysis results to calculate the maximum inter-story displacement of the seismic structure d max Compared with the maximum inter-story displacement value D, when d max <D时,设计满足要求;当 d max ≥D, first observe whether the masonry building wall in the finite element model tilts outward. If so, adjust the prestress of the external cable and repeat the simulation until the masonry building wall does not tilt. If not, modify the cross-sectional shape of the internal support frame or the installation position of the external cable to increase the stability of the structure. Repeat the simulation calculation and modification until the design meets the requirements.

[0016] Preferably, in the step 1, the maximum inter-story displacement value D generated by the masonry cultural relic building in a rare earthquake situation is obtained according to the geographical location of the masonry cultural relic building.

[0017] Preferably, in the step 2, the inner support frame and the masonry cultural relic building are arranged in a surface-to-surface contact manner.

[0018] Preferably, in step 3, the stress ratio limit values ​​of the vertical steel support, the first transverse steel beam and the second transverse steel beam are determined according to the following formula: R lim it Perform the calculation:

[0019]

[0020] in,

[0021]

[0022] Where:

[0023] S ——Design values ​​of combined seismic internal forces in structural members, including the combined bending moment, axial force and shear force design values;

[0024] ——gravity load partial factor;

[0025] —— The effect of the representative value of the gravity load;

[0026] 、 —— The partial seismic action coefficients in the horizontal and vertical directions respectively;

[0027] 、 —— The effects of the standard values of the horizontal and vertical seismic actions respectively;

[0028] —— The partial coefficient of the i-th permanent load not included in the gravity load;

[0029] —— The effect of the standard of the i-th permanent load not included in the gravity load;

[0030] —— The combination coefficient of the i-th variable load not included in the gravity load;

[0031] —— The partial coefficient of the i-th variable load not included in the gravity load, which shall not be less than 1.5;

[0032] —— The effect of the standard of the i-th variable load not included in the gravity load;

[0033] R —— The design value of the bearing capacity of the structural member, which is determined according to the strength design value of the structural material;

[0034] —— The seismic adjustment coefficient of the bearing capacity.

[0035] Preferably, the prestress of the external cable in step five T The calculation formula is:

[0036]

[0037] In the formula, is the breaking stress of the cable, A is the cross-sectional area of the cable.

[0038] Preferably, the maximum inter-story drift of the seismic structure in step six d max The calculation formula is:

[0039]

[0040] In the formula: d n is the time history of the roof displacement of the extracted story, dn-1 It is the time history of the bottom displacement of the extracted layer.

[0041] Preferably, the seismic wave input during the finite element analysis in step six is the numerical value of the maximum earthquake situation in the region where the masonry cultural relic building is located.

[0042] Preferably, in step seven, when d max ≥D, and the masonry building wall does not tilt outwards, first modify the cross-sectional shape of the vertical steel strut, the first horizontal steel beam or the second horizontal steel beam; increase the cross-sectional shape until the total mass of the internal support frame increases by 1.5 times but still 50% of the components do not meet d max <D, then modify the structure of the internal support frame or the installation position of the external cable. If this modification still does not meet the requirements, finally adjust the maximum inter-story displacement value D until the design requirements are met.

[0043] In the present invention, the load borne by the internal support frame is obtained based on the existing situation of the masonry cultural relic building, and then the maximum displacement value of the reinforcement structure is obtained by finite element simulation analysis d max , according to the maximum displacement value of the reinforcement structure d max By comparing with the maximum inter-story displacement value D, it can be obtained whether the designed structure meets the design requirements. Under the condition of meeting the requirements for improving the seismic capacity of the masonry cultural relic building, the consumption of the steel section of the support internal support frame is saved and the cost is reduced. For the reinforcement of the masonry cultural relic building, the internal support frame and the external cable are used in cooperation to form a hoop effect of internal support and external tightening, which improves the overall structural stability and seismic capacity without damaging the original cultural relic building. The internal support frame is arranged along the force transmission path of the original masonry cultural relic building, without changing the force transmission path of the original structure, realizing a way of cultural relic repair with minimal intervention and reversible measures, and enhancing the structural safety without damaging the cultural relics. Brief Description of the Drawings

[0044] Figure 1 It is a schematic left view of the overall structure of the present invention;

[0045] Figure 2 It is an axonometric schematic view of a part of the structure of the present invention;

[0046] Figure 3 It is a top view of the overall structure of the present invention;

[0047] Figure 4 It is a schematic side view of the local structure at I of the present invention;

[0048] Figure 5 It is an axonometric schematic view of the masonry cultural relic building of the present invention;

[0049] Figure 6 It is a schematic diagram of the process of the present invention;

[0050] Table 1 shows the lateral displacement limits of the main structure;

[0051] In the figure: 1. masonry building wall; 2. roof; 3. internal support frame; 4. external cable; 10. building exterior wall; 11. floor; 12. door; 13. window; 30. vertical steel support column; 31. first horizontal steel beam; 32. second horizontal steel beam; 33. support column; 40. steel tie rod; 41. fastener; 42. cable. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with the accompanying drawings:

[0053] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 A method for improving the performance of a masonry cultural relic building structure is shown, and a method for improving the performance of a masonry cultural relic building structure is characterized by comprising the following steps:

[0054] Step 1: Assess the seismic performance. Assess the strength of the masonry building wall 1 in the existing masonry cultural relic building. In this embodiment, the strength degradation of the cultural relic material to be repaired is relatively serious. The estimated strength of the first-floor wall masonry mortar is 5.3Mpa, and the assessed strength grade is M5. The second-floor wall is 0.8MPa, and the assessed strength grade is less than M1. Wall brick strength: The estimated strength grade is less than MU7.5. The overall structure has no ring beam structural columns, and the spacing between some transverse walls is 21m, which exceeds the minimum transverse wall spacing of 11m specified in the current specification. The maximum inter-story displacement value D generated by the masonry cultural relic building in the event of an earthquake is estimated;

[0055] The maximum inter-layer displacement D of the structure is determined according to the fortification intensity of the area where the masonry cultural relic building is located, the structural layer height or the customized requirements of the owner. Refer to Table 1 to obtain the maximum inter-layer displacement value D of the masonry cultural relic building under rare earthquake conditions, where D is the displacement value of the top of the main structure.

[0056] Table 1

[0057]

[0058] In the table, H is the total height of the main structure.

[0059] In this embodiment, this masonry cultural relic building is located in the 8-degree zone and has a serious risk of collapse under earthquake action. According to the requirements of the "Cultural Relics Earthquake-proof Masonry Ancient Building Assessment Standard", in this embodiment, the maximum inter-story displacement value D of the masonry cultural relic building under rare earthquake conditions is taken as 1 / 100 of the floor height. According to the floor height of this embodiment, the maximum inter-story displacement value of the first floor is 37mm, and the maximum inter-story displacement value of the second floor is 68mm. Finally, the installation positions of the inner support frame 3 and the outer cable 4 are arranged according to the force transmission path of the masonry cultural relic building. Specifically, the inner support frame 3 and the masonry cultural relic building are arranged in a face-to-face contact manner.

[0060] The masonry cultural relic building comprises a masonry building wall 1 and a roof 2 fixedly arranged on the masonry building wall 1. The masonry building wall 1 comprises an outer building wall 10 and a floor slab 11 arranged in the outer building wall 10. The floor slab 10 divides the masonry building wall 1 into at least two layers. A plurality of doors 12 and windows 13 are arranged on the masonry building wall 1. The floor slab 11 is also a masonry structure. In the present embodiment, the north-south length of the masonry building wall 1 is 57.88m, the east-west width is 30.52m, the floor height of the first floor is 3.8m, the floor height of the second floor is 6.7m, the eaves height is 8.8m, and the roof span is 12m.

[0061] Step 2, preliminary construction of the earthquake-resistant structure, arrange the installation positions of the inner support frame 3 and the outer cable 4 according to the force transmission path of the masonry cultural relic building, wherein the inner support frame 3 is set inside the masonry cultural relic building, and the outer cable 4 is tied to the outside of the masonry cultural relic building corresponding to the inner support frame 3.

[0062] The inner support frame 3 and the masonry cultural relic building are arranged in a face-to-face contact manner. The inner support frame 3 includes a vertical steel support column 30, a first transverse steel beam 31 and a second transverse steel beam 32. The vertical steel support column 30 is attached to the inner surface of the building exterior wall 10, and is specifically arranged between two adjacent windows 13 and on both sides of the door 12. One end of the first transverse steel beam 31 is fixedly installed on the vertical steel support column 30 by welding. The first transverse steel beam 31 is attached to the bottom of the floor slab 11, and a support column 33 is arranged at the bottom of the other end of the first transverse steel beam 31; the second transverse steel beam 32 is attached to the bottom of the roof 2, and both ends of the second transverse steel beam 32 are fixedly arranged on the vertical steel support column 30 by welding. The first transverse steel beam 31 and the second transverse steel beam 32 are both tightly attached to the surface of the masonry building wall 1, and the original force transmission path of the masonry building wall 1 is not changed. A longitudinal steel beam 34 is arranged between two adjacent vertical steel pillars 30 , the top surface of the longitudinal steel beam 34 is attached to the bottom of the floor 11 or the roof 2 , and the side surface of the longitudinal steel beam 34 is attached to the inner wall of the building exterior wall 10 .

[0063] Step 3: Design of the internal support frame 3. Estimate the vertical load and horizontal load of the internal support frame 3 according to the degree of mortar strength degradation of the masonry building wall 1. Based on the "Steel Structure Design Standard" GB50017-2017, design and calculate the cross-sections of the vertical steel columns 30, the first transverse steel beam 31, and the second transverse steel beam 32 in combination with the vertical load and horizontal load borne by the internal support frame 3. In this embodiment, the vertical load borne by a single internal support frame 3 is 90.2 kN, and the horizontal load is 72 kN. Take 50% of the vertical load of the internal support frame 3 as the vertical force borne by the internal support frame 3 according to the protection level of this masonry cultural relic building.

[0064] Step 4: Verification calculation of the internal support frame 3. Calculate the stress ratio limits of the vertical steel columns 30, the first transverse steel beam 31, and the second transverse steel beam 32 respectively. R lim it , and calculate the stress ratio limits of the vertical steel columns 30, the first transverse steel beam 31, and the second transverse steel beam 32 respectively according to the following formula: R lim it Perform the calculation:

[0065]

[0066] Among them,

[0067]

[0068] In the formula:

[0069] S ——The design value of the internal force under earthquake combination in the structural member, including the combined bending moment, axial force, shear force design value, etc.;

[0070] ——The partial coefficient of gravity load, adopted according to Table 4.3.2-1 of the "General Code for Seismic Design of Buildings and Municipal Engineering";

[0071] ——The effect of the representative value of gravity load. When there is a crane, it should also include the effect of the standard value of the gravity of the suspended object;

[0072] 、 ——The partial coefficients of horizontal and vertical earthquake actions respectively, and their values should not be lower than the provisions of Table 4.3.2-2 of the "General Code for Seismic Design of Buildings and Municipal Engineering";

[0073] 、 ——The effects of the standard values of horizontal and vertical earthquake actions respectively;

[0074] —— The partial coefficient of the $i$-th permanent load not included in the gravity load shall be adopted in accordance with Table 4.3.2-1 of the General Code for Seismic Design of Buildings and Municipal Engineering;

[0075] —— The effect of the standard value of the $i$-th permanent load not included in the gravity load;

[0076] —— The combination coefficient of the $i$-th variable load not included in the gravity load shall be adopted in accordance with Table 4.3.2-1 of the General Code for Seismic Design of Buildings and Municipal Engineering;

[0077] —— The partial coefficient of the $i$-th variable load not included in the gravity load shall not be less than 1.5;

[0078] —— The effect of the standard value of the $i$-th variable load not included in the gravity load;

[0079] R —— The design value of the bearing capacity of the structural member is determined according to the strength design value of the structural material;

[0080] —— The seismic adjustment coefficient of the bearing capacity shall be adopted in accordance with Table 4.3.1 of the General Code for Seismic Design of Buildings and Municipal Engineering.

[0081] When R lim it the value of is in the range of 0.7 to 0.9, it indicates that the cross-section design of the vertical steel column 30, the first transverse steel beam 31 or the second transverse steel beam 32 meets the design requirements; when R lim it >0.9, it indicates that the selected cross-section size of the vertical steel column 30, the first transverse steel beam 31 or the second transverse steel beam 32 is relatively small, and its cross-section size needs to be increased; when R lim it <0.7, it indicates that the selected cross-section size of the vertical steel column 30, the first transverse steel beam 31 or the second transverse steel beam 32 is relatively large, and its cross-section size needs to be reduced.

[0082] Step 5, design of the external cable 4. Two external cables 4 are provided, with a diameter d not exceeding 20 mm, and the selected value of the prestress T shall not exceed 40% of the breaking force of the external cable 4. The prestress T of the external cable 4 is calculated by the following formula:

[0083]

[0084] In the formula, is the breaking stress of the cable, Ais the cross-sectional area of the cable. In this embodiment, 2 cables 42 with a diameter d = 12 mm are selected. The breaking force of the cable 42 is 140 kN. Considering the relatively long cable 42, to prevent the cable 42 from loosening, the magnitude of the prestress T is taken as 40 kN.

[0085] The external cable 4 includes a steel tie rod 40, a plurality of fasteners 41, and two cables 42. The two cables 42 are arranged in contact with each other on the outer surface of the masonry building wall 1 and are arranged in parallel at intervals through a plurality of fasteners 41. The fasteners 41 are connected to the vertical steel strut 30 through a tie rod 40 penetrating through the building exterior wall 10. The two cables 42 are respectively arranged at the bottom of the roof 2 and the lower side of the eaves; the external cable 4 and the internal support frame 3 form a hoop effect on the masonry cultural relic building to achieve the fastening effect of internal support and external pressure.

[0086] Step six, simulation analysis and calculation of the seismic structure. According to the structure of the masonry cultural relic building and the seismic structure, a finite element model is built. Considering the interface slip characteristics between the blocks of the masonry building wall 1, the interface between the blocks forming the masonry building wall 1 is set as frictional contact; the interface between the vertical steel strut 30 and the building exterior wall 10, between the first transverse steel beam 31 and the floor slab 11, and between the second transverse steel beam 32 and the roof 2 are all set as frictional contact; three seismic waves are applied to the built finite element model, and response calculations are carried out and the maximum inter-story displacement of the seismic structure is obtained d max , where the seismic wave is the numerical value of the maximum earthquake situation in the area where the masonry cultural relic building is located, and specifically is selected in accordance with the "Code for Seismic Design of Buildings" GB50011-2010 (2016 Edition). The maximum inter-story displacement d max of the seismic structure has the following calculation formula:

[0087]

[0088] In the formula: d n is the time history of the top displacement of the extracted story, d n-1 is the time history of the bottom displacement of the extracted story.

[0089] Step seven, post-processing of the simulation analysis calculation results. Compare the maximum inter-story displacement d max of the seismic structure with the maximum inter-story displacement value D. When d max < D, the design meets the requirements; when d maxWhen it is ≥D, first observe whether the masonry building wall 1 in the finite element model tilts outwards. If the masonry building wall 1 tilts outwards, adjust the prestress of the external cable 4 and repeat the simulation until the masonry building wall 1 does not tilt. If the masonry building wall 1 does not tilt outwards, modify the cross-sectional shape of the internal support frame 3 or the installation position of the external cable 4 to increase the stability of the structure. Among them, when the masonry building wall does not tilt outwards, first modify the cross-sectional shape of the vertical steel strut 30, the first horizontal steel beam 31 or the second horizontal steel beam 32, and increase the cross-sectional shape until the total mass of the internal support frame 3 increases by 1.5 times but still 50% of the components do not meet d max When it is <D, then modify the structure of the internal support frame or the installation position of the external cable. If this modification still does not meet the requirements, finally adjust the maximum inter-story displacement value D until the design requirements are met; repeat the simulation calculation and modification until the design meets the requirements. In this embodiment, the maximum displacement value of the reinforcement structure d max = 32 mm, and it occurs on the second floor, d max <D, meeting the design requirements.

[0090] The above embodiments are only several explanations of the concept and implementation of the present invention, and are not intended to limit it. Under the concept of the present invention, the technical solutions without substantial transformation are still within the protection scope.

Claims

1. A method for improving the structural performance of masonry cultural relic buildings, characterized in that, The following steps are involved: Step 1, seismic performance assessment, assessing the strength of the masonry building wall (1) in the existing masonry cultural relic building, and estimating the maximum inter-story displacement value D generated by the masonry cultural relic building in an earthquake situation; The masonry cultural relic building comprises a masonry building wall (1) and a roof (2) arranged on the masonry building wall (1); the masonry building wall (1) comprises an exterior building wall (10) and a floor slab (11) arranged inside the exterior building wall (10); the floor slab (11) divides the masonry building wall (1) into at least two layers; and a plurality of doors (12) and windows (13) are arranged on the masonry building wall (1); Step 2: preliminary construction of the earthquake-resistant structure. According to the force transmission path of the masonry cultural relic building, the installation positions of the inner support frame (3) and the outer cable (4) are arranged, wherein the inner support frame (3) is arranged inside the masonry cultural relic building, and the outer cable (4) is tied to the outside of the masonry cultural relic building corresponding to the inner support frame (3); The inner support frame (3) comprises a vertical steel support column (30), a first transverse steel beam (31) and a second transverse steel beam (32); the vertical steel support column (30) is attached to the inner surface of the building outer wall (10); one end of the first transverse steel beam (31) is fixedly mounted on the vertical steel support column (30); the first transverse steel beam (31) is attached to the bottom of the floor slab (11); a support column (33) is arranged at the bottom of the other end of the first transverse steel beam (31); the second transverse steel beam (32) is attached to the bottom of the roof (2); both ends of the second transverse steel beam (32) are fixedly arranged on the vertical steel support column (30); a longitudinal steel beam (34) is arranged between two adjacent vertical steel support columns (30); the top surface of the longitudinal steel beam (34) is attached to the bottom of the floor slab (11) or the roof (2); and the side surface of the longitudinal steel beam (34) is attached to the inner wall of the building outer wall (10); Step 3, designing the inner support frame (3), estimating the vertical load and horizontal load of the inner support frame (3) according to the degree of degradation of the mortar strength of the masonry building wall (1), and designing and calculating the cross-sections of the vertical steel support (30), the first transverse steel beam (31) and the second transverse steel beam (32) according to the vertical load and horizontal load borne by the inner support frame (3); Step 4: Verify and calculate the internal support frame (3), and calculate the stress ratio limits of the vertical steel struts (30), the first horizontal steel beam (31), and the second horizontal steel beam (32) respectively R lim it ; When R lim it is within the range of 0.7 to 0.9, it indicates that the cross-section design of the vertical steel strut (30), the first horizontal steel beam (31), or the second horizontal steel beam (32) meets the design requirements; when R lim it > 0.9, it indicates that the cross-sectional dimensions of the vertical steel strut (30), the first horizontal steel beam (31), or the second horizontal steel beam (32) are selected to be relatively small, and it is necessary to increase their cross-sectional dimensions; when R lim it < 0.7, it indicates that the cross-sectional dimensions of the vertical steel strut (30), the first horizontal steel beam (31), or the second horizontal steel beam (32) are selected to be relatively large, and it is necessary to reduce their cross-sectional dimensions; Step 5, design of the external cable (4). Two cables (42) are provided, and the diameter of the cable (42) d does not exceed 20 mm, and the selected value of the prestress of the cable (42) T does not exceed 40% of its breaking force; The external cable (4) comprises a plurality of steel tie rods (40), a plurality of fasteners (41) and two cables (42); the two cables (42) are arranged on the outer surface of the masonry building wall (1) in a close fit and are arranged in parallel and spaced apart via the plurality of fasteners (41); the fasteners (41) are connected to the vertical steel pillars (30) via tie rods (40) arranged in the building outer wall (10); the two cables (42) are arranged at the bottom of the roof (2) and the lower side of the eaves, respectively; the external cable (4) and the internal support frame (3) form a hoop effect on the masonry cultural relic building, achieving a tightening effect of internal support and external pressure; Step 6, simulation analysis and calculation of the seismic structure. According to the structure of the masonry cultural relics building and the seismic structure, a finite element model is built. The interfaces between the blocks that make up the masonry building wall (1) are set as frictional contacts; the interfaces between the vertical steel struts (30) and the building exterior wall (10), between the first horizontal steel beam (31) and the floor slab (11), and between the second horizontal steel beam (32) and the roof (2) are all set as frictional contacts; three seismic waves are applied to the built finite element model, response calculations are carried out, and the maximum inter-story displacement of the seismic structure is obtained. d max ; Step 7, post-processing of the simulation analysis calculation results, comparing the maximum inter-story displacement of the seismic structure d max with the maximum inter-story displacement value D. When d max < D, the design meets the requirements; when d max ≥ D, first observe whether the masonry building wall (1) in the finite element model tilts outwards. If the masonry building wall (1) tilts outwards, adjust the prestress of the external cable (4) and repeat the simulation until the masonry building wall (1) does not tilt. If the masonry building wall (1) does not tilt outwards, modify the cross-sectional shape of the internal support frame (3) or the installation position of the external cable (4) to increase the structural stability, and repeat the simulation calculation and modification until the design meets the requirements.

2. The method for improving the structural performance of masonry cultural relics buildings according to claim 1, wherein: In the step 1, according to the geographical location of the masonry cultural relic building, the maximum inter-story displacement value D generated by the masonry cultural relic building in the event of a rare earthquake is obtained.

3. The method for improving the structural performance of masonry cultural relics buildings according to claim 1 or 2, characterized in that: In the second step, the inner support frame (3) is arranged in a face-to-face contact manner with the masonry cultural relic building.

4. The method for improving the structural performance of masonry cultural relic buildings according to claim 1, characterized in that: In the third step, the stress ratio limits of the vertical steel strut (30), the first horizontal steel beam (31), and the second horizontal steel beam (32) are calculated according to the following formula R lim it as follows: Among them, In the formula: S —— Design values of seismic combined internal forces in structural members, including design values of combined bending moment, axial force, shear force, etc.; —— Partial factor for gravity load; —— Effect of representative value of gravity load; , —— the partial coefficients of horizontal and vertical seismic actions respectively; , —— Effects of the standard values of horizontal and vertical seismic actions respectively; —— Partial factor of the ith permanent load not included in the gravity load; —— The effect of the i-th permanent load standard not included in the gravity load; —— combination coefficient of the ith variable load not included in the gravity load; —— The partial factor of the ith variable load not included in the gravity load shall not be less than 1.5; —— The effect of the standard value of the ith variable load not included in the gravity load; R —— The design value of the bearing capacity of structural members is determined according to the strength design value of structural materials; ——Seismic adjustment coefficient for bearing capacity.

5. The method for improving the structural performance of masonry cultural relic buildings according to claim 1, characterized in that: The prestress of the external cable (4) described in step five T The calculation formula is as follows: In the formula, is the breaking stress of the cable, A is the cross-sectional area of the cable.

6. The method for improving the structural performance of masonry cultural relics buildings according to claim 1, characterized in that: The maximum inter-story displacement of the seismic structure in Step 6 d max The calculation formula is as follows: In the formula: d n is the time history of the top displacement of the extracted layer, d n-1 is the time history of the bottom displacement of the extracted layer.

7. The method for improving the structural performance of masonry cultural relic buildings according to claim 1 or 6, characterized in that: The seismic wave input during the finite element analysis in the sixth step is the numerical value of the maximum earthquake situation in the area where the masonry cultural relic building is located.

8. The method for improving the structural performance of masonry cultural relics buildings according to claim 1, characterized in that: In step seven, when d max ≥ D and the masonry building wall does not tilt outwards, first modify the cross-sectional shape of the vertical steel strut (30), the first horizontal steel beam (31) or the second horizontal steel beam (32); increase the cross-sectional shape until the total mass of the internal support frame (3) increases by 1.5 times but still 50% of the components do not meet d max < D, then modify the structure of the internal support frame or the installation position of the external cable. If this modification still does not meet the requirements, finally adjust the maximum inter-story displacement value D until the design requirements are met.

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