Anti-seismic property analysis method for complex high-rise structure

Abstract

The invention discloses an anti-seismic property analysis method for a complex high-rise structure. The method comprises the following steps: determining a boundary range of a super high-rise building; the anti-seismic requirement of the over-limit high-rise building is determined, the height limit is determined based on different structural forms, and it is ensured that at least one aspect of the height, the height-width ratio and the body regularity of the house meets specifications and regulations; step 3, structural finite element modeling: based on the general situation of the constructional engineering, simplifying a finite element model to enable the finite element model to be consistent with an actual structure, and establishing the finite element model; 4, analyzing dynamic characteristics of the structure, wherein the inherent dynamic performance of the structure is reflected by the similar characteristics of the structure; and step 5, structural seismic response spectrum applying: applying the seismic response spectrum to the whole structure to research the maximum response of the structure under the seismic load effect of fortification intensity. According to the anti-seismic performance analysis method for the complex high-rise structure, multiple key aspects of super high-rise building boundary range determination, clear anti-seismic design requirements, structural finite element modeling, dynamic characteristic analysis, seismic response spectrum analysis and the like are comprehensively covered, and a set of systematic and complete analysis process is formed; and the anti-seismic performance of the complex high-rise structure can be deeply and carefully analyzed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of seismic analysis of building engineering, in particular to a seismic performance analysis method of a complex high-rise structure. BACKGROUND

[0002] With the progress of modern society and the rapid development of economic level, super high-rise buildings rise like mushrooms. Super high-rise buildings not only play an important role in urban functions, but also have diversified structural systems, increasingly complex building plan layout and vertical shape, and highly complex and uncertain stress conditions. These complex building forms bring many new challenges and problems to structural seismic analysis and seismic design.

[0003] For super high-rise building structures, horizontal load has become the main control factor in design. In the design of low-rise building structures, the internal force and displacement generated by horizontal load are usually small and can be ignored. In multi-story buildings, the effect of horizontal load gradually appears and increases. In super high-rise buildings, although vertical load still has an important influence on structural design, horizontal load (including wind and seismic action) plays a decisive role. At the same time, with the increase of building height, the lateral displacement increases rapidly, and excessive horizontal displacement will affect the comfort of building use, so the control of lateral displacement is crucial. In addition, when the building height is very large, the problems of vertical temperature internal force, displacement, stability and overturning resistance of the building become increasingly prominent.

[0004] At present, in the seismic analysis of complex high-rise structures, the existing methods have certain limitations. On the one hand, the analysis of structural dynamic characteristics is not deep and comprehensive, which cannot accurately grasp the response law of the structure under the action of earthquake, so it is difficult to provide reliable design basis. On the other hand, when different software is used for calculation, there is a lack of systematic and effective comparative analysis, so that the reliability of the calculation results is difficult to evaluate. In addition, the influence of seismic input dimension on structural response is not fully studied, which cannot provide comprehensive and scientific reference for seismic design, resulting in potential safety hazards or unreasonable design. SUMMARY

[0005] In view of the above problems existing in the prior art, the purpose of the present application is to provide a seismic performance analysis method of a high-rise structure.

[0006] To solve the above problems, the present application adopts the following technical scheme: a seismic performance analysis method of a complex high-rise structure, the method comprising the steps of:

[0007] Step 1, determining the boundary range of super high-rise building, determining the maximum applicable height and height-width ratio grade of reinforced concrete building structure;

[0008] Step two, determine the seismic requirements of super high-rise building, based on different structure form to determine the height limit, to ensure that at least one of the building height, aspect ratio and body shape regularity meets the provisions of the specification, regulation;

[0009] Step three, structure finite element modeling, based on the construction engineering profile, simplify the finite element model to be consistent with the actual structure, establish the finite element model, wherein the beam, column in the structure is simulated by three-dimensional beam element BEAM188, shear wall and floor are simulated by three-dimensional shell element shell43, the whole structure is discretized into 63827 units and 33111 nodes, the bottom constraint of the structure is simulated by fixed support;

[0010] Step four, structure dynamic characteristic analysis, structure rationality reflects the inherent dynamic performance of structure itself, including the natural period of structure, the overall mode of structure and material damping, in the finite element software ANSYS, the structure modal calculation method is extracted, the calculation method is suitable for different structure forms and complexity;

[0011] Based on the selected structure modal, the structure natural period is analyzed, and the mode diagram of the structure is output;

[0012] Step five, structure seismic response spectrum, the overall structure is subjected to seismic response spectrum to study the maximum response of the structure under the seismic load of fortification intensity;

[0013] The mode decomposition response spectrum method is calculated by ANSYS, and the calculation results are compared and analyzed to obtain the structure interlayer displacement angle, average interlayer displacement, average floor displacement and maximum floor displacement data of the overall structure under the action of X direction earthquake;

[0014] Taking the data as the research object, the seismic waves are input along the X direction, X+Y bidirectional and X+Y+Z three-direction of the structure respectively, and the influence of seismic wave input dimension on the displacement response of the structure is obtained.

[0015] Step two, the determination of the seismic requirements of super high-rise building, specifically includes:

[0016] (21) determine the height limit when using different structure forms, specifically, for reinforced concrete frame structure and seismic wall structure, the height does not exceed the maximum applicable height specified in the specification; for reinforced concrete frame-seismic wall structure and cylinder structure, the height does not exceed the maximum applicable height specified in the specification for 9 degree fortification, the height does not exceed 20% of the maximum applicable height specified in the specification for 8 degree fortification, the height does not exceed 30% of the maximum applicable height specified in the specification for 6 degree and 7 degree fortification;

[0017] (22) At least one of the height, the height-width ratio and the regularity of the shape of the building meets the requirements of the regulations and rules to ensure the basic stability and seismic performance of the structure;

[0018] (23) Two or more mechanical models that meet the actual situation of the structure are used in the calculation and analysis; the calculation and analysis of multiple mechanical models are verified and supplemented by each other;

[0019] (24) For structures with a height exceeding the maximum applicable height of the regulations by a large margin, a particularly complex shape, or a special structural type, seismic performance test research on small-scale overall structural models and large-scale local structural models, and dynamic characteristic testing on actual structures are conducted.

[0020] (25) For special super-high-rise buildings and super-high-rise buildings with obvious weak layers, perform elastic-plastic time history analysis of the structure.

[0021] The finite element model simplification of step three includes the steps of:

[0022] (321) For the reinforcement in the building structure, the effect of the reinforcement is equivalent to the concrete in a whole and dispersed manner;

[0023] (322) The self-weight of the secondary component and the load acting on the secondary component are equivalent to the main structure connected to the secondary component;

[0024] (323) Small holes in the floor and wall piers on the wall stem that have little effect on the overall performance of the structure are ignored.

[0025] The finite element model establishment of step three includes the steps of:

[0026] (331) The beams and columns in the structure are simulated by three-dimensional beam elements BEAM188;

[0027] (332) The shear walls and floors are simulated by three-dimensional shell elements shell43, and the three-dimensional shell element has 4 nodes, each node has 6 spatial degrees of freedom;

[0028] (333) The entire structure is discretized into 63827 elements and 33111 nodes; the cross section of the steel reinforced concrete column and beam is simulated by mixed materials;

[0029] (334) The bottom constraint of the structure is simulated by a fixed support.

[0030] In the finite element software ANSYS, there are seven common calculation methods for extracting structural modal, which are Block Lanczos, Subspace, PowerDynamics, Reduce, damp, QR damp and Umsymmetrics.

[0031] In step five, the earthquake response spectrum is applied to the overall structure, specifically, the X-direction earthquake acceleration spectrum is applied to the finite element model, and the full open method in the mode decomposition response spectrum method is used to calculate the seismic response of the structure under the action of the excitation spectrum;

[0032] The calculation formula of the method of seismic response spectrum analysis is:

[0033] (1)

[0034] Wherein, is the cross-correlation coefficient between two modes, which depends on the frequency ratio of two modes and the respective damping ratio of two modes.

[0035] (2)

[0036] Wherein, is the frequency ratio of two modes, is the damping ratio.

[0037] Through the analysis of the calculation results, the interlayer displacement angle, the average interlayer displacement, the average floor displacement and the maximum floor displacement of the overall structure under the action of X-direction earthquake are obtained.

[0038] Compared with the prior art, the beneficial technical effects of the present application are:

[0039] 1. The seismic performance analysis method of the complex high-rise structure provided by the present application comprehensively covers multiple key aspects such as determination of the limit range of super high-rise buildings, clear seismic design requirements, structure finite element modeling, dynamic characteristic analysis and seismic response spectrum analysis, forms a systematic and complete analysis process, can deeply and carefully analyze the seismic performance of the complex high-rise structure, and provides a solid theoretical basis and technical support for structure design and performance evaluation.

[0040] 2. The present application can accurately evaluate the advantages and disadvantages of various software in the seismic analysis of complex high-rise structures by detailed comparative analysis of the calculation results of different software (PKPM, ETABS and ANSYS), improving the reliability and accuracy of the calculation results, providing a scientific reference for structural engineers in selecting calculation software and determining design parameters, and helping to avoid design errors caused by improper software selection or unreasonable parameter setting, thereby improving the quality and safety of structural design.

[0041] 3. The present application conducts in-depth and comprehensive analysis of the dynamic characteristics of the structure, not only clarifies the theoretical basis and calculation method of dynamic characteristic parameters such as natural period, mode shape and damping, but also elaborates in detail how to obtain these parameters through modal analysis and evaluate them through practical engineering cases. This helps structural engineers to more accurately understand the response law of the structure under earthquake action, provides more reasonable parameters for the seismic design of the structure, optimizes the structural design and improves the seismic performance of the structure.

[0042] 4. The systematic analysis of the influence of seismic input dimension in the present application fills the gap in this aspect of the prior art. Through the study of structural displacement response under different seismic input dimensions (X direction, X+Y two-way and X+Y+Z three-way), the influence law of seismic input dimension on structural response is revealed, providing more comprehensive consideration factors for the seismic analysis of complex high-rise structures. In practical engineering, engineers can reasonably select the seismic input method based on these research results, more accurately evaluate the seismic performance of the structure, take more effective seismic measures, and ensure the safety and stability of the structure under earthquake action. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1: Overall finite element model of the structure;

[0044] Figure 2: Truss arrangement of the structure's strengthening layer (26~27);

[0045] Figure 3: Comparison of the natural period of the structure;

[0046] Figure 4: First-order mode shape of the structure;

[0047] Figure 5: Second-order mode shape of the structure;

[0048] Figure 6: Third-order mode shape of the structure;

[0049] Figure 7: Displacement nephogram of the structure;

[0050] Figure 8: Stress nephogram of the structure;

[0051] Figure 9: Stress nephogram of the shear wall;

[0052] Figure 10: Average inter-story drift curve of the structure;

[0053] Figure 11: Inter-story drift angle curve of the structure;

[0054] Figure 12: Average inter-story drift curve of the structure;

[0055] Figure 13: Maximum inter-story drift curve of the structure;

[0056] Figure 14: Floor drift ratio curve of the structure;

[0057] Figure 15: X-direction floor displacement envelope of the structure;

[0058] Figure 16: Y-direction floor displacement envelope of the structure;

[0059] Figure 17: Z-direction floor displacement envelope of the structure. DETAILED DESCRIPTION

[0060] The technical solutions of the present application will be further described in detail below in combination with embodiments and drawings.

[0061] The technical solutions of the present application will be further described in detail below in combination with embodiments and drawings.

[0062] The method for analyzing the seismic performance of a complex high-rise structure comprises the following steps:

[0063] Step one, determination of the limit range of super high-rise buildings:

[0064] (1) According to the current mandatory norms and regulations in China, such as "Technical Specification for Concrete Structures of Tall Building" (JGJ3-2010), the maximum applicable height of reinforced concrete building structure and the A-level and B-level division standards of height-width ratio are clearly defined. The maximum applicable height of reinforced concrete high-rise building and the maximum height-width ratio of reinforced concrete high-rise building of A-level and B-level height are shown in "High Rules" (JGJ3-2010) 4.2.3; the maximum applicable height and height-width ratio of B-level high-rise building structure can be appropriately relaxed compared with A-level, but the structure seismic grade, relevant calculation and construction measures should be correspondingly strengthened, and meet the relevant provisions of "High Rules".

[0065] (2) According to the Ministry of Construction Order No. 111 "Provisions on Seismic Fortification Management of Super High-rise Building Engineering" and "Technical Points for Special Examination of Seismic Fortification of Super High-rise Building Engineering", super high-rise building engineering is strictly judged.

[0066] Specifically includes:

[0067] 21) Height out of limit: i.e. the height of the building exceeds the maximum allowable height specified in the codes and regulations. For reinforced concrete structures, the provisions of Chapter 6 of the Code for Seismic Design of Buildings shall be adopted; for steel structures, the provisions of Chapter 8 of the Code for Seismic Design of Buildings (hereinafter referred to as the "Code") shall be adopted; for steel-concrete hybrid structures, the provisions of Chapter 11 of the Technical Specification for Concrete Structures of Tall Buildings (hereinafter referred to as the "Technical Specification") shall be adopted; the seismic fortification of B-class high-rise buildings shall be included in the management scope of high-rise buildings out of limit. For shear wall structures with many short-pier walls, the maximum allowable height shall be adopted according to the provisions of Article 7.1.2 of Chapter 7 of the Technical Specification, i.e. 100m and 60m for 7-degree and 8-degree seismicity, respectively, and 120m is recommended for 6-degree seismicity; the maximum allowable height of staggered structures shall be adopted according to the provisions of Chapter 10 of the Technical Specification, and 100m is recommended for 6-degree seismicity;

[0068] 22) Special irregular arrangement of building structure: the height is not out of limit, but the arrangement of building structure belongs to the special irregular high-rise structure specified in the Code and the Technical Specification.

[0069] Specific manifestations are:

[0070] High-rise buildings with two or more than two plan and vertical irregularities or with one irregularity exceeding the specified value by a large margin. The main types of plan irregularity include torsional irregularity, concave-convex irregularity, and local discontinuity of floor slab; the main types of vertical irregularity include lateral stiffness irregularity, discontinuity of vertical lateral force resisting members, and sudden change of floor bearing capacity. When the height of the podium exceeds 20% of the height of the main building, and the setback size of the main building relative to the podium is > 25%, the lateral stiffness irregularity shall be considered.

[0071] High-rise buildings with complex structures and hybrid structures with obviously irregular arrangement of structure, such as:

[0072] High-rise buildings with two or more than two complex types (with transfer floors, with strengthened floors, and with staggered structures, connected structures, and multi-towers);

[0073] Staggered structures and connected structures with different number of stories, arrangement of structure, or stiffness, etc.

[0074] High-rise buildings with large podium (podium) whose single tower or multi-towers of different sizes are deviated too much;

[0075] High-rise buildings with thick plate transfer for 7-degree and 8-degree seismicity.

[0076] The transfer floor location height specified in Article 10.2.2 of the Code is mainly for frame-shear wall structures. For frame-core wall structures with transfer floors at the bottom and tube-in-tube structures with the outer tube as a dense column frame, the transfer floor location height can be appropriately increased.

[0077] Step two, the requirements of seismic design of super high-rise buildings are clear:

[0078] (21) The height limit when using different structural forms is clearly defined: the height of reinforced concrete frame structures and seismic wall structures shall not exceed the maximum applicable height specified in the Code. For reinforced concrete frame-seismic wall structures and tube structures, the height shall not exceed the maximum applicable height specified in the Code for 9 degree seismic fortification, 20% of the maximum applicable height for 8 degree seismic fortification, and 30% of the maximum applicable height for 6 and 7 degree seismic fortification.

[0079] (22) Ensure that at least one of the building height, aspect ratio, and body shape regularity meets the relevant provisions of the Code to ensure the basic stability and seismic performance of the structure.

[0080] (23) Use more stringent seismic measures than specified in the Code, such as strengthening the design of joint connections, increasing the reinforcement ratio of key components, and optimizing structural construction measures to improve the seismic capacity of the structure.

[0081] (24) Two or more mechanical models that meet the actual situation of the structure should be used for calculation and analysis, and the calculation program should be identified and recognized by the construction administrative department of the State Council. Through the calculation and analysis of multiple mechanical models, mutual verification and supplementation are carried out to improve the reliability and accuracy of the calculation results.

[0082] (25) For structures with a height exceeding the maximum applicable height of the Code by a large margin, a particularly complex body shape, or a special structural type, seismic performance test research on small-scale overall structural models and large-scale local structural models should be conducted, as well as dynamic characteristic testing of the actual structure. Through experimental research, the actual response and failure mechanism of the structure under earthquake action are deeply understood, providing more intuitive and reliable basis for structural design.

[0083] (26) Special super high-rise buildings and super high-rise buildings with obvious weak layers should conduct elastic-plastic time history analysis of the structure. Elastic-plastic time history analysis can more accurately simulate the nonlinear response of the structure under strong earthquake action, evaluate the seismic performance and weak parts of the structure, and provide important reference for structural seismic design and reinforcement.

[0084] Step three, structure finite element modeling, as shown in Figure 1

[0085] ​(31) Project overview analysis: Detailed understanding of the project location, building function, height, number of floors, structural form and other information.

[0086] (32) Finite element model simplification: To maintain the consistency of the numerical calculation model with the actual structure and highlight the problems studied, the structure is simplified as follows:

[0087] 321) Since the problem studied is only the response of the overall structure within the elastic or plastic range, the reinforcement is treated in a whole dispersion manner, and the effect of the reinforcement is equivalent to the concrete to simplify the calculation process.

[0088] 322) Ignore the secondary components that have little effect on the overall performance of the structure, such as the secondary beams of the structure, etc., but the weight of the secondary components and the load acting on the secondary components are equivalent to the main structure connected to the secondary components, to ensure that the stress state of the structure is reasonably simulated.

[0089] 323) Ignore the small holes in the floor and the small wall piers on the wall piers of the shear wall, which have little effect on the overall performance of the structure, to facilitate modeling and calculation, while not affecting the main mechanical properties of the structure.

[0090] 324) Considering the effect of the structure's own weight, the density of the floor material is adjusted locally to make the model more consistent with the actual situation.

[0091] (3) Finite element model establishment:

[0092] 331) The beams and columns in the structure are simulated by three-dimensional beam elements BEAM188, which can accurately simulate the bending, shear and torsion of beams and columns.

[0093] 332) The shear wall and floor are simulated by three-dimensional shell element shell43, which has 4 nodes per node, with 6 spatial degrees of freedom per node, which can well coordinate with spatial beam elements, has high calculation accuracy, and can effectively simulate the mechanical properties of shear walls and floors in and out of the plane.

[0094] 333) The entire structure is discretized into 63827 elements and 33111 nodes. The cross section of the steel reinforced concrete column and beam is simulated by mixed material, without considering the slip between the steel and the concrete, to simplify the calculation model while meeting the engineering precision requirements. The form of the cross section is shown in the following figure.

[0095] 334) The bottom constraint of the structure is simulated by a fixed support to simulate the constraint effect of the foundation on the upper structure and ensure that the boundary conditions of the model meet the actual situation.

[0096] Step four, structural dynamic property analysis:

[0097] (41) Theoretical basis: the dynamic characteristics of the structure reflect the inherent dynamic performance of the structure itself, which mainly includes the natural period of the structure, the overall mode of the structure and the material damping and some other parameters irrelevant to dynamic load, which are called structural dynamic characteristic parameters.

[0098] According to the related knowledge and formula derivation in structural mechanics, the dynamic characteristic parameters of the structure are determined by the inherent stiffness, mass, physical properties of the material and boundary conditions of the structure, and are irrelevant to dynamic load.

[0099] 411) Natural frequency of the structure: when the structure is subjected to horizontal external force, it will produce lateral displacement. When the external force is removed, the structure will make reciprocating vibration on both sides of the original position, which is the equilibrium position. This vibration is called free vibration of the structure. The time required for the structure to make one cycle of free vibration from the original point is called the period of the structure. For a single degree of freedom system, the number of times the structure vibrates in 1 s is called the frequency of the structure. For a multi-degree of freedom system, the structure has multiple natural frequencies, and the number of frequencies is the same as the number of degrees of freedom assumed by the structure system. Through calculation, the natural frequencies of the structure are arranged in descending order to form an array, which is called the frequency spectrum of the structure. Different materials and different types of structural systems have different frequency spectra, so the frequency spectrum can reflect the characteristics of the material and the structure. Among the many frequencies, the smallest frequency of the structure is called the basic frequency, and the others are called the second frequency, the third frequency, etc.

[0100] 412) Mode shape of the structure: in the frequency spectrum, each natural frequency of the structure has a corresponding deformation shape when the structure makes free vibration. Such deformation shape is called the main mode shape of the structure, simply called the mode shape of the structure. The mode shape corresponding to the smallest frequency of the structure, i.e. the basic frequency, is called the basic mode shape of the structure, and the remaining mode shapes of the structure are called the second, third mode shapes, etc. For linear elastic structures, the linear combination of the mode shapes of the structure can be used to solve the lateral displacement of the structure under external force.

[0101] 413) Damping of the structure: the damping of the structure reflects the energy dissipation of the structure. The free vibration of the structure is actually a process of mutual conversion of kinetic energy and potential energy. If there is no energy loss during the free vibration of the structure, according to the law of conservation of energy, the amplitude of the structure will not decrease. However, in actual life, such ideal situation is impossible, and energy dissipation is inevitable. This is because there is internal friction in the material, friction in the boundary connection parts of the structure and damping effect of the surrounding medium on the structure, etc. These factors can be summarized as the damping of the structure. Therefore, in nature, due to the influence of damping, the free vibration of the structure is always attenuated until it finally returns to equilibrium.

[0102] (42) Modal analysis method selection: In the finite element software ANSYS, there are 7 common calculation methods for extracting the structure modal, which are Block Lanczos, Subspace, PowerDynamics, Reduce, damp, QR damp, and Umsymmetrics. For different structural forms and the complexity of the structure, these seven methods have their own advantages and disadvantages. Users need to judge based on their own needs, weigh the pros and cons of various methods, and find the most suitable finite element method for the built model. Since the Block Lanczos method can ensure the accuracy of the calculation results, and the calculation speed is not too slow, and this method is suitable for modal analysis of high-rise symmetrical structures, in some preferred embodiments, this method is selected for modal analysis of the structure.

[0103] The modal analysis process of ANSYS includes four parts of finite element model establishment, modal solution, modal expansion and post-processing. It is worth noting that the nonlinear factors considered in finite element modeling will be ignored in modal analysis, and the program only considers the linear characteristics of the structure when calculating.

[0104] (43) Modal calculation results and analysis:

[0105] 431) Natural period of the structure: As shown in Figure 3 , since the research object of this paper is a single tower structure with a large podium, the mode is more than the conventional structure, and the distribution law of its modal is much more complex than the conventional structure. Therefore, when performing structural modal analysis, the first few modes of the structure cannot be taken for calculation. In order to improve the calculation accuracy of the complex super-high-rise structure, the number of modes calculated should be much more than that of the conventional structure. According to the Technical Specification for Concrete Structures of Tall Building, for B-grade high-rise building structures and complex high-rise building structures specified in this specification, the torsional effect of the structure should be considered when calculating the seismic resistance, and the number of vibration modes should not be less than 15, and the calculation of the number of vibration modes should make the vibration mode participation quality not less than 90% of the total quality. In this paper, the first 50 modes are taken for calculation. Through finite element calculation, the natural frequency, period and mode participation quality of the first 50 modes of the structure are obtained. The first 10 frequency and period of the structure are shown in the table below.

[0106]

[0107] It can be seen that the three software calculation results are close in the first 10 modal. The maximum difference between ETABS and ANSYS is not more than 10%, which shows that the model established by ANSYS is reasonable and reliable. According to the regulation of the fourth regulation of the fourth regulation, the ratio of the first natural period of structure torsion Tt to the first natural period of translation T1 should not be greater than 0.85 for complex high-rise buildings.

[0108]

[0109] As can be seen from the table, the torsion-translation ratio of the structure calculated by the three kinds of software is less than 0.85, which shows that the torsion effect of the structure is not obvious, and the torsional stiffness meets the requirements. From the results, it can be seen that the calculation results of the three kinds of software are very close, and all meet the basic requirements of the specification.

[0110] 432)Structure mode chart: as Figures 4-6 , see the first, second and third mode charts of the structure, the first mode is the translation in Y direction and the second mode is the translation in X direction, and the first and second periods are quite different, which can be judged that the stiffness distribution of the structure is uneven, and the stiffness in Y direction is lower than that in X direction. Through the analysis of the mode chart, the deformation characteristics of the structure under different modes can be further understood, which provides more intuitive basis for structure design, and helps to take targeted measures to optimize the stiffness distribution of the structure and improve the seismic performance of the structure.

[0111] Step five, seismic response spectrum analysis of structure

[0112] (51) Seismic response spectrum comparative analysis: In this study, the seismic response spectrum will be applied to the overall structure to study the maximum response of the structure under the seismic load equivalent to the fortification intensity. The mode decomposition response spectrum method is used to calculate ANSYS, and the calculation results of ANSYS, PKPM and ETABS are compared and analyzed.

[0113] According to the actual engineering region, the seismic intensity is 7 degrees (0.1g), the design earthquake group is the second group, the site category is II, the characteristic period is 0.40s, and the damping ratio is 0.05. The spectrum curve is shown in the following figure (the clear and accurate seismic response spectrum diagram is attached). The X direction seismic acceleration spectrum is applied to the finite element model, and the complete open plane method (CQC) in the mode decomposition response spectrum method is used to calculate the seismic response of the model under the excitation spectrum.

[0114] The calculation formula of CQC (The complete quadratic combination method) method of seismic response spectrum analysis is:

[0115] S =∑i=1m∑j=1mρ ij S i S j (1)

[0116] where, ρ ij is the cross-correlation coefficient between two modes, which depends on the frequency ratio of two modes and the damping ratio of two modes.

[0117] ρ ij = (λij2-1)2+4ζ2λij2ζλij(λij2+2ζ2) (2)

[0118] where, λ ij is the frequency ratio of two modes, ζ is the damping ratio.

[0119] Through the analysis of the calculation results, the inter-story drift angle, the average inter-story drift, the average floor displacement, and the maximum floor displacement of the structure under the X-direction earthquake are obtained, and the calculation results of the three software are compared.

[0120] As Figures 7-9 shown in the displacement nephogram of the structure, the maximum displacement of the structure occurs at the top of the structure, with a value of 113mm. The stress at the bottom of the shear wall structure is large, and stress concentration occurs at the coupling beam of the shear wall, which conforms to the destruction principle of the shear wall coupling beam "strong shear and weak bending".

[0121] From the average inter-story displacement curve of the structure, the inter-story drift angle curve of the structure, the average inter-story displacement curve of the structure, the maximum inter-story displacement curve of the structure, and the floor displacement ratio curve of the structure, it can be seen that the calculation results of the three software are close, among which the result value calculated by PKPM is larger, indicating that the calculation result is conservative. From the maximum inter-story displacement curve of the structure, it can be seen that the 45th floor is the large roof layer of the structure, and the structure displacement is the vertex displacement of the structure. The calculation results of PKPM, ETABS, and ANSYS are 134mm, 112mm, and 113mm respectively. The calculation result of ANSYS is 15.6% smaller than that of PKPM, indicating that the result calculated by PKPM is conservative and the structure stiffness is small. Therefore, when using PKPM for structure design, attention should be paid to the factors that have a greater impact on the structure stiffness, and appropriate selection of each parameter should be made to make the design product safe and economical.

[0122] From the inter-story drift angle curve of the structure, it can be seen that the maximum inter-story displacement angle of the floor meets the requirement of less than 1 / 800 for the frame-shear structure. The inter-story drift angle of the structure at the top of the 8th floor and the 26th floor appears a larger mutation, which is because the top of the 8th floor is the top of the podium, and the 26th floor is set as a strengthened layer, and the layer height changes.

[0123] From the floor displacement ratio curve of the structure and the X-directional shear weight ratio table of the structure (the table is attached and the relevant information is marked), it can be seen that the torsional effect caused by the plan irregularity is also controlled within the requirements of the specification, that is, the maximum horizontal displacement of the vertical member of the floor and the interlayer displacement of the B-class high-rise building should not be greater than 1.2 times the average value of the floor, and should not be greater than 1.5 times the average value of the floor; the shear weight ratio (floor seismic shear coefficient) also meets the requirements of the specification.

[0124] (52) Seismic input dimensionality analysis: Taking the numerical model of the structure as the research object, seismic waves are input along the X direction, X+Y two directions and X+Y+Z three directions of the structure respectively, and FIG. 11-FIG. 13 respectively represent the influence of the input dimensionality of the seismic wave on the displacement response of the structure; Figures 15-17 is FIG. 15: X-direction floor displacement envelope of the structure, Y-direction floor displacement envelope of the structure, Z-direction floor displacement envelope of the structure.

[0125] As can be seen from FIG. 11, when the X-direction one-dimensional input seismic wave is input, the maximum displacement value of each layer of the structure in the X direction is the same as that when the two-dimensional and three-dimensional seismic waves are input, and the top layer Y-direction displacement value is very small. When two-dimensional input, the X-directional seismic acceleration has no effect on the Y-direction displacement (as shown in FIG. 12), it can be seen that for such a symmetrical structure, the seismic action in one direction has little effect on the vertical plane, and there is almost no in-plane coupling effect, and the relatively large vertical displacement value is caused by the dead weight of the structure. As can be seen from FIG. 13, when the dimensionality of the input seismic wave is changed, the vertical displacement caused by the change is relatively large, and the vertical displacement value when the three-dimensional input is the largest, therefore, when performing seismic analysis on the structure, it is best to consider three-dimensional seismic wave input, so as to more comprehensively and accurately evaluate the response of the structure under the action of the earthquake, and provide more reliable basis for the seismic design of the structure.

[0126] Specifically, the application is used for seismic performance analysis of a complex high-rise structure,

[0127] 1. Project overview:

[0128] Take a super high-rise building in the center of a northern city as an example, the project covers an area of about 1.17 square meters, the main building is 188.2m high, 45 floors above ground; The height of the attached podium is 42.4m, 8 floors above ground; The main building and podium are connected without joints. 3 floors below ground, the bottom plate surface elevation is -14.3m. The building has shops, cinemas, conference centers, restaurants and office functions. The engineering fortification intensity is 7 degrees, the design basic seismic acceleration is 0.10g, the site category is II, the design seismic group is the second group, and the site characteristic period is 0.40s; The main building adopts steel reinforced concrete frame-reinforced concrete shear wall-stretching truss-ring truss structure, as shown in Figure 2 , wherein the stretching truss and ring truss are set at the 26th floor, which is the equipment floor and the refuge floor; The podium adopts reinforced concrete frame-shear wall structure system, which belongs to the key project of national B class building engineering seismic review.

[0129] 2. Determine the boundary range of super high-rise building

[0130] According to “Technical Specification for Concrete Structures of Tall Building” (JGJ3-2010), determine whether the height and structure of the building meet the relevant provisions of A and B levels. The main building of the building is 188.2m high, which has exceeded the maximum applicable height of A level high-rise building, belongs to B level high-rise building, and needs to be designed and reviewed according to stricter regulations.

[0131] According to the Ministry of Construction Order No. 111 “Provisions on Seismic Fortification Management of Super High-rise Building Engineering” and “Technical Points for Special Seismic Fortification Review of Super High-rise Building Engineering”, the main building of the building is 188.2m high, which exceeds the relevant provisions of B level high-rise building under 7 degree seismic intensity, and belongs to super high-rise building engineering with height overrun. At the same time, check the building structure arrangement in detail to determine whether there are plane or vertical irregularities, etc. so as to take corresponding seismic measures.

[0132] 3. Implementation of seismic design requirements of super high-rise building

[0133] (31) Determine that the structure adopted by the building meets the corresponding height limit requirements, such as the height limit of steel reinforced concrete frame-reinforced concrete shear wall-stretching truss-ring truss structure and reinforced concrete frame-shear wall structure under 7 degree seismic intensity. Strengthen the design of key components and joints of the structure to improve the seismic capacity of the structure.

[0134] (32) Check the building in terms of building height, height-width ratio and body regularity, and ensure that at least one aspect meets the relevant provisions of the code and regulations. After analysis, the building meets the relevant requirements in terms of height-width ratio, but has certain irregularities in terms of body regularity, and corresponding measures need to be taken to optimize and strengthen.

[0135] (33) Adopt more stringent seismic measures than specified in the code and regulations, such as strengthening the design of structural connection nodes, increasing the reinforcement ratio of components, and optimizing structural construction measures. For example, special design of the connection nodes of steel reinforced concrete columns and beams to improve the seismic performance of the nodes; increase the reinforcement ratio of shear walls to enhance the shear capacity of shear walls.

[0136] (34) Use PKPM, ETABS and ANSYS three kinds of mechanical models that meet the actual situation of the structure for calculation and analysis, and these three kinds of calculation programs are identified and recognized by the competent administrative department of construction of the State Council. In the calculation process, the results of the three software are compared and analyzed in detail, verified and supplemented each other, and the reliability and accuracy of the calculation results are improved.

[0137] (35) Due to the fact that the building height exceeds the maximum applicable height of the code by a large margin, seismic performance test research on small-scale overall structural model and large-scale local structural model and dynamic characteristic test of the actual structure are carried out. Through experimental research, the actual response data of the structure under earthquake action are obtained, which are compared and analyzed with the calculation results, and the structure design is further optimized.

[0138] (36) For the special situation of the building, perform elastic-plastic time history analysis of the structure. Use appropriate seismic waves to perform elastic-plastic time history analysis of the structure, simulate the nonlinear response of the structure under strong earthquake action, evaluate the seismic performance and weak parts of the structure, and provide important reference for the seismic design and reinforcement of the structure.

[0139] 4. Finite element modeling of structure

[0140] (41) Model simplification: use the overall dispersion method to process steel bars; ignore secondary components such as secondary beams of the structure, and equivalent the self-weight and load of the secondary components to the main structure; ignore small holes on the floor and small wall piers on the shear wall wall, etc.; consider the influence of the structure's self-weight, and adjust the density of the floor material locally to [specific adjusted density value] to more accurately simulate the stress state of the structure.

[0141] (42) Model establishment: using ANSYS software, beams and columns are simulated by three-dimensional beam element BEAM188, shear walls and floors are simulated by three-dimensional shell element shell43. Define material properties, the elastic modulus of Q345B steel is 2.06E + 05MPa, the Poisson's ratio is 0.3, and the density is 7850kg / m³; the elastic modulus of C30 concrete is 3.00E + 04MPa, the Poisson's ratio is 0.2, and the density is 2500kg / m³; the elastic modulus of C40 concrete is 3.25E + 04MPa, the Poisson's ratio is 0.2, and the density is 2500kg / m³; the elastic modulus of C50 concrete is 3.45E + 04MPa, the Poisson's ratio is 0.2, and the density is 2500kg / m³; the elastic modulus of C60 concrete is 3.60E + 04MPa, the Poisson's ratio is 0.2, and the density is 2500kg / m³. The whole structure is discretized into 63827 elements and 33111 nodes, the cross section of steel reinforced concrete column and beam is simulated by mixed material, the slip between steel and concrete is not considered, and the bottom constraint of the structure is simulated by fixed support. In the modeling process, the size and parameters of the actual project are strictly set to ensure the accuracy and reliability of the model.

[0142] 5. Analysis of structural dynamic characteristics

[0143] (51) Modal analysis: modal analysis is performed in ANSYS using the Block Lanczos method. After establishing the finite element model, modal solution, modal expansion and post-processing are performed. The first 50 modes are calculated to obtain the natural frequency, period and mode participation mass of the first 50 modes of the structure. The first 10 natural periods of the structure calculated by PKPM, ETABS and ANSYS are compared, and the results are shown in the table above. Through comparative analysis, the rationality and reliability of the ANSYS model are verified. At the same time, the torsion ratio of the structure is calculated and analyzed to determine whether the torsional effect and torsional stiffness of the structure meet the requirements.

[0144] (52) Mode analysis: the mode diagram of the structure is analyzed in detail. Through the translational movement of the first mode in the Y direction and the translational movement of the second mode in the X direction, as well as the large difference between the first and second periods, it is judged that the stiffness distribution of the structure is uneven, and the stiffness in the Y direction is lower than that in the X direction. According to the mode analysis results, specific suggestions for structural optimization are put forward, such as increasing the stiffness of the structure in the Y direction to improve the seismic performance of the structure.

[0145] 6. Seismic response spectrum analysis of structure

[0146] (61) Seismic response spectrum comparative analysis: According to the actual engineering seismic parameters, the whole structure is subjected to the seismic response spectrum. The mode decomposition response spectrum method is calculated by using ANSYS, and the calculation results of ANSYS, PKPM and ETABS are compared and analyzed. Through detailed analysis of the calculation results, the interlayer displacement angle, average interlayer displacement, average floor displacement, maximum floor displacement and other data of the structure under the action of X direction earthquake are obtained. By comparing the calculation results of the three software, it is found that the calculation result of PKPM is conservative, and the calculation results of ANSYS and ETABS are close. According to the analysis results, reasonable parameter suggestions are provided for the structure design, such as considering the conservatism of the calculation result of PKPM in the design, and appropriately adjusting the stiffness and reinforcement parameters of the structure.

[0147] (62) Seismic input dimension influence analysis: Taking the numerical model of the structure as the research object, the seismic input is input along the X direction, X+Y two-way and X+Y+Z three-way of the structure respectively. Through the analysis of the influence of seismic input dimension on the displacement response of the structure, it is concluded that for the symmetrical structure, the seismic action in one direction has little influence on the vertical plane, and there is almost no in-plane coupling effect, and the vertical displacement value of three-dimensional input is the largest. Therefore, when carrying out the seismic analysis of the structure, it is suggested to consider the three-dimensional seismic wave input, so as to more comprehensively evaluate the seismic performance of the structure.

[0148] Finally, it is necessary to point out that: the above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for analyzing the seismic performance of complex high-rise structures, characterized in that, The method includes the following steps: Step 1: Determine the boundary of super high-rise buildings and determine the maximum applicable height and height-to-width ratio of reinforced concrete building structures; Step 2: Determine the seismic requirements for super high-rise buildings, determine height limits based on different structural forms, and ensure that at least one aspect of the building's height, height-to-width ratio, and regularity of form meets the requirements of the codes and regulations. Step 3: Structural finite element modeling. Based on the above-mentioned architectural project overview, the finite element model is simplified to be consistent with the actual structure. A finite element model is established, in which beams and columns in the structure are simulated using three-dimensional beam elements BEAM188, and shear walls and floor slabs are simulated using three-dimensional shell elements shell43. The entire structure is discretized into 63,827 elements and 33,111 nodes. The bottom constraints of the structure are simulated using fixed supports. Step 4: Structural dynamic characteristics analysis. Structural similarity characteristics reflect the inherent dynamic performance of the structure itself, including the natural period of the structure, the overall mode shape of the structure, and material damping. In the finite element software ANSYS, the structural modal calculation method is extracted. The calculation method is applicable to different structural forms and complexities. Based on the selected structural modes, the structure's natural vibration period is analyzed, and the mode shape diagram of the structure is output. Step 5: Structural Seismic Response Spectrum. Apply a seismic response spectrum to the entire structure to study the maximum response of the structure under seismic loads of the design intensity. The modal decomposition response spectrum method was used to calculate the overall structure under seismic loading in the X direction. The calculation results were compared and analyzed to obtain the data of inter-story drift angle, average inter-story drift, average story drift, and maximum story drift of the structure. Using the data as the research object, seismic motions were input along the X direction, X+Y bidirectional, and X+Y+Z tridirectional directions of the structure to obtain the influence of the seismic wave input dimension on the structural displacement response.

2. The seismic performance analysis method for complex high-rise structures according to claim 1, characterized in that, Step two, which involves determining the seismic requirements for super high-rise buildings, specifically includes: (21) Determine the height limits for different structural forms. Specifically, for reinforced concrete frame structures and shear wall structures, the height shall not exceed the maximum applicable height specified in the code; for reinforced concrete frame-shear wall structures and tube structures, the height shall not exceed the maximum applicable height specified in the code and regulations for seismic fortification intensity of 9 degrees, the height shall not exceed 20% of the maximum applicable height specified in the code and regulations for seismic fortification intensity of 8 degrees, and the height shall not exceed 30% of the maximum applicable height specified in the code and regulations for seismic fortification intensity of 6 degrees and 7 degrees. (22) The building shall meet the requirements of the code and regulations in at least one aspect of the building height, height-to-width ratio and regularity of shape, so as to ensure the basic stability and seismic performance of the structure; (23) Two or more mechanical models that conform to the actual situation of the structure are used in the calculation and analysis; the calculation and analysis of multiple mechanical models are used to verify and supplement each other; (24) For structures whose building height exceeds the maximum applicable height of the code by a large margin, whose shape is particularly complex or whose structural type is special, conduct seismic performance test studies on small-scale overall structural models and large-scale local structural models, and test the dynamic characteristics of the actual structures. (25) For special super-high-rise buildings and super-high-rise buildings with obvious weak layers, conduct elastoplastic time history analysis of the structure.

3. The performance analysis method for complex high-rise structures according to claim 1, characterized in that, Step 3, the finite element model simplification, includes the following steps: (321) For steel reinforcement in building structures, the function of steel reinforcement is equivalent to that of concrete in an overall diffuse manner; (322) The self-weight of the secondary component and the loads acting on the secondary component are equivalent to the main structure connected to the secondary component; (323) Ignore small openings on floor slabs that have little impact on the overall structural performance, and wall piers on shear wall members.

4. The performance analysis method for complex high-rise structures according to claim 1, characterized in that, Step 3, the establishment of the finite element model, includes the following steps: (331) The beams and columns in the structure are simulated using the three-dimensional beam element BEAM188; (332) The shear walls and floor slabs are simulated using the three-dimensional shell element shell43. The three-dimensional shell element has 4 nodes, and each node has 6 degrees of freedom in space. (333) The entire structure is discretized into 63,827 elements and 33,111 nodes; the cross-sections of steel-concrete columns and beams are simulated using hybrid materials; (334) The bottom constraint of the structure is simulated using fixed supports.

5. The performance analysis method for complex high-rise structures according to claim 1, characterized in that, In the finite element software ANSYS, there are seven calculation methods for extracting structural modes: BlockLanczos method, Subspace method, PowerDynamics method, Reduce method, Damping method, QR damping method, and Umsysmmetics method.

6. The performance analysis method for complex high-rise structures according to claim 1, characterized in that, Step 5 describes applying a seismic response spectrum to the overall structure, specifically by applying an X-axis seismic acceleration spectrum to the finite element model and using the fully open method in the modal decomposition response spectrum method to calculate its seismic response under the excitation spectrum. The calculation formula for the seismic response spectrum analysis method is as follows: （1） in, The cross-correlation coefficient between two modes depends on the frequency ratio of the two modes and the damping ratio of each mode. （2） in, It is the frequency ratio of the two modes. The damping ratio; Analysis of the calculation results yielded the inter-story drift angle, average inter-story drift, average story drift, and maximum story drift of the overall structure under X-direction seismic loading.

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