A seismic isolation analysis method based on the structure established by a building model

Abstract

The present invention discloses a seismic isolation analysis method based on the building model establishment structure. Establishing a reliable analysis model is the basis for static and dynamic analysis of structures. A reliable analysis model can truly reflect the dynamic characteristics of the structure and can accurately analyze the dynamic response of the structure in the elastic stage. In order to accurately perform seismic isolation analysis on this project, a three-dimensional finite element model of the elastic seismic isolation structure and the non-seismic isolation structure was established using ETABS software. The finite element model of the non-seismic isolation structure established by ETABS can accurately reflect the mass distribution of the actual structure, and can be used as a benchmark model for calculating the dynamic response of the non-seismic isolation structure and also as an initial model for subsequent seismic isolation analysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction engineering and relates to a seismic isolation analysis method based on a building model establishment structure. Background Art

[0002] A seismic isolation building refers to a building that uses seismic isolation technology to set up a seismic isolation device at the base or a certain position of the building to form a seismic isolation layer, separating the upper structure from the lower foundation, so as to consume seismic energy, avoid or reduce the transmission of seismic energy upward, and can more effectively ensure the safety of the upper structure and the internal personnel and equipment. Judging from the actual effect of applying seismic isolation technology to construction projects, for buildings higher than six floors in seismic fortification areas of intensity 8 and above, after applying seismic isolation technology, the fortification intensity can be reduced by 2 degrees, thus saving investment costs. For a 9-story building of about 10,000 square meters, only the steel bars can save more than 1 million yuan in investment; for buildings designed according to the specifications, the seismic isolation technology has a high seismic fortification goal for the building, and the safety is significantly improved; for government head offices, high-rise commercial housing, lifeline projects, and important construction projects prone to secondary disasters, applying seismic isolation technology can improve the building safety. The present invention provides a seismic isolation analysis method for building model establishment by pre-establishing an analysis model, performing static and dynamic analysis on the model, and conducting scientific analysis, so as to judge the dynamic response of the building and understand the seismic isolation situation of the building. Summary of the Invention

[0003] The purpose of the present invention is to provide a seismic isolation analysis method based on a building model establishment structure. Establishing a reliable analysis model is the basis for performing static and dynamic analysis of the structure. A reliable analysis model can truly reflect the dynamic characteristics of the structure and can accurately analyze the dynamic response of the structure in the elastic stage.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: a seismic isolation analysis method based on a building model establishment structure, which is specifically carried out according to the following steps:

[0005] Step 1: Use ETABS software to establish a non-seismic isolation finite element model according to the seismic fortification intensity of 8 degrees. The beam and column members adopt spatial bar elements, and the floor slab adopts shell elements. The shell elements can be used to simulate shells, membranes, and plates in planar and three-dimensional structures. Among them, the floor slab in the floor slab structure will adopt the membrane element in the program, and the structural weight and distributed load are distributed to the corresponding nodes of the floor load to form node loads and corresponding line loads;

[0006] The assumption of rigid floor slabs is adopted, which greatly reduces the degrees of freedom of the structure in space, thereby shortening the time used in the structural analysis. When the rigid floor slabs are assumed, the floor slab only has translation and rotation in its own plane and does not change its own shape;

[0007] By comparing the first six natural periods of the ETABS and PKPM models and calculating that the absolute value of the period error between the two should not exceed 3%;

[0008] By comparing the model of ETABS with the structural mass of PKPM software and keeping the total structural mass error less than the allowable error of the project;

[0009] Step 2: Based on the finite element analysis model of the non - isolated structure, establish a finite element analysis model of the isolated structure, conduct dynamic time - history response analysis on them respectively, compare the torsional vibration effects between the two, and analyze the structural dynamic characteristics of the isolation layer through the three - dimensional structure model diagram;

[0010] Through the analysis of multiple actual earthquake response records and simulated earthquake shaking table test results of the base friction isolation structure, the base sliding isolation system can significantly reduce the seismic response of the structure;

[0011] Step 3: In the non - isolated finite element analysis model, add isolation bearings, input the bearing parameters, connect them with the connecting element Isolator2 and construct a new model;

[0012] Step 4: Select natural waves and artificial waves and use the envelope value of the time - history analysis method as the final calculation result and input the seismic motion evaluation;

[0013] Input the seismic wave according to the friction coefficient and the isolation intensity, and conduct time - history analysis without lateral restraint to calculate the maximum sliding displacement, the residual sliding displacement and the seismic response value;

[0014] Step 5: Since the dynamic characteristics of the isolated structure change continuously with the change of the horizontal deformation of the isolation bearing, use the RITZ vector method to calculate the results of the first 30 dynamic characteristics of the isolated system before 100% shear strain;

[0015] Step 6: Design seismic shear force analysis, calculate and analyze the base shear force of the elastic non - isolated structure through the curve, and analyze according to the shear force to judge whether the base shear force of the non - isolated structure under time - history analysis meets the requirements of the code for seismic waves. After adding the friction pendulum isolation unit to the example structure, due to the large damping in the isolation layer, it can be seen that the periods corresponding to each vibration mode of the isolated model are significantly extended, which exactly verifies the principle that the isolated structure weakens the structural dynamic response by extending the structure's period and illustrates the effectiveness of the friction pendulum isolation bearing.

[0016] The present invention is based on the building model to establish a structural isolation analysis method. The non - isolated structure finite element model established by using ETABS can accurately reflect the mass distribution of the actual structure, and can be used as the benchmark model for calculating the dynamic response of the non - isolated structure and also as the initial model for subsequent isolation analysis.

[0017] In the design method of the present invention, establishing a reliable analysis model is the basis for static and dynamic analysis of structures. A reliable analysis model can truly reflect the dynamic characteristics of the structure and can accurately analyze the dynamic response of the structure in the elastic stage. In order to perform accurate seismic isolation analysis on this project, a three-dimensional finite element model of the elastic seismic isolation structure and the non-seismic isolation structure was established using ETABS software. Brief Description of the Drawings

[0018] Figure 1 It is a three-dimensional view of the non-seismic isolation finite element model.

[0019] Figure 2 It is the acceleration time history curve of the natural wave 1 of the present invention.

[0020] Figure 3 It is the acceleration time history curve of the natural wave 2 in the embodiment of the present invention.

[0021] Figure 4 It is the acceleration time history curve of the artificial wave in the embodiment of the present invention.

[0022] Figure 5 It is the main direction response spectrum of the natural wave 1 in the embodiment of the present invention.

[0023] Figure 6 It is the main direction response spectrum of the natural wave 2 in the embodiment of the present invention.

[0024] Figure 7 It is the main direction response spectrum of the artificial wave in the embodiment of the present invention.

[0025] Figure 8 It is the average spectrum in the embodiment of the present invention. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Embodiment

[0028] 1. Establishment of the non-seismic isolation model:

[0029] Refer to Figure 1 , a non-seismic isolation finite element model of this project was established using ETABS software according to the fortification intensity of 8 degrees. The beam and column members adopt spatial bar elements, and the floor slab adopts shell elements.

[0030] Under the combination of ETABS and PKPM models, the first 6 natural periods of the non-isolated structure are compared. If the maximum absolute value of the period error between the two is no more than 3.0%, it indicates that the established ETABS and PKPM models are basically the same. As shown in the following table, the comparison data of the first 6 natural periods of PKPM and ETABS:

[0031]

[0032] From the comparison results of the structural mass between the ETABS model and PKPM software, it can be obtained that the total structural mass error is less than 1.93%, which is less than the engineering allowable error. As shown in the following table, the mass distribution of the non-isolated structure:

[0033]

[0034] The above data analysis shows that the finite element model of the non-isolated structure established by ETABS can accurately reflect the mass distribution of the actual structure, and can be used as the benchmark model for calculating the dynamic response of the non-isolated structure, and also as the initial model for subsequent seismic isolation analysis.

[0035] 2. Establishment of the seismic isolation model:

[0036] Refer to Figure 1 , based on the finite element analysis model of the non-isolated structure, a finite element analysis model of the seismic isolation structure is established. This project is a base isolation project. In the non-isolated finite element analysis model, seismic isolation bearings are added and the bearing parameters are input. Among them, the friction pendulum seismic isolation bearing element adopts the connection element Isolator2 in the ETABS software 。

[0037] The dynamic characteristics of the seismic isolation structure will change continuously with the change of the horizontal deformation of the seismic isolation bearing. The results of the first 30 dynamic characteristics of the seismic isolation system under 100% shear strain are calculated by the RITZ vector method. The period of the seismic isolation system increases a lot compared with the original structure, and the fundamental period is extended from the original 1.13 s to 2.63 s. As shown in the following table, the first 6 natural periods of the non-isolated structure and the seismic isolation structure.

[0038]

[0039] 3. Evaluation of the input ground motion:

[0040] When using the time history analysis method, actual strong earthquake records and artificially simulated earthquake acceleration time history curves should be selected according to the building site category and the design earthquake grouping. The number of actual strong earthquake records should not be less than 2 / 3 of the total. In this project, 2 natural waves and 1 artificial wave are selected for time history analysis, and the envelope value of the three time history methods is taken as the final calculation result. The design seismic fortification intensity of this project is 8 degrees, the design basic seismic acceleration is 0.20g, and the maximum value of the design basic seismic acceleration adopted for the isolation analysis is 200 m / s². The maximum value of the earthquake acceleration under rare earthquakes is 400 cm / s².

[0041] 4. Selection of design ground motion:

[0042] Reference Figures 2 - 8 , when using the time history analysis method to conduct seismic response analysis on the structure, it is necessary to directly input the existing earthquake wave acceleration time history curve. The time history analysis results show that the input of different earthquake waves has a great impact on the structural dynamic response results. Therefore, it is very important to reasonably select the earthquake wave for the reliability of the structural time history analysis results;

[0043] The average seismic influence coefficient curve of the selected time history curve is consistent with the seismic influence coefficient curve adopted by the mode superposition response spectrum method in terms of statistics, and each time history curve is consistent with the seismic influence curve adopted by the mode superposition response spectrum method in terms of statistics. Therefore, the selection of each time history curve is reasonable.

[0044] 5. Seismic shear force analysis of design ground motion:

[0045] Through the calculation and analysis of the time history curve, it is obtained that the base shear force of the elastic non-isolated structure calculated by each group of time history curves is greater than 65% of the response spectrum calculation result. The average value of the structural base seismic shear force calculated by the 3 groups of time history curves is greater than 80% of the response spectrum calculation result, and the result of each group of time history does not exceed 135% of the response spectrum result, and the result of the 3 groups of time history does not exceed 120% of the response spectrum result, all of which meet the code requirements. The maximum seismic response value under the action of the 3 groups of time history curves is used as the final calculated value of the time history analysis, and the result is reliable and can be used for engineering design. And the shear force of each floor of the non-isolated structure under the frequent earthquake of 8 degrees is given. As shown in the following table, the comparison of the base shear force under the frequent earthquake:

[0046]

[0047]

[0048] It can be seen from the above table that the base shear force of the non-isolated structure under the time history analysis meets the code requirements for earthquake waves, and the above three earthquake waves can be used for isolation analysis.

Claims

1. A seismic isolation analysis method for a structure based on a building model, characterized in that: Follow these steps: Step 1: Use ETABS software to establish a non-isolated finite element model according to the design earthquake intensity of 8 degrees. The beams and columns are made of spatial bar elements, and the floor slabs are made of shell elements. By comparing the first 6-order cycles under the ETABS and PKPM models, and calculating that the absolute value of the cycle error between the two cannot exceed 3%; By comparing the ETABS model with the PKPM software structural quality, and keeping the total structural quality error less than the engineering allowable error; Step 2: Based on the finite element analysis model of the non-isolated structure, a finite element analysis model of the isolated structure is established, and the dynamic time-history response analysis is performed on each of them. The torsional vibration effects between the two are compared, and the structural dynamic characteristics of the isolation layer are analyzed through the three-dimensional structural model diagram; The three-dimensional structural model analyzes the actual earthquake response records of the friction isolation structure and the results of the simulated earthquake shaking table test. The base sliding isolation system can significantly reduce the seismic response of the structure. Step 3: In the non-isolated finite element analysis model, add isolation bearings, input the bearing parameters, and connect the friction pendulum isolation bearing unit with the connection unit Isolator2 using ETABS software to build a new model; Step 4: Select the envelope values ​​of natural waves and artificial waves through the time history analysis method as the final calculation results and input them into the seismic motion evaluation; By using the friction coefficient according to the seismic isolation intensity, inputting the seismic wave, and then performing time history analysis without limiting the position, the maximum slip, residual slip and seismic response value can be calculated; Step 5: Since the dynamic characteristics of the isolation structure will change with the change of the horizontal deformation of the isolation support, the RITZ vector method is used to calculate the results of the 30-order dynamic characteristics of the isolation system before 100% shear strain; Step 6: Design earthquake shear analysis, obtain the bottom shear of the elastic non-isolated structure through curve calculation and analysis, and analyze based on the shear force, and determine whether the base shear under the time-history analysis of the non-isolated structure meets the requirements of the code for seismic waves, and add a friction pendulum isolation unit to the example structure.

2. The seismic isolation analysis method for establishing a structure based on a building model as claimed in claim 1, characterized in that: In step 1, the absolute value of the period error between the two calculated should not exceed 3%.

3. The seismic isolation analysis method for establishing a structure based on a building model as claimed in claim 1, characterized in that: In step 1, the total mass error between the ETABS model and the PKPM software structure is less than the allowable error of the project.

4. The seismic isolation analysis method for establishing a structure based on a building model as claimed in claim 1, characterized in that: In step 4, the RITZ vector method is used to calculate the dynamic characteristics of the shear strain of the isolation system.

5. The seismic isolation analysis method for establishing a structure based on a building model as claimed in claim 1, characterized in that: In step 5, the time history curve analysis method includes a response spectrum analysis method.

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