JP7369673B2 - Seismically isolated buildings and their design methods - Google Patents

Description

The present invention relates to a seismically isolated building supported by laminated rubber bearings or elastic sliding bearings, and a method for designing the same.

Conventionally, there are seismically isolated buildings that use elastic sliding bearings as seismic isolation bearings. This elastic sliding bearing has a structure in which laminated rubber slides horizontally on a sliding plate, and seismic energy is absorbed by the frictional force between the laminated rubber and the sliding plate caused by the axial force of the column. This elastic sliding bearing is often placed directly under the center column where the axial force fluctuation is small, and in the past, lifting of the elastic sliding bearing was not allowed. Furthermore, when designing seismically isolated buildings, the compressive rigidity (relationship between compressive axial force and compressive displacement) of the laminated rubber of elastic sliding bearings was approximated by a straight line.
Incidentally, in recent years, elastic sliding bearings are sometimes provided in buildings that are long in a predetermined direction when viewed from above, such as plate-shaped condominiums. In addition, the expected seismic force is increasing, and in addition to horizontal shaking, vertical shaking is also expected. In such a case, a large pull-out force would act on the elastic sliding bearing, potentially causing the actual behavior of the seismically isolated building to differ significantly from the design.

Patent Document 1 shows a method for designing a seismic isolation structure applied to a building. The building includes a superstructure, a substructure, and a seismic isolation structure. The upper structure includes a first mass element, a second mass element, and an upper resilient element. The seismic isolation structure includes a lower elastic element, an inertial mass element, and a viscoelastic element. This seismic isolation structure design method uses a first function including the elastic modulus of the lower elastic element, the elastic modulus of the connected elastic element, and the mass of the first mass element of the upper structure to generate the connected damping element. obtaining a damping coefficient; obtaining a first equivalent elastic coefficient by using the elastic coefficient of the lower elastic element and the elastic coefficient of the connected elastic element; obtaining the mass of the inertial mass element using a second function including the mass, the first equivalent elastic modulus, and the elastic modulus of the upper elastic element.
Patent Document 2 discloses a seismic isolation device including a strip-shaped sliding plate fixed to one of the upper and lower structures and a laminated rubber support member fixed to the other of the upper and lower structures. A sliding member is interposed between the laminated rubber support member and the sliding plate.

JP2017-203297A Patent No. 3941251

An object of the present invention is to provide a highly reliable seismically isolated building design method and a seismically isolated building designed using this design method.

As a design method for highly reliable seismically isolated buildings, the present inventors investigated the compressive stiffness of the laminated rubber that constitutes laminated rubber bearings and elastic sliding bearings on full-scale test specimens when generating an analytical model of seismically isolated buildings. By using a nonlinear function based on experimental results and performing vibration analysis using this analytical model, we can reduce the uplift of laminated rubber bearings and elastic sliding bearings by ensuring that the response values of the building and laminated rubber are below the thresholds. The present invention has been achieved by focusing on the point that it is possible to construct a seismically isolated building with acceptable seismic isolation.
A design method for a seismically isolated building according to the first invention includes a laminated rubber bearing (e.g., laminated rubber bearing 20 described later) using laminated rubber (e.g., laminated rubber 22 described later) and/or an elastic sliding bearing (e.g., laminated rubber bearing 20 described later). A method for designing a seismically isolated building (for example, seismically isolated building 1 described later) supported by an elastic sliding bearing 21), the seismically isolated The seismic isolation building is designed by generating an analytical model of the building and performing vibration analysis using the analytical model.

A design method for a seismically isolated building according to the second invention includes a laminated rubber bearing (e.g., laminated rubber bearing 20 described later) using laminated rubber (e.g., laminated rubber 22 described later) and/or an elastic sliding bearing (e.g., laminated rubber bearing 20 described later). A design method for a seismically isolated building (e.g., seismic isolation building 1 described below) supported by elastic sliding bearings 21), the seismic isolated building comprising a lower structure (e.g., lower structure 10 described later). , a seismic isolation layer (for example, seismic isolation layer 11 described below) including the laminated rubber bearing or the elastic sliding bearing provided on the lower structure, and an upper structure provided on the seismic isolation layer. (for example, the upper structure 12 described later), generates an analytical model (multi-mass point system model, three-dimensional frame model) of the seismically isolated building, and calculates the relationship between the compressive axial force and compressive displacement of the laminated rubber. An analysis step (e.g., steps S1 and S2 described later) of inputting horizontal and vertical seismic forces into the analysis model as nonlinear functions to obtain a response, and a response acceleration of the lower structure and the upper structure. It is determined whether each response displacement amount is less than a predetermined threshold value, and if this determination is positive, the next step is performed, and if negative, the design of the seismically isolated building is determined. A first verification step (for example, steps S3 and S5 described later) that returns to the analysis step after changing the It is determined whether the response value of at least one of the pressures is below a predetermined threshold value, and if this determination is positive, the design is terminated; if the determination is negative, the above-mentioned exemption is completed. The present invention is characterized by comprising a second verification process (for example, steps S4 and S6 described later) in which the design of the earthquake building is changed and the process returns to the analysis process.

When designing a seismically isolated building, the seismic isolation bearings such as laminated rubber bearings and elastic sliding bearings installed in the building are modeled and vibration analysis is performed. Conventionally, in this vibration analysis, the compressive stiffness (gradient), which represents the relationship between the compressive axial force and compressive displacement of the laminated rubber of the seismic isolation bearing, was set to be larger than the compressive rigidity obtained in the load test of the laminated rubber. (For example, Architectural Institute of Japan: Seismic Isolation Structure Design Guidelines, pp. 25-31, September 10, 2001, 3rd edition). In other words, in an actual elastic sliding bearing, with only the building's own weight acting before the earthquake, the amount of compressive displacement of the laminated rubber is greater than the value assumed by conventional design methods, and the bearing sinks by a certain amount. (In other words, it has been greatly crushed by the axial force of the column). Therefore, in reality, when uplift is applied to an elastic sliding bearing, the uplift phenomenon does not occur because the bearing sinks more than the expected value based on vibration analysis, but there have been cases in which the vibration analysis indicates that the bearing has lifted up significantly. Therefore, in the past, if the seismic isolation bearing was lifted, it was necessary to reconsider the seismic isolation plan. Specifically, when tensile force acts on the seismic isolation bearing, a pull-out type seismic isolation bearing is provided to alleviate the pulling force.
Therefore, according to the first and second inventions, in the vibration analysis, the compression stiffness of the laminated rubber constituting the seismic isolation layer is made into a nonlinear function. This makes it possible to perform a realistic analysis of the behavior of seismic isolation bearings during earthquakes, taking into account uplift, and to optimize the number of seismic isolation bearings to design highly reliable seismic isolation buildings.

The design method for a seismically isolated building according to the third invention is such that the nonlinear function indicating the relationship between the compressive axial force and the compressive displacement of the laminated rubber is approximated to test results using a full-scale test specimen or analysis results of simulation analysis. It is characterized by being a polygonal line or a curved line.

According to the present invention, the nonlinear function representing the relationship between the compressive axial force and the compressive displacement of the laminated rubber is made into a polygonal line or a curve that approximates the test results of the full-scale test specimen of the laminated rubber or the analysis results of the simulation analysis. , reliability in the design of seismic isolation buildings can be further improved.

A seismically isolated building according to a fourth aspect of the present invention is designed by the above-described method for designing a seismically isolated building.
According to this invention, a highly reliable seismically isolated building can be constructed.

According to the present invention, it is possible to provide a highly reliable seismic isolation building design method and a seismic isolation building designed using this design method.

1 is a longitudinal sectional view of a seismically isolated building designed by a seismic isolation bearing design method according to an embodiment of the present invention. FIG. 2 is a side view of a laminated rubber bearing and an elastic sliding bearing used in a seismically isolated building. It is a flowchart of the design method of a seismic isolation building. It is a figure which shows the compression rigidity set to the analytical model of the laminated rubber which comprises a laminated rubber bearing and an elastic sliding bearing. 1 is a diagram showing the arrangement of a framework and a seismic isolation support of a seismically isolated building that is an embodiment of the present invention. It is a diagram modeling an elastic sliding bearing of an example. It is a figure which shows the relationship between the surface pressure set to the shear spring of the analytical model of the elastic sliding bearing of an Example, and a friction coefficient. It is a figure which shows the relationship between the surface pressure set to the shear spring of the analytical model of the elastic sliding bearing of an Example, and shear force. It is a figure which shows the compression rigidity set to the nonlinear vertical spring of the analytical model of the elastic sliding bearing of an Example. It is a figure which shows the compression rigidity set to the analytical model of the laminated rubber bearing (φ1200) of an Example. It is a figure which shows the compression rigidity set to the analytical model of the laminated rubber bearing (φ1100) of an Example. FIG. 3 is a diagram comparing the compression rigidity of the elastic sliding bearing and the laminated rubber bearing of the example. FIG. 2 is a diagram (part 1) showing vibration analysis results (time history response results of compressive displacement and surface pressure of elastic sliding bearings) of the base-isolated building of the example. FIG. 2 is a diagram (part 2) showing vibration analysis results (time history response results of compressive displacement and surface pressure of elastic sliding bearings) of the base-isolated building of the example.

The present invention aims to design a seismically isolated building that generates an analytical model of a seismically isolated building using the compressive stiffness of laminated rubber as a nonlinear function based on experimental results of full-scale test specimens, and performs vibration analysis using this analytical model. This is a seismically isolated building designed using this method and its design method.
Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a seismic isolation building 1 designed by a seismic isolation building design method according to an embodiment of the present invention.
The seismic isolation building 1 includes a lower structure 10, a seismic isolation layer 11 including a laminated rubber bearing 20 and an elastic sliding bearing 21 provided on the lower structure 10, and an upper portion provided on the seismic isolation layer 11. A structure 12 is provided. The laminated rubber bearings 20 are placed directly under the columns 13 on the outer periphery of the seismic isolation building 1, and the elastic sliding bearings 21 are placed directly under the columns 13 on the inner periphery of the seismic isolation building 1 (see FIG. 2). (see a), (b)). Hereinafter, the laminated rubber bearing 20 and the elastic sliding bearing 21 will be collectively referred to as a seismic isolation bearing.
2(a) is a side view of the laminated rubber bearing 20, and FIG. 2(b) is a side view of the elastic sliding bearing 21.
The laminated rubber support 20 is composed of a single layered rubber 22. The laminated rubber 22 includes a lower flange 30 fixed on the lower structure 10, a laminated rubber main body 31 provided on the lower flange 30, and configured by alternately laminating rubber and steel plates, An upper flange 32 provided on the rubber body 31 and fixed to the upper structure 12 is provided.
The elastic sliding support 21 includes a sliding plate 23 fixed on the lower structure 10 and a laminated rubber 22 that is slidably provided on the sliding plate 23 and supports the upper structure 12. In this elastic sliding bearing 21, the laminated rubber 22 that receives the axial force of the column 13 slides on the sliding plate 23, thereby absorbing seismic energy.

FIG. 3 is a flowchart of the design method for the seismically isolated building 1.
In step S1, an analytical model (multi-material point system model, three-dimensional frame model) of the seismically isolated building 1 is generated in a three-dimensional virtual space.
In step S2, horizontal and vertical seismic forces are input to the generated analytical model to obtain a response. At this time, as shown in FIG. 4, in the conventional design method, the compressive rigidity (relationship between compressive axial force and compressive displacement) of the laminated rubber 22 of the laminated rubber bearing 20 and the elastic sliding bearing 21 was linear; In the present invention, it is assumed to be nonlinear.
In step S3, it is determined whether the response acceleration and response displacement amount of the lower structure 10 and the upper structure 12 are respectively lower than predetermined threshold values. If this determination is Yes (affirmative), the process moves to the next step S4, and if it is No (negative), the process moves to step S5.

In step S5, the design of the seismic isolation building 1 is changed and the process returns to step S1.
In step S4, the amount of shear deformation and amount of vertical deformation of the laminated rubber 22 of the laminated rubber bearing 20 and the elastic sliding bearing 21, and the response value of the surface pressure of the seismic isolation bearing (the laminated rubber bearing 20 and the elastic sliding bearing 21) are calculated, respectively. , it is determined whether or not the value is below a predetermined threshold. When this determination is Yes (affirmative), the design is ended, and when this determination is No (negative), the process moves to step S6.
In step S6, the design of the seismic isolation building 1 is changed and the process returns to step S1.

〔Example〕
Hereinafter, embodiments to which the seismically isolated building design method of the present invention is applied will be described. In this example, a seismically isolated building was modeled and vibration analysis (three-dimensional finite element analysis) was performed.
[1. Structure of seismic isolation building]
FIG. 5(a) is a front view and a side view showing the framework of a seismically isolated building that is the design target of this example. FIG. 5(b) is a plan view showing the arrangement of seismic isolation bearings in a seismically isolated building. The structure of this seismic isolation building is as follows.
Number of floors: 19 floors Building height: Approx. 60m
Floor height: 3.1m
Structure type: Reinforced concrete structure with base isolation Frame type: Rigid-frame structure in the girder direction, continuous shear wall in the direction between the beams Aspect ratio: 4.9 at the highest point

Here, elastic sliding bearings (SA80-1200-8.0 x 3) with a diameter of 1200 mm are placed in the central part of the seismically isolated building (Y5 to Y8 streets). On the other hand, the ends of the seismic isolation building (Y1 to Y4 streets, Y9 to Y12 streets) are equipped with φ1200mm laminated rubber bearings (R40-1200-9.0×26) or φ1100mm laminated rubber bearings (R40-1100-8 .3×26) are arranged.

[2. Modeling of elastic sliding bearings]
The elastic sliding bearing, which is the gap element between the lower structure and upper structure of a seismically isolated building, was modeled as shown in Figure 6. In other words, an elastic sliding bearing is expressed as a combination of two vertical springs arranged in series in the vertical direction and two shear springs that expand and contract in the X direction and Y direction that intersect with each other in the shear direction (horizontal direction). Ta.
For the shear spring, the slip characteristics of the elastic sliding bearing were expressed by setting the initial stiffness and friction coefficient. In this example, by considering the surface pressure dependence of the friction coefficient, it is possible to analyze the horizontal characteristics of an elastic sliding bearing with high accuracy.
Further, as will be described in detail later, the upper elastic vertical spring is made rigid, and the compression rigidity of the lower nonlinear vertical spring is made nonlinear so that lifting can be taken into account. In this example, by arranging two vertical springs in series in this way, deformation characteristics in the compression direction are expressed while maintaining surface pressure dependence.

The friction coefficient μ of the shear spring is not set to a constant value, but is set to vary depending on the surface pressure. Specifically, as shown in FIG. 7, a straight line that approximates the manufacturer's evaluation formula is set in the range from 10 N/mm ² to 30 N/mm ² . Then, the relationship between surface pressure and shear force becomes as shown in FIG.

By setting the tensile stiffness of the lower nonlinear vertical spring to zero, we expressed the uplift of the elastic sliding bearing.
Furthermore, the compression stiffness of the lower nonlinear vertical spring was expressed by a trilinear nonlinear function consisting of three straight lines, as shown in FIG.
Conventionally, when modeling elastic sliding bearings, compressive stiffness was assumed to be linear based on the longitudinal elastic modulus of the rubber, the total rubber layer thickness, and the cross-sectional area (for example, Architectural Institute of Japan: Seismic Isolation Structure Design Guidelines, pp. 25-31, September 10, 2001, 3rd edition). Hereinafter, this analytical model in which the compression stiffness is linear will be referred to as a compression linear model.

On the other hand, in the present invention, when modeling the elastic sliding bearing, the compression rigidity is made trilinear and nonlinear. Hereinafter, this analytical model in which the compression stiffness is nonlinear will be referred to as a compression nonlinear model. Specifically, first, we conducted a force application experiment on an elastic sliding bearing. In this loading experiment, the reference surface pressure was set to 20 N/ ^mm2 , and the load was applied to the reference surface pressure +30% (experimental data P), and then, after 3 cycles of loading between the reference surface pressure +30% and -30%, Unloaded (experimental data Q). As shown in experimental data P and Q, the laminated rubber is hard when it is first loaded, but once force is applied, the physical properties of the rubber adapt and the rigidity decreases.
Next, in the experimental data of the elastic sliding bearing, the point at which the surface pressure is 2.0 N/mm ² is set as the first bending point a, the point at which the reference surface pressure is -30% is set as the second bending point b, and the point at which the reference surface pressure is +30% is set as the first bending point a. Let the point be the end point c. Next, the straight line connecting the origin and the first bending point a is defined as a first slope A, the straight line connecting the first bending point a and the second bending point b is defined as a second slope B, and the second bending point b and the end point Let the straight line connecting c be the third gradient C. The ratios of the first slope A, second slope B, and third slope C were determined, and a nonlinear function was set so that the third slope C coincided with conventional linear data.
Further, the compression rigidity of the upper elastic vertical spring was set to be 1000 times the third slope C.

[3. Modeling of laminated rubber bearing]
Although the compression rigidity of laminated rubber bearings also differs depending on the type and diameter of the bearing, and the reference surface pressure is also different from that of elastic sliding bearings, it was modeled based on the results of loading experiments, similar to elastic sliding bearings. That is, the laminated rubber bearing was modeled using a single vertical spring, and the settings were made as follows. Regarding the vertical spring of this laminated rubber bearing, the reference surface pressure was set to 15 N/mm ² , and the compression rigidity was determined in the same manner as for the elastic sliding bearing described above. As a result, the vertical spring of the laminated rubber support became a trilinear nonlinear function consisting of three straight lines, as shown in FIGS. 10 and 11. Further, the tensile rigidity of the vertical spring of the laminated rubber support was set to, for example, 1/10 of the third slope.
The elastic sliding bearings with a diameter of 1200 mm (SA80-1200-8.0×3), the laminated rubber bearings with a diameter of 1200 mm (R40-1200-9.0×26), and the laminated rubber bearings with a diameter of 1100 mm (R40 -1100-8.3×26), the compression stiffness of the laminated rubber is summarized as shown in FIG.

[4. Vibration analysis]
Input the NS phase and UD phase of the notification jMA-Kobe (level 2) multiplied by a predetermined multiplier into the above analysis model of a seismic isolation building, and The time history response of the vertical displacement and surface pressure of the elastic sliding bearing at Y5 street was determined.
Figure 13 shows the case where H1.5-V1.5 (horizontal motion 1.5 times, vertical motion 1.5 times) is used as the input earthquake motion, and Figure 14 shows the case where H1.5-V3.0 is used as the input earthquake motion. (Horizontal movement 1.5 times, vertical movement 3.0 times) is used.
In the case of H1.5-V1.5 shown in FIG. 13, the maximum lift amount of the compressed linear model is 0.071 cm, whereas the maximum lift amount of the compressed nonlinear model is 0.002 cm. Although a very small amount of lifting occurs in both compression models, it can be seen that the amount of lifting is suppressed overall in the compression nonlinear model.
In the case of H1.5-V3.0 shown in FIG. 14, significant lifting occurs around 15 to 17 seconds, similar to the case of H1.5-V1.5. Regarding the vertical displacement, the maximum displacement is 0.230 cm for the compression linear model and 0.119 cm for the compression nonlinear model, and as with H1.5-V1.5 shown in Figure 13, the compression nonlinear model is better than the compression linear model. It's suppressed. This is thought to be because the compressive stiffness of the elastic sliding bearing was simulated using a trilinear type, which increased the strain in the compressive direction due to long-term axial force and decreased the amount of uplift of the bearing. The maximum surface pressure when the bearing is seated after the maximum lifting occurs (16.6 seconds) is H1.5-V1.5, 16.8 N/mm ² for the compression linear model, and 17.5 N for the compression nonlinear model. / ^mm2 , both of which correspond to the standard surface pressure. In H1.5-V3.0, the compression linearity is 23.7N/mm ² and the compression nonlinearity is 23.3N/mm ² , which is less than the short-term allowable surface pressure. Regardless of the difference in the linear and nonlinear characteristics of compression stiffness, both models received the same amount of surface pressure, so the difference in the amount of lift had little effect on the surface pressure when seated.
As mentioned above, based on the vertical loading test of the elastic sliding bearing, we considered the nonlinear characteristics of the compressive stiffness and investigated the uplift behavior of the bearing in response to vertical motion. In the example, it was confirmed that the uplift of the elastic sliding bearing was reduced or eliminated compared to the conventional case.

According to this embodiment, there are the following effects.
(1) Regarding the laminated rubber bearing 20 and the laminated rubber 22 of the elastic sliding bearing 21 that constitute the seismic isolation layer 11, the relationship between the compressive axial force and the compressive displacement was made into a nonlinear function. As a result, it is possible to perform a realistic analysis of the behavior of the seismic isolation support during an earthquake, taking into account uplift, and to design a highly reliable seismic isolation building 1.
(2) The nonlinear function that indicates the relationship between the compressive axial force and the compressive displacement of the laminated rubber 22 is made trilinear (multiple polygonal lines) that approximates the analysis results of the simulation analysis, so the reliability in the design of the seismic isolation building 1 is improved. You can improve.

(3) In the design method for a seismically isolated building of the present invention, when modeling the seismic isolation bearing, the compressive stiffness is set to be low and nonlinear. As a result, it is possible to greatly evaluate the amount of subsidence displacement in a state where only long-term axial force is applied before an earthquake occurs, consistent with the actual situation, and the amount of potential energy due to subsidence becomes large, so vibration analysis can also be performed. The floating phenomenon no longer occurs as in actual observation records. Therefore, by setting the compressive stiffness of the analysis model of the seismic isolation bearing to be nonlinear and low, it is possible to model large strain energy to support the experimental results.

Note that the present invention is not limited to the above-described embodiments, and any modifications, improvements, etc. that can achieve the purpose of the present invention are included in the present invention.

1... Seismic isolation building 10... Lower structure 11... Seismic isolation layer 12... Upper structure 13... Column 20... Laminated rubber bearing 21... Elastic sliding bearing 22... Laminated rubber 23... Sliding plate 30... Lower flange 31... Laminated rubber main body 32... Upper flange P, Q... Experimental data a... First bending point b... Second bending point c... End point A... First slope B... Second slope C... Third slope

Claims (3)

A method for designing a seismically isolated building supported by laminated rubber bearings and/or elastic sliding bearings using laminated rubber, comprising:
An analytical model of the seismically isolated building is generated using the relationship between compressive axial force and compressive displacement of the laminated rubber as a nonlinear function, and vibration analysis is performed using the analytical model to design the seismically isolated building. Characteristic design method for seismically isolated buildings. A method for designing a seismically isolated building supported by laminated rubber bearings and/or elastic sliding bearings using laminated rubber, comprising:
The seismic isolation building includes a lower structure, a seismic isolation layer including the laminated rubber bearing or the elastic sliding bearing provided on the lower structure, and an upper structure provided on the seismic isolation layer. and,
An analysis step of generating an analytical model of the seismically isolated building, using the relationship between the compressive axial force and compressive displacement of the laminated rubber as a nonlinear function, and inputting horizontal and vertical seismic forces into the analytical model to obtain a response. and,
It is determined whether the response acceleration and the response displacement amount of the lower structure and the upper structure are respectively lower than predetermined threshold values, and if this determination is positive, the process moves to the next step and is negative. a first verification step of changing the design of the seismically isolated building and returning to the analysis step;
Determine whether at least one response value of the shear deformation amount, the vertical deformation amount, and the surface pressure of the seismic isolation support of the laminated rubber constituting the seismic isolation layer is each lower than a predetermined threshold, and make this determination. If the result is positive, the design is terminated; if the result is negative, the design of the seismically isolated building is changed and the process returns to the analysis process. A design method for seismically isolated buildings. A seismically isolated building supported by laminated rubber bearings and/or elastic sliding bearings using laminated rubber,
A seismically isolated building characterized in that the compression rigidity of the laminated rubber is determined by a non-linear function, and lifting of the laminated rubber bearing and/or the elastic sliding bearing is allowed.

Images