JP2022068948A - Base-isolated building provided with failsafe mechanism - Google Patents

Abstract

To provide a base-isolated building 1 provided with a failsafe mechanism 30 mitigating impact force upon collision of an upper structure 10 to a protection wall 23 without impeding clearance uc between the upper structure 10 and the protection wall 23 for the base-isolated building 1.SOLUTION: The base-isolated building 1 provided with the failsafe mechanism 30 is provided with a base isolation mechanism 22. The base-isolated building 1 is provided with the failsafe mechanism 30 in the upper structure 10 upper than the base isolation mechanism 22. The failsafe mechanism 30 includes a synchronous type mass damper 32 exhibiting a synchronous effect on at least one of secondary or higher unique oscillation modes of the base-isolated building 1.SELECTED DRAWING: Figure 1

Description

Application for application of Article 30, Paragraph 2 of the Patent Law Issuer name: "Architectural Institute of Japan", Publication name: "Architectural Institute of Japan 2020 Annual Conference Academic Lecture Summary / Architectural Design Presentation Summary", Publication date: "July 20, 2nd year of Reiwa"

The present invention relates to a seismic isolated building provided with a fail-safe mechanism.

The seismic isolated building includes a substructure including a foundation, for example, in which a seismic isolation mechanism is installed, and an upper structure supported by the seismic isolation mechanism. Suppress the transmission to.

In general, seismic isolated buildings are provided with a clearance between the side surface of the superstructure and the retaining wall to allow horizontal movement of the superstructure. In Patent Document 1, a rubber shock absorbing member is provided on the retaining wall to cushion the impact when the superstructure and the retaining wall collide with each other when a large horizontal shaking occurs in the seismic isolated building. Has been proposed.

Japanese Unexamined Patent Publication No. 2014-77229

However, according to the invention of Patent Document 1, since the rubber shock absorbing member is provided on the retaining wall, the clearance is reduced by the thickness of the shock absorbing member, or the clearance is reduced by the thickness of the shock absorbing member. Needed to be set large.

Therefore, the present invention provides a seismic isolated building provided with a fail-safe mechanism that alleviates the impact force when the superstructure collides with the retaining wall without obstructing the clearance between the superstructure and the retaining wall in the seismic isolated building. The purpose is to provide.

The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following aspects or application examples.

[1] One aspect of the seismic isolated building provided with the fail-safe mechanism according to the present invention is
It is a seismic isolated building equipped with a seismic isolation mechanism.
The seismic isolated building has a fail-safe mechanism in the upper structure above the seismic isolation mechanism.
The fail-safe mechanism is characterized by including a tuned mass damper that exerts a tuned effect on at least one of the secondary or higher natural vibration modes of the seismic isolated building.

[2] In one aspect of a seismic isolated building equipped with the above fail-safe mechanism,
The fail-safe mechanism can be provided in the lower layer of the lower half of the superstructure.

[3] In one aspect of a seismic isolated building equipped with the above fail-safe mechanism,
The tuning mass damper may be optimized to minimize the peak value of the transfer function of the load shear force or interlayer displacement in the layer in which the tuning mass damper is installed or in a specific layer different from the layer. can.

According to one aspect of the seismic isolated building provided with the fail-safe mechanism according to the present invention, the impact force when the superstructure collides with the retaining wall is alleviated without obstructing the clearance between the superstructure and the retaining wall. ..

It is a schematic diagram of the seismic isolated building which concerns on this embodiment. This is a mass point model of a seismic isolated building according to this embodiment. It is the response ratio to the maximum value distribution of the load shear force of the main frame at the time of earthquake input and the maximum value of the load shear force of the main frame when the fail-safe mechanism is not present. It is a time history acceleration waveform of the seismic input wave. It is the layer shear force and Hilbert-Huang conversion (HHT) analysis result of the seismic isolation mode and the collision mode in each layer of the seismic isolation building. It is a figure which shows the real part of the 2nd and 3rd order complex eigenmode of the main frame model. It is a figure which shows the real part of the complex eigenmode from the 1st order to the 6th order of a main frame model and a tuning type mass damper addition model.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unreasonably limit the content of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

One aspect of the seismic isolated building provided with the fail-safe mechanism according to the present embodiment is a seismic isolated building provided with a seismic isolation mechanism, and the seismic isolated building fails on an upper structure above the seismic isolation mechanism. The fail-safe mechanism comprises a tuned mass damper that exerts a tune effect on at least one of the secondary or higher intrinsic vibration modes of the seismic isolated building.

1. 1. Outline of Seismic Isolation Building With reference to FIG. 1, a seismic isolation building 1 provided with a fail-safe mechanism 30 according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram of a seismic isolated building 1 according to the present embodiment.

As shown in FIG. 1, the seismic isolation building 1 includes a seismic isolation mechanism 22. The seismic isolated building 1 is configured such that the horizontal relative positions of the superstructure 10 and the foundation 21 can be changed via the seismic isolation mechanism 22. The seismic isolated building 1 is provided with a fail-safe mechanism 30 in the upper structure 10 above the seismic isolated mechanism 22.

The upper structure 10 has, for example, a 6-story steel-framed structural frame whose lower end is supported by the seismic isolation mechanism 22. The superstructure 10 may be a reinforced concrete structure, a steel-framed reinforced concrete structure, or the like. The superstructure 10 can have two or more floors, and is particularly applicable to high-rise buildings. The outer peripheral surface of the superstructure 10 is the side surface 12. The lower half of the upper structure 10 below the third floor is the lower layer 14.

The lower structure 20 is, for example, a retaining wall 23 formed with a predetermined clearance _uc from the foundation 21, the seismic isolation mechanism 22 installed on the foundation 21, and the side surface 12 of the upper structure 10. And prepare. The clearance _uc is a distance that allows the superstructure 10 to move horizontally with respect to the foundation 21, and is set according to an earthquake assumed in the seismic isolated building 1. Therefore, for an earthquake exceeding the assumption of the seismic isolated building 1, the clearance _uc may not be sufficient and the side surface 12 of the superstructure 10 may collide with the retaining wall 23.

The seismic isolation mechanism 22 is a mechanism that supports the superstructure 10, reduces horizontal shaking such as an earthquake transmitted to the superstructure 10, and imparts a force to restore the change in the relative position of the superstructure 10. Is. As the seismic isolation mechanism 22, known isolators such as laminated rubber, elastic sliding bearings, and rolling bearings can be adopted, and a damper for imparting damping may be further provided.

2. 2. Fail-safe mechanism The fail-safe mechanism 30 will be described with reference to FIGS. 1 to 3. FIG. 2 is a mass point system model 1a of the seismic isolated building 1 according to the present embodiment, and FIG. 3 shows the maximum value distribution of the load shear force of the main frame at the time of earthquake input and the main frame when the fail-safe mechanism is not provided. It is the response ratio to the maximum value of the burden shear force of.

As shown in FIG. 1, the fail-safe mechanism 30 is provided in the superstructure 10. The fail-safe mechanism 30 is preferably provided in the lower layer portion 14 of the lower half of the upper structure 10. Since the vibration at the time of the retaining wall collision propagates from the lower layer to the upper layer, the increase in response at the time of impact can be effectively suppressed by providing the fail-safe mechanism 30 in the lower layer portion 14. In the present embodiment, the fail-safe mechanism 30 is provided so as to be bridged between the first floor and the third floor, but the present invention is not limited to this, and the fail-safe mechanism 30 may be provided only on one floor, for example, on the third floor.

The mass point system model 1a in FIG. 2 is a seismic isolated building 1 as an equivalent shear type 6 mass point system model. The seismic isolation mechanism 22 is composed of laminated rubber, elastic sliding bearings, and an oil damper. The laminated rubber is an elastic shear spring, the elastic sliding bearing is a shear spring with a fully elasto-plastic restoring force, and the oil damper has bilinear characteristics. Each was modeled as a Maxwell model. The superstructure 10 is modeled by a trilinear type elasto-plastic spring, and the structural damping of the main frame can be set to, for example, 2% in the initial rigidity proportional type with respect to the primary natural frequency at the time of fixing the foundation. Between the side surface 12 of the seismic isolation building 1 and the retaining wall 23, the retaining wall rigidity (retaining wall spring kW), the ground rigidity (ground spring _{kg), and the damping (ground dashpot C g ) are} provided through the clearance uc. Set. The fail-safe mechanism 30 is set in the area surrounded by the broken line.

The fail-safe mechanism 30 includes a tuning mass damper 32 that exerts a tuning effect on at least one of the secondary or higher natural vibration modes of the seismic isolated building 1. This is because when the seismic isolated building 1 collides with the retaining wall 23, the vibration component of the second order or higher is predominant as the vibration mode peculiar to the building. The synchronized mass damper 32 is attached to, for example, a steel frame support member 33 that connects the first floor and the third floor. A plurality of synchronized mass dampers 32 may be provided in the superstructure 10. As the secondary or higher natural vibration mode to be tuned, it is preferable to target, for example, a secondary mode or a tertiary mode in which the amplitude in the lower layer portion 14 is large. The tuning effect of the tuning type mass damper 32 is the interlayer displacement of a specific layer or the burden on the main structure of the superstructure 10 caused by the impact when the side surface 12 of the superstructure 10 collides with the retaining wall 23 in the selected mode. It is to reduce the shear force, preferably to minimize it. The tuning procedure will be described later using examples.

As shown by modeling in FIG. 2, the fail-safe mechanism 30 includes a mass body (equivalent mass m _d ) of the tuning type mass damper 32, a viscous member (viscosity coefficient cd ₎ of the tuning type mass damper 32, and a support member 33. It can be configured with (support member rigidity k _b ). Although the viscous member is shown by a dash pot in FIG. 2, the viscous member may have elasticity (spring component) in addition to viscosity (damping component). As the synchronized mass damper 32, a known mechanism, for example, a vibration control device disclosed in Japanese Patent Application Laid-Open No. 2016-173014 and a mounting structure thereof can be adopted.

The tuning mass damper 32 may be optimized to minimize the peak value of the transfer function of the load shear force or interlayer displacement in the layer in which the tuning mass damper 32 is installed or in a specific layer different from the layer. can. The specific layer may be any floor as long as it is above the seismic isolation layer (foundation 21), but since the vibration at the time of collision propagates from the bottom to the top, the floor on which the synchronized mass damper 32 is installed. It is preferable to use a layer directly above because it can suppress the propagation of vibration to the upper layer. When the tuning type mass damper 32 is bridged from the 1st floor to the 3rd floor as in the present embodiment, the specific layer may be set according to, for example, the load shear force or the interlayer displacement in the 4th floor which is the immediately above layer. preferable. In this embodiment, an example using a load shear force will be described.

The left side of FIG. 3 shows the maximum value distribution of the load shear force of the main frame at the time of earthquake input, and the right side of FIG. 3 shows the load shear of the damper application model provided with the synchronized mass damper 32 based on the result on the left side. It is the response ratio obtained by dividing the maximum value of the force by the maximum value of the load shear force of the original design model without a damper. As shown in FIG. 3, by providing the fail-safe mechanism 30, the load shear force of the fourth layer or higher is reduced, and in particular, the load shear force of the sixth layer near the upper end is reduced by, for example, 20%.

As described above, according to the seismic isolated building 1, the impact force when the superstructure 10 collides with the retaining wall 23 is alleviated without obstructing the clearance _uc between the superstructure 10 and the retaining wall 23. Can be done. Even if the retaining wall 23 is provided with a rubber shock absorbing member, it is easy to secure a clearance _uc by downsizing the shock absorbing member.

The procedure for tuning the tuning type mass damper 32 will be specifically described with reference to FIGS. 1 to 7. FIG. 4 shows the time history acceleration waveform of the seismic input wave, and FIG. 5 shows the layer shear force of the seismic isolation mode and the collision mode in the second, fourth, and sixth layers of the seismic isolated building 1 (upper stage of each layer). Figure) and the Hilbert-Huang transformation (HHT) analysis results (lower figure of each layer), FIG. 6 is a diagram showing the real part of the quadratic and tertiary complex eigenmodes of the main frame model. FIG. 7 is a diagram showing a real part of a complex eigenmode from the first order to the sixth order of the main frame model and the synchronized mass damper addition model. It should be noted that this embodiment is simulated based on FIGS. 1 and 2, and the result is shown in FIG. Further, in FIG. 5, the instantaneous amplitude value of the layer shear force is shown by a gradation, and the closer to black, the larger the amplification factor.

The tuning procedure can be executed, for example, by confirming the dominant frequency, determining the installation floor of the tuning type mass damper 32, deriving the optimum parameters, and confirming the effect.

A. Confirmation of predominant frequency When the side surface 12 of the seismic isolated building 1 in FIG. 1 collides with the retaining wall 23 due to an earthquake exceeding the assumption, the original design model is set in order to confirm the predominant frequency at the time of collision with the original design model. , The seismic motion for analysis was set, and the predominant frequency at the time of collision when the seismic motion for analysis was applied to the original design model was analyzed.

The portion of FIG. 2 excluding the fail-safe mechanism 30 is the original design model. The original design model was a 6-story steel-framed foundation seismic isolated building, and was an equivalent shear type 6-mass point system model. The seismic isolation mechanism 22 is composed of, for example, laminated rubber, elastic sliding bearings, and an oil damper. Laminated rubber can be modeled as an elastic shear spring, and elastic sliding bearings can be modeled as a fully elasto-plastic restoring force. The oil damper can be a Maxwell model with bilinear characteristics. The upper structure was modeled with a trilinear type elasto-plastic spring, and the structural damping of the main frame was set to 2% in the initial rigidity proportional type with respect to the primary natural frequency when the foundation was fixed. In addition, the clearance _{uc between the side surface 12 of the seismic isolation building 1 and the retaining wall 23 is set to 600 mm, and the retaining wall rigidity (retaining wall spring k w )} , ground rigidity (ground spring k _g ), and damping (ground dashpot C _g ) are set. It was set between the retaining wall 23 and the retaining wall 23.

The seismic motion that the seismic isolated building 1 is considered to collide with the retaining wall 23 is mainly considered to be an earthquake caused by a trench-type long fault having a long duration and a long-period pulse wave caused by a fling step or a directional pulse. Here, the EW component of the Taiwan Central Weather Bureau TCU068 observation record of the 1999 Chi-Chi earthquake was used for long-period pulse waves that are more likely to collide with the retaining wall 23. The input magnification was adjusted so that the maximum horizontal displacement of the seismic isolation mechanism 22 when there was no retaining wall 23 was 650 mm. The time history acceleration waveform of the input wave is shown in FIG.

Since the non-linear behavior is predominant at the time of a retaining wall collision, for example, the Hilbert-Huang Transform (HHT) (HHT) (Huang et al.), Which can extract instantaneous frequency characteristics and can be applied to signal analysis with strong unsteadiness. (1998): The Empirical Mode Decomposition Method and the Hilbelt Spectrum for Non-Stationary Time Series Analysis, Proc. T. Soc. London A, Vol.454, pp.903-995.) can.

As an analysis procedure, first, a time history response analysis is performed on the original design model, the layer shear force time history waveform of each layer is obtained, and the empirical mode decomposition method (EMD) is applied to the obtained layer shear force time history waveform. Then, it is decomposed into a simple natural vibration mode (IMF). Next, assuming that the seismic isolation mode is predominant on the low frequency side and the mode excited by collision is predominant on the high frequency side, HHT analysis is performed on each decomposed IMF to correspond to the maximum instantaneous frequency amplitude in the main moving parts. For example, the total of IMFs having a predominant frequency of 0.4 Hz or less is set as the seismic isolation mode, and the total of the IMFs having a frequency higher than that is set as the collision mode, and HHT analysis is performed on both sides.

As shown in FIG. 5, the seismic isolation mode does not change significantly before and after the collision (the vertical line in the figure indicates the collision time), whereas the collision mode is 4 Hz in the collision floor (second layer) immediately after the collision. It was found that the above high frequency band was dominant (black color became darker), and then the component near 2 Hz was dominant as it propagated to the upper layer. Therefore, in the superstructure 10, the dominant frequency can be confirmed immediately after the collision, and in this example, it can be confirmed that the component near 2 Hz is dominant. Although not shown, similar results were obtained by simulating with other seismic motions, and similar results were obtained by reducing the rigidity and damping.

Table 1 shows the calculation of the natural frequency (f (Hz)) and damping constant (h) in each mode by performing complex eigenvalue analysis of the original design model using an equivalent linearization model with the seismic isolation layer clearance ultimate displacement (600 mm). The result of was obtained.

From Table 1, it can be confirmed that the predominant component of about 2 Hz obtained by HHT analysis is approximately an intermediate value between the second order (1.26 Hz) and the third order (2.5 Hz). Since the higher-order modes separated during the HHT analysis contain a plurality of mode components, it is considered that an intermediate value between the second and third orders was detected. From the above, it is considered that these two modes are mainly excited by the collision, and the parameters of the tuned mass damper shown in the following sections are set with the main purpose of suppressing the amplification of both.

B. Determining the floor on which the synchronous mass damper is installed When a retaining wall collides, the impact force input to the floor directly above (1st floor) of the seismic isolation mechanism 22 propagates to the upper floors as an ascending wave. Therefore, in order to suppress the response amplification in the upper floors, it is effective to install the tuning type mass damper 32 in the lower layer portion 14 to block the amplification of the dominant component.

As shown in the real part of the second-order and third-order complex eigenmodes to be controlled in FIG. 6, the interlayer mode of the lower layer portion 14 in the mode is not larger than that of the upper layer portion, so that more efficient control can be performed. Therefore, it is preferable to install the tuning type mass damper 32 so that the mode amplitude difference of the target order becomes large, for example, connecting the first floor and the third floor by layer skipping.

C. Derivation of optimum parameters A method of deriving the optimum parameters of the damper that minimizes the load shear force of the main frame in a specific layer by numerical optimization calculation will be described.

Calculation that the horizontal forced external force F acts on the floor directly above the seismic isolation layer (1st floor) with respect to the equivalent linearization model with the seismic isolation layer clearance reaching displacement (600 mm) shown in the left part of the clearance uc in _FIG . Think of a model. When the force balance equations of each floor are added up from the upper floor with the inter-story displacement δ as a variable, the vibration equation for this calculation model is expressed by the following equation (1). Here, M, C, and K are the main frame mass, the viscosity coefficient, and the rigidity.

The damping force (D) of the tuned mass damper 32 is represented by the following equation (2).

From the above equation (1), the interlayer displacement δ is obtained by the following equation (3) using the transfer function G.

From this, the transfer function Q _j / F of the load shear force Q _j of the main frame of the j layer can be obtained by the following equation (4).

An optimization calculation is performed for the above equation (4), and the support member rigidity kb and the damper that minimize the peak value of the transfer function after the secondary mode of the fourth layer (j layer), which is the layer directly above the damper installation layer, and the _damper . The viscosity coefficient _cd of was obtained. The j layer may be a damper installation layer, but for the above reason, it is preferably a specific layer other than the damper installation layer, and by minimizing the transfer function of the fourth layer close to the seismic isolation layer, The aim was to suppress vibration propagation to the upper layers. A Generalized Rediced Gradient (GRG) algorithm (generalized reduction gradient method) was used as the solution of the optimization calculation, and a fixed-point theoretical solution was given as the initial value.

From the eigenmode of FIG. 6, the fixed-point theoretical solution was obtained for the tertiary mode in which a mode amplitude larger than that of the secondary mode can be obtained. The peak value of the transfer function ( _Q4 / F) by the above optimization calculation with the mass ratio μ to the generalized mass of the tertiary mode of the main frame as a parameter (μ = 0.05 to 0.11 @ 0.01). Asked.

In the peak value obtained by the optimization calculation, the peak value of the transfer function ( _Q4 / F) in the secondary mode to be controlled showed an almost constant value, and no performance difference due to the mass ratio μ was observed. Therefore, the mass ratio μ = 0.09, in which the peak value of the primary mode showed the minimum value, was adopted as the optimum parameter used for the response analysis described later.

Using the damper parameter with a mass ratio of μ = 0.09, a complex eigenvalue analysis was performed on a model with a tuned mass damper 32 (hereinafter, “damper-added model”). The real part of the complex eigenmode is shown in FIG.

As shown in FIG. 7, there is a large mode difference between the main frame (solid line) and the damper (dashed line) in a plurality of modes from the 3rd to the 5th order, and it is a mode type in which the damper works effectively. It could be confirmed. Further, even in the secondary stage, there is a slight mode difference between the main frame and the damper, and the suppression effect by the damper can be expected.

D. Effect confirmation Response analysis using the optimum parameters was performed to verify the effect of amplification suppression during a retaining wall collision.

In the damper application model of FIG. 2, the damper parameters at a mass ratio μ = 0.09 are that the equivalent mass md of the tuned mass damper 32 is 238.7 ton, the viscosity coefficient cd is _{0.288 kNs} / mm, and the rigidity of the supporting member. Response analysis was performed when the retaining wall collided with k _b set to 169.9 kN / mm. The result is shown in FIG. In modeling the tuning mass damper 32, the viscosity coefficient _cd is a linear dashpot and the axial force limiting mechanism is not considered in order to clarify the control effect for the higher-order mode, which is the purpose of this study. ..

As shown in FIG. 3, the response was reduced compared to the original design model in the fourth and higher layers optimized when deriving the damper parameters, and the targeted effect could be confirmed. The reduction effect in the uppermost layer was the highest, and the reduction rate was about 20%.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes substantially the same configurations as those described in the embodiments (eg, configurations with the same function, method, and result, or configurations with the same purpose and effect). The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the present invention includes a configuration having the same action and effect as the configuration described in the embodiment or a configuration capable of achieving the same object. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

1 ... Seismic isolation building, 1a ... Seismic isolation model, 10 ... Upper structure, 12 ... Side, 14 ... Lower layer, 20 ... Lower structure, 21 ... Foundation, 22 ... Seismic isolation mechanism, 23 ... Retaining wall, 30 ... Fail-safe mechanism, 32 ... Synchronized mass damper, 33 ... Support member, _cd ... Viscosity coefficient, _md ... Equivalent mass, _kb ... Support member rigidity, _kg ... Ground spring, _kW ... Retaining wall spring, C _g … Ground dashpot, _uc … clearance

Claims (3)

It is a seismic isolated building equipped with a seismic isolation mechanism.
The seismic isolated building has a fail-safe mechanism in the upper structure above the seismic isolation mechanism.
The fail-safe mechanism includes a tuned mass damper that exerts a tuning effect on at least one of the secondary or higher natural vibration modes of the seismic isolated building. .. In claim 1,
The fail-safe mechanism is a seismic isolated building provided with a fail-safe mechanism, which is provided in the lower layer of the lower half of the superstructure. In claim 1 or 2,
The tuning mass damper is optimized so that the peak value of the transfer function of the load shear force or the interlayer displacement in the layer in which the tuning mass damper is installed or a specific layer different from the layer is minimized. A seismic isolated building with a fail-safe mechanism.

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