JP4931491B2 - A method for determining a natural period of a structure, a method for designing a structure, and a structure. - Google Patents

Description

The present invention relates to a method for determining a natural period of a structure, a method for designing a structure, and a structure in the case where a vibration damping device that suppresses the vibration of the structure with respect to earthquake motion is provided in the structure using the rotational inertia of the auxiliary mass. About.

  In the seismic design of buildings, which are structures, response deformation increases if the response absolute acceleration is suppressed by a viscous damper, etc. or a vibration-isolating structure. If it tries to suppress, the response absolute acceleration increases, and it is generally considered difficult to perform a design that suppresses both the response absolute acceleration and the response deformation.

Here, the present applicant configures a vibration system in which the outer ring and the inner ring can be rotated relative to each other. The element that generates kinetic energy in accordance with the speed difference between the outer ring and the inner ring is an inertial connection element. We propose a vibration damping mechanism that reduces the response absolute acceleration and response deformation by extending the period of, reducing the damping constant, exhibiting the effect of reducing the input to ground acceleration. (Patent Document 1)
The vibration control mechanism includes a shaft body, a cylindrical auxiliary mass body into which the shaft body is inserted, a holding body that rotatably supports the auxiliary mass body, an outer peripheral surface of the shaft body, and an inner peripheral surface of the auxiliary mass body. And a screwing means for changing the axial displacement of the shaft body in the axial direction to the rotational displacement of the auxiliary mass body, and a mechanism for changing the linear motion displacement of the shaft body to the rotational displacement of the auxiliary mass. It has become.
According to this vibration control mechanism, an inertial force is generated by rotating an auxiliary mass using a rotary lever mechanism, so that an earthquake caused by ground motion or the like does not move the auxiliary mass greatly with respect to the structure. Input can be reduced.

However, regarding the vibration damping mechanism using the inertia connecting element, the response absolute acceleration and response displacement state when the natural period of the structure is changed are unknown. For this reason, in consideration of the trade-off relationship described above, depending on the natural period of the structure to be designed, the absolute acceleration increases by using the vibration damping mechanism, and an excessive response shear force acts on the building.
Japanese Patent Application No. 2004-317077

  The present invention has been made in view of the above-described facts, and an object thereof is to obtain a method for determining a natural period of a structure in which an inertial connection element is used, a method for designing a structure, and a structure.

The invention according to claim 1, by utilizing the rotational inertia of the auxiliary mass mf A method for determining the natural period of the swing suppressing inertia connecting element structure used for the ground motion, have the auxiliary mass mf displacement X of the structure when a predetermined ground motion is given to the system without the mass m of the structure, the mass m to be represented using the auxiliary mass inside diameter and a ratio of the outer diameter of the displacement amplification factor βf '= Βf ² · mf, damping coefficient c, spring constant k, and vibration equation obtained as m' = 0 in equation (7) obtained as equation (7), or the displacement X, natural circular frequency ω, viscosity The maximum displacement Xmax calculated by performing a one-mass system response analysis using the vibration equation with η = 1 in the equation (8) obtained as the input reduction effect η obtained by the damping constant h, the ground motion displacement Y, and the mass m ′. , Natural circular frequency ω = 2π as natural period T / T is the pseudo speed ωX, the natural period T is changed, and the response spectrum Sa in which the value of the pseudo speed ωX is plotted is obtained from the mass m of the structure and the auxiliary mass mf (9 ) And the ground motion acceleration component (1-η) y ″ max determined by the input reduction effect η determined using the equation and the maximum acceleration y ″ max of the earthquake motion, and the natural circular frequency of the structure. The response frequency Sb obtained by plotting the value of the pseudo speed Vb by changing the natural period T using the natural circular frequency ω = 2π / T as the pseudo speed Vb divided by ω , and the response A periodic point Tv at which the magnitudes of the pseudo speed ωX of the spectrum Sa and the pseudo speed Vb of the response spectrum Sb are interchanged is obtained , and a natural period shorter than the periodic point Tv is defined as a natural period of the structure. And the process It is characterized by having.

  According to the above configuration, when designing a structure to be damped using an inertia connecting element, the pseudo speed response spectrums Sa and Sb are obtained in advance, and the periodic points at which the magnitudes of the pseudo speed ωX and the pseudo speed Vb are switched. By obtaining Tv, the conversion point of absolute acceleration when pseudo inertial connection element is used and when it is not used can be known.

  Further, a period is determined from a response spectrum Sa of a pseudo speed when a predetermined ground motion is given to a system having no auxiliary mass mf and a response spectrum Sb obtained by using past maximum acceleration data y ″ max of the ground motion. Since the point Tv is obtained and it is not necessary to solve the vibration equation including the auxiliary mass mf, the periodic point Tv can be easily obtained.

  Therefore, it is possible to easily determine the natural period of the structure that can obtain the damping effect of the inertial connection element, and it is possible to effectively use the inertial connection element.

  Furthermore, for a structure that has already been built, the vibration damping effect by the inertial connection element can be obtained by reinforcing the structure so as to have the natural period obtained by the natural period determining method.

According to a second aspect of the present invention, there is provided a structure design method using an inertia connecting element that suppresses a shake with respect to seismic motion using the rotational inertia of the auxiliary mass mf . Mass m ′ = βf ² · expressed using displacement X 1 of the structure when a seismic motion is applied, mass m of the structure, displacement amplification factor βf which is a ratio of the inner diameter to the outer diameter of the auxiliary mass. mf, a damping coefficient c, a spring constant k, and a vibration equation where m ′ = 0 in the equation (7) obtained as the ground motion displacement Y, or the displacement X, the natural circular frequency ω, the viscous damping constant h, As the natural period T, the maximum displacement Xmax calculated by performing a one-mass system response analysis using the vibration equation with η = 1 in the equation (8) obtained as the input reduction effect η by the ground displacement Y and the mass m ′ Multiplying natural circular frequency ω = 2π / T Is a pseudo speed ωX, the natural period T is changed, and the response spectrum Sa in which the value of the pseudo speed ωX is plotted is obtained, and the mass m and the auxiliary mass mf of the structure are used to calculate the response spectrum Sa. The ground motion acceleration component (1-η) y ″ max obtained by the required input reduction effect η and the maximum acceleration y ″ max of the ground motion is divided by the natural circular frequency ω of the structure. was a pseudo speed Vb, using the peculiar circular vibration frequency ω = 2π / T, and obtaining a response spectrum Sb that by changing the natural period T is plotted the value of the pseudo speed Vb, the pseudo of the response spectrum Sa And a step of obtaining a periodic point Tv at which the magnitude of the pseudo velocity Vb of the response spectrum Sb is switched, and a structure having a natural period shorter than the periodic point Tv is designed. It is characterized by a door.

  According to the above configuration, when designing a structure to be damped using an inertia connecting element, the pseudo speed response spectrums Sa and Sb are obtained in advance, and the periodic points at which the magnitudes of the pseudo speed ωX and the pseudo speed Vb are switched. By obtaining Tv, it is possible to determine the natural period of the structure from which the damping effect of the inertial connection element can be obtained, so that the inertial connection element can be used effectively.

The invention according to claim 3 is a structure in which an inertia connecting element that suppresses the shaking with respect to the earthquake motion using the rotational inertia of the auxiliary mass mf is used, and the method for determining the natural period of the structure according to claim 1 or The structure is designed using the structure designing method according to claim 2 .

  According to the above configuration, the inertial connection element is a structure obtained by obtaining the response spectrums Sa and Sb of the pseudo speed in advance and obtaining the periodic point Tv where the magnitudes of the pseudo speed ωX and the pseudo speed Vb are switched. Can be used effectively.

  Since the present invention is configured as described above, it is possible to determine the natural period of the building that can suppress the absolute acceleration and deformation by effectively using the inertial connection element.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a vibration damping device 34 according to the embodiment.

  In FIG. 1, a floor 12 (lower slab) is provided with a base 12 that can remove reaction force and transmit force. A shaft 14 is fixed to the base 12 in a cantilever state so as to be parallel to the floor portion 10.

  A right male thread groove 16 is formed on the outer peripheral surface of the shaft 14 from the center to the tip. The shaft 14 is inserted into a cylindrical auxiliary mass 20 in which an internal thread that engages with the right external thread groove 16 is engraved on the inner peripheral surface.

  Both ends of the auxiliary mass 20 are rotatably held by a cylindrical holder 22. Flange 24 is formed at both ends of the holder 22, and is in contact with the end 20 </ b> A of the auxiliary mass 20. Thereby, although the auxiliary | assistant mass 20 rotates, the movement to an axial direction is controlled.

  Here, the energy absorbing member L is installed between the inner peripheral surface of the holder 22 and the outer peripheral surface of the auxiliary mass 20. When the energy absorbing member L is filled with a viscous liquid (for example, mineral oil or silicon oil), it has a mass + viscous effect, and if a friction material is incorporated, it has a mass + rigidity effect. Of course, when the two are combined, a damper having mass + rigidity + viscosity is obtained.

  Furthermore, the holder 22 is suspended from the ceiling portion 28 by a suspension member 32, and when the floor portion 10 and the ceiling portion 28 of the building 30 are relatively moved by an earthquake motion or the like, the shaft 14 moves integrally with the floor portion 10, The auxiliary mass 20 is configured to move integrally with the ceiling portion 28.

  Next, the operation of the vibration damping device 34 will be described.

  As illustrated in FIG. 2, it is assumed that the building 30 is deformed to the right side due to earthquake motion or the like, and the floor 10 and the ceiling 28 are relatively moved. Then, the shaft 14 provided on the floor 10 is linearly displaced in parallel with the ceiling 28 with respect to the ceiling 28. On the other hand, since the auxiliary mass 20 moves integrally with the ceiling portion 28, relative displacement occurs between the shaft 14 and the auxiliary mass 20.

  Since the shaft 14 and the auxiliary mass 20 are engaged with the right male screw groove 16 and the female screw, the relative linear displacement of the shaft 14 is changed to the rotational displacement of the auxiliary mass 20. That is, the auxiliary mass 20 is rotated by a rotary lever mechanism, and the earthquake input due to ground motion or the like can be reduced on the spot without the auxiliary mass 20 moving greatly with respect to the structure due to the rotational inertia force. For this reason, the vibration of the building 30 can be suppressed.

  Further, since the energy absorbing member L is installed between the inner peripheral surface of the holder 22 and the outer peripheral surface of the auxiliary mass 20, the rotational kinetic energy of the auxiliary mass 20 is attenuated by rotating the auxiliary mass 20. Can do.

  Here, the principle of the vibration damping device 34 will be described using a schematic diagram.

  In the following, an element that connects the nodes of the rotating vibration system such as the auxiliary mass 20 and generates kinetic energy in accordance with the speed difference between the nodes will be referred to as an inertial connection element.

  FIG. 3 shows a schematic diagram of the inertial connection element.

  In FIG. 3, assuming that the inner peripheral surface of the auxiliary mass 20 is applied with an acceleration α in the tangential direction due to the linear displacement of the shaft 14, the displacement amplification factor βf of the linear motion displacement of the shaft 14 is The ratio of the inner diameter r1 to the outer diameter r2 is βf = r2 / r1.

Therefore, the magnitude of the inertial force for accelerating the mass mf of the auxiliary mass 20 is inertial force: F = mf ( βf · α) .

Force that pushes the inner peripheral surface of the auxiliary mass 20 in the tangential direction: reaction force R is R = βf · F = βf · mf ( βf · α) = βf ² · mf · α = m′α , that is, outside the system Inertial force having a magnitude corresponding to the mass m ′ = βf ² · mf is generated with respect to the acceleration α applied in the tangential direction of the inner circumferential surface of the auxiliary mass 20.

  It should be noted that the amount of rotation of the auxiliary mass 20 can be determined by changing the linear displacement of the shaft 14 depending on the size of the lead of the right male screw groove. For example, by reducing the lead, the rotational speed of the auxiliary mass 20 with respect to the amount of linear motion displacement of the shaft 14 is increased, and the acceleration α is also increased.

  Here, consider a vibration system in which a rotating body such as the auxiliary mass 20 is incorporated in a one-mass system vibration system as shown in FIG. The rotational motion of the rotating body is only affected by the displacement x of the structure from the ground of the mass point, and is not directly affected by the ground motion displacement y.

  Assuming that the kinetic energy of the entire system is T, the energy dissipation function is F, the potential energy is V, the spring constant is k, and the damping coefficient is c,

(1)

(2)

(3)
And the Euler-Lagrange equation is

(4)

(5)

(6)

(7)
Here, the relational expression 2hω = c / (m + m ′ ), ω2 obtained by dividing both sides of the expression (7) by (m + m ′ ) and using the relational expression of the viscous damping constant h, the circular frequency ω, and the critical damping. When formula (7) is rearranged using = K / (m + m ′ ), formula (8) is obtained.

(8)
In the equation (8), η means an input reduction effect due to the mass m ′, and has the relationship of the equation (9). η = 1 indicates a state where the inertia connecting element is not used.

(9)
Equation (7) or (8) is a vibration equation for analysis. Further, the circular frequency ω can be converted using the relationship of ω = 2π / T, where T is the natural period of the structure.

  By solving the vibration equation of the equation (7) or (8) by giving the viscous damping constant h, the input reduction effect η, and the ground motion acceleration y ″ that is the data of the past earthquake motion, the natural period T and the structure A relative response spectrum with displacement X, velocity x ′, and acceleration x ″ is obtained. Here, the displacement X of the structure represents the response deformation.

  Further, the absolute acceleration (x ″ + y ″) including the ground acceleration is obtained from the vibration equation of the equation (7) or the equation (8).

  Next, analysis of response spectrum using actual earthquake motion data will be described.

  FIG. 5 is a graph showing a state in which the response spectrum of the natural period T and the relative displacement X in the past earthquake motion in each region changes with the input reduction effect η. Note that EL_CENTRO1940 (NS), HACHINOHE 1968 (NS), and TAFT1952 (EW) were used as earthquake motion data.

  As shown in FIGS. 5a to 5c, in each natural period, the relative displacement of η = 1 without using the inertial connection element is the largest, and the relative displacement becomes smaller as the value of η becomes smaller than 1. It can be seen that the relative displacement is reduced when the element is used.

  On the other hand, FIG. 6 shows a state in which the response spectrum of the natural period T with h = 0.05 and the absolute acceleration (x ″ + y ″) in the past earthquake motion in each region changes due to the input reduction effect η. It is the shown graph. Note that EL_CENTRO 1940 (NS), HACHINOH 1968 (NS), and TAFT 1952 (EW) were used as the seismic motion data as in FIG.

  6A to 6C, depending on the value of η, the absolute acceleration (x ″ + y ″) due to the input reduction effect η with the natural period T = 1.5 to 2.0 s as a boundary. It can be seen that the tendency of reduction is different.

  In a periodic region shorter than the natural period T = 1.5 to 2.0 s, the value of the absolute acceleration (x ″ + y ″) decreases as the value of the input reduction effect η decreases.

  On the other hand, in the period region longer than the natural period T = 1.5 to 2.0 s, the value of the absolute acceleration (x ″ + y ″) increases as the value of the input reduction effect η decreases. It gradually converges to (1-η) y ″.

This convergence is obtained by substituting x ″ = − ηy ″ obtained as C = 0, k = 0, m ′ ≠ 0 in (x ″ + y ″) in the vibration equation of Equation (7), and x It can also be seen from the fact that “+ y” = − ηy ″ + y ″ = (1−η) y ″.

  In this way, even if it is attempted to reduce the absolute acceleration (x ″ + y ″) using the inertia connecting element, depending on the natural period T, the absolute acceleration (x ″ + y ″) may be increased, and an excessive shear force may be applied. When using elements, it is important to determine the natural period T of the structure.

  Next, a method for determining the natural period in which the inertial connection element can be effectively used will be described.

  FIG. 7 shows, as an example, the natural period T and the response spectrum of each pseudo speed when the viscous damping constant h = 0.4 using the EL_CENTRO1940 (NS) seismic motion data.

  The graph of the response spectrum of the pseudo speed is a triaxial graph, and in FIG. 7, the direction from the upper left to the lower right indicates the decreasing direction of the absolute acceleration. Further, the direction from the upper right to the lower left indicates the direction of decreasing displacement. Thereby, absolute acceleration, speed, and displacement can be read from the graph of the response spectrum of the pseudo speed.

The response spectrum Sa has a natural circular frequency ω as the maximum displacement Xmax calculated by performing a one-mass system response analysis using the vibration equation of Equation (7) where m ′ = 0 or Equation (8) where η = 1. A value obtained by multiplying = 2π / T is a pseudo speed ωX, and the value of the pseudo speed ωX is plotted by changing the natural period T.

  The response spectrum Sb is a ground acceleration component (obtained from the input reduction effect η obtained from the mass m of the structure and the auxiliary mass mf of the inertial connection element as described above and the maximum acceleration y ″ max of the ground motion of EL_CENTRO ( 1−η) y ″ max divided by the natural circular frequency ω of the structure is set as a pseudo speed Vb, and the natural period T is changed using the natural circular frequency ω = 2π / T to change the pseudo speed. The value of Vb is plotted.

  Tv40 is a periodic point where the magnitudes of the pseudo speed ωX of the response spectrum Sa and the pseudo speed Vb of the response spectrum Sb are interchanged.

  Here, as can be seen from the graph of the relative displacement in FIG. 5 and the absolute acceleration in FIG. 6, the relative displacement and the absolute acceleration are reduced by using the inertia connecting element on the short cycle side from the periodic point Tv40. It can be said that amplification of absolute acceleration due to the input reduction effect η hardly occurs.

  Here, in order to confirm the validity of the periodic point Tv40, the response absolute acceleration when the input reduction effect η = 1 (without inertia connection element) and the input reduction effect η = 0.5 (with inertia connection element) is obtained. The pseudo speed response spectrum divided by the natural circular frequency is shown in FIG.

  TABS represents a periodic point where the pseudo speed in the state where there is no inertia connection element and the pseudo speed in the state where the inertia connection is used is switched, and TABS and Tv40 are fairly close values. I understand.

  Moreover, as shown in FIG. 8, when the periodic points TABS and Tv40 were compared using the data of HACHINOHE1968 (NS) and TAFT1952 (EW) which are other earthquake motions, the values were similarly close.

  Furthermore, when analysis was performed using 52 actual vibration waveforms in regions other than the above shown in Table 1, as shown in FIG. 9, the average value of the ratio of TABS and Tv40 was close to 1, and the standard deviation was also It became about 10%. As a result, it was found that Tv40 was used as a substitute for TABS.

Therefore, the method of determining the natural period of the structure in which the inertial connection element is used using the periodic point Tv40 is effective in that the inertial connection element is effectively used.

  Next, the operation of the embodiment of the present invention will be described.

First, when designing a structure to be damped using an inertial connection element, the maximum displacement calculated using the vibration equation of Equation (7) with m ′ = 0 or Equation (8) with η = 1 The value of the pseudo speed ωX obtained by multiplying Xmax by the natural circular frequency ω is plotted while changing the natural period T to obtain a response spectrum Sa.

  Next, the ground motion acceleration component (1-η) y ″ max obtained from the input connection reduction effect η of the inertial connection element and the maximum acceleration y ″ max of the past earthquake motion data in a predetermined area is obtained from the structure. The value of the pseudo speed Vb divided by the natural circular frequency ω is plotted while changing the natural period T to obtain a response spectrum Sb.

  Next, a periodic point Tv40 where the magnitudes of the pseudo speed ωX of the response spectrum Sa and the pseudo speed Vb of the response spectrum Sb are obtained is obtained.

  Next, the structure is designed so that the natural period T is equal to or less than the periodic point Tv40.

  When actually building a structure, install a damping device for inertial connection elements.

  The built structure is resistant to earthquakes because the absolute acceleration, velocity, and displacement are reduced by the input reduction effect η of the damping device of the inertial connection element even if earthquake motion occurs.

  As described above, in the embodiment of the present invention, when designing a structure to be damped using the inertia connecting element, the pseudo speed response spectrums Sa and Sb are obtained in advance, and the pseudo speed ωX and the pseudo speed are obtained. By obtaining the periodic point Tv at which the magnitude of Vb is switched, the conversion point of the absolute acceleration when the pseudo inertial connection element is used and when it is not used can be known.

  Moreover, since it is not necessary to solve the vibration equation including the auxiliary mass mf, the periodic point Tv can be easily obtained.

  Therefore, it is possible to easily determine the natural period of the structure that can obtain the damping effect of the inertial connection element, and it is possible to effectively use the inertial connection element.

  In addition, for a structure that has already been built, the vibration damping effect by the inertial connection element can be obtained by reinforcing the structure so as to have the natural period obtained by the natural period determining method.

  In addition, this invention is not limited to said embodiment.

  The vibration damping device as the inertia connecting element is not limited to the form shown in FIG. 1, and various forms can be used as long as they utilize the rotational inertia of the auxiliary mass.

It is a perspective view of the vibration damping device concerning an embodiment. It is sectional drawing of the damping device which concerns on embodiment. It is a schematic diagram of the inertial connection element which concerns on embodiment. It is a mimetic diagram of a vibration system with a rotating body concerning an embodiment. It is a graph of the relative displacement spectrum which concerns on embodiment. It is a graph of the absolute acceleration spectrum which concerns on embodiment. It is a graph of the pseudo speed response spectrum concerning an embodiment. It is a graph of the pseudo speed response spectrum concerning an embodiment. It is the graph which showed the relationship between the input reduction effect (eta) which concerns on embodiment, and the ratio of periodic point TABS / Tv40.

Explanation of symbols

20 Auxiliary mass (Auxiliary mass)
34 Damping device (Inertial connection element)
Sa response spectrum (response spectrum)
Sb response spectrum (response spectrum)
Tv40 periodic point (periodic point)

Claims (3)

A method for determining a natural period of a structure in which an inertia connecting element that suppresses a shake with respect to a ground motion using a rotational inertia of an auxiliary mass mf is used,
Displacement X of the structure when a predetermined ground motion is given to the system without the auxiliary mass mf, mass m of the structure, the auxiliary mass inside diameter and a ratio of the outer diameter of the displacement amplification factor βf The mass equation m ′ = βf ² · mf expressed by using , the damping coefficient c, the spring constant k, and the vibration equation with m ′ = 0 in the equation (7) obtained as the ground motion displacement Y, or the displacement X, One-mass system response analysis is performed using the vibration equation with η = 1 in the equation (8) obtained as the input reduction effect η obtained by the natural circular frequency ω, the viscous damping constant h, the ground motion displacement Y, and the mass m ′. A response spectrum Sa in which a value obtained by multiplying the calculated maximum displacement Xmax by the natural period T and the natural circular frequency ω = 2π / T is a pseudo speed ωX, and the value of the pseudo speed ωX is plotted by changing the natural period T. The process of seeking


The ground acceleration component (1-η) obtained from the input reduction effect η obtained from the mass m of the structure and the auxiliary mass mf using the equation (9) and the maximum acceleration y ″ max of the earthquake motion. A value obtained by dividing y ″ max by the natural circular frequency ω of the structure is set as a pseudo speed Vb. Using the natural circular frequency ω = 2π / T, the natural period T is changed to change the pseudo speed Vb. Obtaining a response spectrum Sb plotting the values ;

A periodic point Tv at which the magnitudes of the pseudo speed ωX of the response spectrum Sa and the pseudo speed Vb of the response spectrum Sb are interchanged is obtained , and the natural period on the short period side of the periodic point Tv is determined as the natural period of the structure. and a step shall be the,
A method for determining the natural period of a structure, comprising: In a method for designing a structure using an inertia connecting element that suppresses a shake with respect to an earthquake motion using the rotational inertia of the auxiliary mass mf,
The displacement X 1 of the structure when a predetermined seismic motion is applied to a system that does not have the auxiliary mass mf, the mass m of the structure, and the displacement amplification factor βf that is the ratio of the inner diameter to the outer diameter of the auxiliary mass. The mass equation m ′ = βf ² · mf expressed by using , the damping coefficient c, the spring constant k, and the vibration equation with m ′ = 0 in the equation (7) obtained as the ground motion displacement Y, or the displacement X, One-mass system response analysis is performed using the vibration equation with η = 1 in the equation (8) obtained as the input reduction effect η obtained by the natural circular frequency ω, the viscous damping constant h, the ground motion displacement Y, and the mass m ′. A response spectrum Sa in which a value obtained by multiplying the calculated maximum displacement Xmax by the natural period T and the natural circular frequency ω = 2π / T is a pseudo speed ωX, and the value of the pseudo speed ωX is plotted by changing the natural period T. The process of seeking


The ground acceleration component (1-η) obtained from the input reduction effect η obtained from the mass m of the structure and the auxiliary mass mf using the equation (9) and the maximum acceleration y ″ max of the earthquake motion. A value obtained by dividing y ″ max by the natural circular frequency ω of the structure is set as a pseudo speed Vb. Using the natural circular frequency ω = 2π / T, the natural period T is changed to change the pseudo speed Vb. Obtaining a response spectrum Sb plotting the values ;

Obtaining a periodic point Tv at which the magnitudes of the pseudo speed ωX of the response spectrum Sa and the pseudo speed Vb of the response spectrum Sb are switched;
And having
A structure design method, wherein a structure having a natural period shorter than the periodic point Tv is designed. 3. A method for determining a natural period of a structure according to claim 1 or a method for designing a structure according to claim 2, wherein an inertia connecting element is used to suppress the vibration against the earthquake motion using the rotational inertia of the auxiliary mass mf. A structure characterized by being designed using