Support structure
In a boiler support structure in which certain seismic isolators are provided with a pullout countermeasure, the seismic isolators to be provided with the pullout countermeasure are individually identified according to whether the seismic isolator satisfies Formula (1): N Dn +N EQn >N tn . . . Formula (1), where N Dn (N Dn <0) is a compressive load occurring on each of the seismic isolators and calculated on the basis of a permanent load imposed on the boiler support structure; N EQn (N EQn >0) is a pullout force occurring on each of the seismic isolators and calculated on the assumption that an earthquake has occurred; and N tn (N tn >0) is an allowable pullout force of each of the seismic isolators and calculated using an allowable pullout stress of each of the seismic isolators.
1. A boiler support structure comprising:
a boiler main body;
a boiler support steel frame supporting the boiler main body in a suspended state, the boiler support steel frame comprising column bases, a plurality of columns erected on a foundation via the column bases, and a plurality of beams connecting adjacent columns to each other; and
a plurality of seismic isolators supporting at least one of the columns, the seismic isolators being provided on the foundation,
wherein each of the seismic isolators that satisfy the following Formula (1) is provided with a pullout countermeasure:
N Dn +N EQn >N tn Formula (1),
wherein N Dn , N EQn , and N tn are defined as follows:
N Dn (N Dn <0) is a compressive load occurring on each of the seismic isolators and calculated on the basis of a permanent load imposed on the boiler support structure;
N EQn (N EQn >0) is a pullout force occurring on each of the seismic isolators and calculated on the assumption that an earthquake has occurred; and
N tn (N tn >0) is an allowable pullout force of each of the seismic isolators and calculated using an allowable pullout stress of the seismic isolator.
2. The boiler support structure according to claim 1 , wherein the pullout force N EQn is calculated on the basis of the following Formula (2):
N EQn =M/B n Formula (2),
wherein M and B n of Formula (2) are defined as follows:
M is an overturning moment occurring on a seismic isolation layer when a horizontal force P acts at a center of gravity G of a superstructure and calculated on the basis of the following Formulae (3) and (4), the superstructure being a part of the structure located above the seismic isolation layer; and
B n is a length of an arm of the overturning moment M on each of the seismic isolators,
P=Sa×m Formula (3),
M=P×L Formula (4),
wherein Sa, m, P, and L of Formulae (3) and (4) are defined as follows:
Sa is a response acceleration in a natural period T of the superstructure and calculated from a response spectrum of a design earthquake wave;
m is a mass of the superstructure;
P is a horizontal force on the superstructure; and
L is a distance in a vertical direction from the center of gravity G of the superstructure to the center of the seismic isolation layer in a height direction.
3. The boiler support structure according to claim 1 , wherein the pullout countermeasure is configured such that a pullout proof strength of the respective seismic isolator is increased.
4. The boiler support structure according to claim 2 , wherein the pullout countermeasure is configured such that a pullout proof strength of the respective seismic isolator is increased.
5. The boiler support structure according to claim 1 , wherein the pullout countermeasure includes load transfer member that transfers the pullout force from the column supported by the respective seismic isolator to another of the columns.
6. The boiler support structure according to claim 2 , wherein the pullout countermeasure includes a load transfer member that transfers the pullout force from the column supported by the respective seismic isolator to another of the columns.
7. The boiler support structure according to claim 1 , wherein the pullout countermeasure includes:
a first form in which a pullout proof strength of the respective seismic isolator is increased; and
a second form including a load transfer member that transfers the pullout force from the column supported by the respective seismic isolator to another of the columns.
8. The boiler support structure according to claim 2 , wherein the pullout countermeasure includes:
a first form in which a pullout proof strength of the respective seismic isolator is increased; and
a second form including a load transfer member that transfers the pullout force from the column supported by the respective seismic isolator to another of the columns.
9. The boiler support structure according to claim 3 , wherein the pullout countermeasure is further configured so that a neutral axis of a seismic isolation layer does not shift from a position thereof before the pullout countermeasure is installed.
10. The boiler support structure according to claim 3 , wherein, in the first form, the pullout countermeasure is further configured so that a neutral axis of a seismic isolation layer shifts from a position thereof before the pullout countermeasure is installed.
11. The boiler support structure according to claim 5 , wherein the boiler support structure further comprises a tie beam and/or a horizontal beam, the column supported by the respective seismic isolator and another of the columns are coupled together by the the tie beam and/or the horizontal brace.
12. The boiler support structure according to claim 5 , wherein the boiler support structure further comprises an RC slab, the RC slab being provided between the column supported by the respective seismic isolator and another of the columns.
13. The boiler support structure according to claim 11 , further comprising a pullout prevention mechanism that couples together the tie beam and the foundation in parallel to the seismic isolator.
14. The boiler support structure according to claim 12 , wherein the boiler support structure is configured such that equipment is installed on the RC slab in a region around the column supported by the respective seismic isolator.
15. A method of identifying, by a computer, seismic isolators to be provided with a pullout countermeasure in a boiler support structure including a plurality of seismic isolators,
the boiler support structure comprising a boiler main body; a boiler support steel frame supporting the boiler main body in a suspended state, the boiler support steel frame comprising column bases, a plurality of columns erected on a foundation via the column bases, and a plurality of beams connecting adjacent columns to each other; and the plurality of seismic isolators supporting at least one of the columns, the plurality of seismic isolators being provided on the foundation; and
the method comprising individually determining, by the computer, whether the seismic isolators satisfy the following Formula (1), and identifying each of the seismic isolators that satisfy Formula (1) as a seismic isolator to be provided with a respective pullout countermeasure:
N Dn +N EQn >N tn Formula (1),
wherein N Dn , N EQn , and N tn are defined as follows:
N Dn (N Dn <0) is a compressive load occurring on each of the seismic isolators and calculated on the basis of a permanent load imposed on the boiler support structure;
N EQn (N EQn >0) is a pullout force occurring on each of the seismic isolators and calculated on the assumption that an earthquake has occurred; and
N tn (N tn >0) is an allowable pullout force of each of the seismic isolators and calculated using an allowable pullout stress of the seismic isolator.
16. The method according to claim 15 , wherein the pullout force N EQn is calculated on the basis of the following Formula (2):
N EQn =M/B n Formula (2),
wherein M and B n of Formula (2) are defined as follows:
M is an overturning moment occurring on a seismic isolation layer when a horizontal force P acts at a center of gravity G of a superstructure and calculated on the basis of the following Formulae (3) and (4), the superstructure being a part of the structure located above the seismic isolation layer; and
B n is a length of an arm of the overturning moment M on each of the seismic isolators,
P=Sa×m Formula (3),
M=P×L Formula (4),
where Sa, m, P, and L of Formulae (3) and (4) are defined as follows:
Sa is a response acceleration in a natural period T of the superstructure and calculated from a response spectrum of a design earthquake wave;
m is a mass of the superstructure;
P is a horizontal force on the superstructure; and
L is a distance in a vertical direction from the center of gravity G of the superstructure to the center of the seismic isolation layer in a height direction.
17. A method of identifying, by a computer, seismic isolators to be provided with a pullout countermeasure in a boiler support structure including a plurality of seismic isolators,
the method comprising individually determining, by the computer, whether the seismic isolators satisfy the following Formula (1), and identifying each of the seismic isolators that satisfy Formula (1) as a seismic isolator to be provided with a respective pullout countermeasure:
N Dn +N EQn >N tn Formula (1),
wherein N Dn , N EQn , and N tn are defined as follows:
N Dn (N Dn <0) is a compressive load occurring on each of the seismic isolators and calculated on the basis of a permanent load imposed on the boiler support structure;
N EQn (N EQn >0) is a pullout force occurring on each of the seismic isolators and calculated on the assumption that an earthquake has occurred; and
N tn (N tn >0) is an allowable pullout force of each of the seismic isolators and calculated using an allowable pullout stress of the seismic isolator.