Bridges – Bridge construction method
Reexamination Certificate
2002-05-08
2004-03-02
Hartmann, Gary S. (Department: 3671)
Bridges
Bridge construction method
C052S167100, C052S741300
Reexamination Certificate
active
06698053
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an elevated bridge, particularly to a railway elevated bridge infrastructure and the design method thereof.
Moreover, the present invention relates to a seismic reinforcement process for reinforcing a reinforced concrete (RC) member in which shear failure precedes bending failure against earthquakes.
Furthermore, the present invention relates to a seismic frame structure requiring seismic properties and the design method thereof, particularly to a seismic frame structure and design method which are applied to the infrastructure of an elevated bridge for use in roads, railways, and the like.
A bridge on which railways, and transport vehicles such as cars run includes a bridge crossing rivers, straits, and the like in a narrow sense, and also includes a so-called elevated bridge continuously constructed in the streets. Such elevated bridge is continuously constructed on the road, the railway, or the space over the river from the viewpoint of efficient land utilization, and the road or the railway under the elevated bridge is three-dimensionally crossed, which also contributes to the relief of traffic jams.
Additionally, such elevated bridge infrastructure is usually constructed as a rigid frame structure of a reinforced concrete (RC) in many cases, but during design/construction, of course, the soundness of the elevated bridge itself during an earthquake, and also the safety of the running transport vehicle have to be sufficiently studied.
Under the circumstances, the present applicants have proposed an elevated bridge infrastructure in which a damper-brace is disposed in the rigid frame of the reinforced concrete, and it has been found that both the seismic property and the running safety can be enhanced according to the constitution.
However, no seismic design method has been established, and the development of a design technique which can efficiently and economically secure the seismic property and running safety has been desired.
Moreover, different from the bending failure, the shear failure of an RC member rapidly advances due to lack of ductility, and brings a fatal damage to the structure in many cases. Particularly, the shear failure of a pillar material caused by the action of a seismic load causes large damage to the structure in many cases, and for a short pillar which has a small shear span ratio and onto which a large axial force acts, and the like, the concrete of a pillar core part bursts into destruction by the compound action of a large axial direction stress and shear stress, and the pillar rapidly loses its load bearing capacity.
Therefore, in the structure design, the shear failure has to be avoided to the utmost, and for the current RC member in which the shear failure possibly precedes bending failure, seismic reinforcement is necessary, such as the winding of carbon fibers around a periphery and the winding of steel plates.
In this method, it is possible to enhance the shear load bearing capacity of an RC member and prevent the shear failure beforehand, but on the other hand, since the carbon fiber has to be wound over the entire member length, construction requires much time, and the method cannot necessarily be optimum as the seismic reinforcement process from an economical point of view.
Moreover, the infrastructure of the elevated bridge in which the damper-brace is disposed in the RC rigid frame is expected in the future because the seismic property can be enhanced as described above. However, when a steel frame eccentric brace is disposed in the RC rigid frame and a damper is interposed between the steel frame eccentric brace and the RC rigid frame, and when the damper has a small allowable deformation amount, such as a hysteresis shear damper, the damper is first ruptured in a big earthquake, and there has been a problem in that the ductility of the RC rigid frame cannot sufficiently be utilized.
Furthermore, when the damper is ruptured with a relatively small deformation, the load bearing capacity of the damper or the RC rigid frame has to be increased, but in this case, a foundation and a pile are naturally required to have a load bearing capacity increase, and consequently, the entire structure has a large section, which has caused a cost problem.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an elevated bridge infrastructure and the design method thereof in which the seismic property and running safety can more efficiently and economically be secured.
It is a further object of the present invention to provide a seismic reinforcement process of an RC frame in which shear failure can be prevented beforehand without requiring much construction time.
It is another object of the present invention to provide a seismic frame structure and the design method thereof which can enhance the seismic property without providing a damper or an RC rigid frame with a large section.
With the foregoing object in view, the present invention provides a method for designing an elevated bridge infrastructure that includes an RC rigid frame and a damper-brace disposed in a structural plane. The method comprises the steps of: setting a target ductility factor &mgr;
d
and a target natural period T
d
for the infrastructure in an assumed earthquake motion; obtaining a yield seismic coefficient corresponding to the target ductility factor &mgr;
d
and the target natural period T
d
from a yield seismic coefficient spectrum corresponding to the assumed earthquake motion to provide a design seismic coefficient K
h
, and obtaining a target yield rigidity K
d
corresponding to the target natural period T
d
; using the design seismic coefficient K
h
to obtain a design horizontal load bearing capacity H
d
and obtaining a displacement corresponding to the design horizontal load bearing capacity H
d
as a design yield displacement &dgr;
d
from the target yield rigidity K
d
; distributing the design horizontal load bearing capacity H
d
to a horizontal force H
f
to be borne by the RC rigid frame and a horizontal force H
b
to be borne by the damper-brace; and setting member sections of the RC rigid frame and the damper-brace so that the RC rigid frame and the damper-brace resist the horizontal forces H
f
, H
b
with an ultimate load bearing capacity, and displacements corresponding to the horizontal forces H
f
, H
b
equal a product of the design yield displacement &dgr;
d
and the target ductility factor &mgr;
d
.
Here, by performing the steps until setting the member sections of the RC rigid frame and the damper-brace as described above, the section design of the elevated bridge infrastructure is completed once, but subsequently the set member sections may be checked.
The present invention also provides an elevated bridge infrastructure comprising an RC rigid frame and a damper-brace disposed in a structural plane, wherein member sections of the RC rigid frame and the damper-brace are set by setting a target ductility factor &mgr;
d
and a target national period T
d
of the infrastructure in an assumed earthquake motion, obtaining is a yield seismic coefficient corresponding to the target ductility factor &mgr;
d
and the target natural period T
d
from a yield seismic coefficient spectrum corresponding to the assumed earthquake motion to provide a design seismic coefficient K
h
, obtaining a target yield rigidity K
d
corresponding to the target natural period T
d
, using the seismic coefficient K
h
to obtain a design horizontal load bearing capacity H
d
, obtaining a displacement corresponding to the design horizontal load bearing capacity H
d
as a design yield displacement &dgr;
d
from the target yield rigidity K
d
, and distributing the design horizontal load bearing capacity H
d
to a horizontal force H
f
to be borne by the RC rigid frame and a horizontal force H
b
to be borne by the damper-brace, so that the RC rigid frame and the damper-brace resist the horizontal forces H
f
, H
b
with an ultimate load bearing capacity and displacements corresponding to the
Arita Hiroyuki
Mastsumoto Nobuyuki
Okano Motoyuki
Ouchi Hajime
Sogabe Masamichi
Hartmann Gary S.
Obayashi Corporation
Wenderoth , Lind & Ponack, L.L.P.
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