Static structures (e.g. – buildings) – Vertically curved arch with terminal support
Reexamination Certificate
1999-01-11
2001-06-12
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Vertically curved arch with terminal support
C052S089000, C052S223900, C052S749100, C052S745080, C405S126000, C405S135000, C014S026000
Reexamination Certificate
active
06243994
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the general art of large pre-cast concrete arch structures, and to the particular field of joints for large pre-cast concrete arch structures.
BACKGROUND OF THE INVENTION
Large span pre-cast concrete arch structures are often used in road building and the like. As used herein, the term “large arch structure” will mean an arch structure large enough for pedestrian or vehicular passageways, parking or large enough to support vehicle traffic over a roadway or a waterway as opposed to conduits and the like which enclose cables or drainage. These large structures need to be built from two or more arch segments due to transporting size and weight restrictions. Such arch segments are connected on site. A structure formed of twin-leaf arch sections is shown in FIG.
3
.
Quite often, a rigid connection of precast concrete elements is made from reinforced cast-in-place concrete. The simplest and most commonly used joint for reinforcing steel is a lap splice. The present invention uses reinforced cast-in-place concrete for a joint and lap splices for reinforcement.
There are several methods presently employed to join twin-leaf arch sections together. As shown in
FIG. 1
, two cranes C
1
and C
2
are used in one method, and as shown in
FIG. 2
, one crane C
3
and a scaffolding SC can be used.
With regard to
FIG. 1
, it can be seen that crane C
1
will support section S
1
of a pre-cast concrete twin-leaf arch structure
10
in place while crane C
2
moves section S
2
into place adjacent thereto, or vice versa as those skilled in the art will understand. Referring to
FIG. 2
, it will be seen that a single crane C
3
will position section S
2
in place with crown area CA
2
supported on scaffold SC and then move section S
1
into position with its crown area CA
1
being placed in abutting contact with crown area CA
2
on scaffold SC.
Quite often, the arch spans a body of water or a railway or highway in operation. The use of a central scaffolding is then not possible and two cranes are used for the installation. Using this method, an initial abutting contact is established between the twin units. Preferably, the joint includes mechanical elements for aligning and locking the two arch sections together when brought into abutting contact. Also, the joint should allow a controlled transmission of the abutting force and the use of a (temporary) connection for safety reasons.
For the same reasons that a central scaffolding may not be used, there is also a need that a cast-in-place concrete can be poured without an extra formwork to be installed.
In a prior art method of joining the twin-leaf arch sections, the crown areas are placed in abutting contact and filled in situ with concrete to complete the joint. As shown in
FIGS. 4 and 5
, the sections have crown areas, such as CA
1
shown in
FIG. 5
that include a stepped portion CA
1
S and a shoulder SH
1
joining stepped portion CA
1
S to top surface TS
1
of section S
1
. Section S
1
has an end E
1
that abuts end E
2
of section S
2
as indicated in
FIG. 4
when the two sections are set up. A joint-forming portion JS is formed by the co-operating stepped sections CA
1
and CA
2
of sections S
1
and S
2
respectively, As shown in
FIG. 3
, portion JS is then filled in with concrete CT to complete the joint.
This method is meant to be used in connection with the erection method shown in
FIG. 2
, and in a method in which the joint concrete is poured and cured before the scaffolding is removed. If used with the method of
FIG. 1
, it is time consuming to properly orient the two arch sections with respect to each other. The joint is not locked when in abutting contact, and often, the uncontrolled transmission of the abutting force leads to spalling of the concrete.
Therefore, there is a need for a joint for precast concrete twin-leaf arch sections which is efficiently formed, can be formed over long spans and/or bodies of water or the like, allows a controlled transmission of abutting force and will retain the proper orientation of the two arch sections during the joint forming process.
In the case of a joint for large cast-in-place arches, the inventor has found that the joint needs to fulfill the following requirements:
The joint should be rigid and moment transmitting;
The joint should allow normal lap splices for reinforcement;
The joint should not require a form for pouring the cast-in-place concrete; and
A continuous (load distributing) connection of the individual arch rings in the longitudinal direction at the arch crown should be possible.
Therefore, there is a need for a joint for large cast-in-place concrete arch segments that will fulfil the just-mentioned requirements.
OBJECTS OF THE INVENTION
It is a main object of the present invention to provide a joint for precast concrete twin-leaf arch sections which is efficiently and accurately formed.
It is another object of the present invention to provide a joint for precast concrete twin-leaf arch sections which is efficiently accurately formed and which can be efficiently used over spans which are not suitable for scaffolding.
It is another object of the present invention to provide a joint for precast concrete twin-leaf arch sections which is efficiently and accurately formed and will maintain the desired orientation of one section relative to the other during erection.
It is another object of the present invention to provide a joint for precast concrete twin-leaf arch sections that allows the use of simple lap splices of the joint reinforcement.
It is another object of the present invention to provide a joint for precast concrete twin-leaf arch sections which includes a self-aligning and locking feature that allows a controlled transmission of the abutting force and includes the possibility to temporarily secure the twin-leaf units.
It is another object of the present invention to provide a joint for precast concrete twin-leaf arch sections that allows a continuous connection of the individual arch rings in the longitudinal direction for load distributing purposes.
It is another object of the present invention to provide a joint for precast concrete twin-leaf arch sections which does not require an extra formwork for the cast-in-place joint concrete to be poured.
SUMMARY OF THE INVENTION
These, and other, objects are achieved by a joint for precast concrete twin-leaf arch sections that includes self-aligning elements on each arch section that engage co-operating elements on the other section when the two arch sections are initially brought into abutting contact with each other. The self-aligning elements then co-operate to mechanically lock one arch section to the other and hold the two sections locked during the remainder of the joint formation process. The self-aligning elements co-operate to allow a controllable transmission of the abutting force. It is here noted that the joint of the present invention is described as being “mechanical” in order to distinguish it from other means, such as adhesive or the like for holding two elements together.
Specifically, the mechanical lock embodying the best mode of carrying out the present invention includes a protrusion on the end of one arch section and a depression defined in the end of the other arch section to receive the protrusion when the two arch sections are brought into initial abutting contact with each other.
The joint of the present invention includes means to temporarily secure the twin units until the joint is completed, and further provides sufficient open space to be filled with cast-in-place concrete for accommodating re-bar elements that form simple lap splices. The joint of the present invention also provides means to link two adjacent arch rings together by means of re-bars and concrete or by dowels for longitudinal load distribution. The joint of the present invention further allows the cast-in-place concrete to be poured without the need for extra formwork.
The joint of the present invention further includes areas for accommodating re-bar elements
Bebo of America, Inc.
Friedman Carl D.
Gernstein Terry M
Yip Winnie
LandOfFree
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