Pipe joints or couplings – Flexible joint – rigid members – Concrete – clay – or masonry pipe
Reexamination Certificate
2003-08-15
2004-12-28
Bochna, David (Department: 3679)
Pipe joints or couplings
Flexible joint, rigid members
Concrete, clay, or masonry pipe
C285S336000, C052S223130
Reexamination Certificate
active
06834890
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO MICROFICHE APPENDIX
Not applicable.
1. Field of the Invention
The present invention relates to the assembly and installation of precast concrete segments used in construction activities, such as bridge and highway construction. More particularly, the present invention relates to couplers for joining the ends of interior ducts of such precast concrete segments in end-to-end liquid-tight relationship.
2. Description of the Prior Art
Precast segmental bridges are known and commonly used throughout the world as a means to forge roadways through mountainous terrain or across rivers or other barriers. Such bridges are typically constructed in accordance with the following sequence: First, a series of upright piers are formed along the bridge span. Thereafter, cantilevered bridge section are built out of each pier by successively mounting the precast segments to previously completed bridge components and post-tensioning the segments thereto. The cantilevered bridge sections are built out from each pier in a symmetrical fashion so that the piers are not subjected to undue bending loads. When the cantilevered sections are complete, the ends thereof are post-tensioned together to form a continuous bridge deck. Typically, two such bridge spans are constructed to accommodate the two directions of travel. These spans are generally side-by-side, but need not be parallel (horizontally or vertically) nor at the same elevation.
FIGS. 1-4
illustrate a form of such precast segmental bridge construction in accordance with the teachings of U.S. Pat. No. 5,231,936, issued on Aug. 3, 1993 to G. Sauvagiot. This form of segmental precast bridge construction is particularly disclosed as used with a rapid transit viaduct system.
Referring to
FIG. 1
, a rapid transit viaduct section two includes a central load bearing span or body member
4
supported by a pair of upright pier members
6
and
8
. Extending laterally from opposite lower side portions of the central body
4
are a pair of lateral platform structures
10
and
12
. Each of the platform structures
10
and
12
has a pair of rails
14
mounted thereon for carrying a rapid transit vehicle. In addition, each of the platform sections may be provided with an upright sidewall section
16
as required for safety, noise pollution and other considerations. One or more sets of rails
14
are carried by each of the lateral platform structures depending on the requirements of the transit systems.
The platform structures
10
and
12
each include respective upper platform decks and respective lower support struts
22
and
24
. The lower support struts
22
and
24
are mounted as close to the bottom of the central load bearing body
4
as practicable. Deck members
18
and
20
are mounted to the central body
4
at an intermediate portion thereof above the support struts
22
and
24
. The support struts angle upwardly from their point of attachment with the load bearing body
4
until they intersect the deck members. As such, the deck members
18
and
20
and support struts
22
and
24
form a box section providing resistance to torsional loading caused by track curvature and differential train loading. This box section may be considered a closed base. The load bearing body
4
bisects the closed base and extends vertically upwardly therefrom to provide span-wise bending resistance. Preferably, the entire duct section
2
is cast as a single reinforced concrete cross-section.
The platform sections
10
and
12
each include lower pier mounts
26
and
28
. These are mounted respectively to the bottom of the support structures
22
and
24
. The pier mounts
26
and
28
are, in turn, supported, respectively, on the piers
6
and
8
using a plurality of neoprene pads
30
, which provide a cushioned support for the structure.
As shown in
FIG. 1
, the viaduct section
2
forms part of a viaduct system supporting rails
14
for carrying rapid transit vehicles
32
and
34
. The viaduct section
2
may be formed as a precast modular segment. The viaduct section
2
is then combined with other viaduct sections to form a precast segmental structure. To facilitate such construction, the load bearing body
4
may be formed with interlock member
36
, while the lateral platform structures
10
and
12
may be each formed with interlock members
38
.
Referring to
FIG. 2
, a viaduct system is formed from a plurality of precast sections
2
formed as modular segments and combined as a precast segmental structure extending between sequentially positioned piers (not shown). The sections
2
are placed in longitudinally abutting relationship. To facilitate that construction, the sections are match cast so that the abutting end portions thereof fit one another in an intimate interlocking relationship. Each successive section is therefor cast against a previously cast adjacent section to assure interface continuity.
The connection between adjacent modular sections is further secured by way of the interlock members
36
and
38
. On one end of each section
2
, the interlock members
36
and
38
are formed as external keys. On the opposite end of each section
2
, the interlock members are formed as an internal slot or notch, corresponding to the key members of the adjacent viaduct system. Match casting assures that corresponding keys and slots, as well as the remaining interface surfaces, properly fit one another.
As seen in
FIG. 2
, the sections
2
are bound together with one or more post-tensioning cables or tendons
40
,
42
and
44
. The number of cables used will depend on a number of factors such as cable thickness, span length and loading requirements. The tensioning cables are each routed along a predetermined path which varies in vertical or lateral position along the span of the segmental structure.
FIG. 3
illustrates, diagrammatically, the manner in which the post-tensioning cables
40
,
42
and
44
extend through the concrete structure of the spans. As can be seen in
FIG. 3
, the post-tensioning cables are sometimes positioned within the concrete segment themselves, and at other times are positioned externally thereof.
It is important to note that multiple post-tension cables are often used as extending through ducts within the concrete structure. In
FIG. 4
, it can be seen that the sections
2
are formed with appropriate guide ducts
50
at locations where the post-tensioning cables passed through the structure. The post-tensioning cable identified collectively by reference numeral
52
in
FIG. 4
, are routed through the guide ducts
50
. To facilitate this routing, a continuous flexible conduit
54
is initially inserted through the guide ducts, and the post-tensioning cables
52
are thereafter placed in the conduit. The conduit
54
may advantageously be formed from polyethylene pipe but could also be formed from flexible metallic materials. The post-tensioning cables
52
are tensioned using conventional post-tensioning apparatus and the interior of the conduit
54
is cement grouted along the entire length thereof for corrosion protection.
One form of duct that is commercially available is shown in FIG.
5
. The corrugated polymeric duct
56
is of a type presently manufactured by General Technologies, Inc. of Stafford, Tex., licensee of the present inventor. As can be see in
FIG. 5
, duct
56
has a plurality of corrugations
58
extending radially outwardly from the generally tubular body
60
. The duct
56
has ends
62
and
64
through which post-tensioning cables can emerge. In
FIG. 5
, it can be seen that there are longitudinal channels
66
,
68
and
70
extending along the outer surface of the tubular body
60
. The longitudinal channels
66
,
68
and
70
allow any grout that is introduced into the interior of the duct
56
to flow easily and fully through the interior of the duct
56
. The longitudinal channels
66
,
68
and
70
also add structural integrity to the length of the duct
56
. It is important to realize that
Bochna David
Harrison & Egbert
LandOfFree
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