U.S. patent application number 13/960166 was filed with the patent office on 2014-02-13 for joints between precast concrete elements.
The applicant listed for this patent is John Siegfried Stehle. Invention is credited to John Siegfried Stehle.
Application Number | 20140041328 13/960166 |
Document ID | / |
Family ID | 46935067 |
Filed Date | 2014-02-13 |
United States Patent
Application |
20140041328 |
Kind Code |
A1 |
Stehle; John Siegfried |
February 13, 2014 |
Joints Between Precast Concrete Elements
Abstract
A joint between two adjacent faces (14) of concrete elements is
formed by overlapping headed bar (16) with transverse studs (22)
between the bars.
Inventors: |
Stehle; John Siegfried;
(London, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stehle; John Siegfried |
London |
|
GB |
|
|
Family ID: |
46935067 |
Appl. No.: |
13/960166 |
Filed: |
August 6, 2013 |
Current U.S.
Class: |
52/250 |
Current CPC
Class: |
E04B 5/21 20130101; E04B
1/043 20130101; E04B 5/023 20130101; E04B 5/10 20130101; E04B 1/483
20130101; E04B 5/19 20130101; E04C 5/0645 20130101; E01C 11/14
20130101; E04B 1/41 20130101 |
Class at
Publication: |
52/250 |
International
Class: |
E04B 1/41 20060101
E04B001/41 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2012 |
GB |
1214123.0 |
Claims
1. A longitudinal joint between two precast concrete elements each
having headed bars projecting from adjoining faces of the elements
to be joined; the elements being positioned so that their
respective headed bars are interleaved and overlap but are not in
contact with one another; and headed studs positioned transversely
to a length of the joint and transversely to and between the headed
bars, the bars and studs being enclosed in concrete.
2. A joint as claimed in claim 1, wherein the headed studs are
double headed studs supported on a rail which rests on the
overlapped headed bars.
3. A joint as claimed in claim 1, wherein the headed studs are
welded to a beam beneath the joint.
4. A joint as claimed in claim 1 wherein each element edge has a
double row of headed bars.
5. A joint as claimed in claim 1, wherein at least one longitudinal
bar is positioned along the length of the joint.
6. A joint between two precast concrete elements substantially as
herein described with reference to the accompanying drawings.
Description
[0001] The present invention relates to the use of headed anchor
reinforcement bars in the creation of joints between precast
concrete elements.
[0002] Headed deformed bars are deformed reinforcing bars, such as
ribbed carbon steel reinforcing bars, with a head attached at one
or both ends. Smooth reinforcing bars are also used with heads. In
this specification a reinforcing bar with a head attached at both
ends is described as a double headed stud whether or not the shank
is deformed for better anchorage.
[0003] The use of lap splices anchored by headed bars in creating
joints between precast elements is described in a technical paper
entitled Lap Splices Anchored by Headed Bars by M. Keith Thompson,
Antonio Ledesma, James O. Jirsa, and John E. Breen published in ACI
Structural Journal V 103, No 2 March April 2006. This primarily
addresses their use in bridge structures. This paper describes the
mechanics of such joints. A more detailed report by the same
authors from May 2002 has been published by the Center for
Transportation and Research, The University of Texas, Austin as
Report 1855-3. These documents are herein referred to as the Texas
papers. A typical joint width under consideration in these
documents is 10 inches (0.254 m).
[0004] Headed bars are also used in the reinforcement of flat
slabs, particularly to deal with localised high shear stresses
around column heads. The RFA-Tech SHEARTECH.RTM. system proposes
the use of double headed shear studs welded to carrier/spacer
rails. These stud carrying rails are designed to be placed liked
rays within the slab surrounding a column in order to provide shear
reinforcement. The studs are positioned vertically within the
surrounding slab parallel to the axis of the column. There are
other proprietary systems for use around column heads offered by
Halfen and Max Frank of Germany.
[0005] The present invention is particularly concerned with the
problems of the construction of floors within large multi-storey
structures requiring flat slab constructions to create a framework
defining multiple floors. These floors can be assembled from
precast concrete planks. The joints between these planks and
between other structural elements such as concrete columns, beams,
walls which are used in a variety of configurations, must be
structurally robust. It is also desirable to minimise the use of
high strength concrete in making of these joints.
[0006] The present invention provides a longitudinal joint between
two precast concrete elements each having headed bars projecting
from adjoining faces of the elements to be joined; the elements
being positioned so that their respective headed bars are
interleaved and overlap but are not in contact with one another;
and headed studs positioned transversely to a length of the joint
and transversely to and between the headed bars, the bars and studs
being enclosed in concrete. Preferably a joint structure is
employed in which headed bars are interlaced in the manner of a lap
joint as described in the Texas papers with the addition of a stud
carrying rail along the length of the joint supported on the
overlapping headed bars and suspending double headed studs between
them. When such a reinforcement structure is embedded in
high-strength concrete, a robust structural joint of relatively
small dimensions can be constructed. In analytical terms, the
transfer of forces can be considered as a series of compression
struts and tension ties according to normal strut and tie theory,
with the strength of the compression struts enhanced by the
confining effect of the intermediate studs on their carrying
rail.
[0007] Where joints are required to be formed above a steel beam
element, single headed studs can be pre-welded to the beam top
flange to provide the intersecting studs between the overlapping
headed bars.
[0008] Using this form of joint construction, the precast
structural elements of the system can be manufactured as large
elements. The elements will be typically produced using lightweight
concrete to reduce their weight and ease handling and
transportation logistics.
[0009] Joints of the system between adjacent slab elements, beam
and slab elements, wall and slab elements and other similar
scenarios, require temporary supporting of one element from the
other element. This is typically provided by temporary steel
channels bolted on top of one element and which rest on the
adjacent element through cantilevering action.
[0010] In order that the invention may be well understood, an
embodiment of a joint between adjacent floor planks will now be
described by reference to the accompanying diagrammatic drawings,
in which:
[0011] FIG. 1 shows a perspective view of an embodiment of a partly
constructed floor using the joint of the present invention;
[0012] FIG. 2 shows a perspective view of adjacent planks with
reinforcement to construct a joint in accordance with the invention
in place;
[0013] FIG. 3 shows a view of the joint from above; and
[0014] FIG. 4 shows a perspective view of an alternative embodiment
of a partly constructed floor using the joint of the present
invention.
[0015] A floor in a multi-storey construction is assembled from
precast lightweight concrete (LWC) planks 10. The planks 10 are
supported by concrete beams 26 and columns 28 and prior to the
construction of the joints between the beams and planks and
adjoining planks, the elements are supported by means of steel
channels 30.
[0016] Joints 12 are constructed as shown in FIGS. 2 to 3. Each
edge face 14 of a beam or plank 10 has a series of headed bars 16
projecting from it. In this example, the bars are shown in two
vertically spaced layers. The reinforcement is precast into the
planks so that they can be laid edge to edge with the headed bars
of one plank interlaced and overlapping with those of the adjacent
plank without the bars coming into contact or conflict with one
another. The edge faces of both the beams and planks have similar
arrays of headed bars at the same spacing so that joints of the
same form can be made between all the elements.
[0017] Two longitudinal bars 18 are laid along the length of the
joint and a rail 20 which supports a series of double headed studs
22 rests on the uppermost headed bars. The studs are spaced along
the rail so that they can be positioned centrally between the
headed bars. The double headed studs 22 hang vertically from the
rail 20.
[0018] In this embodiment, the rail comprises two rods to which the
heads 24 of the double headed studs are welded. The rail is there
to keep the double headed studs 22 in position at the required
spacing and performs no structural part of the joint. It may be
relatively lightweight. The lowermost head of the double headed
studs lies within the joint.
[0019] Shuttering is provided beneath the joint so that concrete
can be poured into the gap to surround the reinforcement and bring
the surface of the joint up to the level of the adjoining surfaces
of the precast planks. Once joints have been completed, the
channels 30 are removed.
[0020] It is envisaged that a joint width typically of 200 mm can
be employed with a lap length of 100 mm using reinforcing bars of a
typical diameter of 16 to 25 mm.
[0021] In FIG. 4, a steel framework 4 is made up of steel beams 6
that define a perimeter of the floor and at least one horizontal
beam 8 within it. This framework 4 is used to support a plurality
of lightweight concrete (LWC) planks 10, which are laid on the
framework 4 and connected to it. The joints are then made as
previously described.
[0022] Where a joint overlies a beam 6, the rail supported double
headed studs, can be replaced by a series of single headed studs
welded to the top of the beam. These perform the same function
within the joint.
* * * * *