U.S. patent application number 10/261587 was filed with the patent office on 2003-05-08 for repair of structural members.
Invention is credited to Potts, Andrew Elmhirst, Sincock, Paul.
Application Number | 20030085482 10/261587 |
Document ID | / |
Family ID | 25645416 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030085482 |
Kind Code |
A1 |
Sincock, Paul ; et
al. |
May 8, 2003 |
Repair of structural members
Abstract
A method of increasing the structural strength of a load bearing
member such as a pile (12), particularly for the purpose of
repairing a damaged pile, includes the steps of securing a rigid,
structural sleeve (17) around the pile (12) and spaced therefrom to
form an interspace (18), filling the interspace (18) with an
expansive filler (19), and allowing the filler (19) to set and
expand in the interspace (18) to a prestress of at least 3 MPa and
impose tensile hoop stresses in the sleeve (17) and corresponding
compressive hoop stresses in the pile (12) to enhance the load
transfer between the pile (12) and the sleeve (17).
Inventors: |
Sincock, Paul; (Victoria,
AU) ; Potts, Andrew Elmhirst; (Victoria, AU) |
Correspondence
Address: |
BARNES & THORNBURG
Suite 900
750 17th Street, N.W.
Washington
DC
20006
US
|
Family ID: |
25645416 |
Appl. No.: |
10/261587 |
Filed: |
October 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10261587 |
Oct 2, 2002 |
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09423210 |
Jan 21, 2000 |
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09423210 |
Jan 21, 2000 |
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PCT/AU98/00331 |
May 7, 1998 |
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Current U.S.
Class: |
264/32 ;
249/90 |
Current CPC
Class: |
E02D 5/64 20130101; E02D
2300/0004 20130101; E02D 5/60 20130101 |
Class at
Publication: |
264/32 ;
249/90 |
International
Class: |
E04B 001/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 1997 |
AU |
PO 6665 |
Claims
The claims defining the invention are as follows:
1. A method of increasing the structural strength of a load bearing
member including the steps of: (a) fitting a rigid, structural
sleeve to the member, with the sleeve having internal dimensions
greater than the external dimensions of the member; (b) supporting
the sleeve so that it is spaced from the member whereby to provide
a continuous interspace from the member to the sleeve; (c) sealing
the continuous interspace at its lower end; (d) filling the
continuous interspace with an expansive filler; and (e) allowing
the filler to set, or cure, and expand within the confines of the
continuous interspace to generate an expansive pressure of at least
3 MPa which imparts at least radial prestress forces on the member
and tensile hoop stresses in the sleeve, whereby the generated
forces effect a transition of loading forces from one section to
another of the load bearing member through the sleeve and expansive
filler.
2. A method according to claim 1 including the step of securing two
or more parts together to form the sleeve about the member.
3. A method according to claim 1 wherein the interspace is filled
from its upper end.
4. A method according to claim 1 including the step of providing
spacers to evenly space the sleeve from the member.
5. A method according to claim 1 including the steps of providing
at least one toroidal bladder attached to the lower end of the
sleeve with a filler tube extending to the upper end of the sleeve,
and filling the bladder with expansive filler through the filler
tube before filling the interspace.
6. A method according to claim 1 including the step of sealing the
interspace at its upper end.
7. A method according to claim 1 wherein the step of filling the
interspace with an expansive filler comprises filling the space
with a cementitious grout containing an expansive agent of a
calcium-sulpho-aluminate structure.
8. A method according to claim 1 including the step of providing
shear keys on either or both the member and the sleeve to key into
the filler.
9. A method according to claim 1 wherein the step of filling the
interspace with an expansive material results in direct contact
between the filler and the member and between the filler and the
sleeve.
10. Apparatus for increasing the structural strength of a load
bearing member including a rigid, structural sleeve formed of one,
two or more elongate sections to be fastened about a load bearing
member, a plurality of spacers adapted to space the sleeve from the
member to form a continuous interspace from the member to the
sleeve, a seal around the lower end of the continuous interspace,
and a set or cured expansive filler to fill the continuous
interspace which generates and imparts at least radial prestress
compressive forces of at least 3 MPa on the member and the sleeve
such as to set up compressive hoop stresses in the member and
tensile hoop stresses in the sleeve, the filler forming a rigid
interface between the member and the sleeve.
11. Apparatus according to claim 10 wherein the sleeve is formed of
two parts adapted to be connected together.
12. Apparatus according to claim 10 wherein said seal comprises at
least one flexible toroidal bladder attached to the lower end of
the respective sleeve part and adapted to be filled with said
filler, the bladder having a filler line or tube extending from an
upper end of the respective sleeve part.
13. Apparatus according to claim 10 wherein said sleeve is formed
of two parts hinged together along one longitudinal edge and
adapted to be fastened together along another longitudinal
edge.
14. Apparatus according to claim 10 wherein the expansive filler is
a cementitious grout containing an expansive agent of a
calcium-sulpho-aluminate structure.
15. A method of repairing a pile having a damaged area including
the steps of: (a) securing a sleeve which has inner dimensions
greater than outer dimensions of the pile around the pile, the
sleeve having an axial length to, and being secured so as to,
extend beyond the area of damage in both directions; (b) providing
spacers to space the sleeve from the pile to form a continuous
interspace from the pile to the sleeve; (c) sealing a lower end of
the continuous interspace; (d) introducing an expansive filler
through the upper end of the continuous interspace, displacing any
water or air in the continuous interspace, to thereby fill the
interspace with the expansive filler; (e) permitting the filler to
set, or cure, and to expand within the confines of the continuous
interspace to generate a compressive pressure of at least 3 MPa and
impart at least radial prestress forces which tension the sleeve
and apply compressive forces to the pile and produce compressive
hoop stresses in the pile and tensile hoop stresses in the sleeve,
whereby the filler facilitates load transfer primarily by friction
across the filler-to-pile and filler-to-sleeve interfaces.
16. A method according to claim 15 wherein the expansive filler is
a cementitous grout containing an expansive agent of a
calcium-sulpho-aluminate structure or a lime based agent.
17. A method according to claim 15 wherein the lower end of the
interspace is sealed by at least one flexible bladder attached to
the lower end of the sleeve and having a filler line or tube
extending from an upper end of the respective sleeve, the bladder
being filled with the expansive filler or grout so as to expand and
seal against the pile and retain said filler in the interspace.
18. A method according to claim 15 wherein the lower end of the
interspace is sealed by a plurality of pocket seals attached to the
sleeve at its lower end, the pockets seals being open at their
upper end to receive the filler introduced into the interspace, the
filler filling the pockets causing inner edges thereof to engage
and seal against the pile.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to the repair of structural members
and relates particularly to improved methods and apparatus for
effecting repairs of structures such as piles in situ.
[0003] The invention will be described with particular reference to
effecting repairs of structures such as piles, but it will be
understood that the invention has wider application to maintenance,
protection and repair of a wide range of structural members
including steel jacket offshore structures, structural members on
bridges or the like, tubular and non-tubular posts of all types,
columns, poles and pillars.
[0004] The invention will also be described particularly with
reference to cylindrical metal piles although it will be understood
that the invention is applicable to other forms of structures,
including concrete piles, timber piles and the like.
[0005] 2. Description of the Prior Art
[0006] Piles, such as those used to support jetties, wharves,
piers, offshore structures such as steel jacket platforms and
similar structures are subject to damage caused by erosion,
corrosion and related chemical or electro-chemical erosion, and by
impact such as from marine vessels and the like. Piles which are
immersed in water, particularly sea water, are generally subject to
most corrosion on that area of the pile between tide levels. That
portion of the pile is periodically immersed in water and then
exposed to atmosphere causing accelerated corrosion as compared to
other parts of the pile. As the structural integrity of the jetty,
wharf, pier, bridge, offshore structure or the like can be
substantially impaired by damage to the piles, it is necessary to
repair or replace any piles which suffer substantial damage.
[0007] Heretofore, the repair of hollow, steel tubular piles has
been effected by welding full or part sleeves to the pile so that
the sleeves overlie the affected damaged portion.
[0008] A full sleeve may be formed by welding two half sleeves to
the pile along longitudinal and end edges thereof thus effectively
adding an outer skin to the damaged pile. However, as most damage
to piles occurs in the area between maximum and minimum water
levels, and as the repair sleeve or part sleeve must extend
substantially beyond the damaged area to provide the necessary
strength to effect a proper repair, it is generally necessary to
effect the welding of such sleeves in the tidal zone or underwater.
Such welding is relatively expensive and time consuming, may
require special equipment, and 1-0 the welds so made, unless
carried out with great skill, can be less than perfect, thus,
compromising the structural integrity of the repaired pile.
[0009] Australian Patent Specification No 59285/86 discloses a
method of repairing a concrete pile by using a steel sleeve and
filling the space between the sleeve with a grout. The method
includes removing damaged concrete from the pile before placing the
sleeve. The specification discloses the method in relation to a
square pile and the sleeve is provided with internal, integral
metal spacers formed as part of the sleeve and which bear on the
surfaces of the pile.
[0010] Such sleeves are relatively expensive and need to be custom
made for each different type, shape and dimension of pile.
[0011] U.S. Pat. No. 4,306,821 discloses a method for
reconditioning structural piles whereby a building filler is placed
into a space between a flexible sheet form and the damaged piling.
The filler provides a protective and structural coating to the
damaged piling. With this method, the strength of the repaired pile
is dependent solely on the strength of the filler material, which
is preferably an epoxy material and on the adhesive interface with
the pile. Therefore, the amount of filler required is that amount
necessary to provide the desired strength to the pile.
[0012] U.S. Pat. No. 4,697,649 discloses a method of reinforcing a
damaged post in the ground by providing a split casing having
helical threads at one end which are driven into the ground by a
casing rotary drive mechanism. An annulus between the casing and
the post is filled with a suitable filler material. However, this
system is designed for above ground posts and not for underwater
piles. Further, the driving mechanism is relatively complex and
expensive and adds substantially to the repair costs.
[0013] U.S. Pat. No. 4,439,070 relates to a method of restoring an
under waterpile which uses a flexible jacket placed around the pile
and filling the formed annular space between the pile and the
jacket with an appropriate epoxy resin compound. Upper and lower
seals are provided between the jacket and the pile and the jacket
has inlet ports for injection of the epoxy resin and outlet ports
for venting water from the annular space. Again, the strength of
the repaired pile is dependent on the strength and amount of epoxy
resin and on the adhesive interface with the pile, and the system
relies on the effective operation of the seals at each end to form
the closed annular space. A similar system is shown in Swiss Patent
No 573520.
DESCRIPTION OF THE INVENTION
[0014] It is therefore desirable to provide an improved method and
apparatus which enables a repair of a damaged pile to be
efficiently and effectively carried out.
[0015] It is also desirable to provide a method for effecting the
repair of a damaged pile which obviates the need for tidal zone or
underwater welding.
[0016] It is also desirable to provide a method and apparatus for
carrying out the repair of a damaged pile which can be used in a
wide variety of applications and in respect of a wide variety of
piles, columns, posts and the like as referred to above.
[0017] It is also desirable to provide a method and apparatus for
repairing piles which is relatively inexpensive and which enables
the repair to be carried out relatively quickly and
economically.
[0018] It is also desirable to provide an improved method and
apparatus for carrying out the repair of piles which can be used by
relatively unskilled personnel.
SUMMARY OF THE INVENTION
[0019] In accordance with one aspect of the invention there is
provided a method of increasing the structural strength of a load
bearing member, such as a pile, including, inter alia, the steps of
fitting a rigid, structural sleeve to the member, the sleeve having
internal dimensions greater than the external dimensions of the
member to provide a continuous interspace from the member to the
sleeve, supporting the sleeve so that it is spaced from the member,
sealing the continuous interspace, filling the space between the
sleeve and the member with an expansive filler, allowing the filler
to set, cure and expand within the confines of the continuous
interspace to generate an expansive pressure of at least 3 MPa
which imparts at least radial prestress forces on the member and
tensile hoop stresses in the sleeve, whereby the generated forces
effect a transition of loading forces from one section to another
of the load bearing member through the sleeve and expansive
filler.
[0020] The sleeve may be a single piece sleeve for those
applications where a single piece sleeve is able to be engaged with
the member. Otherwise, the sleeve may be formed of two or more
parts which are interconnected, as by welding, bolts or other
mechanical connectors, by clipping, by adhesion or chemical
bonding, by the use of hinge means or by a combination of
these.
[0021] The sleeve is spaced from the member by the use of spacer
means, which may include spacing tabs, indentations or other
deformations of the sleeve material or separate spacers including
spacers formed of synthetic plastic or rubber materials or the like
attached to the inner surfaces of the sleeve. Alternatively, spacer
means may be attached to the member prior to engagement of the
sleeve thereon or spacer means may be inserted between the member
and the sleeve after the engagement of the sleeve on the
member.
[0022] In a further aspect of the invention there is provided, an
apparatus for increasing the structural strength of a load bearing
member including a rigid, structural sleeve formed of one, two or
more elongate sections to be fastened about a load bearing member,
a plurality of spacers adapted to space the sleeve from the member
to form a continuous interspace and a set or cured expansive filler
prestressed to at least 3 MPa to fill the continuous interspace
which generates and imparts at least radial prestress on the member
an sleeve such as to set up compressive hoop stresses in the member
and tensile hoop stresses in the sleeve, the filler forming a rigid
interface between the member and the sleeve.
[0023] In the above form of the invention, a seal is provided
between the lower edge of the sleeve and the member to seal the
continuous interspace between the sleeve and the member at the
lower end thereof. A second seal may also be provided spaced from
the first seal, and preferably at the upper edge of the sleeve. The
seal or seals act to retain the expansive filler within the space
between the sleeve and the member before the filler has set and
expanded. When the sleeve is composed of two or more parts, seals
may also be used between the parts of the sleeve, depending on the
means of fixing the sleeve parts together.
[0024] The expansive filler may comprise a grout, such as a
cementitious grout to which an expansive agent is added so that the
grout sets and expands on curing. For a cementitious grout, the
expansive filler may be a calcium-sulpho-aluminate or lime based
mixture. The applicant has found that after the expansive filler is
applied to the continuous interspace between the member and the
sleeve it begins to cure. The expansive agent used to cause the
grout to increase in volume begins to react within the grout. This
causes a build up of pressure within the annulus and hence creates
a prestress between the structure under repair and the outer
sleeve. This pressure or prestress creates an outward force or
tensile hoop stresses on the sleeve and an inward or compressive
force on the structure under repair. These forces cause extra
frictional forces that allow for increased overall capacity of the
joint.
[0025] Due to losses in prestress through creep and shrinkage over
time, the applicant has found an initial minimum level of prestress
of 3 MPa is necessary to ensure that the beneficial effects of the
application of prestress according to the invention are not
negated. This ensures that the generated forces are imparted
throughout the lifetime of the sleeve applied to the load bearing
member. Depending on the expansive material used, a prestress of 12
Mpa or more is achievable.
[0026] In a further aspect of the invention, there is provided, an
apparatus for increasing the structural strength of a load bearing
member including a rigid, structural sleeve formed on one, two or
more elongate sections to be fastened about a load bearing member,
a plurality of spacers adapted to space the sleeve from the member
to form a continuous interspace and a set or cured expansive filler
prestressed to at least 3 MPa to fill the continuous interspace
which generates and imparts at least radial prestress on the member
and sleeve such as to set up compressive hoop stresses in the
member and tensile hoop stresses in the sleeve, the filler forming
a rigid interface between the member and the sleeve.
[0027] In one form of the invention, shear keys are provided to
positively and rigidly connect the sleeve with the expansive filler
and to connect the filler with the member. Where the member is a
timber pile, shear keys may be engaged with the pile prior to the
engagement of the sleeve. The shear keys may comprise studs, bolts,
including coach bolts or the like fastened to the member. The
sleeve itself may also have inwardly extending shear keys formed by
any suitable means including bolts, punched or pressed deformations
of the sleeve, welded pins or the like. The shear keys may be
preformed so as to also constitute the or some of the spacer
means.
[0028] According to another aspect of the invention there is
provided a method of repairing a pile having a damage area
including the steps of:
[0029] (a) securing a sleeve which has inner dimensions greater
than outer dimensions of the pile around the pile;
[0030] the sleeve having an axial length and being secured so as to
extend beyond the area of damage in both directions;
[0031] (b) providing spacers to space the sleeve from the pile to
form a continuous interspace from the pile to the sleeve;
[0032] (c) sealing a lower end of the continuous interspace;
[0033] (d) introducing an expansive filler through the upper end of
the continuous interspace, displacing any water or air in the
continuous interspace, to thereby fill the interspace with the
expansive filler; and
[0034] (e) permitting the filler to set or cure and to expand
within the confines of the continuous interspace to generate an
expansive pressure of at least 3 MPa and imparts at least radial
prestress forces which tension the sleeve and apply compressive
forces to the pile and produce compressive hoop stresses in the
pile and tensile hoop stresses in the sleeve, whereby the filler
facilitates load transfer primarily by friction across the
filler-to-pile and filler-to-sleeve interfaces.
[0035] In order that the invention may be more readily understood,
embodiments thereof will now be described with reference to the
accompanying drawings wherein.
[0036] FIG. 1 is a part sectional view of a jetty pile and an
encasing repair sleeve in accordance with the present
invention;
[0037] FIG. 2 is a cross-sectional plan view of a cylindrical,
tubular pile and an encasing sleeve in accordance with one
embodiment of the invention;
[0038] FIG. 3 is a part cross-sectional elevational view of a lower
end of an encasing sleeve in accordance with a further embodiment
of the invention;
[0039] FIG. 4 is a schematic, perspective view of a further form of
sleeve of the invention;
[0040] FIG. 5 is a view of a part sleeve illustrating a further
embodiment of a sleeve seal in accordance with the invention;
and
[0041] FIG. 6 is a cross-sectional plan view of a timber pile and
encasing sleeve in accordance with another embodiment of the
invention.
[0042] Referring to the drawings, the embodiments illustrated in
FIGS. 1 to 5 are designed particularly for the repair of a
cylindrical, tubular pile 12 such as those used for jetties and the
like. FIG. 1 illustrates a jetty superstructure 14 supported by a
pile 12 in a sea water environment. The sea water 15 has, over a
period of time, caused corrosive damage 16 to the pile 12 over an
area on the pile 12 generally corresponding to the tidal
limits.
[0043] In order to effect a proper repair and reinstate the
integrity of the pile 12, and to provide protection against
corrosion, it is necessary to secure a sleeve 17 to the pile 12 so
that the sleeve can carry at least part of the load on the pile 12.
In accordance with the present invention, the repair is effected by
locating the sleeve 17 about the pile 12 and spacing the sleeve 17
from the pile to form a substantially annular space 18. The space
18 is then filled with an expansive grout 19 which expands when it
sets thereby tensioning the sleeve 17 and forming a substantially
firm or rigid interface between the pile 12 and the sleeve 17.
[0044] In order that the grout is retained in the annular space 18
before setting, a seal 21 is provided at least around the lower
edge of the sleeve 17 to extend between the sleeve and the pile 12.
The seal shown in FIG. 1 is formed by a flexible, deformable rubber
ring separated at a location to allow the separated 1.0 ends to be
spaced to engage the ring or the pile. However, the seal 21 may be
formed by any suitable means or material, including synthetic
plastic material, mastic or the like.
[0045] Preferably, a second seal 22 is provided at the upper end of
the annular space 18 to maintain the grout within that annular
space during the initial setting and expanding period. Such a seal
22 is fitted in place after the grout has been conveyed into the
annular space 18 and all water and air expelled, otherwise,
provision needs to be made to allow the water and air to
escape.
[0046] It will be appreciated that the sleeve 17, which may be
formed of two or more parts, is, when assembled, a load bearing
member which is able to carry at least part of the load on the
pile. Further, the expansive grout must also be of a material
which, on setting, is able to apply a prestress of at least 3 MPa
and facilitates load transfer between the pile and the sleeve. The
preferred grout for use in this invention is a cementitious grout
mixture having as an expansive agent a calcium-sulpho-aluminate
formulation.
[0047] Such a formulation has an initial setting period during
which the grout hardens. The initial setting period is followed by
a curing period during which the grout expands and generates radial
prestress forces of at least 3 MPa resulting in tensile hoop
stresses in the sleeve 17 and compressive hoop stresses in the pile
12. After approximately 28 days from the time of application of the
grout the level of prestress that builds between the sleeve and the
repaired structure reaches a maximum value. Grout that experiences
constant forces often suffers from loss of strength over time.
There are several reasons for the loss of grout strength over time,
they include shrinkage of the grout and thus relaxation in any
prestress that may exist, creep of the grout due to the applied
load and other factors that may occur during the life of the
structure.
[0048] If the grout is allowed to cure in the air, the water within
the grout will be lost and the size of the grout will be reduced.
In the case of a grouted connection, the losses due to shrinkage
will be lower than other fully exposed grouted structures. By
applying an expansion agent to the grout the present invention
overcomes this shrinkage problem.
[0049] With the constant application of load to the grout some
increase in strain, hence movement in the grout, or relaxation in
prestress may be expected. Depending on the type of grout and the
way in which the load is applied the phenomenon of creep can
manifest itself in many different ways. By allowing for a high
enough level of prestress the present invention overcomes any
possible losses due to creep and ensures that more than a
negligable level of prestress remains throughout the life of the
repair.
[0050] Further, by roughening the inner surface of the sleeve 17, a
greater degree of resistance to slip-between the grout and the
sleeve is achieved. The surface roughness may be increased by any
suitable means including machining, stamping, shot blasting or the
like.
[0051] Referring to FIG. 2, a sleeve 17 is illustrated formed of
two parts 17a and 17b which are held together with two axially
extending rows of bolts 24 which engage threaded holes 26 or
captive nuts in the opposed sleeve half. The sleeve 17 is assembled
around the pile 12 and is spaced therefrom by a series of internal
deformable rubber spacers 27 which are fixed to the inside surface
of each sleeve part 17a and 17b, such as by adhesive or mechanical
fastening. The spacers 27 are provided at several locations along
the length of the sleeve parts whereby, when the sleeve parts are
connected as illustrated, the spacers act to centre the sleeve 17
on the pile 12 so that a substantially annular space 18 exists
between the sleeve 17 and the pile 12. This space is then filled
with the expansive grout mixture aforesaid which, on setting,
expands and produces tensile stresses in the sleeve 17 and
compressive stresses in the pile 12, the grout being of a material
which facilitates load transfer between the pile and the
sleeve.
[0052] Referring to FIG. 3, there is illustrated an alternate form
of spacer 28 which comprises a part cylindrical ring 28 formed of a
flexible material, such as a spring steel or the like, and which is
able to be clipped around the pile 12. The ring 28 has a number of
depending, inwardly extending legs 29 the inner edges of which are
adapted to engage the surface of the pile so that the body of the
ring 28 is spaced therefrom. The ring 28 engages over the lower end
of the sleeve 17 thereby supporting that end such that the sleeve
17 is evenly spaced from the pile 12.
[0053] FIG. 3 also illustrates a lower seal 21 formed of one or
more pockets 31 of a flexible material, such as rubber, synthetic
plastic material, fabric or the like. The pockets 31 are open at
their upper end and are secured to the lower edge portion of the
sleeve 17 by bonding or by any other suitable fastening means.
[0054] In use, when the expansive grout 19 is introduced into the
annular space 18 from the upper end, the grout fills the pockets 31
causing the inner face thereof 32 to engage and seal against the
outer surface of the pile 12. The grouted pockets 31 thus form a
seal preventing the expansive grout 1.9 passing downwardly and out
of the annular space 18. It will be understood that when the sleeve
17 is formed of two or more interconnected part circular parts such
as is shown in FIG. 2, the pockets 31 are provided on each of the
individual sleeve parts and end pockets abut each other when the
sleeve parts are interconnected.
[0055] Referring to FIG. 4, a modified form of sleeve 17 is
illustrated. The sleeve 17 is formed of two parts 17a and 17b
connected together with a continuous hinge 33 which is fixed to the
sleeve parts by rivets 34 or welding or other suitable fastening
means. The sleeve 17 of this embodiment is able to engage over the
pile 12 by opening the sleeve parts about the hinge axis and then
closing and securing the parts by means of fastening bolts 24.
Appropriate spacers 27 are provided to space the sleeve 17 from the
pile 12 and a seal 21 is located at the lower end of the annular
space 18 to enable that space to be filled with an expansive filler
material, preferably the aforesaid cementitious grout mixture
containing an expansive agent which causes the grout to expand on
setting.
[0056] Referring to FIG. 5 there is illustrated a further
embodiment of the invention in which the sleeve part 17a is
provided with an active seal 21 at its lower end which comprises a
bag structure or bladder 36 of substantially toroidal shape
attached to the inner surface of the sleeve part 17a by bonding
with adhesive, or by fastening means 37. The bag structure or
bladder 36 is flexible and is therefore able to conform to the
surface of the pile 12 to which the sleeve part 17a is to be
fitted.
[0057] A grout line 38 extends from an upper end of the sleeve part
17a to the bag structure 36 and through which the bag 36 is adapted
to be filled with grout. In use, the sleeve 17a is connected with a
corresponding sleeve (not shown) about a pile 12, the two parts
being secured together by bolts passing through the holes 25. Grout
is introduced into the opening 39 of the grout line 38 and fills
the bag structure 36 thus forming a close fitting seal against the
pile. Adjacent ends of the bag structures of the co-operating
sleeve parts abut when the sleeve parts are assembled and the
respective bag structures 36 are filled with grout material.
[0058] It will be appreciated that any suitable seal may be
provided at the lower end of the annular space 18 to support the
expansive grout within that space until such time as the grout has
set. Such a seal may be formed of any suitable material, including
synthetic plastic material, foamed plastics material, or even
welding. Similarly, the upper end of the annular interspace 18 may
be sealed 1.0 by welding (in the case of a steel pile 12) or other
sealing means.
[0059] It will also be appreciated that the features of the
invention can be applied to piles or other structures of
non-circular cross-section. In this case, the shape of the sleeve
17 may, if desired, be made to correspond to the shape of the
structural member and to provide a space there between into which
an expansive filler material can be introduced.
[0060] Referring to FIG. 6, the sleeve 17 illustrated is used to
repair a damaged timber pile 12. In this embodiment, shear keys 42
are embedded in the pile 12 and extend into the substantially
annular interspace 18. If desired, the sleeve parts 17a and 17b may
also be formed with internally extending shear key formations 43.
It will be understood that such shear keys 42 and 43 may be used in
the embodiments of FIGS. 1 to 5.
[0061] The sleeve 17 is spaced from the pile 12 by deformable
spacers 27, and a seal, similar to that shown in FIG. 5, is used to
seal the lower end of the interspace.
[0062] The filler material 19 is introduced into the interspace 18
through the upper end thereof. The filler may be introduced through
one or more tubes or pipes 44 which can extend to the lower end of
the interspace to ensure delivery of the filler 19 to that lower
end. Any water or air in the interspace 18 is displaced by the
filler 19 as it is delivered thereto. When filled, the interspace
may be sealed at its upper end to retain the filler during setting
or curing.
[0063] The filler, on curing or setting over a period of time such
as between five (5) minutes and twelve (12) hours, generates
tensile hoop stress in the sleeve and corresponding compressive
stress in the member. These stresses enhance the load transfer
between the member and the sleeve which is primarily effected by
friction across the interfaces.
EXAMPLE 1
[0064] Due to the uncertainty in the expected behaviour of the
grout within the sleeve the best method for prediction of the
possible losses in prestress is from observation of experimental
results. From recent research by Yee Teck Lee, (Yee Teck Lee,
Masters Thesis, "Grouted Sleeve Connections of Circular Hollow
Steel Members Under Large Deformation Cyclic Loading," Monash
University, 2002), the loss of prestress in grouted sleeves occur
in the first 10 to 20 weeks. Further losses appear to be
insignificant beyond this time. The average loss of prestress
observed in Yee Teck Lee's research was approximately 2.6 MPa, this
confirms that a prestress greater than 3 MPa would allow for this
expected loss.
EXAMPLE 2
[0065] A method for calculating the capacity of a stressed grouted
connection is given in the UK Department of Energy, Offshore
Technology Report on Grouted and Mechanical Strengthening and
Repair of Tubular Steel Offshore Structures. (R G Harwood, E P
Shuttleworth, Department of Energy, "Grouted And Mechanical
Strengthening and Repair of Tubular Steel Offshore Strucutres,"
Offshore Technical Report, 1988) These equations have been applied
(see below) to determine the strength of the present invention for
several different configurations. It can be seen from these
calculations that if the initial prestress is 3 MPa and this
prestress reduces to 0.4 MPa over the joints lifetime the capacity
of the section is twice the capacity of the same section without
the application of prestress.
[0066] The capacity of the present invention is from the bond
between the grout and the sleeve and the friction caused by the
application of the prestress. If there were no prestress applied,
or if it was at a level such that it may deteriorate to no
prestress, the capacity of the joint would be from the bond alone,
there would be no contribution from the extra frictional forces
from the expansive grout.
[0067] As can be seen in the calculations the capacity of the joint
is also dependent on the length of the sleeve. The longer the
sleeve the larger the area of contact with the area under repair.
If the length of the sleeve is reduced it is necessary to increase
the contact force in some way so as to maintain the capacity. By
increasing the prestress the contact force increases, this
increases the capacity of the joint, therefore the length of the
sleeve required can be reduced to maintain a similar capacity, thus
decreasing the cost of the repair.
[0068] The capacity of the present invention is greater than that
for other such repairs as the prestress developed in the sleeve
allows for significant increases in the overall capacity of the
connection.
[0069] It will be understood that features described in relation to
any one of the described embodiments may be used in the other of
the embodiments.
[0070] by Martin Hewitt
[0071] Sep. 24, 2002.
[0072] from "Grouted and Mechanical Strengthening of Tubular Steel
Offhsore Structures"
[0073] Offshore Technology Report (OTR) OTH 88 283 from Department
of Energy section 1.8.7 pg 56
EXAMPLE 3 (a)
[0074] Static Strength of Stressed Grouted Connections:
[0075] Assess Static Strength with no prestress. Resistance
provided by surface friction 1 P p := 0.22 ( F n C s ' + 1.75 10 -
3 A C s b ) [ 1 + 33 ( D T ) - 1 ] Eqn . 1.8 .3 OTR report
EXAMPLE 3(b)
[0076] Assess Static Strength with 1 MPa prestress. Assume 3 MPa
with 2.6 MPa loss over 1 year see Yee Teck Lee "Grouted Sleeve
Connection of Circular Hollow Steel Members Under Large Deformation
Cyclic Loading". 2 P p := 0.22 ( F n C s ' + 1.75 10 - 3 A C s b )
[ 1 + 33 ( D T ) - 1 ] Eqn . 1.8 .3 OTR report
[0077] Therefore application of a prestress of 3 MPa with a
subsequent 2.6 MPa loss of prestress results in a doubling of the
capacity.
EXAMPLE 4(a)
[0078] Assess Static Strength of the present invention grouted
connection with 10 MPa Prestress and length of 1 D 3 P p := 0.22 (
F n C s ' + 1.75 10 - 3 A C s b ) [ 1 + 33 ( D T ) - 1 ] Eqn . 1.8
.3 OTR report
EXAMPLE 4(b)
[0079] Assess required Length to create similar capacity with no
prestress. 4 P p := 0.22 ( F n C s ' + 1.75 10 - 3 A C s b ) [ 1 +
33 ( D T ) - 1 ] Eqn . 1.8 .3 OTR report
[0080] Therefore for an equivalent permissible load, the required
length of the sleeve using the present invention is approximately
{fraction (1/26)}.sup.th of that required for a grouted repair with
no prestress
* * * * *