CA2502065A1 - Method for in situ repair of timber piles using synthetic reinforcing fabric - Google Patents
Method for in situ repair of timber piles using synthetic reinforcing fabric Download PDFInfo
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- CA2502065A1 CA2502065A1 CA002502065A CA2502065A CA2502065A1 CA 2502065 A1 CA2502065 A1 CA 2502065A1 CA 002502065 A CA002502065 A CA 002502065A CA 2502065 A CA2502065 A CA 2502065A CA 2502065 A1 CA2502065 A1 CA 2502065A1
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/64—Repairing piles
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G23/0225—Increasing or restoring the load-bearing capacity of building construction elements of circular building elements, e.g. by circular bracing
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G2023/0248—Increasing or restoring the load-bearing capacity of building construction elements of elements made of wood
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G2023/0251—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements
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- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Structural Engineering (AREA)
- Civil Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Mechanical Engineering (AREA)
- Paleontology (AREA)
- Mining & Mineral Resources (AREA)
- General Engineering & Computer Science (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Piles And Underground Anchors (AREA)
Abstract
In a method for in situ repair of a surficially decayed or damaged timber pile, unsound material is removed from the section to be repaired. A grout form is placed around the repair section of the pile, and a fluid grout is introduced into the form so as to fill the space inside. After the grout has solidified, the form is removed, and at least one layer of a non-biodegradable synthetic reinforcing fabric is bonded to the surface of the grout in the repair area using a suitable adhesive resin. The reinforcing fabric has a least one layer of primary fibers that are adapted to withstand tensile stress. The primary fibers of the reinforcing fabric layers are selectively oriented, either perpendicular, parallel, or obliquely relative to the axis of the pile, as appropriate to achieve desired structural reinforcing effects. In an alternative embodiment, the damaged section of the pile may be cut out and replaced with a timber infill section, which is anchored to the stub of the cut-off pile using double-hooked tension bars placed in corresponding grooves and holes formed in the infill section and the pile stub. At least one layer of reinforcing fabric is then wrapped around and bonded to the infill section and the pile stub so as to envelope the region having tension bars, using a suitable adhesive resin.
Description
METHOD FOR IN SITU REPAIR OF TIMBER PILES
USING SYNTHETIC REINFORCING FABRIC
FIELD OF THE INVENTION
The present invention relates in general to methods for in situ repair of ground-penetrating wooden structural elements, such as timber piles and utility poles, that have been damaged by fungi or other causes.
BACKGROUND OF THE INVENTION
It is well known to use timber piles to support buildings and other structures.
Timber piles are commonly driven into pre-drilled pilot holes, or may be driven directly into the ground without pre-drilling. Depending on the soil conditions, the required load-carrying capacity is developed by driving the piles to a subsurface hardpan or bedrock, or to a sufficient depth to develop the required capacity by way of "skin friction" between the circumferential surfaces of the piles and the surrounding soil. In some applications, the piles must be capable of resisting lateral forces due to wind or other lateral loads acting on the supported structure. In such cases, the upper sections of the piles are subject to transverse flexural stresses in addition to the vertical compressive stresses induced by the weight of the supported structure.
Timber piles are preferably treated with creosote or other preservatives to prevent or inhibit deterioration due to fungal attack. Various fungi that are naturally prevalent in the environment will consume organic material provided that the requisite conditions of oxygen, moisture, and temperature are present. These conditions are commonly present (particularly in the spring) in the upper few feet of soil under structures supported by timber piles, particularly where there is an air space between the piles and the supported structure (e.g., buildings with crawl spaces). Where the piles are inadequately protected against fungal attack, or where the piles' preservative treatment has deteriorated or has been impaired for some reason, the piles will be susceptible to rot or decay, particularly near the ground surface.
Such rot or decay causes serious impairment of the piles' capacity to resist both vertical and transverse structural loads. This effect is particularly pronounced with S respect to the piles' flexural resistance, since the loss of material thickness from the outer surface of a structural member causes an exponential reduction in flexural strength and stiffness. For these reasons, it is critically important to repair or replace timber piles that have been damaged by fungal attack or other phenomena, in order to ensure that the piles will have sufficient strength to resist all loads that may be imposed by the supported structure, and with an adequate factor of safety. It is also highly desirable to be able to repair the piles in situ.
There are a number of known methods for dealing with the problem of decayed timber piles, including underpinning methods that involve the installation of new piles to replace the damaged piles. The main object of the present invention is to provide an improved method for in situ repair of timber piles to restore all or part of the structural integrity and strength that has been lost due to decay or other damage.
BRIEF DESCRIPTION OF THE INVENTION
In general terms, the present invention is a method for repairing, in situ, a timber pile that has experienced deterioration due to fungal attack or other type of damage. In one aspect, the invention is a method for repairing a damaged timber pile in situ, comprising the steps of:
(a) removing unsound material from a damaged timber pile within a selected repair section, so as to expose a core section of sound material;
(b) installing a grout form enclosing the repair section of the pile so as to form a grout space within the form, said form having a grout opening and being configured so as to generally correspond to the original surface contours of the pile in the repair section;
USING SYNTHETIC REINFORCING FABRIC
FIELD OF THE INVENTION
The present invention relates in general to methods for in situ repair of ground-penetrating wooden structural elements, such as timber piles and utility poles, that have been damaged by fungi or other causes.
BACKGROUND OF THE INVENTION
It is well known to use timber piles to support buildings and other structures.
Timber piles are commonly driven into pre-drilled pilot holes, or may be driven directly into the ground without pre-drilling. Depending on the soil conditions, the required load-carrying capacity is developed by driving the piles to a subsurface hardpan or bedrock, or to a sufficient depth to develop the required capacity by way of "skin friction" between the circumferential surfaces of the piles and the surrounding soil. In some applications, the piles must be capable of resisting lateral forces due to wind or other lateral loads acting on the supported structure. In such cases, the upper sections of the piles are subject to transverse flexural stresses in addition to the vertical compressive stresses induced by the weight of the supported structure.
Timber piles are preferably treated with creosote or other preservatives to prevent or inhibit deterioration due to fungal attack. Various fungi that are naturally prevalent in the environment will consume organic material provided that the requisite conditions of oxygen, moisture, and temperature are present. These conditions are commonly present (particularly in the spring) in the upper few feet of soil under structures supported by timber piles, particularly where there is an air space between the piles and the supported structure (e.g., buildings with crawl spaces). Where the piles are inadequately protected against fungal attack, or where the piles' preservative treatment has deteriorated or has been impaired for some reason, the piles will be susceptible to rot or decay, particularly near the ground surface.
Such rot or decay causes serious impairment of the piles' capacity to resist both vertical and transverse structural loads. This effect is particularly pronounced with S respect to the piles' flexural resistance, since the loss of material thickness from the outer surface of a structural member causes an exponential reduction in flexural strength and stiffness. For these reasons, it is critically important to repair or replace timber piles that have been damaged by fungal attack or other phenomena, in order to ensure that the piles will have sufficient strength to resist all loads that may be imposed by the supported structure, and with an adequate factor of safety. It is also highly desirable to be able to repair the piles in situ.
There are a number of known methods for dealing with the problem of decayed timber piles, including underpinning methods that involve the installation of new piles to replace the damaged piles. The main object of the present invention is to provide an improved method for in situ repair of timber piles to restore all or part of the structural integrity and strength that has been lost due to decay or other damage.
BRIEF DESCRIPTION OF THE INVENTION
In general terms, the present invention is a method for repairing, in situ, a timber pile that has experienced deterioration due to fungal attack or other type of damage. In one aspect, the invention is a method for repairing a damaged timber pile in situ, comprising the steps of:
(a) removing unsound material from a damaged timber pile within a selected repair section, so as to expose a core section of sound material;
(b) installing a grout form enclosing the repair section of the pile so as to form a grout space within the form, said form having a grout opening and being configured so as to generally correspond to the original surface contours of the pile in the repair section;
(c) introducing a fluid grout into the grout space through the opening in the grout form, so as to substantially fill the grout space;
(d) allowing the grout to solidify;
(e) removing the grout form, thus exposing the grouted area; and (f) bonding a first layer of non-biodegradable reinforcing fabric to the exposed surface of the grouted area using an impregnation resin.
In a second aspect, the invention is a method for repairing a damaged, substantially vertical timber pile in situ, comprising the steps of:
(a) exposing a portion of the pile, including the damaged region plus a portion extending below the damaged region to a ground surface;
(b) cutting off an upper portion of the pile by severing the pile at a substantially horizontal cutting plane located below the damaged region, leaving a pile stub projecting above the ground surface, said pile stub having a substantially horizontal top surface and a circumferential outer surface;
(c) forming a plurality of substantially vertical grooves in the circumferential outer surface of the pile stub, each said groove being of a selected length and extending downward from the top surface of the pile stub;
(d) forming a hole at or near the lower end of each groove in the pile stub, each said hole extending radially into the pile;
(e) providing a round timber infill section of selected length, said infill section having an upper end, a lower end, and a circumferential outer surface, said lower end having a substantially planar bearing surface oriented substantially transverse to the longitudinal axis of the infill section, with the diameter of said infill section substantially matching the diameter of the pile stub;
(d) allowing the grout to solidify;
(e) removing the grout form, thus exposing the grouted area; and (f) bonding a first layer of non-biodegradable reinforcing fabric to the exposed surface of the grouted area using an impregnation resin.
In a second aspect, the invention is a method for repairing a damaged, substantially vertical timber pile in situ, comprising the steps of:
(a) exposing a portion of the pile, including the damaged region plus a portion extending below the damaged region to a ground surface;
(b) cutting off an upper portion of the pile by severing the pile at a substantially horizontal cutting plane located below the damaged region, leaving a pile stub projecting above the ground surface, said pile stub having a substantially horizontal top surface and a circumferential outer surface;
(c) forming a plurality of substantially vertical grooves in the circumferential outer surface of the pile stub, each said groove being of a selected length and extending downward from the top surface of the pile stub;
(d) forming a hole at or near the lower end of each groove in the pile stub, each said hole extending radially into the pile;
(e) providing a round timber infill section of selected length, said infill section having an upper end, a lower end, and a circumferential outer surface, said lower end having a substantially planar bearing surface oriented substantially transverse to the longitudinal axis of the infill section, with the diameter of said infill section substantially matching the diameter of the pile stub;
(f) forming a plurality of substantially vertical grooves in the circumferential outer surface of the infill section, each said groove being of a selected length and extending upward from the lower end of the pile stub, with the number and circumferential spacing of said grooves matching the number and spacing of the grooves in the pile stub;
(g) forming a hole at or near the upper end of each groove in the infill section, each said hole extending radially into the stub;
(h) positioning the infill section upon the pile stub, such that the lower bearing surface of the infill section bears on the top surface of the pile stub, with the vertical grooves in the infill section being aligned with the vertical grooves in the pile stub, thus forming a plurality of tension bar channels each comprising an infill section groove and a matching groove in the pile stub plus their corresponding radial holes;
(i) for each tension bar channel, providing a double-hooked tension bar having a straight elongate center section and having a hooked section at each end, said hooked sections being substantially perpendicular to the center section, with the distance between the hooked sections matching the distance between the radial holes of the corresponding tension bar channel;
(j) applying grout to the radial holes in the infill section and the pile stub;
(k) before the grout has set, inserting a double-hooked tension bar into each tension bar channel such that the center section of each tension bar is disposed substantially completely beneath the circumferential outer surfaces of the infill section and the pile stub, and such that each hooked section of the tension bar is extends into one of the tension bar channel's radial holes forming part of the tension bar channel, said step of inserting the tension bars into the tension bar channels causing displacement of grout such that there remains a layer of grout substantially surrounding each hook within its corresponding radial hole;
(1) bonding a first layer of non-biodegradable reinforcing fabric to the circumferential surfaces of the infill section and the pile stub using an impregnation resin, said first layer of reinforcing fabric being of sufficient dimensions to substantially cover all of the tension bars.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:
FIGURE 1 is a conceptual depiction of a damaged timber pile prior to being repaired in accordance with a first aspect of the present invention.
FIGURE 2 depicts the repair section of the damaged timber pile of Figure 1, after removal of unsound material.
FIGURE 3 illustrates the repair section of the pile of Figure 2 with the grout form in place.
FIGURE 4 illustrates the repair section of the pile of Figure 2 after application of grout and reinforcing fabric.
FIGURE 5 is an elevation of a damaged timber pile repaired in accordance with a second aspect of the present invention, illustrating a grooved infill section positioned on the grooved pile stub of a timber pile that has been cut off below the zone of damage.
FIGURE 6 is an exemplary cross-section through either the infill section or the pile stub in Figure 5, further illustrating the grooves formed therein.
(g) forming a hole at or near the upper end of each groove in the infill section, each said hole extending radially into the stub;
(h) positioning the infill section upon the pile stub, such that the lower bearing surface of the infill section bears on the top surface of the pile stub, with the vertical grooves in the infill section being aligned with the vertical grooves in the pile stub, thus forming a plurality of tension bar channels each comprising an infill section groove and a matching groove in the pile stub plus their corresponding radial holes;
(i) for each tension bar channel, providing a double-hooked tension bar having a straight elongate center section and having a hooked section at each end, said hooked sections being substantially perpendicular to the center section, with the distance between the hooked sections matching the distance between the radial holes of the corresponding tension bar channel;
(j) applying grout to the radial holes in the infill section and the pile stub;
(k) before the grout has set, inserting a double-hooked tension bar into each tension bar channel such that the center section of each tension bar is disposed substantially completely beneath the circumferential outer surfaces of the infill section and the pile stub, and such that each hooked section of the tension bar is extends into one of the tension bar channel's radial holes forming part of the tension bar channel, said step of inserting the tension bars into the tension bar channels causing displacement of grout such that there remains a layer of grout substantially surrounding each hook within its corresponding radial hole;
(1) bonding a first layer of non-biodegradable reinforcing fabric to the circumferential surfaces of the infill section and the pile stub using an impregnation resin, said first layer of reinforcing fabric being of sufficient dimensions to substantially cover all of the tension bars.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:
FIGURE 1 is a conceptual depiction of a damaged timber pile prior to being repaired in accordance with a first aspect of the present invention.
FIGURE 2 depicts the repair section of the damaged timber pile of Figure 1, after removal of unsound material.
FIGURE 3 illustrates the repair section of the pile of Figure 2 with the grout form in place.
FIGURE 4 illustrates the repair section of the pile of Figure 2 after application of grout and reinforcing fabric.
FIGURE 5 is an elevation of a damaged timber pile repaired in accordance with a second aspect of the present invention, illustrating a grooved infill section positioned on the grooved pile stub of a timber pile that has been cut off below the zone of damage.
FIGURE 6 is an exemplary cross-section through either the infill section or the pile stub in Figure 5, further illustrating the grooves formed therein.
FIGURE 7 is an exemplary illustration of a double-hooked tension bar for use in the method of the second aspect of the invention.
FIGURE 8 is an enlarged cross-sectional detail through one of the tension bars after completion of a pile repair in accordance with the method of the second aspect of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
1. First Aspect of the Invention Figure 1 illustrates a timber pile 10 supporting an elevated structure S, where the pile 10 has experienced decay or damage near the ground surface. The particular structural arrangement shown in Figure 1 is for exemplary purposes only. The method of the present invention is readily adaptable for use in the repair of damaged timber piles in other types of structural systems, and also for use in repair of other timber foundation elements including utility poles.
After excavating as required to expose the damaged section 20 of pile 10, unsound material is removed from pile 10 so as to expose undamaged pile material, thus creating a repair section 12. As shown in Figure 2, the repair section 12 must include a core section 18 by which pile 10 maintains at least a minimal degree of structural continuity across the repair section 12. The repair section 12 is preferably prepared with a bevelled section 16 adjacent to and on each side of core section 18, and a transition section 14 between each bevelled section 16 and adjacent undamaged portions of pile 10.
The prepared surfaces of repair section 12 do not need to be uniform or smooth, and in fact a certain degree of surface irregularity may be beneficial to enhance the effectiveness of the bond with the grout that is to be applied in repair section 12.
The primary purpose of transition sections 14 is to provide for a minimum thickness of grout within repair section 12, and for this purpose it may be necessary to remove a certain amount of undamaged pile material. Each transition section 14 preferably will preferably be at least 150 millimetres long, as shown in Figure 2. The primary purpose of bevelled sections 16 is to eliminate or minimize the stress-raising effects of abrupt changes in cross-sectional configuration of the grout to be applied in repair section 12. Preferably, bevelled sections 16 will be conically bevelled at an angle between 30 and 45 degrees relative to horizontal, as shown in Figure 2.
However, other bevel angles may be used, and in fact it is not essential that bevelled sections 16 be completely conical in configuration; for instance, bevelled sections 16 could include curvilinear portions (as viewed in elevation). Whatever configuration bevelled sections 16 may take, it will typically be necessary to remove a certain amount of undamaged pile material to obtain the desired geometrical configuration for the bevelled sections 16.
In the preferred embodiment of the method, the timber in the repair section prior to the introduction of grout, preferably such that the moisture content in the repair section is reduced to approximately 18 per cent by weight, or less.
After repair section 12 has been prepared as described above, it is ready to be grouted. In the preferred embodiment of the method, the surfaces within repair section 1 S 12 that will be in contact with grout are coated with a suitable bonding agent. As shown in Figure 3, the next step in the method is to place a grout form 30 around repair section 12, thereby forming a grout space 34 between the inner surfaces of grout form 30 and the surfaces of repair section 12. Grout form 30, which incorporates a grout opening 32, is preferably configured to generally match the original shape of pile 10 in repair section 12, such that the introduction of grout into grout space 34 will restore pile 10 to substantially its full original section within repair section 12. Grout form 30 may be fashioned in any suitable way, in accordance with apparatus and methods well known in the art of formwork, such that it will be readily removable after completion of the grouting process. For example, in the preferred embodiment of the method, grout form 30 is a two-piece steel form that may be clamped in place around repair section 12.
When grout form 30 is in place, a fluid grout material 40 is introduced through grout opening 32 so as to substantially fill grout space 34 with grout 40.
Preferably, grout 40 is an epoxy grout, such as Sikadur 42 Multiflo.TM After grout 40 has sufficiently cured and solidified, grout form 30 is removed to expose grout surface 42.
Next, a first layer of non-biodegradable reinforcing fabric 50 is bonded over grout surface 42, using a suitable adhesive resin (such as Sikadur 300TM) that will bond to grout surface 42 and will also impregnate and bond with fabric 50. In the preferred embodiment of the method, fabric 50 is a carbon fiber fabric having unidirectional primary fibers (such as Sikawrap 103CTM). In the sense used in this specification, primary fibers are the fabric fibers that are particularly adapted and oriented so as to receive and resist tensile stresses (as opposed to secondary fibers that have comparatively less significant structural strength and function). Preferably, the process of bonding fabric 50 to grout surface 42 involves first applying a coat of resin to grout surface 42, then tightly wrapping fabric 50 over grout surface 42 so that the resin becomes dispersed within the fibers of fabric 50.
To enhance the effectiveness of the bond, fabric 50 may receive a coat of resin before being wrapped over grout surface 42. Preferably as well, a further coat of resin is applied to fabric 50 after it has been applied over grout surface 42.
The first layer of fabric 50 may be applied to repair section 12 of pile 10 with its 1 S primary fibers either parallel or perpendicular to the axis of pile 10. In cases where pile 10 is subject to vertical loading only, a satisfactory repair may be achieved using a first layer of fabric 50 with its primary fibers perpendicular to the pile axis. In cases where pile 10 is subject to axial compressive stress only (i.e., no bending stresses), it is desirable for the primary fibers of the reinforcing fabric 50 to be wrapped circumferentially around the pile so as to provide "hoop strength" to hold grout 40 in place so that it can absorb imposed compressive loads and transfer them to undamaged sections of pile 10 below repair section 12.
When a structural member is subject to bending stresses, the member will be under longitudinal tensile stresses on one side of the member, and counteracting longitudinal compressive stresses on the opposite side. The magnitude of these tensile and compressive bending stresses is greatest at the outermost surfaces of the member (i.e., farthest from the member's neutral axis). In the case of a laterally-loaded pile, therefore, one side of the pile is under longitudinal tensile stress, with the stress intensity being greatest at the outer surface of the pile. Decay or other damage to the surface of a timber pile thus removes material that would otherwise have been available to resist these tensile bending stresses, making it necessary for any repair method to restore longitudinal tensile strength across the repair zone.
Accordingly, in cases where pile 10 is also subject to lateral loadings that will induce flexural stresses in pile 10, the method of the present invention preferably provides at least one layer of reinforcing fabric 50 with its primary fibers oriented parallel to the axis of pile 10. It may be sufficient in some cases for this layer of fabric 50 to be the only layer of fabric used in the repair (for example, where the damaged pile retains sufficient capacity to safely carry all anticipated vertical loads, but the decay or other damage has seriously impaired the pile's lateral bending strength). In most cases, however, it will be preferable to use two layers of fabric 50 - one with its primary fibers substantially perpendicular to the pile axis, and one with its primary fibers substantially parallel to the pile axis. In such cases, the second layer is applied in substantially the same way as previously described with respect to the first layer.
Where two layers of fabric 50 are applied to pile 10, it is not critical for them to be applied in any particular order. In other words, the first layer may be applied with its primary fibers perpendicular to the pile axis, with the primary fibers of the second layer being parallel to the pile axis, or, alternatively, the first layer may be applied with its primary fibers parallel to the pile axis, with the primary fibers of the second layer being perpendicular to the pile axis.
Beneficial structural effects may also be achieved by applying any one or more layers of fabric 50 with their primary fibers obliquely oriented (e.g., diagonally). Using this method of fabric application, it may be possible (depending on the loads acting on the pile in question) to achieve a satisfactory degree of structural repair and reinforcement for purposes of both vertical and lateral loadings, using only a single layer of fabric 50. This is due to the fact that an obliquely-oriented primary fiber can be resolved, in accordance with well known structural engineering principles, into two components, one being oriented parallel to the pile axis and the other being perpendicularly oriented relative to the pile axis.
FIGURE 8 is an enlarged cross-sectional detail through one of the tension bars after completion of a pile repair in accordance with the method of the second aspect of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
1. First Aspect of the Invention Figure 1 illustrates a timber pile 10 supporting an elevated structure S, where the pile 10 has experienced decay or damage near the ground surface. The particular structural arrangement shown in Figure 1 is for exemplary purposes only. The method of the present invention is readily adaptable for use in the repair of damaged timber piles in other types of structural systems, and also for use in repair of other timber foundation elements including utility poles.
After excavating as required to expose the damaged section 20 of pile 10, unsound material is removed from pile 10 so as to expose undamaged pile material, thus creating a repair section 12. As shown in Figure 2, the repair section 12 must include a core section 18 by which pile 10 maintains at least a minimal degree of structural continuity across the repair section 12. The repair section 12 is preferably prepared with a bevelled section 16 adjacent to and on each side of core section 18, and a transition section 14 between each bevelled section 16 and adjacent undamaged portions of pile 10.
The prepared surfaces of repair section 12 do not need to be uniform or smooth, and in fact a certain degree of surface irregularity may be beneficial to enhance the effectiveness of the bond with the grout that is to be applied in repair section 12.
The primary purpose of transition sections 14 is to provide for a minimum thickness of grout within repair section 12, and for this purpose it may be necessary to remove a certain amount of undamaged pile material. Each transition section 14 preferably will preferably be at least 150 millimetres long, as shown in Figure 2. The primary purpose of bevelled sections 16 is to eliminate or minimize the stress-raising effects of abrupt changes in cross-sectional configuration of the grout to be applied in repair section 12. Preferably, bevelled sections 16 will be conically bevelled at an angle between 30 and 45 degrees relative to horizontal, as shown in Figure 2.
However, other bevel angles may be used, and in fact it is not essential that bevelled sections 16 be completely conical in configuration; for instance, bevelled sections 16 could include curvilinear portions (as viewed in elevation). Whatever configuration bevelled sections 16 may take, it will typically be necessary to remove a certain amount of undamaged pile material to obtain the desired geometrical configuration for the bevelled sections 16.
In the preferred embodiment of the method, the timber in the repair section prior to the introduction of grout, preferably such that the moisture content in the repair section is reduced to approximately 18 per cent by weight, or less.
After repair section 12 has been prepared as described above, it is ready to be grouted. In the preferred embodiment of the method, the surfaces within repair section 1 S 12 that will be in contact with grout are coated with a suitable bonding agent. As shown in Figure 3, the next step in the method is to place a grout form 30 around repair section 12, thereby forming a grout space 34 between the inner surfaces of grout form 30 and the surfaces of repair section 12. Grout form 30, which incorporates a grout opening 32, is preferably configured to generally match the original shape of pile 10 in repair section 12, such that the introduction of grout into grout space 34 will restore pile 10 to substantially its full original section within repair section 12. Grout form 30 may be fashioned in any suitable way, in accordance with apparatus and methods well known in the art of formwork, such that it will be readily removable after completion of the grouting process. For example, in the preferred embodiment of the method, grout form 30 is a two-piece steel form that may be clamped in place around repair section 12.
When grout form 30 is in place, a fluid grout material 40 is introduced through grout opening 32 so as to substantially fill grout space 34 with grout 40.
Preferably, grout 40 is an epoxy grout, such as Sikadur 42 Multiflo.TM After grout 40 has sufficiently cured and solidified, grout form 30 is removed to expose grout surface 42.
Next, a first layer of non-biodegradable reinforcing fabric 50 is bonded over grout surface 42, using a suitable adhesive resin (such as Sikadur 300TM) that will bond to grout surface 42 and will also impregnate and bond with fabric 50. In the preferred embodiment of the method, fabric 50 is a carbon fiber fabric having unidirectional primary fibers (such as Sikawrap 103CTM). In the sense used in this specification, primary fibers are the fabric fibers that are particularly adapted and oriented so as to receive and resist tensile stresses (as opposed to secondary fibers that have comparatively less significant structural strength and function). Preferably, the process of bonding fabric 50 to grout surface 42 involves first applying a coat of resin to grout surface 42, then tightly wrapping fabric 50 over grout surface 42 so that the resin becomes dispersed within the fibers of fabric 50.
To enhance the effectiveness of the bond, fabric 50 may receive a coat of resin before being wrapped over grout surface 42. Preferably as well, a further coat of resin is applied to fabric 50 after it has been applied over grout surface 42.
The first layer of fabric 50 may be applied to repair section 12 of pile 10 with its 1 S primary fibers either parallel or perpendicular to the axis of pile 10. In cases where pile 10 is subject to vertical loading only, a satisfactory repair may be achieved using a first layer of fabric 50 with its primary fibers perpendicular to the pile axis. In cases where pile 10 is subject to axial compressive stress only (i.e., no bending stresses), it is desirable for the primary fibers of the reinforcing fabric 50 to be wrapped circumferentially around the pile so as to provide "hoop strength" to hold grout 40 in place so that it can absorb imposed compressive loads and transfer them to undamaged sections of pile 10 below repair section 12.
When a structural member is subject to bending stresses, the member will be under longitudinal tensile stresses on one side of the member, and counteracting longitudinal compressive stresses on the opposite side. The magnitude of these tensile and compressive bending stresses is greatest at the outermost surfaces of the member (i.e., farthest from the member's neutral axis). In the case of a laterally-loaded pile, therefore, one side of the pile is under longitudinal tensile stress, with the stress intensity being greatest at the outer surface of the pile. Decay or other damage to the surface of a timber pile thus removes material that would otherwise have been available to resist these tensile bending stresses, making it necessary for any repair method to restore longitudinal tensile strength across the repair zone.
Accordingly, in cases where pile 10 is also subject to lateral loadings that will induce flexural stresses in pile 10, the method of the present invention preferably provides at least one layer of reinforcing fabric 50 with its primary fibers oriented parallel to the axis of pile 10. It may be sufficient in some cases for this layer of fabric 50 to be the only layer of fabric used in the repair (for example, where the damaged pile retains sufficient capacity to safely carry all anticipated vertical loads, but the decay or other damage has seriously impaired the pile's lateral bending strength). In most cases, however, it will be preferable to use two layers of fabric 50 - one with its primary fibers substantially perpendicular to the pile axis, and one with its primary fibers substantially parallel to the pile axis. In such cases, the second layer is applied in substantially the same way as previously described with respect to the first layer.
Where two layers of fabric 50 are applied to pile 10, it is not critical for them to be applied in any particular order. In other words, the first layer may be applied with its primary fibers perpendicular to the pile axis, with the primary fibers of the second layer being parallel to the pile axis, or, alternatively, the first layer may be applied with its primary fibers parallel to the pile axis, with the primary fibers of the second layer being perpendicular to the pile axis.
Beneficial structural effects may also be achieved by applying any one or more layers of fabric 50 with their primary fibers obliquely oriented (e.g., diagonally). Using this method of fabric application, it may be possible (depending on the loads acting on the pile in question) to achieve a satisfactory degree of structural repair and reinforcement for purposes of both vertical and lateral loadings, using only a single layer of fabric 50. This is due to the fact that an obliquely-oriented primary fiber can be resolved, in accordance with well known structural engineering principles, into two components, one being oriented parallel to the pile axis and the other being perpendicularly oriented relative to the pile axis.
In an alternative embodiment of the method, the reinforcing fabric 50 has bi-directional primary fibers; e.g., with two sets of primary fibers disposed substantially perpendicular to each other. Using fabric of this type facilitates timber pile repairs that require the application of only one layer of fabric 50, while obtaining the structural benefits of two layers of fabric 50 having unidirectional primary fibers as described above. In other words, bi-directional fabric 50 will provide primary fibers that are effective for purposes of both hoop strength and flexural strength, regardless of the fabric's orientation. Bi-directional fabric 50 may be applied to pile 10 with one set of primary fibers parallel to the pile axis, and the other set perpendicular to the pile axis.
Alternatively, the desired structural benefits may also be achieved by applying bi-directional fabric 50 with its two sets of primary fibers oriented obliquely (e.g., diagonally) relative to the pile axis.
2. Second Aspect of the Invention The first aspect of the present invention, as described above, is directed to repairing damaged timber piles in which the damage is surficial only; i.e., where there remains a continuous core of undamaged timber along the full length of the pile. The second aspect of the invention is directed to repairing a timber pile in which the damage is so extensive that the pile does not retain a sound, undamaged core, or where any such undamaged core is too small to provide sufficient residual structural strength to make a repair according to the first aspect of the invention a practical option.
In such situations, the damaged pile may be repaired using an alternative method in accordance with the second aspect of the invention, which is illustrated in Figures 5-8.
In accordance with this method, a portion of the damaged pile 10 is exposed (excavating as required) down to a grade level G for a selected distance below the damaged region of the pile 10. Pile 10 is then cut off on a substantially horizontal plane C
located below the damaged region, leaving a pile stub 60 extending upward from grade level G and having a length Lla (length Lla being a selected distance that will provide adequate working room for completion of the repair, as further described hereinbelow). Pile stub 60 has a substantially horizontal top surface 61 and a circumferential outer surface 63.
Next, a plurality of substantially vertical grooves 62 are formed in the circumferential outer surface 63 of pile stub 60, extending downward from the top surface 61 of the pile stub for a distance Llb (the determination of which is discussed below). At or near the lower end of each groove 62, a radially-oriented hole 64 is drilled into the pile stub 60 to a depth L3a.
A round timber infill section 70, having a length appropriate to the repair being carried out, is then provided. Infill section 70 has an upper end, a lower end (which has a substantially planar bearing surface 71 oriented substantially transverse to the longitudinal axis of infill section 70), and a circumferential outer surface 73. Infill section 70 has a nominal diameter substantially corresponding with that of pile stub 60.
A plurality of substantially vertical grooves 72 are formed in the circumferential outer surface 73 of infill section 70, extending upward from the lower end of infill section 70 for a distance Llc (the determination of which is discussed below). At or near the upper end of each groove 72, a radially-oriented hole 74 is drilled into infill section 70 to a depth L3a. For purposes which will be explained, the circumferential spacing of grooves 72 in infill section 70 substantially matches the circumferential spacing of grooves 62 in pile stub 60.
The preceding description suggests that grooves 72 and radial holes 74 may be formed in infill section 70 on site, after infill section 70 has been positioned on pile stub 60. Alternatively, however, grooves 72 and radial holes 74 may be pre-formed in infill section 70. Those skilled in the art of the invention will appreciate that the particular stage or location at which grooves 72 and radial holes 74 are formed in infill section 70 is not critical to the method.
In Figure 5, grooves 62 and 72 are shown in a staggered pattern, with the ends of adjacent grooves offset a selected distance L4. This is preferred in order to minimize stress concentrations in pile stub 60 and infill section 70, but it is not essential. Grooves 62 and 72 may be non-staggered without departing from the scope of the method.
Once grooves 72 and radial holes 74 have been formed, infill section 70 is positioned on top of and in substantially coaxial alignment with pile stub 60, such that the lower bearing surface 71 of infill section 70 bears on top surface 61 of pile stub 60, with each vertical groove 72 in infill section 70 being aligned with a corresponding vertical groove 62 in pile stub 60, thus forming a plurality of tension bar channels 78 each comprising a pile stub groove 62 and a corresponding infill section groove 72, along with their corresponding radial holes 64 and 74. As illustrated in Figure S, each tension bar channel 78 has an overall length L2a. Figures 5, 6, and 8 show a total of eight tension bar channels 78, but this is exemplary only; the actual number will depend on the particular structural requirements of the pile repair.
In a preferred alternative embodiment of the method, as shown in Figure 5, a layer of a suitable fluid grout 75 (such as Sikadur 42 MultifloTM) is disposed between bearing surface 71 and top surface 61 to provide enhanced uniformity of vertical load transfer from infill section 70 to pile stub 60, and also to facilitate the proper and desired alignment of infill section 70 relative to pile stub 60, particularly in cases where bearing surface 71 and top surface 61 do not have sufficiently uniform and matching contours to ensure satisfactory load transfer and axial alignment.
The next step in the method is to install a double-hooked tension bar 80 in each tension bar channel 78. Each tension bar 80 has an elongate center section 82 having an overall length L2b, and a hooked section 84 at each end of (and substantially perpendicular to) center section 82, with each hooked section 84 having an overall length L3b. Prior to installation of tension bars 80, a suitable amount of fluid grout 85 is deposited into radial holes 64 and 74, the diameter of which is greater than that of hooked sections 84. As best seen in Figure 8, a tension bar 80 is then installed in each tension bar channel 78, until center section 82 is substantially fully disposed within grooves 62 and 72 of the corresponding tension bar channel 78, with the hooked sections 84 of tension bar 80 being inserted into the radial holes 64 and 74 of the tension bar channel 78, thus partially displacing the grout 85 within radial holes 64 and 74 so as to substantially fill any spaces between hooked sections 84 and the interior surfaces of radial holes 64 and 74. Any excess grout 85 extruded out of radial holes 64 and 74 during the insertion of hooked sections 84 is preferably removed and discarded. After the grout 85 remaining inside radial holes 64 and 74 has cured, the hooked sections 84 of each tension bar 80 will be firmly embedded within the pile stub 60 or the infill section 70 (as the case may be).
S From the foregoing discussion, it will be appreciated that the depth L3a and cross-sectional dimensions of radial holes 64 and 74 must be sufficient to receive hooked sections 84 while also allowing space for grout 85. Furthermore, in the preferred embodiment, the cross-sectional dimensions of grooves 62 and 72 will be such that the center section 82 of tension bar 80 can lie largely or completely beneath the circumferential surfaces 63 and 73 of pile stub 60 and infill section 70 respectively.
Lengths Llb, Llc, L2b, and L3b are determined or selected according to well-known structural engineering principles, to suit the anticipated maximum tensile load in each tension bar 80, and to suit the structural properties of the construction materials used for the tension bars 80, pile 10, and infill section 70.
In the preferred embodiment of the method, additional fluid grout 87 is deposited along grooves 62 and 72 prior to the installation of tension bars 80. As tension bars 80 are being installed, and their hooked section 84 are being inserted into corresponding radial holes 64 and 74, the center sections 82 of tension bars 80 press into and become at least partially jacketed by grout 87. Excess grout 87 squeezed out of grooves 62 and 72 is preferably removed and discarded. The provision of grout 87 in grooves 62 and 72 is generally desirable to enhance the solidity of the anchorage of tension bar 80 to pile stub 60 and infill section 70. However, grout 87 is not essential to the method.
The primary consideration in the anchorage of tension bars 80 is for their hooked sections 84 to be anchored to pile stub 60 and infill section 70 with sufficient solidity that tensile loads in tension bars 80 can be transferred to pile stub 60 and infill section 70 by way of the hooked sections 84, without the consequent development of any significant axial displacement between pile stub 60 and infill section 70.
After grout 85 (and grout 75 and/or grout 87, as the case may be) has cured and hardened, a first layer of non-biodegradable reinforcing fabric 90 (such as Sikawrap 103CTM) is wrapped around and bonded to the circumferential surfaces of pile stub 60 and the infill section 70 using a suitable impregnation resin (such as Sikadur 300TM).
First fabric layer 90 preferably will be large enough to substantially cover all of the tension bars 80, and preferably will extend beyond the end of each tension bar 80 for a selected distance L5, which is preferably at least 50 mm. First fabric layer 90 provides desirable general protection to the repair area, but a more fundamental function is to securely retain and prevent dislodgement of tension bars 80.
As with the method of the first aspect of the present invention, the reinforcing fabric may have predominately unidirectional primary fibers, and it may be applied to the repair area with its primary fibers oriented either transversely or longitudinally relative to the axis of pile 10. Alternatively, the primary fibers may be oriented obliquely. In a preferred embodiment of the method, two layers of fabric are used, with one layer having its primary fibers oriented transversely and the other layer having its fibers oriented longitudinally, and with the two layers being bonded to each other using a suitable l S impregnation resin. Other variations of the reinforcing fabric and its application, described previously in connection with the first aspect of the present invention, will be equally applicable with respect to the method of the second aspect of the invention.
Tension bars 80 may be fabricated from a metallic or other structural material capable of safely carrying the design tension forces (which are determined on a case-by-case basis in accordance with established structural engineering principles).
Tension bars 80 could be made of carbon steel, but in that case would preferably be galvanized, coated, plated, or otherwise protected to resist corrosion. In the preferred embodiment of the method, tension bars 80 are made of fiber reinforced polymer (FRP), which has excellent tensile characteristics and will not corrode when buried in the ground or otherwise exposed to moisture. Alternatively, tension bars 80 may be fashioned from stainless steel.
It will be readily appreciated by those skilled in the art that the use of any of the described embodiments of the method of the invention may entail the further step of providing temporary shoring for any structure supported by the timber pile or piles being repaired. However, shoring will not necessarily be required in all cases. For example, the pile to be repaired might retain an undamaged core section having sufficient structural strength to withstand the weight imposed on it by the supported structure during the repair procedure, and in such a case the pile may be repaired in accordance with the first aspect of the invention, without need for shoring (although shoring might be optionally provided as a safety enhancement).
In cases where the pile does not have a substantial or any undamaged core, the pile will have to be repaired in accordance with the second aspect of the invention, and it will commonly be necessary to use temporary shoring during the repair procedure. Even in such cases, however, shoring might not be required if the supported structure can safely bridge the damaged pile and temporarily redistribute the load that would have been supported by the pile under repair to other support elements. In summary, the need for temporary shoring will depend at least in part on the characteristics of the supported structure.
It should be understood that the term "timber pile", as used in this patent document, is not intended to be limited to piles that support loads from a building or other substantial structure. The term is intended to have a broad meaning that includes any timber member embedded in the ground in a substantially vertical orientation, regardless of whether it is so embedded by being driven into the ground (using pile-driving equipment), by being inserted into an excavated or augered hole and backfilled, or by any other means. Understood in this sense, the term "timber pile" covers not only piles for supporting substantial structures, but also utility poles, flag poles, soldier piles, and analogous structural elements.
It will also be readily appreciated that various modifications of the present invention may be devised without departing from the essential concept of the invention, and all such modifications are intended to be included in the scope of the claims appended hereto.
In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following that word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element.
Alternatively, the desired structural benefits may also be achieved by applying bi-directional fabric 50 with its two sets of primary fibers oriented obliquely (e.g., diagonally) relative to the pile axis.
2. Second Aspect of the Invention The first aspect of the present invention, as described above, is directed to repairing damaged timber piles in which the damage is surficial only; i.e., where there remains a continuous core of undamaged timber along the full length of the pile. The second aspect of the invention is directed to repairing a timber pile in which the damage is so extensive that the pile does not retain a sound, undamaged core, or where any such undamaged core is too small to provide sufficient residual structural strength to make a repair according to the first aspect of the invention a practical option.
In such situations, the damaged pile may be repaired using an alternative method in accordance with the second aspect of the invention, which is illustrated in Figures 5-8.
In accordance with this method, a portion of the damaged pile 10 is exposed (excavating as required) down to a grade level G for a selected distance below the damaged region of the pile 10. Pile 10 is then cut off on a substantially horizontal plane C
located below the damaged region, leaving a pile stub 60 extending upward from grade level G and having a length Lla (length Lla being a selected distance that will provide adequate working room for completion of the repair, as further described hereinbelow). Pile stub 60 has a substantially horizontal top surface 61 and a circumferential outer surface 63.
Next, a plurality of substantially vertical grooves 62 are formed in the circumferential outer surface 63 of pile stub 60, extending downward from the top surface 61 of the pile stub for a distance Llb (the determination of which is discussed below). At or near the lower end of each groove 62, a radially-oriented hole 64 is drilled into the pile stub 60 to a depth L3a.
A round timber infill section 70, having a length appropriate to the repair being carried out, is then provided. Infill section 70 has an upper end, a lower end (which has a substantially planar bearing surface 71 oriented substantially transverse to the longitudinal axis of infill section 70), and a circumferential outer surface 73. Infill section 70 has a nominal diameter substantially corresponding with that of pile stub 60.
A plurality of substantially vertical grooves 72 are formed in the circumferential outer surface 73 of infill section 70, extending upward from the lower end of infill section 70 for a distance Llc (the determination of which is discussed below). At or near the upper end of each groove 72, a radially-oriented hole 74 is drilled into infill section 70 to a depth L3a. For purposes which will be explained, the circumferential spacing of grooves 72 in infill section 70 substantially matches the circumferential spacing of grooves 62 in pile stub 60.
The preceding description suggests that grooves 72 and radial holes 74 may be formed in infill section 70 on site, after infill section 70 has been positioned on pile stub 60. Alternatively, however, grooves 72 and radial holes 74 may be pre-formed in infill section 70. Those skilled in the art of the invention will appreciate that the particular stage or location at which grooves 72 and radial holes 74 are formed in infill section 70 is not critical to the method.
In Figure 5, grooves 62 and 72 are shown in a staggered pattern, with the ends of adjacent grooves offset a selected distance L4. This is preferred in order to minimize stress concentrations in pile stub 60 and infill section 70, but it is not essential. Grooves 62 and 72 may be non-staggered without departing from the scope of the method.
Once grooves 72 and radial holes 74 have been formed, infill section 70 is positioned on top of and in substantially coaxial alignment with pile stub 60, such that the lower bearing surface 71 of infill section 70 bears on top surface 61 of pile stub 60, with each vertical groove 72 in infill section 70 being aligned with a corresponding vertical groove 62 in pile stub 60, thus forming a plurality of tension bar channels 78 each comprising a pile stub groove 62 and a corresponding infill section groove 72, along with their corresponding radial holes 64 and 74. As illustrated in Figure S, each tension bar channel 78 has an overall length L2a. Figures 5, 6, and 8 show a total of eight tension bar channels 78, but this is exemplary only; the actual number will depend on the particular structural requirements of the pile repair.
In a preferred alternative embodiment of the method, as shown in Figure 5, a layer of a suitable fluid grout 75 (such as Sikadur 42 MultifloTM) is disposed between bearing surface 71 and top surface 61 to provide enhanced uniformity of vertical load transfer from infill section 70 to pile stub 60, and also to facilitate the proper and desired alignment of infill section 70 relative to pile stub 60, particularly in cases where bearing surface 71 and top surface 61 do not have sufficiently uniform and matching contours to ensure satisfactory load transfer and axial alignment.
The next step in the method is to install a double-hooked tension bar 80 in each tension bar channel 78. Each tension bar 80 has an elongate center section 82 having an overall length L2b, and a hooked section 84 at each end of (and substantially perpendicular to) center section 82, with each hooked section 84 having an overall length L3b. Prior to installation of tension bars 80, a suitable amount of fluid grout 85 is deposited into radial holes 64 and 74, the diameter of which is greater than that of hooked sections 84. As best seen in Figure 8, a tension bar 80 is then installed in each tension bar channel 78, until center section 82 is substantially fully disposed within grooves 62 and 72 of the corresponding tension bar channel 78, with the hooked sections 84 of tension bar 80 being inserted into the radial holes 64 and 74 of the tension bar channel 78, thus partially displacing the grout 85 within radial holes 64 and 74 so as to substantially fill any spaces between hooked sections 84 and the interior surfaces of radial holes 64 and 74. Any excess grout 85 extruded out of radial holes 64 and 74 during the insertion of hooked sections 84 is preferably removed and discarded. After the grout 85 remaining inside radial holes 64 and 74 has cured, the hooked sections 84 of each tension bar 80 will be firmly embedded within the pile stub 60 or the infill section 70 (as the case may be).
S From the foregoing discussion, it will be appreciated that the depth L3a and cross-sectional dimensions of radial holes 64 and 74 must be sufficient to receive hooked sections 84 while also allowing space for grout 85. Furthermore, in the preferred embodiment, the cross-sectional dimensions of grooves 62 and 72 will be such that the center section 82 of tension bar 80 can lie largely or completely beneath the circumferential surfaces 63 and 73 of pile stub 60 and infill section 70 respectively.
Lengths Llb, Llc, L2b, and L3b are determined or selected according to well-known structural engineering principles, to suit the anticipated maximum tensile load in each tension bar 80, and to suit the structural properties of the construction materials used for the tension bars 80, pile 10, and infill section 70.
In the preferred embodiment of the method, additional fluid grout 87 is deposited along grooves 62 and 72 prior to the installation of tension bars 80. As tension bars 80 are being installed, and their hooked section 84 are being inserted into corresponding radial holes 64 and 74, the center sections 82 of tension bars 80 press into and become at least partially jacketed by grout 87. Excess grout 87 squeezed out of grooves 62 and 72 is preferably removed and discarded. The provision of grout 87 in grooves 62 and 72 is generally desirable to enhance the solidity of the anchorage of tension bar 80 to pile stub 60 and infill section 70. However, grout 87 is not essential to the method.
The primary consideration in the anchorage of tension bars 80 is for their hooked sections 84 to be anchored to pile stub 60 and infill section 70 with sufficient solidity that tensile loads in tension bars 80 can be transferred to pile stub 60 and infill section 70 by way of the hooked sections 84, without the consequent development of any significant axial displacement between pile stub 60 and infill section 70.
After grout 85 (and grout 75 and/or grout 87, as the case may be) has cured and hardened, a first layer of non-biodegradable reinforcing fabric 90 (such as Sikawrap 103CTM) is wrapped around and bonded to the circumferential surfaces of pile stub 60 and the infill section 70 using a suitable impregnation resin (such as Sikadur 300TM).
First fabric layer 90 preferably will be large enough to substantially cover all of the tension bars 80, and preferably will extend beyond the end of each tension bar 80 for a selected distance L5, which is preferably at least 50 mm. First fabric layer 90 provides desirable general protection to the repair area, but a more fundamental function is to securely retain and prevent dislodgement of tension bars 80.
As with the method of the first aspect of the present invention, the reinforcing fabric may have predominately unidirectional primary fibers, and it may be applied to the repair area with its primary fibers oriented either transversely or longitudinally relative to the axis of pile 10. Alternatively, the primary fibers may be oriented obliquely. In a preferred embodiment of the method, two layers of fabric are used, with one layer having its primary fibers oriented transversely and the other layer having its fibers oriented longitudinally, and with the two layers being bonded to each other using a suitable l S impregnation resin. Other variations of the reinforcing fabric and its application, described previously in connection with the first aspect of the present invention, will be equally applicable with respect to the method of the second aspect of the invention.
Tension bars 80 may be fabricated from a metallic or other structural material capable of safely carrying the design tension forces (which are determined on a case-by-case basis in accordance with established structural engineering principles).
Tension bars 80 could be made of carbon steel, but in that case would preferably be galvanized, coated, plated, or otherwise protected to resist corrosion. In the preferred embodiment of the method, tension bars 80 are made of fiber reinforced polymer (FRP), which has excellent tensile characteristics and will not corrode when buried in the ground or otherwise exposed to moisture. Alternatively, tension bars 80 may be fashioned from stainless steel.
It will be readily appreciated by those skilled in the art that the use of any of the described embodiments of the method of the invention may entail the further step of providing temporary shoring for any structure supported by the timber pile or piles being repaired. However, shoring will not necessarily be required in all cases. For example, the pile to be repaired might retain an undamaged core section having sufficient structural strength to withstand the weight imposed on it by the supported structure during the repair procedure, and in such a case the pile may be repaired in accordance with the first aspect of the invention, without need for shoring (although shoring might be optionally provided as a safety enhancement).
In cases where the pile does not have a substantial or any undamaged core, the pile will have to be repaired in accordance with the second aspect of the invention, and it will commonly be necessary to use temporary shoring during the repair procedure. Even in such cases, however, shoring might not be required if the supported structure can safely bridge the damaged pile and temporarily redistribute the load that would have been supported by the pile under repair to other support elements. In summary, the need for temporary shoring will depend at least in part on the characteristics of the supported structure.
It should be understood that the term "timber pile", as used in this patent document, is not intended to be limited to piles that support loads from a building or other substantial structure. The term is intended to have a broad meaning that includes any timber member embedded in the ground in a substantially vertical orientation, regardless of whether it is so embedded by being driven into the ground (using pile-driving equipment), by being inserted into an excavated or augered hole and backfilled, or by any other means. Understood in this sense, the term "timber pile" covers not only piles for supporting substantial structures, but also utility poles, flag poles, soldier piles, and analogous structural elements.
It will also be readily appreciated that various modifications of the present invention may be devised without departing from the essential concept of the invention, and all such modifications are intended to be included in the scope of the claims appended hereto.
In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following that word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element.
Claims (30)
1. A method for in situ repair of a timber pile having a zone of surficial decay or damage, said method comprising the steps of:
(a) removing unsound material from a damaged timber pile within a selected repair section, so as to expose a core section of sound material;
(b) installing a grout form enclosing the repair section of the pile so as to form a grout space within the form, said form having a grout opening and being configured so as to generally correspond to the original surface contours of the pile in the repair section;
(c) introducing a fluid grout into the grout space through the opening in the grout form, so as to substantially fill the grout space;
(d) allowing the grout to solidify;
(e) removing the grout form, thus exposing the grouted area; and (f) bonding a first layer of non-biodegradable reinforcing fabric to the exposed surface of the grouted area using an impregnation resin.
(a) removing unsound material from a damaged timber pile within a selected repair section, so as to expose a core section of sound material;
(b) installing a grout form enclosing the repair section of the pile so as to form a grout space within the form, said form having a grout opening and being configured so as to generally correspond to the original surface contours of the pile in the repair section;
(c) introducing a fluid grout into the grout space through the opening in the grout form, so as to substantially fill the grout space;
(d) allowing the grout to solidify;
(e) removing the grout form, thus exposing the grouted area; and (f) bonding a first layer of non-biodegradable reinforcing fabric to the exposed surface of the grouted area using an impregnation resin.
2. The method of Claim 1 wherein the reinforcing fabric has predominately unidirectional primary fibers.
3. The method of Claim 2 wherein the primary fibers of the reinforcing fabric are substantially parallel to the axis of the pile.
4. The method of Claim 3, comprising the further step of bonding a second layer of non-biodegradable reinforcing fabric to the first layer of fabric using an impregnation resin, said second layer of fabric having predominately unidirectional primary fibers, and said primary fibers being oriented substantially perpendicular to the axis of the pile.
5. The method of Claim 2 wherein the primary fibers of the reinforcing fabric are substantially perpendicular to the axis of the pile.
6. The method of Claim 5, comprising the further step of bonding a second layer of non-biodegradable reinforcing fabric to the first layer of fabric using an impregnation resin, said second layer of fabric having predominately unidirectional primary fibers, and said primary fibers being oriented substantially parallel to the axis of the pile.
7. The method of Claim 2 wherein the primary fibers of the reinforcing fabric are oriented obliquely relative to the axis of the pile.
8. The method of Claim 1, comprising the further step of drying the timber in the repair section prior to the introduction of grout.
9. The method of Claim 8 wherein the timber in the repair section is dried to an average moisture content of approximately 18 per cent by weight, or less.
10. The method of Claim 1, comprising the further step of applying a bonding agent to the surfaces of the repair section of the pile.
11. The method of Claim 1 wherein the grout is an epoxy grout.
12. The method of Claim 1wherein the reinforcing fabric is a carbon fiber fabric.
13. The method of Claim 1 wherein the reinforcing fabric has bi-directional primary fibers.
14. The method of Claim 13 wherein the primary fibers of the reinforcing fabric are obliquely oriented relative to the axis of the pile.
15. A method for in situ repair of a timber pile having a zone of surficial decay or damage, said method comprising the steps of:
(a) exposing a portion of the pile, including the damaged region plus a portion extending below the damaged region to a ground surface;
(b) cutting off an upper portion of the pile by severing the pile at a substantially horizontal cutting plane located below the damaged region, leaving a pile stub projecting above the ground surface, said pile stub having a substantially horizontal top surface and a circumferential outer surface;
(c) forming a plurality of substantially vertical grooves in the circumferential outer surface of the pile stub, each said groove being of a selected length and extending downward from the top surface of the pile stub;
(d) forming a hole at or near the lower end of each groove in the pile stub, each said hole extending radially into the pile;
(e) providing a round timber infill section of selected length, said infill section having an upper end, a lower end, and a circumferential outer surface, said lower end having a substantially planar bearing surface oriented substantially transverse to the longitudinal axis of the infill section, with the diameter of said infill section substantially matching the diameter of the pile stub;
(f) forming a plurality of substantially vertical grooves in the circumferential outer surface of the infill section, each said groove being of a selected length and extending upward from the lower end of the pile stub, with the number and circumferential spacing of said grooves matching the number and spacing of the grooves in the pile stub;
(g) forming a hole at or near the upper end of each groove in the infill section, each said hole extending radially into the infill section;
(h) positioning the infill section upon the pile stub, such that the lower bearing surface of the infill section bears on the top surface of the pile stub, with the vertical grooves in the infill section being aligned with the vertical grooves in the pile stub, thus forming a plurality of tension bar channels each comprising an infill section groove and a matching groove in the pile stub plus their corresponding radial holes;
(i) for each tension bar channel, providing a double-hooked tension bar having a straight elongate center section and having a hooked section at each end, said hooked sections being substantially perpendicular to the center section, with the distance between the hooked sections matching the distance between the radial holes of the corresponding tension bar channel;
(j) applying grout to the radial holes in the infill section and the pile stub;
(k) before the grout has set, inserting a double-hooked tension bar into each tension bar channel such that the center section of each tension bar is disposed substantially completely beneath the circumferential outer surfaces of the infill section and the pile stub, and such that each hooked section of the tension bar is extends into one of the tension bar channel's radial holes forming part of the tension bar channel, said step of inserting the tension bars into the tension bar channels causing displacement of grout such that there remains a layer of grout substantially surrounding each hook within its corresponding radial hole;
(l) bonding a first layer of non-biodegradable reinforcing fabric to the circumferential surfaces of the infill section and the pile stub using an impregnation resin, said first layer of reinforcing fabric being of sufficient dimensions to substantially cover all of the tension bars.
(a) exposing a portion of the pile, including the damaged region plus a portion extending below the damaged region to a ground surface;
(b) cutting off an upper portion of the pile by severing the pile at a substantially horizontal cutting plane located below the damaged region, leaving a pile stub projecting above the ground surface, said pile stub having a substantially horizontal top surface and a circumferential outer surface;
(c) forming a plurality of substantially vertical grooves in the circumferential outer surface of the pile stub, each said groove being of a selected length and extending downward from the top surface of the pile stub;
(d) forming a hole at or near the lower end of each groove in the pile stub, each said hole extending radially into the pile;
(e) providing a round timber infill section of selected length, said infill section having an upper end, a lower end, and a circumferential outer surface, said lower end having a substantially planar bearing surface oriented substantially transverse to the longitudinal axis of the infill section, with the diameter of said infill section substantially matching the diameter of the pile stub;
(f) forming a plurality of substantially vertical grooves in the circumferential outer surface of the infill section, each said groove being of a selected length and extending upward from the lower end of the pile stub, with the number and circumferential spacing of said grooves matching the number and spacing of the grooves in the pile stub;
(g) forming a hole at or near the upper end of each groove in the infill section, each said hole extending radially into the infill section;
(h) positioning the infill section upon the pile stub, such that the lower bearing surface of the infill section bears on the top surface of the pile stub, with the vertical grooves in the infill section being aligned with the vertical grooves in the pile stub, thus forming a plurality of tension bar channels each comprising an infill section groove and a matching groove in the pile stub plus their corresponding radial holes;
(i) for each tension bar channel, providing a double-hooked tension bar having a straight elongate center section and having a hooked section at each end, said hooked sections being substantially perpendicular to the center section, with the distance between the hooked sections matching the distance between the radial holes of the corresponding tension bar channel;
(j) applying grout to the radial holes in the infill section and the pile stub;
(k) before the grout has set, inserting a double-hooked tension bar into each tension bar channel such that the center section of each tension bar is disposed substantially completely beneath the circumferential outer surfaces of the infill section and the pile stub, and such that each hooked section of the tension bar is extends into one of the tension bar channel's radial holes forming part of the tension bar channel, said step of inserting the tension bars into the tension bar channels causing displacement of grout such that there remains a layer of grout substantially surrounding each hook within its corresponding radial hole;
(l) bonding a first layer of non-biodegradable reinforcing fabric to the circumferential surfaces of the infill section and the pile stub using an impregnation resin, said first layer of reinforcing fabric being of sufficient dimensions to substantially cover all of the tension bars.
16. The method of Claim 15 comprising the further step of applying grout to the grooves in the pile stub and infill section, such that the step of inserting the tension bars into the tension bar channels will cause displacement of the grout in the grooves such that there will remain a layer of grout between the center section of each tension bar and the timber surfaces of the corresponding grooves.
17. The method of Claim 15 comprising the further step of disposing a layer of grout between the top surface of the pile stub and the bearing surface of the infill section.
18. The method of Claim 15 wherein the reinforcing fabric has predominately unidirectional primary fibers.
19. The method of Claim 18 wherein the primary fibers of the reinforcing fabric are substantially parallel to the axis of the pile.
20. The method of Claim 19, comprising the further step of bonding a second layer of non-biodegradable reinforcing fabric to the first layer of fabric using an impregnation resin, said second layer of fabric having predominately unidirectional primary fibers, and said primary fibers being oriented substantially perpendicular to the axis of the pile.
21. The method of Claim 18 wherein the primary fibers of the reinforcing fabric are substantially perpendicular to the axis of the pile.
22. The method of Claim 21, comprising the further step of bonding a second layer of non-biodegradable reinforcing fabric to the first layer of fabric using an impregnation resin, said second layer of fabric having predominately unidirectional primary fibers, and said primary fibers being oriented substantially parallel to the axis of the pile.
23. The method of Claim 18 wherein the primary fibers of the reinforcing fabric are oriented obliquely relative to the axis of the pile.
24. The method of Claim 15 wherein the grout is an epoxy grout.
25. The method of Claim 15 wherein the reinforcing fabric is a carbon fiber fabric.
26. The method of Claim 15 wherein the reinforcing fabric has bi-directional primary fibers.
27. The method of Claim 26 wherein the primary fibers of the reinforcing fabric are obliquely oriented relative to the axis of the pile.
28. The method of Claim 15 wherein the tension bars are fabricated from steel.
29. The method of Claim 28 wherein the steel is stainless steel.
30. The method of Claim 15 wherein the tension bars are fabricated from a fiber-reinforced polymer material (FRP).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002502065A CA2502065A1 (en) | 2005-03-23 | 2005-03-23 | Method for in situ repair of timber piles using synthetic reinforcing fabric |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002502065A CA2502065A1 (en) | 2005-03-23 | 2005-03-23 | Method for in situ repair of timber piles using synthetic reinforcing fabric |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2502065A1 true CA2502065A1 (en) | 2006-09-23 |
Family
ID=37054293
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002502065A Abandoned CA2502065A1 (en) | 2005-03-23 | 2005-03-23 | Method for in situ repair of timber piles using synthetic reinforcing fabric |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2502065A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101936074A (en) * | 2010-08-05 | 2011-01-05 | 北京特希达科技有限公司 | Fast building earthquake-resisting reinforcing method and device |
| CN105714818A (en) * | 2015-05-26 | 2016-06-29 | 温州东瓯建设集团有限公司 | Pile splicing formwork |
| CN114592507A (en) * | 2022-03-21 | 2022-06-07 | 陈倩 | Pile-in-pile structure formed based on construction of defective cast-in-place piles |
-
2005
- 2005-03-23 CA CA002502065A patent/CA2502065A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101936074A (en) * | 2010-08-05 | 2011-01-05 | 北京特希达科技有限公司 | Fast building earthquake-resisting reinforcing method and device |
| CN105714818A (en) * | 2015-05-26 | 2016-06-29 | 温州东瓯建设集团有限公司 | Pile splicing formwork |
| CN114592507A (en) * | 2022-03-21 | 2022-06-07 | 陈倩 | Pile-in-pile structure formed based on construction of defective cast-in-place piles |
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