Patent Publication Number: US-2015059926-A1

Title: Wood column repair, reinforcement, and extension

Description:
TECHNICAL FIELD 
     This application relates generally to construction. More specifically, this application relates to methods and apparatus for extending and/or reinforcing and repairing wood columns and piles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings, when considered in connection with the following description, are presented for the purpose of facilitating an understanding of the subject matter sought to be protected. 
         FIG. 1  shows an example deteriorated column suitable to be repaired and reinforced by the disclosed method; 
         FIGS. 2A and 2B  show an example step in a process of replacing and reinforcing a wood column; and 
         FIGS. 3A and 3B  show an example of additional steps in the process of replacing and reinforcing a wood column. 
     
    
    
     DETAILED DESCRIPTION 
     While the present disclosure is described with reference to several illustrative embodiments described herein, it should be clear that the present disclosure should not be limited to such embodiments. Therefore, the description of the embodiments provided herein is illustrative of the present disclosure and should not limit the scope of the disclosure as claimed. In addition, while the following description references using example reinforcement layers and materials, it will be appreciated that the disclosure may include fewer or more reinforcement layers and other types of materials. 
     Briefly described, a method and a system are disclosed for adding to or replacing a part of wood columns/piles and externally reinforcing the wood columns/piles (hereinafter referred to as either “column” or “pile”). Wood columns are widely used to support buildings, bridges, floors, utility and electrical power lines and the like. In general, timber piles are extensively used in the construction industry. There are large number of piles in buildings, bridges, ports, railroad bridges, etc. that require repair and strengthening worldwide. For example, many piers in ports are supported on timber piles. Due to successful efforts of agencies such as the Environmental Protection Agency (EPA), the cleaning of waterways and lakes has resulted in a resurgence of marine borers and other creatures that could not survive in polluted water. This has resulted in an alarming increased rate of deterioration in such piles. These bugs eat away the wood from outside or inside, reducing the cross sectional area of the pile which can result in disastrous failure of the structure being supported on such piles. These piles require an effective method for repair and strengthening. 
     In another example, many beach-front homes are supported on timber piles that are embedded in soil or water. Global warming and change in climate patterns have led to development of frequent strong storms and rise in water elevations that can topple these homes. The recent 2012 Hurricane Sandy, for example, resulted in major loss of property along the coastlines in New Jersey. In response to such disasters, government agencies such as the Federal Emergency Management Administration (FEMA) have redrawn flood maps and many property owners are mandated to raise their homes by several feet to be eligible for insuring their buildings. The existing technique for addressing this problem is to support the home on a series of stiff steel beams and jacks. Piles are cut and homes are raised by multiple jacks. In many cases homes must be also moved away from their original locations. The piles are replaced with new taller piles and the houses are driven back to the original locations and are set atop their new piles. It is obvious that this operation is very expensive and requires the homes to be on large enough lots to accommodate the homes while the piles are being fixed; however, most beach front homes are on very small lots and the aforementioned repair technique is not a viable solution. As a result, there is a tremendous interest in techniques for extending the length of a pile without the need to move the house away from its footprint. 
     Another example of repair is timber utility poles. These poles become weaker as they age. At the same time, addition of new power lines or antennas for telecommunication and wireless services to these aging poles place heavier loads on the poles. This leads to the need for strengthening of these poles. The strong winds during storms and tornados result in breakage of the poles and lead to power outages. 
     Timber piles are also used extensively in construction of railroad bridges. These piles have also weakened after decades of use. The present methods can repair and strengthen these piles as well. The above are only samples of the applications of the present methods. Numerous other applications in mining industry and other fields also exist which are obvious to those skilled in the art. 
     The disclosed methods and systems may be used to: (1) Repair and/or strengthen damaged timber piles by removing and replacing the damaged portion, and/or (2) Extend the height of a pile, which may be otherwise in good shape. In these applications, since the pile is cut, there may be one or more splice locations that usually become the weakest point in the pile. Disclosed methods strengthen the splice connections in such a way that the repaired or the extended columns become even stronger than the remaining original portions of the piles. 
       FIG. 1  shows an example timber pile  100  with the portion  110  of the pile severely deteriorated, which requires strengthening. Without repair or strengthening, portion  110  of pile  100  may buckle under load. In one embodiment, the damaged section  110  of the pile  100  is cut and removed. The splice cut can be of many types used in wood construction, such as a half-lap splice (Shown in  FIGS. 2A and 2B ), bevel-lap splice, flush cut, diagonal (sloping) cut, etc. Care must be taken to ensure that the structure does not collapse during this stage of the operation. Such preventive methods are commonly known to those skilled in the art and therefore are not discussed here in great detail. For example, in some cases the structure can be supported by positioning temporary columns in the vicinity of the damaged pile  100  such that the temporary columns carry the loads while the damaged pile  100  is being repaired. In another example, temporary sister piles, made of steel or timber, are bolted to the damaged pile  100  at points above and below the damaged area  110 . This allows the loads to bypass the damaged area  110  and pile  100  will maintain its original height while the damaged portion  110  is being cut and removed. 
       FIGS. 2A and 2B  show an example step in the process of replacing and reinforcing wood column  200 . In this example, the deteriorated section of column  200  has already been cut away using two half-lap splices  220  and  230 , shown in  FIG. 2A , and has been replaced by a new section  210  of timber pile or other material such as steel, preferably with the same length and cross sectional dimensions as the removed section, as shown in  FIG. 2B . Steel bolts  240  and  250 , or other anchoring means, may also be used to secure the top and bottom of the new pile segment  210  to the original pile. Those skilled in the art will appreciate that the replacement spliced section of the pile may be attached to the pile using other methods, such as using glues, double-sided joints, plates, and the like, without departing from the spirit of the present disclosure. 
       FIG. 3A  shows an example of further steps in the process of replacing and reinforcing a wood column. As shown in this figure and described below, to restore the flexural axial and shear strength of a wood pile after replacement of its deteriorated portion, additional reinforcing elements are placed around the perimeter of the pile. In some embodiments, for example, as shown in  FIG. 3A , reinforcing strips  340 , such as QuakeWrap® GU50C Carbon strips that are supplied in 2 to 4 inch wide by 0.05 inch thick strips and that can be cut to any length, are held substantially longitudinally against wood column  300 . In various embodiments these reinforcing elements  340  may be glued or nailed to column  300  such as by nails  350 , or be held in place by strap  360 . In some embodiments each reinforcing strip  340  may extend over one or two cut joints  320  and  330 . In the embodiment of  FIG. 3A , all reinforcing strips  340  extend over both cut joints  320  and  330 . In some embodiments the reinforcing strips  340  may be separated by a gap; placed side by side and in contact each other; or even partially overlapping each other.  FIG. 3A  only shows reinforcing strips  340  being at a distance from each other. Those skilled in the art will appreciate that in some embodiments the width of one reinforcing element  340  may be as much as the entire perimeter of column  300 , such that a single reinforcing element  340  can cover the entire circumference of column  300 . In such an embodiment, a single reinforcing element  340  replaces and performs as multiple side-by-side reinforcing strips. 
     The reinforcing elements  340  can be made of wood, metals such as steel, stainless steel or non-metallic materials such as Carbon, Glass, Kevlar or Basalt Fiber Reinforced Polymer (FRP) materials, etc., and may be made in the form of solid, twisted fibers, mesh, or other suitable configurations. The reinforcing elements  340  can be in the shape of rods, flat plates, woven fibers and strips as well as a reinforcing grid. While an easy installation technique is to place the reinforcing elements  340  around the pile  300 , the reinforcing elements  340  may even be embedded into vertical/longitudinal grooves that are cut along the length of the timber. To those skilled in the art, this is known as Near-Surface-Mounted (NSM) reinforcement. In various embodiments, the reinforcing elements  340  may vary in thickness, width, and cross sectional shape along their length to provide more reinforcement near joints at splice locations  320  and  330 , while saving material and cost farther away from joints where relatively it is needed less. 
     The length of the reinforcing elements  340  and how far they extend beyond a splice location are design issues, the specifics of which are usually calculated by an engineer. Since the splice locations  320  and  330  are generally the weakest point in the pile  300 , the reinforcing elements  340  are recommended to extend beyond the splice locations a distance at least equal to their development length. This length is a function of the strength of the reinforcing element  340  and its surface texture or bond characteristics. For example, for QuakeWrap® GU50C Carbon strips this length is approximately 12-18 inches, depending on the mechanical characteristics of the resin that is being injected in the annular space, described below. Other reinforcing elements will have shorter or longer development lengths that can be calculated by the design engineer. 
     As shown in  FIG. 3A , after placing reinforcing elements  340  over column  300 , at least one reinforcing sheet  370  is wrapped one or more times around column  300  to form a reinforcing shell that encloses column  300  and reinforcing elements  340 . In various embodiments, the overlapping edges of a wrapped reinforcing sheet  370  are glued or otherwise attached to each other to form the reinforcing shell. In some embodiments a wrapped reinforcing sheet  370  may stay at a distance from reinforcing elements  340  and in other embodiments a wrapped reinforcing sheet  370  may touch the reinforcing elements  340 . It is preferable for a wrapped reinforcing sheet  370  (reinforcing shell) to completely enclose the new part of the pile along with a part of the original pile and completely enclose the reinforcing elements  340 ; however, the reinforcing shell may be made of more than one reinforcing sheet wrapped in succession along the length of the pile. In such embodiments two or more reinforcing sheets may be used to construct a longer reinforcing shell. These partial reinforcing shells may be joined overlappingly or by other means known to those skilled in the art. For example, reinforcing sheet  370  in  FIG. 3A  may be formed by two separate sections A and B which are joined along the dash-line  395 . 
     In addition to providing tensile, bending, shear, and depending on material used, compression strength, the reinforcing elements  340  may also serve as spacers between the surface of the pile  300  and the reinforcing sheet  370 . In other embodiments additional and separate spacers can be used to ensure proper separation between the pile surface and the reinforcing sheet  370 . These spacers can be made of plastic, wood, steel and the like. An inexpensive solution is to use the 2-15 mm diameter wooden rods commonly used in arts and crafts projects. These spacers can be glued or mechanically attached to the timber pile using nails or other fasteners. The space created between the pile and the reinforcing sheet may be filled with reinforcing material, such as grout or concrete, as further described below. 
     For example, to create the reinforcing shell around pile  300 , PileMedic™ PLC 100.60 carbon FRP laminate is coated with an epoxy paste adhesive such as QuakeWrap® 220UR Underwater Resin and is wrapped around pile  300  more than once. The number of layers of this wrap is based on engineering calculations and directly determines the level of strengthening that is introduced to the pile. For example, two layers of PileMedic™ PLC100.60 wrap provide a confining pressure of 800 psi on a 12-inch diameter pile while 3 layers of the same wrap will provide a confining pressure of 1200 psi. Similarly in terms of contribution of forces along the axis of the pile which are significant to flexural strength of the pile, two layers of PileMedic™ PLC100.60 wrap provide 3000 pounds of tensile force per inch around the perimeter of the pile, while three layers of the same wrap provide 4500 pounds per inch of perimeter. The reinforcing sheet  370  is typically supplied in rolls that are 4 feet wide. So, each multilayer wrap will cover 4-feet along the height of a pile. Additional wraps can be applied with overlap lengths that are determined based on engineering calculations. The overlap must be calculated such that it does not constitute a weak point along the length of the pile in the finished shell. As many wraps as necessary will be applied to cover the entire repair area which typically extends 6 inches beyond the ends of the reinforcing elements  340 . 
     The reinforcing sheet  370  can be a pre-cured laminate as described above or it can be a fabric such as QuakeWrap® TB20C Carbon fabric that is saturated in the field with a polymer such as an epoxy resin similar to QuakeBond™ J300SR Saturating Resin to form a composite material. The resin can be applied in advance to the fabric in what is commonly known as a pre-preg fabric. The resin can be cured in the field by ambient condition, heat, ultraviolet rays, etc. Resins that are activated upon contact with water, such as spraying the pre-preg fabric with water, can also be used. 
     At this stage, resin or other adhesive materials is poured or injected in the space between the wrapped reinforcing sheet  370  and column  300 . In  FIGS. 3A and 3B , this space has an annular shape. In some embodiments provisions are made to prevent the leakage of the resin from the bottom of the space between the wrapped reinforcing sheet  370  and column  300 . For example, in some embodiments the bottom of the shell is sealed, for example, by an expansive chemical grout, an epoxy paste, a mechanical band such as a hose clamp, an adhesive tape, or the like. Resin will firmly attach the reinforcing sheet  370 , the reinforcing element(s)  340 , and column  300  together. In some embodiments, before the installation of the reinforcing sheet  370 , resin may be used to glue the reinforcing element(s)  340  to column  300 . 
     For injection of resin into space  380 , one or more injection tubes  390  may be positioned along the height of the pile, which can be of any material such as copper or plastic tubing with a small diameter of about 3-15 mm. The injection tubes  390  may also include large holes along their length for easy dispersion of resin. In another embodiment, the injection tubes  390  can be partially hidden in vertical grooves that are cut along the length of the pile  300 . The injection tubes can be held in position with, for example, tacks or staples and the like. 
     The space between the shell and the pile may be filled, for example, with a polymer such as QuakeBond™ 320LV Low Viscosity resin. This resin can be mixed in advanced and introduced into the space through the injection tubes. As the resin comes out of the bottom of the injection tubes, the injection tube can be slowly pulled up towards the top of the pile  300 . If more than one injection tube is used, they may be connected together through a manifold to make sure that the resin is simultaneously introduced all around pile  300  into the space between the reinforcing sheet  370  and pile  300 . The low viscosity of the mentioned example resin allows it to penetrate into the tiniest voids, cracks and crevices of the pile  300 , including the bolt holes and the cut splice surfaces  320  and  330 , where the new and the old pile sections are joined together. This results in a solid section of the pile that is significantly stronger than the original pile. 
     The above method whereby the epoxy is fed through gravity flow causes a passive confinement of the pile. That is, the shell around the pile will become activated only when the pile is loaded axially and starts to dilate outwards due to Poisson&#39;s effect. In another embodiment, the top portion of the annular space can also be sealed tightly and the resin can be pressurized inside the annular space. This pressurization of the resin causes the reinforcing shell to immediately exert a confining pressure on the pile. This method is known as active confinement and can further enhance the strength of the pile. 
       FIG. 3B  shows a cross-sectional view of column  300  after installation of the reinforcing sheet  370 , the reinforcing elements  340 , and pouring of resin  385  into space  380 . Once pile  300  has been repaired, the temporary pile-supports can be removed and the loads will be transferred to the newly repaired pile  300 , wherein at some locations along the length of column  300  the loads are carried by the entire assembly of pile  300 , reinforcing parts  340  and  370 , and the cured resin  385 . 
     In many cases homes and other coastal buildings have to be raised several feet to new elevations to satisfy the government requirements for minimum clearance above new flood levels. This usually requires that the piles supporting the building (that are not particularly damaged) be extended in height by, for example, several feet. In such cases, it may be most cost effective to cut a short piece of the pile directly below the house, where it is attached to the house, and replace the cut section with a taller section of timber that will be connected to the lower portion of the existing pile according to the disclosed methods. The advantage of cutting the top portion of the pile is that the repair requires strengthening of a single splice and will be more cost effective than adding a taller timber to the middle of the pile. 
     It is important to note that the repair and reinforcement methods disclosed above may be used without the removal of the deteriorated part of a pile. In cases in which the removal of the deteriorated part of a column does not seem to be necessary, all the steps of the mentioned methods may be carried out without the replacement step. In such cases, the limits of the deteriorated part must be treated as splice locations and the reinforcing materials and the reinforcing shell should be extended over the non-deteriorated sections beyond these limits. 
     Changes can be made to the claimed invention in light of the above Detailed Description. While the above description details certain embodiments of the invention and describes the best mode contemplated, no matter how detailed the above appears in text, the claimed invention can be practiced in many ways. Details of the system may vary considerably in its implementation details, while still being encompassed by the claimed invention disclosed herein. 
     Particular terminology used when describing certain features or aspects of the disclosure should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the disclosure with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the claimed invention to the specific embodiments disclosed in the specification, unless the above Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the claimed invention encompasses not only the disclosed embodiments, but also all equivalent ways of practicing or implementing the claimed invention. 
     It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” 
     The above specification, examples, and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. It is further understood that this disclosure is not limited to the disclosed embodiments, but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 
     While the present disclosure has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this disclosure is not limited to the disclosed embodiments, but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.