Field Notching and Drilling of Glued Laminated Timber Beams

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1 T E C H N I C A L N O T E Fiel Notching an Drilling of Glue Laminate Timber Beams Number EWS S560H November 2014 INTRODUCTION Glue laminate timber (glulam) beams are highly engineere components manufacture from specially selecte an positione lumber laminations of varying strength an stiffness. These fabricate beams are often specifie where a certain span, strength an/or stiffness is require. As such, glulam beams are generally esigne for an use in applications where they will be highly stresse uner esign loas. Whenever making fiel moifications such as notching, tapering or rilling not shown on the esign or shop rawings, always follow the guieline provie in this ocument or consult the engineer of recor before making the moifications. As mentione above, glulam beams are fabricate using selecte lumber laminations of various strength, stiffness an species. The beams are assemble with lower grae material in the mi-epth of the beam an higher grae material positione on the top an bottom. The highest grae of material is use as the outermost laminations on the tension sie of the beam. Because of this, any rilling, apping or notching that takes place in these outermost tension laminations has effects on the strength an serviceability of the beam. First, such moifications reuce the section of the beam. Secon, they remove woo fiber from the lamina tions having the highest strength. In aition, stress concentrations may occur in areas moifie by notching or rilling. This Technical Note provies recommenations for fiel notching, tapering an rilling glulam beams. Beams illustrate herein are assume to be simple span subjecte to uniform loas, an are shown with the compression sie up. All equations an notching guielines are presente using the same assumptions. If this information is applie to continuous or cantilevere beams, it shoul be use with extreme caution an only after careful analysis base on soun engineering jugment. It is important to unerstan that improperly mae fiel notches or holes may reuce the capacity of a properly esigne member, possibly causing structural failure. The effects of any fiel notching or rilling shoul be checke by a esigner competent in engineere timber esign.

2 Fiel Notching an Drilling of Glue Laminate Timber Beams NOTCHING Notching of bening members shoul be avoie whenever possible, especially on the tension sie of a member. Tension-sie notching of glulam beams is not permitte except at en bearings an then only uner specific coni tions. The notching of a bening member on the tension sie results in a ecrease in strength cause by stress concentrations which evelop aroun the notch, as well as a reuction of the area resisting the bening an shear forces. Such notches inuce perpenic ular-to-grain tension stresses which, in conjunction with horizontal shear forces, can cause splitting along the grain, typically starting at the insie corner of the notch. Stress concentrations ue to notches can be reuce by using a graually tapere notch configuration in lieu of a square-cornere notch. Rouning the square corner of a notch with a raius of approximately 1/2 inch is also recommene to reuce stress concentrations in these areas. For square-cornere notches occurring at the ens of beams on the tension sie, the esigner may consier the use of reinforcement, such as full-threae lag screws, to resist the tenency to split at the notch (See Figure 1). A number of esign methoologies exist for sizing such screws. The esign methoology selecte an subsequent fabrication etails are the responsibility of the esigner/engineer of recor. If lag screws are use, lea holes shall be prerille in accorance with accepte practice. This proceure can also be use as a fiel remey to minimize further propagation of an existing crack. FIGURE 1 A REINFORCEMENT TECHNIQUE TO MINIMIZE CRACK PROPAGATION AT END BEARING NOTCHES Lag screw extens past the neutral axis into the upper portion of beam 0.1 Depth of or 3 inches, notch whichever is less Bearing length Potential Washer crack zone Use one or more fully threae lag screws Neutral axis Where glulam members are notche at the ens for bearing over a support, the notch epth shall not excee 1/10 of the beam epth. Figure 2(e) is provie to assist in evaluating the associate reuctions to beam strength ue to notching on the tension sie. For notches on the compression sie, a less severe conition exists an equations for the analysis of the effects of these notches are also given in Figure 2. The equations given are empirical in nature an were evelope for the conitions shown. As this guieline is limite to single span, simply supporte beams, the notches shown in Figure 2 occur in areas of high shear an effectively zero moment. For this reason, the esign equations given are shear equations. In situations where compression sie notches exten into areas of significant moment, the bening capacity of the beam shoul also be checke using the remaining section of the beam an the appropriate allowable stresses for those lamina tions remaining at the notch location. Contact APA for more information regaring this type of notch. When it becomes necessary to cut a small notch in the top of a glue laminate timber (in the compression zone) to provie passage for small iameter pipe or conuit, this cut shoul be mae in areas of the beam stresse to less than 50 percent of the esign bening stress. The net section in these areas shoul be checke for shear an bening stresses to ensure aequate performance. All fiel notches shoul be accurately cut. Avoi over cutting at the root of the notch. Drilling a pilot hole in the member at the interior corner location of a notch as a stop point for the saw blae provies both a roune corner an minimizes over cutting at the corner. Form No. S560H 2014 APA The Engineere Woo Association 2

3 Fiel Notching an Drilling of Glue Laminate Timber Beams FIGURE 2 SHEAR DESIGN EQUATIONS FOR NOTCHED AND TAPERED BEAMS Compression sie Compression sie f v = 3V 2b f v = 3V 2b (a) Square En Bearing (b) Slope En Bearing 3 maximum 0.4 max. 3 e or 1/3 of the span, whichever is less e /3 min. e e 0.6 f v = 3V 2b e When e e, 3V f v = 2b ( e) e e (c) Slope En Cut for Roof Drainage When e > e, f v = 3V 2be () Compression-sie Notch e or 3 inches max., whichever is less ( ) 3V 2 f v = 2b e e (e) Tension-sie Notch f v = shear stress (psi) V = shear force at notch location (lb) b = with of beam (in.) = epth of beam (in.) e = effective epth as shown (in.) e = length of notch as shown (in.) Form No. S560H 2014 APA The Engineere Woo Association 3

4 Fiel Notching an Drilling of Glue Laminate Timber Beams HOLES Horizontal Holes Like notches, holes in a glulam beam remove woo fiber, thus reucing the net area of the beam at the hole location an introucing stress concen trations. These effects cause a reuction in the capacity of the beam in the area of the penetration. For this reason, horizontal holes in glue laminate timbers are limite in size an location to maintain the struc tural integrity of the beam. Figure 3 shows the zones of a uniformly loae, simply supporte beam where the fiel rilling of holes may be consiere. These non-critical zones are locate in portions of the beam stresse to less than 50 percent of esign bening stress an less than 50 percent of esign shear stress. For beams of more complex loaing or other than simple spans, similar iagrams may be evelope. FIGURE 3 ZONES WHERE SMALL HORIZONTAL HOLES ARE PERMITTED IN A UNIFORMLY LOADED, SIMPLY SUPPORTED BEAM l l/8 l/8 l/2 l/8 l/8 Uniform Loa (plf) /4 /2 /4 Shear critical zone Bearing critical zone Moment critical zone Moment critical zone Shear critical zone Bearing critical zone Zones where horizontal holes are permitte for passage of wires, conuit, etc. Fiel-rille horizontal holes shoul be use for access only an shoul not be use as attachment points for brackets or other loa bearing harware unless specifically esigne as such by the engineer or esigner. Examples of access holes inclue those use for the passage of wires, electrical conuit, small iameter sprinkler pipes, fiber optic cables, an other small, lightweight materials. These fiel rille horizontal holes shoul meet the following guielines: 1. Hole size: The hole iameter shoul not excee 1-1/2 inches or 1/10 the beam epth, whichever is smaller, with the exception of 1-inch-iameter or smaller holes as note in Item 2 below. 2. Hole location: The hole shoul have a minimum clear istance, as measure from the ege of the hole to the nearest ege of the beam, of 4 hole iameters to the top or bottom face of the beam an 8 hole iameters from the en of the beam. Note that the horizontal hole shoul not be rille in the moment-critical zone, as efine in Figure 3, unless approve by an engineer or architect qualifie in engineere timber esign. Form No. S560H 2014 APA The Engineere Woo Association 4

5 Fiel Notching an Drilling of Glue Laminate Timber Beams FIGURE 4 ZONES WHERE 1-INCH OR SMALLER DIAMETER HORIZONTAL HOLES ARE PERMITTED IN A UNIFORMLY LOADED SIMPLE OR MULTIPLE-SPAN BEAM ( = 7-1/4 INCHES) l/8 Uniform Loa (plf) /4 /2 /4 Minimum 8 x iameter of the larger hole λ λ λ l Zones where 1-inch or smaller iameter horizontal holes are permitte for passage of wire, conuit, etc. a) the maximum number of holes for each span shall not excee 1 hole per 5 feet an b) the hole must not be cut in cantilevers. λ = 6 inches minimum when l/ 10, or l/6 minimum when l/ < 10. A 1-inch-iameter or smaller hole may be cut at the mile half of the beam epth anywhere along the span, except for the area that is within 6 inches of clear istance between the face of the support an the nearest ege of the hole (see Figure 4), provie the following conitions are all met: a. the beam is at least 7-1/4 inches in epth, b. the beam is subject to uniform loas only, c. the span-to-epth ratio (l/) is at least 10,. the hole spacing an maximum number of holes must meet the requirements specifie in Items 3 an 4 below, an e. the hole must not be cut in cantilevers. If the span-to-epth ratio of the beam is less than 10, the 1-inch iameter or smaller hole may be cut in accorance with the provisions liste above except that the location of the hole must maintain a clear istance between the face of the support an the nearest ege of the hole of at least 1/6 of the span. 3. Hole spacing: The minimum clear spacing between ajacent holes, as measure between the nearest ege of the holes, shoul be 8 hole iameters base on the largest iameter of any ajacent hole in the beam. 4. Number of holes: The maximum number of holes shoul not excee 1 hole per 5 feet of beam length. In other wors, the maximum number of holes shoul not excee 4 for a 20-foot-long beam. The hole spacing limitation, as given above, shoul be satisfie separately. For glulam members that have been oversize, the guielines given above may be relaxe base on an engineering analysis. Beam epth, (in.) 7-1/4 7-1/2 8-1/ /4 9-1/2 9-5/8 10-1/ /4 11-7/ /8 13-1/ / /2 17-7/ /4 19-1/ / /2 23-3/8 24 Span when l/ = 10 6'-1" 6'-3" 6'-11" 7'-6" 7'-9" 7'-11" 8'-1" 8'-9" 9'-2" 9'-5" 9'-11" 10'-0" 10'-4" 11'-3" 11'-8" 12'-6" 12'-8" 13'-4" 13'-9" 14'-11" 15'-0" 16'-1" 16'-3" 16'-8" 17'-3" 17'-6" 18'-4" 18'-9" 19'-6" 20'-0" Form No. S560H 2014 APA The Engineere Woo Association 5

6 Fiel Notching an Drilling of Glue Laminate Timber Beams Regarless of the hole location, holes rille hori zon tally through a member shoul be posi tione an size with the unerstaning that the beam will eflect over a perio of time uner in-service loaing coni tions. This eflection coul cause istress to sup porte equipment or piping unless properly consiere. Vertical Holes Whenever possible, avoi rilling vertical holes through glulam beams. As a rule of thumb, vertical holes rille through the epth of a glulam beam cause a reuction in the capac ity at that location irectly proportional to the ratio of 1-1/2 times the iameter of the hole to the with of the beam. For example, a 1-inch hole rille in a 6-inch-wie beam woul reuce the capac ity of the beam at that section by approximately (1 x 1-1/2) = 25%. 6 For this reason, when it is necessary to rill vertical holes through a glulam member, the holes shoul be positione in areas of the member that are stresse to less than 50 percent of esign in bening. In a simply supporte, uniformly loae beam, this area woul be locate from the en of the beam inwar approx imately 1/8 of the beam span. In all cases, the minimum clear ege istance, as measure from either sie of the member to the nearest ege of the vertical hole, shoul be 2-1/2 times the hole iameter. Use a rill guie to mini mize wanering of the bit as it passes through knots or material of varying ensity, an to insure a true alignment of the hole through the epth of the beam. Holes for Support of Suspene Equipment Heavy equipment or piping suspene from glulam beams shoul be attache such that loa is applie to the top of the members to avoi tension perpenicular-to-grain stresses. Any horizontal holes require for support of significant weight, such as suspene heating an cooling units or main water lines, must be locate above the neutral axis of the member an in a zone stresse to less than 50 per cent of the esign flexural stress (See Figure 3). Fasteners supporting light loas, such as light fixtures, must be place at least four laminations or 25 percent of beam epth, whichever is greater, away from the tension face of the member. The esign capacity of the beam shoul be checke for all such loas to ensure proper performance. PROTECTION OF FIELD-CUT NOTCHES AND HOLES Frequently, glulam beams are provie from the manufacturer with the ens seale by a protective coating. This sealer is applie to the en grain of the glulam beams to retar the migration of moisture in an out of the beam ens uring transit an job site storage. Fiel cutting a notch in the en of a beam can change the moisture absorption character istics of the beam at the notch location. This can result in seasoning checks or even localize splitting eveloping at the root of the notch. To minimize this possibility, all notches shoul be seale immeiately after cutting using a water-repellent sealer. Sealing other fiel-cut locations as well as fiel-rille holes is also recommene. These sealers can be applie with a brush, swab, roller or spray gun. Form No. S560H 2014 APA The Engineere Woo Association 6

7 Fiel Notching an Drilling of Laminate Timber Beams We have fiel representatives in many major U.S. cities an in Canaa who can help answer questions involving APA traemarke proucts. For aitional assistance in specifying engineere woo proucts, contact us: APA HEADQUARTERS 7011 So. 19th St. Tacoma, Washington (253) Fax: (253) PRODUCT SUPPORT HELP DESK (253) DISCLAIMER The information containe herein is base on APA The Engineere Woo Association s continuing programs of laboratory testing, prouct research, an comprehensive fiel experience. Neither APA, nor its members make any warranty, expresse or implie, or assume any legal liability or responsibility for the use, application of, an/or reference to opinions, finings, conclusions, or recommenations inclue in this publication. Consult your local jurisiction or esign professional to assure compliance with coe, construction, an performance requirements. Because APA has no control over quality of workmanship or the conitions uner which engineere woo proucts are use, it cannot accept responsibility for prouct performance or esigns as actually constructe. Form No. S560H/Revise November 2014

Field Notching and Drilling of Glued Laminated Timber Beams Number EWS S560F December 2006

Field Notching and Drilling of Glued Laminated Timber Beams Number EWS S560F December 2006 T E C H N I C A L N O T E Fiel Notching an Drilling of Glue Laminate Timber Beams Number EWS S560F December 2006 INTRODUCTION Glue laminate timber (glulam) beams are highly engineere components manufacture