British Columbia Carpenter Apprenticeship Program

Transcription

1 British Columbia Carpenter Apprenticeship Program Level 2 Line G Competency G-5 Install Anchor Bolts and Metal Reinforcing in Concrete

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4 Competency G-5 Install Anchor Bolts and Metal Reinforcing in Concrete Contents Objectives... 2 Learning Task 1: Install Embedded Metals... 3 Learning Task 1: Self-Test Learning Task 2: Install Metal Frames in Concrete Learning Task 2: Self-Test Learning Task 3: Describe Methods of Installing Dock Levelers in Concrete Learning Task 3: Self-Test Learning Task 4: Use Concrete Fastening Systems Learning Task 4: Self-Test Learning Task 5: Identify Steel Reinforcing for Concrete Learning Task 5: Self-Test Learning Task 6: Describe Waterstops Learning Task 6: Self-Test Learning Task 7: Describe Types of Door Frames Used in Concrete and Masonry Walls Learning Task 7: Self-Test BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 1

5 Competency G-5 Install Anchor Bolts and Metal Reinforcing in Concrete Anchor bolts and metal accessories used for construction must be accurately positioned in the fresh concrete. Once the concrete has set, the location of the bolts and metal frames cannot be repositioned. Objectives When you have completed the Learning Tasks in this Competency, you will be able to: describe the installation of embedded metals, anchor bolts and dowels describe the installation of metal frames in concrete describe methods of installing dock accessories in concrete use concrete fastening systems describe reinforcing for concrete describe waterstops describe types of door frames used in concrete and masonry walls Competencies Written: Install Anchor Bolts and Metal Reinforcing in Concrete You will be tested on your knowledge of terminology and installation methods for embedding metal components in concrete. You will be tested on your knowledge of the types and uses of embedded metals and plastics in concrete. 2 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

6 Competency G-5 Learning Task 1 Learning Task 1 Install Embedded Metals Specific procedures must be followed to attach concrete, metal or wood structures to concrete. You must understand the commonly used placement of metal anchor bolts and dowels in concrete formwork. Anchor Bolts Anchor bolts are used to attach wood framing to concrete foundations as shown in Figure 1. The anchor bolts shown in Figure 1 serve two purposes: they hold the building down to the foundation, and provide lateral support to the foundation wall. Lateral support is needed to resist the sideways force of the backfill. The Building Code requires anchor bolts to be spaced at 2.4 m o.c. This is the maximum spacing and most designers and engineers specify a closer spacing of 1.2 m o.c. or less. Figure 1. Anchor bolt at sill plate The length and diameter of the anchor bolts varies; for residential construction the minimum is 6" long and " in diameter. This is the minimum, most often longer and heavier bolts are used. Anchor bolts are usually bent at the end to prevent them from turning or pulling out when their nuts are tightened. Figure 2. Anchor bolt placement If accuracy is not critical, you may insert the anchor bolts for sill plates into the concrete after placement, but before it sets. To consolidate the fresh concrete around the bolt, tap the sides of the form near the bolt with a hammer. When using anchor bolts to attach structural steel to concrete, you must use templates for accurate placement of the bolts. Figure 2. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 3

7 Learning Task 1 Competency G-5 Machine Base Bolts Small machines and equipment are often secured to concrete using anchor bolts, inserts or drilled-in fasteners. Larger machinery is fastened to heavy concrete slabs using machine base bolts. Machine base bolts may be 1200 mm or longer, and have diameters of 75 mm or more. Typical installations for such fastenings are at pulp mills and refineries. It is important to set anchor bolts and machine bolts accurately. Attach templates solidly to the forms before concrete is placed (Figure 3). The carpenter uses shop drawings to make the templates to set machine bolts, and may need to work with a millwright, ironworker or machinist. Pay special attention to concrete consolidation around the bolts, the holding power of the bolt depends on the strength of surrounding concrete. Figure 3. Clustered anchor bolts For bolts clustered together, use string lines over the centerlines of the template to install them accurately. Wire the embedded portions of such groupings to pieces of rebar placing the wire just above the bend in the bolt as in Figure 3. This strengthens them and prevents accidental withdrawal; it also steadies the bolts during concrete placement. Some large machines have oversize holes in their base to allow a little adjustment if the bolts are not set precisely. 4 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

8 Competency G-5 Learning Task 1 Pipe Sleeves A method of accommodating error is to set bolts into pipe sleeves (Figure 4). These sleeves leave a portion of the bolt free of the concrete so that its location may be adjusted after casting by bending it slightly within the pipe. Protection Whether the bolts have sleeves or not, you must protect their threads from being covered with concrete splatter during concrete placement. Wrapping the bolts with tape, or coating them with grease will protect the threads. Prevent physical damage to the bolt by covering the exposed threads with a pipe. The end of the pipe should be covered with a mushroom cap to protect workers who may fall on it. Installation Installers must take great care while machines are lowered onto bolts, especially if the holes are tight fitting. Damaged bolts may need rethreading with a thread chaser or die nut to avoid cross threading of the bolts. Grouting Once in place, metal shims are used to level the machine during installation. The shims leave a gap under the machine base and the concrete support, this gap must be filled with grout. Liquid grout is used to fill the gap left by the shims and the voids left by the sleeves. A low form is built around the entire base of the machine so that the liquid grout will not flow out over the floor. Figure 4. Adjustable machine base bolt BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 5

9 Learning Task 1 Competency G-5 Templates An anchor bolt template is usually made from 19 mm lumber or plywood. If it is to be set inside the form, cut it to the same width as the form. If it is to be set on top of the form, cut it wider than the form. Figure 5. Lay out the holes so that their position matches the holes in the base plate of the structural steel. Figure 5. Anchor bolt template Take great care to be accurate. Use a framing square and tape measure to check diagonals and center-to-center distances. Use string lines to locate points half way between bolt positions. Lay out center marks on the edges of the template (Figure 5). Position the template so that the center marks coincide with the string lines. Also use string lines to position the center point of each bolt. Check all measurements and midpoint marks for accuracy, then drill the template holes. Make the holes the same size as the bolts, not the size of the holes in the column base, which are often bigger to allow for adjustment. Insert the anchor bolts into the template, and attach washers, spacers (if needed), and nuts. These will hold the top of the bolt the required distance above the concrete, allowing for their own thickness and that of the steel base. Position the template over the footing form. (Figure 6) Using duplex nails for easy removal, nail the template to the form, nailing sideways from the outside if the template is set inside the form. Figure 6. Using the template to place anchor bolts 6 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

10 Competency G-5 Learning Task 1 Dowels Dowels are short lengths of reinforcing steel that are used to connect two separate cast-in-place concrete sections. They are made from deformed or smooth steel bars. When it is important to have no movement between the two structures, always use deformed steel. Smooth dowels An expansion joint uses smooth dowels to keep two slabs in alignment. The dowels hold both slabs in place vertically while the smooth surface of the dowels allows the slabs to move horizontally. The dowels were cast into the slab on the left in Figure 7 by inserting them through holes in the form. Insert the dowels so that about half their length will be embedded in the first slab. Figure 7. Smooth dowel in a slab After concrete placement, strip the form, leaving the rods projecting from the first slab. The expansion joint filler is placed against the first slab and dowel sockets or expansion caps are placed on the ends of the exposed dowels. Grease the exposed dowels and cast the second slab against the first. The filler is cut back and the expansion joint is then sealed with caulking. Miscellaneous Iron In many concrete placements, metal must be incorporated into the concrete to give protection, support or provide a welding surface. The examples of miscellaneous iron shown in Figures 8 and 9 serve quite different purposes but the way the metal inserts are installed is similar. The pieces must be precisely located, and securely supported so they do not move during concrete placement. They must also be positioned such that they will not interfere with the removal of the formwork. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 7

11 Learning Task 1 Competency G-5 Figure 8. Protective edge plate Figure 9. Weld plates and joist seats Anchorage Embedded metals are anchored to the concrete by deformed rods, bolts or bent bars. These anchors are welded to the back of the metal components before they are delivered to the job site. Small weld plates may have only one anchor, while protective edge plate (angle) may have anchors welded every 300 mm along their entire length. Edge Protection Angled metal plates are used to protect the edges of loading docks, doorways or on exposed corners of columns or walls in high traffic areas. Before the concrete is placed, attach the protective angle edge plate (Figure 8) to the form, using nails, bolts or wire. If bolts are used, place them with their nuts on the concrete side of the metal. Once the concrete is set, the bolts may be withdrawn, leaving the nuts embedded in the concrete. If nails or wires are used, cut them flush with the exposed face of the metal after form removal. Weld Plates Pre-cast construction methods use weld plates to connect sections. Figure 10 shows a weld plate embedded in the footing so that a pre-cast wall may be connected to it. A corresponding weld plate is cast into the wall. After the wall and footing are in place, the two plates are welded together. Concrete stairs and walkways often have welding plates embedded in them so that railings can be attached to them. 8 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

12 Competency G-5 Learning Task 1 Figure 10. Weld plate Inserts There are many different types of inserts. The size and holding capacity is designed for the load that they are supporting. For all inserts, the strength of the insert depends upon how well the concrete is consolidated around it. Inserts designed to support heavy loads are often fastened to or positioned around the reinforcing steel in the concrete. Tee Bar Ceiling Hangers When a suspended ceiling is installed under a suspended concrete slab in a commercial building, sheet metal tee bar ceiling hangers are used. The layout for the main tees is done on the slab formwork; then the sheet metal hangers are pounded into the slab form. After the forms are stripped, the eyelet of the hanger is exposed and the tee bar hanger wire can be attached (Figure 11). HANGER WIRE ATTACHMENT Figure 11. Tee bar hanger BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 9

13 Learning Task 1 Competency G-5 Loop Inserts The loop insert shown in Figure 12 is designed to use a coil bolt. Other thread types are available but the coil thread is the easiest to thread into the insert. Loop inserts are used to support heavy loads. Lifting rings are used to move pre-cast concrete members. They are screwed into loop inserts cast into the precast members. Figure 12. Loop insert There are many other types of inserts but all are similar. The positioning of all inserts is very important because once the concrete has been cast, the inserts cannot be moved or adjusted. Lifting inserts, used for tilt-up construction, are supporting very heavy loads. Lifting inserts should be inspected carefully before the concrete is cast. Reglets and Inserts A reglet is a continuous groove that is cut or formed into a wall, usually above the point of intersection with a flat roof. Counter flashing strips are caulked or grouted into the reglet. The counter flashing is placed so that it slopes down, directing water away from the joint between wall and roof. The reglet is usually at least 25 mm deep. The counter flashing overlays the roofing material that continues up the wall at the roof edge over a cant strip (Figure 13). Figure 13. Reglet To form the reglet, a wooden strip is nailed to the form, leaving a groove when the formwork is dismantled; a prefabricated metal strip already filled with caulking, which remains in place after the form is removed, may also be used. Inserts are installed permanently in the concrete. They are placed against the formwork, so that when the formwork is removed they are exposed. There is a large assortment of insert types and sizes. They must be placed with great accuracy, and forms must be very stable and well braced during placement. Reglets for concrete formwork are available in many sizes, styles and materials. They are all designed to keep water from infiltrating the joints between building components. 10 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

14 Competency G-5 Learning Task 1 Job-constructed Reglets There are two common ways to build simple, effective reglets for castin-place concrete: creating a groove ready to receive counter flashing, or direct embedding of the counter flashing into the concrete during placement. Figure 14. Reglet blockout Creating a Groove Placing a tapered wooden strip into the concrete will form a groove. The counter flashing is inserted into the groove, and caulked. Embed the flashing at least 25 mm into the groove. Embedding Counter Flashing Counter flashing can be placed into the groove left after stripping a twopiece reglet blockout (Figure 14). The flashing can also be cast directly into the concrete using a one-piece reglet blockout as shown in Figure 15. Figure 15. Casting flashing into the concrete BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 11

15 Learning Task 1 Competency G-5 Manufactured Reglets There are various types of manufactured reglets on the market. All of them restrict the passage of water into a joint between wall and roof or between two kinds of wall surfaces. The first two described, and shown in Figures 16 to 19, are designed to be fastened to the concrete forms before concrete placement; the next two described, and shown in Figure 20 and 21, are attached after wall completion. The final, more unusual one shown in Figure 22 is for window installation in cast-in-place concrete. Figure 16. Removable strip PVC Reglet (duplex nails) This type of polyvinyl chloride (PVC) reglet is fastened 300 mm o.c. with small duplex nails. Install it against the formwork as shown in Figure 17. The reglet remains in place after the formwork is removed. It features removable flashing that requires no caulking (Figure 16). This strip is pulled off just prior to installation of counter flashing. It is easily removed. Figure 17. Installing the reglet Figure 18. Installed reglet and counter flashing 12 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

16 Competency G-5 Learning Task 1 PVC Reglet ( J nails) This second type of cast-in-place reglet also requires no caulking. The reglet is installed against the wall forms using special J nails (Figure 19). Figure 19. PVC reglet installed with J nails Metal and PVC Wall-mounted Reglets These are attached directly to the cured surface of a concrete wall or to other types of wall. In both cases, a flashing snaps into a strip that is wall mounted over a caulking strip. A typical metal one is shown in Figure 20. Figure 21 shows a PVC version. The flashing is easy to install or remove. Figure 20. Wall-mounted metal reglet BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 13

17 Learning Task 1 Competency G-5 Figure 21. PVC wall-mounted reglet with flashing Reglets for Window Installation Reglets can be used to install glazing into cast-in-place concrete. Such reglets are nailed in place from inside the form, or screwed in place from the outside. Just before the window unit is installed, the removable strip is taken off, the nails are clipped or bent over and a neoprene-glazing gasket is inserted. Figure 22. Reglet for window installation in concrete wall This system is used when building curtain walls in concrete buildings. Only the top or bottom of a sealed unit can be set into the concrete. The other three sides are secured with the window-wall framing. Now complete Learning Task 1 Self-Test. 14 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

18 Competency G-5 Learning Task 1 Learning Task 1 Self-Test 1. What is a dowel? 2. How are L-shaped anchor bolts placed when great accuracy is not needed? 3. Of what material are most bolt templates made? 4. What kind of form is often used with dowels? 5. What is done to ensure uniform contact between the base of a machine and its concrete footing? 6. How are anchor bolt threads protected during concrete placement? 7. What type of drawing is used to find the exact locations of machine base bolts? 8. Describe how to make an expansion joint in a slab. 9. How are templates for anchor bolts positioned? 10. What is used to fasten pre-cast concrete members together? 11. List two types of inserts. 12. What two functions do anchor bolts provide? 13. Which kinds of reglet require no caulking? 14. What materials are manufactured reglets made from? BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 15

19 Learning Task 2 Competency G-5 Learning Task 2 Install Metal Frames in Concrete Sewer Access Cover Frames A sewer access (Figure 1) is a barrel-shaped concrete shaft descending from the street or floor level to the storm or sewer main. Figure 1. Pre-cast components Each sewer access is capped with a cast iron frame into which a heavy cast iron lid is set. Pre-cast concrete rings are used to build the sewer access. Installation The cast iron metal frame is set in place on top of the concrete shaft after the shaft has been backfilled. The frame sits into the top concrete section and is held in place by its own weight. Level the frame with metal shims (Figure 2). 16 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

20 Competency G-5 Learning Task 2 Figure 2. Cover frame in place To hold the frame in place and waterproof the joint between it and the shaft, concrete is placed around the frame. The concrete is vibrated into place and finished flush to the top of the frame. Grates, Catch Basins and Drain Troughs A grate is a cast iron metal component installed in a floor to allow water to flow into the drain. The grate must be strong enough to support vehicle and pedestrian traffic on the floor. The grate must be removable to allow the drain to be cleaned out. It fits into a groove in the concrete that is formed slightly larger than the grate. A commonly used strip drain in residential construction is a plastic trough that gets cast-in-place into the slab. A grate sits on a ledge that is part of the trough. Below the grate is a trough or trench that will collect the water and direct it towards the drain. The trough must slope towards the drain and incorporate the groove to fit the grate into. DRAINAGE GRATE DRAINAGE TROUGH Figure 3. Drainage grates BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 17

21 Learning Task 2 Competency G-5 Formwork The troughs are formed into the concrete using blockouts which are shaped to provide a lip to support the grates or drain trough covers. Wire the blockout to the concrete reinforcements, and/or shim the blockout off the sub grade with concrete or bricks. The side forms of the trough are ripped at a taper to provide a slope to the bottom of the trough. Use steel ballast to keep the form from floating on the fresh concrete (Figure 4). CLEATS BALLAST Figure 4. Formwork WIRE TIE Catch Basins Catch basins may be barrel shaped or rectangular, and are topped with cast iron frames and lids. Catch basin installation is the same as for sewer access covers, except that catch basin frames may not have a lip that fits into the concrete box (Figure 5). Figure 5. Catch basin grate Now complete Learning Task 2 Self-Test. 18 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

22 Competency G-5 Learning Task 2 Learning Task 2 Self-Test 1. How are sewer access covers held in place during concrete placement? 2. Why are trough forms held down with ballast? 3. How are trough forms held in position during concrete placement? 4. What are sewer access covers and grates usually made from? 5. What material is used to shim manhole covers to elevation? BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 19

23 Learning Task 3 Competency G-5 Learning Task 3 Describe Methods of Installing Dock Levelers in Concrete A dock leveler is an adjustable deck installed on loading docks used to give level access to the back of freight trucks. It is operated hydraulically, electrically, pneumatically or manually and can be raised or lowered to suit the heights of various trucks (Figure 1). Figure 1. A typical dock leveler There are two types of dock leveler installations: pit mounted or cast-in-place. Figure 2. Pit-mounted Figure 3. Cast-in-place 20 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

24 Competency G-5 Learning Task 3 Pit-Mounted The formwork for pit-mounted dock levelers incorporate a box that is set into the surface of a concrete slab, it will be encased with concrete on five sides. The moisture in the concrete will expand the wooden formwork and trap it in place. Design the form so that it will come apart easily after the concrete is placed. The five-sided form will act like a boat and tend to float on the concrete so it must be braced or weighted down to keep it from floating. The horizontal position is maintained by anchoring it to reinforcing steel with wire ties. Figure 4. Pit-mounted dock leveler formwork using ballast and brick shims An alternative is to first place a base slab at the bottom of the pit, and then secure the edge forms to it using powder actuated fasteners, anchor bolt, or inserts. Figure 5. Pit-mounted dock leveler formwork using a base slab BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 21

25 Learning Task 3 Competency G-5 Cast-in-Place Cast-in-place units require little or no forming, they must be set in place very accurately and securely braced before concrete placement. The unit is attached to adjacent reinforcing steel with heavy wire. It is common to steady the unit with an overhead frame that is removed after the concrete has set around the dock leveler. Controls Dock levelers are activated by electrical controls that are some distance from the unit, usually mounted on a nearby wall. Conduit must be placed in the floor slab from the control area to the installed unit. Templates Templates may be required to support the control conduit while the concrete sets (Figure 6). Figure 6. Conduit for controls of a dock leveler Installation Checklist For either pit-mounted or cast-in-place dock leveling units: 1. Follow the manufacturer s instructions for installing dock leveling units 2. Prior to placing concrete, check the following carefully: control conduits are in place the elevation of the top of the formwork or unit the formwork or the unit is square the formwork or the unit itself for level Now complete Learning Task 3 Self-Test. 22 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

26 Competency G-5 Learning Task 3 Learning Task 3 Self-Test 1. What are the two methods of installing dock levelers? 2. What can be done to support the forms from floating as the concrete is being placed around them? 3. How are the forms held in place horizontally? 4. What is used to support the end of the conduit at the dock leveler? 5. List four things to check prior to placing concrete. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 23

27 Learning Task 4 Competency G-5 Learning Task 4 Use Concrete Fastening Systems Strength and Loading The holding power of screws, bolts and anchors is dependant on several factors: the strength of the fastener the type of the material supporting the fastener the type of material being attached with the fastener the direction of the load the effective area of the fastener s head or nut Fastener Strength Fasteners are usually made from materials that are stronger than the materials they are fastening into. The supporting material will usually give way before the fastener will break or the fastener will pull through materials of lower strength. Supporting Material The fastener can grip securely into dense materials but gripping into soft loose materials is difficult. Special anchors with large wide thread surfaces have been developed to anchor into drywall. The shank of screws and bolts will twist off if the material is too hard and the fastener is installed without the proper sized pilot hole. Attached Material Soft materials like fibreboard or polystyrene require special fastenings to hold them in place. Using large washers will help support soft materials. Hard, strong materials may also need washers if the materials are thin. Concrete Fastenings Expansion Shield Expansion shields are used with lag bolts to fasten items to concrete. The size of the shield must match both the bolt and the hole drilled into the concrete. The hole must be drilled deeper than the length of the bolt being used. 24 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

28 Competency G-5 Learning Task 4 Figure 1. Lag screw and expansion shield Use a hammer to tap the expansion shield flush with the face of the concrete, it should fit snugly. The lag bolt expands the shield against the sides of the hole, providing firm anchorage. Lead Plug Lead plugs are similar to expansion shields but are used for lighter loads. They are inserted into holes drilled into concrete and the attachment is made with a wood screw (Figure 2). The size of the plug must match the size of the screw, and the size of the hole in the concrete must match the size of the plug. Figure 2. Lead plugs Fibre Plug Fibre plugs (Figure 3) are similar to lead plugs, except that they are made from a hard fibrous material. Figure 3. Fibre plug BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 25

29 Learning Task 4 Competency G-5 Wedge, Sleeve or Drop-in Anchors These anchors (Figure 4) are inserted into holes drilled into the concrete. The size of the hole must match the size of the anchor. As the bolt is tightened, the anchor spreads and locks in place. The tighter the bolt, the firmer the anchor. Figure 4. Heavy and medium-duty expansion anchors Insulation Attachment This anchor system (Figure 5) for light-duty functions, such as attaching insulation materials to concrete or block walls, uses a hardened concrete nail that is driven into a predrilled hole. Galvanized steel or plastic stress plates (washers) are used with the nails to support the soft insulation. Figure 5. Concrete anchors and stress plates Pin Bolt The pin bolt is designed for light-duty functions (Figure 6). The anchor is placed into a predrilled hole in the concrete and through a hole in the material it is to hold. When the pin is driven in, the anchor spreads and makes a firm bond to the concrete. Figure 6. Pin bolt 26 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

30 Competency G-5 Learning Task 4 Tapcon Anchors The Tapcon anchor (Figure 7) is known for its ease of installation and holding strength when attaching items to concrete, block and brick. This fastener is made with a coating that is corrosion resistance, and is recommended for use in ACQ pressure-treated lumber. Figure 7. Tapcon blue screw Tapcon fasteners can be applied as a system (Figure 8). Installation Instructions: Drill Using a hammer drill, drill a hole " deeper than anchor embedment. Slide (optional) Slide Condrive installation tool over drill bit and drill adapter and position Tapcon concrete anchor onto tool. Drive Drive Tapcon anchor into pre-drilled hole until anchor is fully seated. Tapcon anchors require a minimum embedment of 1" and a maximum embedment of 13 ". drill a hole 1/4 deeper than anchor drive anchor into hole until fully seated Figure 8. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 27

31 Learning Task 4 Competency G-5 Adhesive Anchor Adhesive anchors use polyester resin to glue the fastener into place. A glass capsule of resin, hardener and quartz aggregate is placed into the hole and then the anchor stud is used to break the capsule and start the chemical reaction. Within a few minutes, the resin hardens and forms a strong bond to the concrete. Made from plated or stainless steel, this anchor is available in various sizes. Figure 9. Adhesive anchors Epoxy Anchor Special two-part epoxies are used to anchor studs to concrete and hollow concrete block or brick. The proper size hole is drilled and cleaned; then a mesh screen is inserted into the hole and the epoxy applied. Finally, the stud is twisted into the hole until it reaches the bottom, and the epoxy is allowed to cure (Figure 10). This epoxy can also be used to repair cracks in concrete or block walls. Figure 10. Epoxy anchors 28 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

32 Competency G-5 Learning Task 4 Powder-Actuated Fasteners Manufacturers of powder-actuated tools have a full line of hardened steel fasteners. These fasteners are designed to penetrate concrete or mild steel. Figure 11 shows a few typical fasteners. Figure 11. Powder-actuated designs Now complete Learning Task 4 Self-Test. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 29

33 Learning Task 4 Competency G-5 Learning Task 4 Self-Test 1. The anchor shown above is: a. a self-tapping screw b. an expansion shield c. a wedge anchor d. a plastic anchor 2. Which method is used to hold adhesive and epoxy anchors in place? a. mechanical fastening methods b. heat-treating methods c. chemical-curing methods d. powder-actuated methods 3. What type of an anchor is used with a lag bolt? 4. Stress plates are used to fasten? 5. Which fastener can be used with pressure-treated lumber? 6. What type of glues are used with adhesive fasteners? 7. What fastening system allows pins to be attached to steel? 30 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

34 Competency G-5 Learning Task 5 Learning Task 5 Identify Steel Reinforcing for Concrete The quality of concrete used for construction is rated by its compressive strength. The strength of concrete is determined by how it is made. The minimum strength required by Building Codes is 15MPa (million Pascals) or 2000 psi (pounds per square inch). By keeping the water-cement ratio low, strengths of as high as 35MPa or 5000 psi can be obtained. Forces Concrete does not have the same resistance to a tension force as it has to a compressive force. The compressive strength of plain concrete is approximately 10 times more than its tensile strength. Figure 1 shows two identical samples of un-reinforced concrete (plain concrete). The sample under compressive force begins to crack when 1000 pounds of force is applied; the identical sample begins to crack when only 100 pounds of tensile force is applied LB COMPRESSIVE FORCE 1000 LB COMPRESSIVE FORCE 100 LB TENSILE FORCE 100 LB TENSILE FORCE Figure 1. Properties of plain concrete BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 31

35 Learning Task 5 Competency G-5 Reinforcement Reinforcing steel is used in concrete beams, girders and slabs to increase its tensile strength. In columns, it is used to increase the compressive strength. A uniform load applied to a suspended concrete member will attempt to crack the member as shown in the top diagram of Figure 2. As the member begins to bend, the bottom side of the member will stretch; because concrete is weaker in tension than compression, the bottom side will crack open. By adding steel reinforcement near the bottom edge of the member, the reinforcing will bond to the concrete and the steel will help the concrete resist the tension forces. LOAD LOAD LOAD LOAD PLAIN CONCRETE LOAD LOAD LOAD LOAD REINFORCED CONCRETE Figure 2. Reinforcing bars resist tension forces Figure 3 shows a horizontal concrete member spanning over more than two supports. Notice that tension occurs in the top of the member over the points of support as well as in the bottom of the member in the middle of the span. For this reason, reinforcement is usually placed near the top of the member as well as near the bottom. The member in Figures 2 or 3 could be a concrete beam, girder or slab. In all cases, the concrete member will be reinforced to resist the tension forces. LOAD LOAD LOAD LOAD LOAD LOAD LOAD LOAD LOAD LOAD LOAD TE NS ION TE NS ION TE NS ION TENSION TENSION Figure 3. Tension occurs in both the top and bottom of spanning members 32 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

36 Competency G-5 Learning Task 5 Reinforcing Concrete Columns The strength of reinforcing steel used in construction is significantly higher than the strength of even the best concrete. The weakest steel reinforcing used in construction has a tensile strength of 300MPa or approx. 45,000 psi. Steel, unlike concrete, also has the advantage that it has equal resistance to compressive forces or tension forces. For example, if it takes 45,000 lbs force to crush a sample of steel it would also take 45,000 lbs. of tension force to pull the sample apart. Since steel is so much stronger than concrete, even in compression, columns supporting heavy construction loads are reinforced with huge re-bars, often 50 mm in diameter. These large bars in columns support the compressive forces caused by the weight of the building. Figure 4 shows the large diameter reinforcing bars in a column. The vertical bars are kept from bowing inward by the concrete in between them and from bowing outward by the smaller bars wrapped around them. The smaller bars are called ties and may be rectangular, circular or in a spiral shape. Figure 4. Column reinforcing Deformed Bar Steel is the best material for reinforcing concrete. One of steel s advantages is that it has almost the same coefficient of expansion as concrete. This means that both concrete and steel will expand and contract at the same rate. Steel reinforcing bars are often referred to as rebar. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 33

37 Learning Task 5 Competency G-5 Steel reinforcing bars have lug-like ridges along them. The lugs interlock with the concrete increasing the bond between the concrete and the steel. Sizes Reinforcing bars are sized by their diameters. In the metric system, the bars are listed with their diameters followed by a capital M, the M stands for metric not metres. A 20M bar has a diameter of 20 mm, and a 15M bar will have a diameter of 15 mm. In the imperial system, a number indicates the diameter of the bar in 8ths of an inch, for example a number 6 is used for a 3 " diameter bar and is the equivalent of a 20M bar. Figure 5 shows a number 10 bar which would have an approximate diameter of 1 8". Steel mills produce the bars in 18 m lengths, and local suppliers stock them in 6 m and 12 m lengths. Strengths The most common strengths of reinforcing are intermediate and hard. Intermediate usually refers to grade 40, which has a tensile strength of 40,000 pounds per square inch (psi) or 300 MPa. Grade 40 bars starts to stretch under a force of 40,000 lbs. Hard rebar is grade 60, which has a strength of 400 MPa (60,000 psi), and is very difficult to bend. The strengths of reinforcing steel are often referred to as the rebar s yield, e.g. a 60,000 psi yield. Figure 5. Rebar identification Rebar is identified by symbols stamped into the bar (Figure 5). When pre-cut reinforcing bar is delivered to the job site, paint marks are used to identify the different lengths. 34 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

38 Competency G-5 Learning Task 5 Dowels Dowels are short lengths of reinforcing steel that are used to connect two separate cast-in-place concrete sections. They are made from deformed or smooth steel bars. When it is important to have no movement between the two structures, always use deformed steel. Usually dowels are tied to the reinforcing steel using the same type of wire that secures the rest of the rebar. This holds the dowels in their correct positions until concrete is placed. Tie the dowels to the rebar in the first section before it is placed. Then before the second section is placed, tie its rebar to the protruding dowels (Figure 6). Figure 6. Tying the dowels to reinforcing steel between placements In footings and pads for light residential construction, dowels are often simply inserted into the fresh concrete. Using this method, you must be careful to keep the bottom ends of the dowels from penetrating through to the soil, because moisture in the soil will rust the steel and destroy it. Engineers usually specify the distance dowels must penetrate each concrete section. If the distance is not specified, an acceptable distance is 24 times the diameter of the dowel. For example: a 12 mm diameter bar should penetrate the concrete in each section by 12 mm 24 = 288 mm; therefore the bar length must be at least mm = 576 mm. Horizontal spacing of the dowels is determined by reinforcing steel to which it attaches. Sometimes dowels are simply protruding sections of the reinforcing steel, rather than separate short sections of rebar. Deformed bars are often used with keyway forms to secure stair, porch or cantilever supports to a foundation as shown in Figure 7. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 35

39 Learning Task 5 Competency G-5 Figure 7. Angled dowels through keyways Dowels such as this are bent to form a right angle, and inserted through the keyway and the form for the exterior foundation wall. After the foundation is placed and stripped, forms are built for the second section, which is secured to the foundation by both the key and the dowels. Expansion Joints An expansion joint uses smooth dowels to keep two slabs in alignment. The dowels hold both slabs in place vertically while the smooth surface of the dowels allows the slabs to move horizontally. The dowels were cast into the slab on the left in Figure 8 by inserting them through holes in the form. Insert the dowels so that about half their length will be embedded in the first slab. Figure 8. Smooth dowel through expansion joint After concrete placement, strip the form, leaving the rods projecting from the first slab. The expansion joint filler is placed against the first slab and dowel sockets or expansion caps are placed on the ends of the exposed dowels. Grease the exposed dowels and cast the second slab against the first. The filler is cut back and the expansion joint is then sealed with caulking. 36 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

40 Competency G-5 Learning Task 5 Sheet and Mesh Steel wire mesh is used as reinforcing in slab-on-grade construction. The mesh is specified on the foundation drawings for the building. The mesh is specified by the spacing of the wires in both directions, and by the cross-sectional area of the wires used in the mesh. For example, if the plan calls for P9/P9 mesh, this indicates that the wires are spaced 150 mm apart in both directions, and that the cross sectional area of the end of the wires will be 9 mm 2. Sheets or Rolls Steel mesh comes in 2288 mm 6100 mm sheets, or in 2288 mm wide 61 m long rolls. The wire in the mesh is available in several grades of strength. The two common strengths are 300 MPa and 400 MPa. Figure 9. Steel wire mesh reinforcement for concrete The wire mesh reinforcing must be kept up in the concrete when the slab is being placed. Allowing it to fall to the bottom of the slab will not allow it to do its job. Now complete Learning Task 5 Self-Test. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 37

41 Learning Task 5 Competency G-5 Learning Task 5 Self-Test 1. What is the main property of steel and concrete that allows steel to be used to reinforce concrete? 2. The compressive strength of concrete is about times its tensile strength. 3. What is the size of a 10 M bar? 4. What name describes a grade 60 bar? 5. What type of construction uses welded wire mesh for reinforcing concrete? 6. Welded wire mesh is available in sheets 6100 mm long, or rolls mm long. How wide is it? 7. In the description P13/P13, what does P13 mean? 8. What does yield mean, as applied to reinforcing steel? 38 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

42 Competency G-5 Learning Task 6 Learning Task 6 Describe Waterstops Waterstop Waterstops are made from plastic or rubber. They are positioned along construction joints between two separate placements of concrete to prevent water seepage due to hydrostatic pressure. Waterstop material is flexible and can be cut and joined to form a continuous watertight seal. Shapes Two of the several common waterstop types are dumb bell and serrated. Examples of these are shown in Figure 1. The split-serrated type is very easy to install because it does not need a split bulkhead. The hollow bulb in the center helps to reduce shearing forces if there is any movement in the concrete. DUMB BELL DUMB BELL SERRATED SPLIT SERRATED Figure 1. Waterstops BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 39

43 Learning Task 6 Competency G-5 Dumb Bell The dumb bell style is used when there is significant expansion and contraction expected. The bulb at the centre is able to shift and move with the concrete movement. The width of this type is usually about 8", which allows 4" to be imbedded into each side of the joint. Serrated Serrated waterstops are used where differential settlement is expected and a firm grip in the concrete is required. Serrated waterstops come in widths from 4" to 12" and thickness of ⅛" to ½". Caulk Grade Waterstop A caulk-type waterstop is a waterstop that does not have to be secured to the formwork as the concrete is poured. Instead it is applied over a construction joint with a caulking gun. A bead is applied over the rough concrete of the first pour, just before buttoning up the forms of the next pour. As the waterstop gets wet from the fresh concrete, it swells many times its original size, making the construction joint watertight. Some polyurethane-based products can swell up to 500% of their original size. Selecting Waterstop Waterstop profiles are usually used in hydraulic structures like water storage towers and sewage treatment plants. The hydrostatic pressure in these structures is great because of the height of liquid contained within them. Waterstops come in various widths and thickness; generally the more hydrostatic pressure, the wider and thicker the waterstop. When choosing water stops consider the following: The overall width of the waterstop should not be more than the thickness of the concrete members being joined. The distance from the face of the concrete to the waterstop must not be less than half the width of the waterstop. The width of the waterstop must be at least 6 times the largest aggregate used in the concrete. This is to allow proper consolidation of the concrete around the waterstop. Now complete Learning Task 6 Self-Test. 40 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

44 Competency G-5 Learning Task 6 Learning Task 6 Self-Test 1. List the two types of waterstop. 2. What pressures are waterstops designed to resist? 3. In what type of construction are waterstops used? 4. List three properties that all waterstops must have. 5. What is the widest water stop that can be used for a wall that is 300 mm thick? 6. What is the narrowest waterstop that can be used with concrete that has a maximum aggregate size of 30 mm? 7. Sketch the location of a dumb bell style of waterstop in the connection between a mm footing and a 250 mm thick wall. Indicate the size of the waterstop in mm. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 41

45 Learning Task 7 Competency G-5 Learning Task 7 Describe Types of Door Frames Used in Concrete and Masonry Walls Because of the long lasting, durable nature of concrete, it is important that the other building components be equally durable. Metal door and window frames are an attractive and rugged option for concrete buildings. Although they are fairly expensive, they are easy to maintain and can stand extremes of poor weather and rough usage. Wooden frames are less frequently used. Wooden Door Jambs It is unusual to find wooden door jambs set in concrete. When they occur, the jambs are most often set after the concrete is in place. They may be set into openings created using rough bucks in the formwork. The jambs are nailed to wooden keys installed with the buck and left behind after the buck's removal. If there are no keys, the wooden doorframe is plumbed, shimmed and leveled as usual, and fastened in place using solid wall fasteners. Occasionally the wood frame is set into the concrete forms and becomes an integral part of the wall. Then they are installed and set like metal frames. It is important that the doorframe is braced vertically, horizontally and diagonally to keep the pressure of the concrete from bending or twisting the frame. It is also important that the frame fits well in the forms, and that no concrete is allowed to leak into the cavity formed by the frame. Sometimes you must fur out or add a strip to the jamb to make it fit the forms more snugly. Wooden keys are usually attached to the outside of the frame so that it does not move in the wall (Figure 1). Figure 1. Plan view of wood doorframe set in wall form 42 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

46 Competency G-5 Learning Task 7 If the wooden doorjamb is to be set in a concrete block or brick wall, the bricklayer builds the wall tight to the frame and attaches metal anchors to it that fit between brick or block courses. Metal Door Jambs Metal jambs are available either knocked down (KD) or welded and ready to install. Either type may be used in concrete or masonry walls either before or after the wall is constructed. Welded jambs have a spreader bar tacked near the bottom to hold the jamb square during installation. Figure 2. Plan view of metal doorframe set in wall form Use the following procedure to install a steel jamb in a concrete form: 1. Set the assembled jamb closely against one side of the concrete form before putting the other side of the form in place. 2. It is critical that you thoroughly brace the frame as shown in Figure 3 to keep it from bending under the pressure of the poured concrete. If this is not done, the door will not work properly. 3. Plug the pre-drilled holes in the frames with rubber stops to prevent concrete from running through. 4. Normally the jamb is the same width as the wall, but if it is narrower, attach wood filler strips to the jamb to equalize the widths. Ensure the side tight to the form is the side the door swings to. BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 43

47 Learning Task 7 Competency G-5 Figure 3. Frame bracing for setting in concrete To install the jamb in a masonry wall, you must carefully brace, support and level the jamb in such a way that it does not interfere with the mason's work (Figure 4). Masons will remove anything that intrudes on the masonry courses, and this can disastrously affect the operation of the door later. Figure 4. Jamb installation in a masonry wall 44 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2

48 Competency G-5 Learning Task 7 When steel frames are for use in a block wall, they have an extra deep header to make up the difference in height between regular door height and a whole number of block courses (Figure 5). Figure 5. Extra deep header of doorframe in block wall To anchor the frame into masonry walls, bricklayers install wire or sheet metal anchors between the courses of blocks or bricks. These are held in place by mortar; and come in a wide variety of shapes and sizes (Figure 6). Figure 6. Types of anchors BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2 45

49 Learning Task 7 Competency G-5 To install metal door jambs in existing concrete or masonry openings, you must screw them in place using the pre-drilled holes. Use hollow or solid wall fasteners, depending on the type of wall to contain the frame. Manufacturer's directions vary somewhat, but the general rule is to secure the frame at three points on each side, roughly corresponding with hinge and strike locations. Do not fasten the header. Knocked down (KD) frames have metal tabs and slots into which the tabs fit. When frame pieces are properly aligned, bend the tabs over with light hammer blows. Sometimes KD frames are tack welded before installation. Figure 7. Typical corner with tabs Now complete Learning Task 7 Self-Test. 46 BC CARPENTER APPRENTICESHIP PROGRAM LEVEL 2