Building Technology 2 PDF - Joints and Splicing

Building Technology 2 Joints and Splicing  Introduction Joints Splices Lecture Outline Introduction  Joints refer to connections between two or more wood members, forming a single, unified structure Range from simple techniques to complex interlocking systems Developed througho...

Building Technology 2 Joints and Splicing  Introduction Joints Splices Lecture Outline Introduction  Joints refer to connections between two or more wood members, forming a single, unified structure Range from simple techniques to complex interlocking systems Developed throughout mankind’s history Advantages Structural integrity and stability Aesthetic appeal Customization Cultural and/or historical significance Increased skill development Introduction  Disadvantages Maintenance challenges Complexity Tools and equipment Skill dependency High learning curve Mechanics of joints improve structural integrity, such as Member movement prevention Improved load distribution Improved shear resistance Improved torsional stability Introduction  Splicing A joint that utilizes short pieces of wood, joined end to end to create a longer piece of wood May be permanent or semi-permanent Advantages Length expansion Resource utilization Cost efficiency Asian joinery Dougong of the Chinese Kanawa tsugi of the Japanese Introduction  Asian joinery Dougong of the Chinese Literally means cap (and) block Introduction  Asian joinery Kanawa tsugi of the Japanese Introduction Joints  Joints can be end, edge, or end-to-edge or angle joints End joint are joints connected with the members’ edges Edge joints are joints connected with the members’ edges End-to-edge joints are joints connected with a member’s end to another member’s edge Edge End Joints  Types Plain Butt Scarf Finger Halved Miter Rabbet Mortise and tenon Dovetail Dado Oblique Coped Splice Joints  Plain joint Also called lap joint A weak joint made by lapping one piece over the other Used for temporary framing and quick construction Butt joint Made by placing full thickness of wood directly against the second piece, with ends of members squared Not suitable for end joint applications requiring strength and durability Can only achieve 25% of tensile strength even with special techniques Joints  Butt joint End butt Edge butt Angled end butt Joints  Butt joint Variations Dowel-reinforced butt Biscuit-reinforced butt Joints  Scarf joint Made by joining ends of members, with ends of members either beveled, chamfered or notched Along with end-grain finger and lap joints, can achieve up to 90% of tensile strength of clear wood Ends’ surface area must be at least ten times greater than the cross sectional area of member Ends’ surface area exceeding twelve times yields highest strength Scarf joints in plywood, typical slope for structural applications is 1:8 (8 times the cross-sectional area) Variations Plain scarf Nibbed scarf Hooked scarf Keyed scarf Joints  Scarf joint Nibbed scarf Keyed scarf Plain scarf Hooked scarf Joints  Finger joint Also known as comb joint Made by cutting a set of complementary, interlocking profiles in two wood pieces Along with end-grain scarf and lap joints, can achieve up to 90% of tensile strength of clear wood Profiles can be cut along the wide side (vertical joint) or the narrow side (horizontal joint) of the end of member Finger joints in plywood, typical slope for structural applications is 1:8 Finger joints with higher slope, such as 1:12, the tip thickness must not be greater than 0.8 mm (1/32 in) Practical minimum for machined tips ranges from 0.4 to 0.8 mm Joints  Finger joint Vertical finger Horizontal finger Joints  Halved joint Also called half lap joint Made by cutting half the thickness of the wood from each piece at the ends to be joined so as to bring the sides flush Purpose of this type of joint is to maintain a level surface at the joint Along with end-grain scarf and finger joints, can achieve up to 90% of tensile strength of clear wood Variations End lap Cross lap Mitered halving Joints  Halved joint Cross lap End lap Mitered halving Joints  Halved joint Other variations Joints  Miter joint Made by cutting each of two parts to be joined, across the main surface, usually at a 45° angle, to form a corner, usually to form a 90° angle A finish joint, can comprise any angle greater than 0 degrees Secured by clamp nails or finishing nails, corrugated fasteners or dowels, or by gluing May have a quirk, an acute angle or groove separating one element from another Variations Plain miter Shoulder miter Tongued miter Joints  Miter joint Shoulder miter Plain miter Tongued miter Joints  Rabbet joint Also called rebate joint in the UK Made by cutting recesses, or rabbets, into the edges of members and joined Typically used in cabinetry and light construction, such as picture frames Along with mortise-and-tenons and dovetails, provides more bondline to transfer loads between members Variations Plain rabbet Dado and rabbet Dado, tongue, and rabbet Joints  Rabbet joint Dado and rabbet Plain rabbet Dado, tongue, and rabbet Joints  Mortise and tenon joint Made by cutting a hole or mortise in one piece and a tenon or tongue in the second piece to fit the hole in the other Tenon may extend fully through the other piece or only part of the way Used for building wooden framework where great strength and rigidity are all important Variations Open/slip/bridle mortise Through tenon Blind mortise and stub tenon Keyed/wedged joint Pinned joint Foxtail wedge and stub tenon Haunched tenon T-bridle Joints  Mortise and tenon joint Open mortise and tenon Through mortise and tenon Stub mortise and tenon Joints  Mortise and tenon joint Keyed mortise and tenon Pinned mortise and tenon Foxtail wedge mortise and tenon Joints  Mortise and tenon joint Other variations Joints  Mortise and tenon joint Haunched mortise and tenon T-bridle joint Joints  Dovetail joint In Europe, also called swallowtail, culvertail, or fantail joint Made by cutting a pin in the shape of a dovetail in one piece to fit a groove similarly shaped in the other piece Strong and durable, used in cabinet and furniture work, and traditional timber framing and log construction Noted for its strong resistance to tensile stress Along with mortise-and-tenons and rabbets, provides more bondline to transfer loads between members Variations Common/plain/through dovetail Lap/half-blind dovetail Secret/blind dovetail Dovetail halving Joints  Dovetail joint Common dovetail Lap dovetail Blind dovetail Dovetail halving Joints  Dado joint Also called housing joint (UK) and trench joint (Europe) Made by cutting a channel, or dado, across the length in one member, in which the corresponding member is fitted into Used in shelving and cabinetry Variations Through dado Stopped/half blind dado Blind dado Dovetail dado Joints  Dado joint Through dado Stopped dado Joints  Dado joint Blind dado Dovetail dado Joints  Oblique joint Made when the two pieces do not meet at right angles, e.g. bracings One piece is cut at an angle to fit the other and the two pieces nailed securely together Stop chamfer Dap Easement Joggle Joints  Coped joint Made by joining a fitted member to a square-cut member, so as to create snug-fit, miter-like corners Typically used in mouldings Joints  Other types of joints Shiplapped joint Tongue and groove joint Spline joint Butterfly wedge Joints  Common wood joints for furniture Joints Splices  Function: connect two or more pieces of timber that is as strong as a single timber of equivalent size Types Compression Tension Bending Splices  Function: connect two or more pieces of timber that is as strong as a single timber of equivalent size Types Compression Tension Bending Splices  Types Compression splices Scabbed/fished splice Made by two, squared pieces of timber, and is fastened on both sides by either two short wood pieces called scabs or metal plates called fishplates Scabs and fishplates keep the splice straight and prevents it from buckling Splices  Types Compression splices Halved splice Made by cutting half the thickness of each piece to the required length and putting the halved sections together, may be secured using scabs or fishplates Good for direct compression, and may be used in some tension when fastened by scabs or fishplates Splices  Types Tension splices Square splice A modification of the compression halved splice Has an extra notch to keep it from slipping and is usually used in combination with scabs or fishplates Splices  Types Bending splices Scarfed splice Combines features of both tension and compression splices, as top part of joint is subjected to compression and the bottom part is to tension Upper part is squared for maximum compression resistance Lower part is beveled on end since there is no tendency to crush the timber Lower part is a securely bolted fishplate or scab to overcome tension Fish Plate Splices Fin