Module 3: Roofing Design Details PDF

MODULE 3 Roofing Design Details COPYRIGHT FOR ONLINE LEARNING EDUCATORS STEEL TRUSSES AND RIGID FRAMES ROOF TRUSSES A truss is a structural framework composed of a series of straight members so arranged and fastened together that external loads applied to it will cause only direct s...

MODULE 3 Roofing Design Details COPYRIGHT FOR ONLINE LEARNING EDUCATORS STEEL TRUSSES AND RIGID FRAMES ROOF TRUSSES A truss is a structural framework composed of a series of straight members so arranged and fastened together that external loads applied to it will cause only direct stress in the members. The upper and lower members of a truss are called the top chord and bottom chord respectively. The members of the truss which are framed between and join the top and bottom members are called web members. COPYRIGHT FOR ONLINE LEARNING EDUCATORS STEEL TRUSSES AND RIGID FRAMES ROOF TRUSSES When the external loads act downward and the truss is supported at the ends, the top chord is always in compression and the lower chord always in tension, similar to the upper and lower flanges of a beam. The web-members are subjected to stresses of either tension or compression. Web-members subjected to tensile stresses are called tension web-members; those which are subjected to compression are called compression web-members. In certain positions, a web-member may be subjected to tension through the action of a load applied at one point, and when applied at another point that load may produce compression in the member so that at one time it will be subjected to tension and at another time to compression. Such a member, design to resist either tension or compression, is called a counterbrace. A member of a truss system which acts only for a particular partial loading, and which has a zero stress when the truss is completely loaded is called a counter. COPYRIGHT FOR ONLINE LEARNING EDUCATORS STEEL TRUSSES AND RIGID FRAMES When a truss is supported at its ends by columns, the truss together with its columns, considered as a unit, is called a bent. The intersection between two or more members of the truss is called a joint or panel joint and the distance between two adjacent joints along either the top or bottom chords is known as the panel or panel length. The quadrangular space, crossed by an inclined web-member, is also referred to as a panel. The axes of all members at each joint should always meet in a common point. The span of a roof truss is the distance between the centers of the supports and its rise is the distance between the apex of the truss and the line joining the points of support. The pitch of a roof truss is the ratio of the rise to the span for a truss symmetrical about its center line. The slope of an inclined member is the tangent of the angle of inclination with the horizontal, usually specified in inches rise per 12” run. The portion of the roof between two adjacent trusses is called a bay. COPYRIGHT FOR ONLINE LEARNING EDUCATORS STEEL TRUSSES AND RIGID FRAMES COPYRIGHT FOR ONLINE LEARNING EDUCATORS TYPES OF TRUSSES A. RELATIVE TO THE NUMBER AND ARRANGEMENT OF THE MEMBERS COMPOSING THE TRUSS. 1. Complete Frame. A complete structural frame, or truss, is one in which is made up of the minimum number of members required to provide a complete system of triangles fixing the relative positions of a given number of panel joints. If the number of panel points in the given structure and n = the number of necessary members. n = 2p – 3 2. Incomplete Frame. One in which the number of members is less than that required by the equation given above. 3. Redundant Frame. A redundant frame is one which contains more members than that required by the equation given above. COPYRIGHT FOR ONLINE LEARNING EDUCATORS TYPES OF TRUSSES Deficient frame and redundant A. RELATIVE TO THE NUMBER AND ARRANGEMENT OF THE MEMBERS COMPOSING THE TRUSS. frame are imperfect frame. A perfect frame/ complete frame is the If n2j−3 then it is known external load. as redundant frame Triangle is the simplest perfect frame. For a perfect frame, n=2j−3. Where, n= number of members and j= number of joints. Now, if in a frame, number of members and number of joints are not given by n=2j−3 then it is called imperfect frame. COPYRIGHT FOR ONLINE LEARNING EDUCATORS B. RELATIVE TO FORM 1. Triangular 2. Quadrangular 3. Crescent 4. Scissors 5. Arched COPYRIGHT FOR ONLINE LEARNING EDUCATORS C. RELATIVE TO METHOD OF SUPPORT 1. Simple Truss. A truss supported at each end-point. 2. Overhanging end span. A truss supported at one end-joint and other joint not an end-joint. 3. Cantilever span. A truss where the entire support is at one end only. Panel Length Peak Truss Plate Continuous Lateral Brace Top Chord Slope Heel Pitch Web Bottom Chord Splice Wedge Block Bearing Point Panel Point Span (Out to Out of Bearings) Cantilever Overhang Bottom Chord Length COPYRIGHT FOR ONLINE LEARNING EDUCATORS D. RELATIVE TO ARRANGEMENT OF THE WEB-BRACING SYSTEM 1. Fink 5. Hammer-beam 2. Howe 6. Sawtooth 3. Pratt 7. Warren 4. Scissors 8. Pettit FINK SAWTOOTH HOWE WARREN PRATT PETTIT SCISSORS COPYRIGHT FOR ONLINE LEARNING EDUCATORS RIGID FRAMES Rigid frames consist of two columns and a beam or girder that are rigidly connected at their joints. Applied loads produce axial, bending and shear forces in all members of the frame since the rigid joints restrain the ends of the members from rotating freely. In addition, vertical loads cause a rigid frame to develop horizontal thrusts at its base. A rigid frame is statically indeterminate and rigid only in its plane. COPYRIGHT FOR ONLINE LEARNING EDUCATORS  ROOF DECKS Reinforced concrete roof slabs (roof decks) are formed and site cast in the same manner as concrete floor systems. Roof decks are normally covered with a type of membrane roofing for insulation and waterproofing. COPYRIGHT FOR ONLINE LEARNING EDUCATORS COPYRIGHT FOR ONLINE LEARNING EDUCATORS  WATERPROOFING Application Locations: Top of roof decks Top of concrete terraces, balconies, ledges and canopies Under-sheathing for wood shingle and tile roofing Interior surfaces of water tanks Exterior surfaces of concrete roof gutters Inside surfaces of plantboxes Kitchen floor Toilets Basement floor and walls Elevator pits Swimming pools and fish ponds Machine, mechanical and pump rooms Refrigeration and cold storage rooms COPYRIGHT FOR ONLINE LEARNING EDUCATORS Four Types of Waterproofing Integral type – powder form waterproofing compound mixed with the cement-aggregate mixture. For example one bag of integral waterproofing compound, such as SAHARA or SAKURA is added to 98 kilos off Portland cement. Membrane type – a hot or cold membrane applied to the surface; for example asphalt paper laid with hot asphalt or self sealing asphalt paper. Examples from WR Grace Co. are BITUTHENE CP for toilet slabs and BITUTHENE 3000 for roof decks; and ICE AND WATER SHIELD self-sealing and self-adhering rubberized membrane for main entrance canopies made of metal. Fluid type – a fluid applied elastomeric coating formulated to waterproof and preserve the substrate of concrete, wood, and steel. The wide temperature range, withstands extreme thermal movement, settling and cracking; resists puncture and tearing; and can be applied by roller, brush, spray or squeegee. Examples of exposed type liquid membrane waterproofing from WR Grace are NEWFLEX and NEWFLEX R100 for ledges. Cementitious type – powder form waterproofing compound mixed with water and applied by brush to the surface to be waterproofed. Examples from WR Grace are MORTASEAL and HYDRATITE for concrete gutters, ledges COPYRIGHT FOR ONLINE LEARNING EDUCATORS FOUNDATION AND SUB-STRUCTURE WATER PROOFING GROUND BEAM WATER PROOFING COPYRIGHT FOR ONLINE LEARNING EDUCATORS  FOUNDATION AND SUB-STRUCTURE WATER PROOFING “THROUGH WALL” PENETRATION WATER PROOFING BASE SLAB - PIPE PENETRATION WATER PROOFING COPYRIGHT FOR ONLINE LEARNING EDUCATORS  FLAT DECK WATER PROOFING UPSTAND DETAIL-SHEAR MEMBER TYPICAL DRAIN DETAIL COPYRIGHT FOR ONLINE LEARNING EDUCATORS  FLAT DECK WATER PROOFING TYPICAL PIPE DETAIL THROUGH ROOF SLAB (SHEET MEMBRANE TYPICAL PIPE DETAIL THROUGH ROOF SLAB DETAIL) (LIQUID MEMBRANE DETAIL) COPYRIGHT FOR ONLINE LEARNING EDUCATORS  FLAT DECK WATER PROOFING EXPANSION JOINT COVER DECK OR WALL JUNCTION COPYRIGHT FOR ONLINE LEARNING EDUCATORS  THERMAL INSULATION 1. Application Locations of heat insulators: Top or bottom of roof decks Below roofing sheets Above suspended ceiling Batt Insulation – A flexible blanket- type thermal insulation, commonly used as insulation between studs or joints in frame construction; also used as an acoustical material or a component in sound- insulating construction. Usually made from rock, slag, or glass fibers. Sometimes has a vapor COPYRIGHT FOR ONLINE LEARNING EDUCATORS barrier on one side or is entirely enclosed in paper with a vapor barrier on one side.  THERMAL INSULATION 2. Types of Thermal Insulators Loose Fill – fibrous type and granular type Blanket Insulation – is made from fibrous materials such as mineral wool, wood fiber, cotton fiber or animal hair and made into batt or boards. Example is PARSEC Thermo Brite II for underneath metal roofing insulation. Block or Rigid Slab Insulation – stiff and inelastic such as foamed plastic, cellular glass, foamed concrete, etc. Example is STYROFOAM ROOFMATE SL extruded polysterene board as manufactured by DOW Chemicals, for inaccessible roof decks. COPYRIGHT FOR ONLINE LEARNING EDUCATORS  THERMAL INSULATION 2. Types of Thermal Insulators Foamed-in Place Insulation – a polyurethane product made by combining a polyisocyanate and a polyester resin. This type of insulation can be applied either by pouring or by spraying. The basic ingredients for both are drawn from their containers, measured and mixed by machine. Sprayed-on Insulation – materials used are polyurethane foam asbestos fiber mixed with inorganic binders; vermiculite aggregate with a binder such as Portland cement or gypsum and perlite aggregate using gypsum as a binder. Machines are used for blowing these insulations into place and as a result, the shape and irregularity of the surface being insulated is of little consequence. Example is MBA SPRAYED-ON POLYURETHANE INSULATION; 25 mm thick x 1.5 Batt Insulation – A flexible blanket- type thermal insulation, commonly used as insulation between studs or joints in frame pcf density for accessible roof decks. construction; also used as an acoustical material or a component in sound-insulating construction. Usually made from rock, slag, or glass fibers. Sometimes has a vapor barrier COPYRIGHT FOR ONLINE LEARNING EDUCATORS on one side or is entirely enclosed in paper with a vapor barrier on one side.