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BUILDING CONSTRUCTION STRUCTURAL STEEL CONSTRUCTION

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Presentation on theme: "BUILDING CONSTRUCTION STRUCTURAL STEEL CONSTRUCTION"— Presentation transcript:

1 BUILDING CONSTRUCTION STRUCTURAL STEEL CONSTRUCTION
IV STRUCTURAL STEEL CONSTRUCTION d c ep

2 4. STRUCTURAL STEEL CONSTRUCTION
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4. STRUCTURAL STEEL CONSTRUCTION 4.0 4.1 4.1 STRUCTURAL STEEL SHAPES The most common shapes of structural steel used in buildings are the American Standard Steel Shapes such as: Square Bars Round Bars Plate Bars Angle Bars Channels – The standard channel has the shape of unsymmetrical balance consisting of two flanges on one side. It requires lateral support to prevent its tendency to buckle. Channels are generally used as parts of built-up sections for columns and are also suitable for framing around floor openings, spandrels and lintels attributed to the absence of flanges on the other side. The channel section is identified as C 15 x 20 which means that the channel has a depth of 20 cm and weights 15 kg per meter length. I-Beams – The use of a standard I-beam as a column is uneconomical because the whirl or revolving action of the member about an axis through the centroid of the web is comparatively small.

3 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 Tee Beams H-Columns Wide Flanges – Wide Flange sections are designated as W 12 x 24 which mean that the flange has a depth of 24 cm and weighs 12 kg per meter length. All wide flange sections are generally with parallel face flange except those with 5% slope inside face produced by Bethlehem Steel Company. Comparatively, wide flange sections are more efficient than standard I-beams with respect to bending resistance. 10. Zees – The zee section is another structural form in a letter Z which is not frequently used in building construction except for the fabrication of steel windows and other frames. 4.1

4 4.2 STRUCTURAL STEEL FRAMING
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.2 STRUCTURAL STEEL FRAMING Structural steel girders, beams, and columns are used to construct a skeleton frame for structures ranging in size from one-story to skyscrapers. Because structural steel is difficult to work with on site, it is normally cut, shaped, and drilled in a fabrication shop according to design specifications; this can result in relatively fast, precise construction of a structural frame. Structural steel may be left exposed in unprotected non-combustible construction, but because steel can lose strength rapidy in a fire, fire-rated assemblies or coatings are required to qualify as fire-resistive construction. 4.2 The three major types of framing systems are the following: 4.2.1 One-Way Beam System – each pair of external columns supports a long-spanning beam or girders. This form of construction is suitable for long, narrow buildings, especially when a column-free space is desired. The absence of columns in the interior is an advantage in structures such as car parks, as freedom from obstruction makes for greater and safer maneuverability, besides allowing the layout of the parking spaces to be altered at any time.

5 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 Two-Way Beam System – a two-layer system, where beams frame into girders, increases floor depth considerably and provides more space for mechanical systems. Steel girders span the short axis of a building bay thus contributing to the lateral stability of the structure. 4.2

6 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.2.3 Three-Way Beam System – is used when a large column-free space is required, where long-spanning plate girders or trusses can be used to carry the primary beam, which in turn support a layer of secondary beams. 4.2

7 4.3 STEEL COLUMNS AND CONNECTIONS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.3 STEEL COLUMNS AND CONNECTIONS STEEL COLUMNS Steel columns are of the following types: 4.3 a. Struts of one or two angles. These are used for compression members in roof trusses, light towers, and lattice girders. The two angles of a double struts are riveted together by rivets driven through washers placed between the two angles at intervals of 4 to 6 ft. b. Starred angles of two or four connected by batten plate spaced at intervals of 3 to 4ft. These are used to support the light loads.

8 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 c. Latticed Columns made up of channels or angles connected by lattice bars are often used where light loads are to be supported on long columns. 4.3 d. Rolled H-columns. These are obtainable with depths ranging from 6” to 16” and are now commonly used instead of built-up columns in steel skeleton construction. e. Built-up Columns. These are usually of H-shaped section formed by a combination of plates and angles although box columns with two or more webs are not uncommonly used in heavy building frames.

9 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 f. Top Chord sections of heavy trusses are usually unsymmetrical and are made of two rolled or built-up channel sections and a cover plate. The open (bottom) side of the section is latticed. g. Columns for bents are sometimes made up of a pair of channels and an I – beam with batten plates at intervals of 3 to 4 ft. connecting the flanges of the channels. Columns made of four angles and a web-plate are commonly used in mill building bents. 4.3 h. Battened columns are those in which two component parts of the column are connected only by batten plates. They are decidedly inferior to latticed columns and should be avoided if a continuous plate or latticing can be used instead.

10 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 In the design of steel columns the following should be taken into consideration: No part of a steel column should be less than 1/4” thick. No material whether in a body of the column or used as a lattice bar or stay plate, shall be of less thickness than 1/32 of its unsupported width, measured between centers of rivets transversely, or 1/6 of the distance between center of rivets in the direction of stress. Tie-plates are to have not less than 4 rivets and are to be spaced so that the ratio of length to the least radius of gyration of the parts connected does not exceed 40, the distance between nearest rivets of two stay plates in this case being considered as length. In built-up columns the thickness of any outstanding member (for example, the outstanding legs of angles) shall not be less than 1/12 of the width of the outstanding portion. Base plates for steel column are usually made of steel plates and shapes. Cast-iron bases are sometimes used for very heavy columns. Ribbed cases may also be used instead of plates and when bolted to the columns, add greatly to the stability of the supporting members because of their greater width. 4.3

11 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 LALLY COLUMNS These are columns made up of a cylindrical steel pipe shell filled with 1:1-1/2:3 Portland cement concrete. The standard type of lally column is reinforced with only the steel pipe shell. Special types of columns are obtainable with additional reinforcement consisting of steel pipe, reinforcing bars or structural steel shapes. The light weight column is 4” in outside diameter with a shell thickness of 0.134”, while the heavy-weight columns are from 3-1/2 to 12-3/4 inches in outside diameter with shell thicknesses of to inches. 4.3 4.3.3 COMPOSITE COLUMNS These are columns in which a concrete core is further reinforced with a steel or cast-iron core designed to support a part of the load. Steel cores may be structural H-sections or four angles, latticed or battened; cast-iron cores are usually either solid shafts or hollow pipe sections. The column may be further reinforced by vertical rods or bars placed at the circumference and enclosed by spirals.

12 4.3.4 STEEL COLUMN CONNECTIONS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 STEEL COLUMN CONNECTIONS 4.3

13 4.4 STEEL BEAMS AND CONNECTIONS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.4 STEEL BEAMS AND CONNECTIONS STEEL BEAMS Steel beams may be rolled in the shape of the letter I (I-beams), channel beams or angles. Beams of T shape were formerly used but have now been restricted to minor uses. The I-beam is the ideal type of steel beam. The horizontal portion is the web. Channels are sections of this shape: They vary in depth from 3” to 15”, and in weight from 4.1lb. per ft. to 55lb. per ft. 4.4

14 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 Girders may be built up of angles and plates riveted together for long spans and for unusual cases of very heavy loading. Those are of two types: a. Plate Girders. A plate girder is a beam composed of a wide plate, known as a web, at the top and bottom of which are riveted angles and plates. The simplest type of plate girder consists of a web and four flange angles. If this does not give sufficient flange area, cover plates may be added. The web may be frequently reinforced against buckling by angles riveted to its sides, known as stiffener angles. 4.4 b. Box Girders. This is a built up beam in which more than one web plate is used.

15 4.4.2 STEEL BEAM CONNECTIONS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 Beams and girders may be connected to columns by either seated connections or framed connections. In a seated connection the bottom flange of the beam rests on and is field-riveted to an angle shop-riveted to the flange or web of the column. Another angle is field-riveted to the column and to the top flange of the beam. In a framed connection the web of the beam or girder is connected by angles or by gusset-plates to the column. In framed connections, angle seats are usually shop-riveted to the columns to hold the beam or girder during erection. 4.4 STEEL BEAM CONNECTIONS Moment Connections – AISC Type 1 – also called Rigid Frame connections are able to hold their original angle under loading by developing a specified resisting moment, usually by means of plates welded or bolted to the beam flanges and the supporting column.

16 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 2. Shear Connections – AISC Type 2 – Simple Frame connections are made to resist only shear and are free to rotate under gravity loads. Shear walls or diagonal bracing is required for lateral stability of the structure. 4.4 3. Semi Rigid Connections – AISC Type 3 – Semi-Rigid Frame connections assume beam and girder connections possess a limited but known moment resisting capacity.

17 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.5 OPEN-WEB STEEL JOISTS Open web joists are lightweight, shop fabricated steel members having a trussed web. A K series joist has a web consisting of a single bent bar, running in a zigzag pattern between the upper and lower chords. The LH and DLH series joists have heavier web and chord members and are for increased loads and spans. 4.5

18 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.6 METAL DECKING Metal decking are corrugated steel panels used as a working platform during construction and eventually as formwork for sitecast concrete slab. The decking panels are secured with puddle-welds or shear welded through the decking to the supporting steel joists or beams. The panels are fastened to each other along their sides with screws, weld, or button punching standing seams. If the deck is to serve as a structural diaphragm and transfer lateral loads to shear walls, its entire perimeter is welded to steel supports. In addition, more stringent requirements to support and side lap fastening may apply. There are three major types of metal decking: 4.6

19 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 Form Decking – serves as a permanent formwork for a reinforced concrete slab until the slab can support itself and its live load. Composite Decking – serves as a tensile reinforcement for the concrete slab to which it is bonded with embossed rib pattern. Composite action between the concrete slab and the floor beams or joists can be achieved by welding shear studs through the decking to the supporting beam below. 4.6 4.6.3 Cellular Decking – is manufactured by welding a corrugated sheet to a flat steel sheet, forming a series of spaces or raceways for electrical and communications wiring; special cutouts are available for floor outlets. The decking may serve as an acoustic ceiling when the perforated cells are filled with glass fiber.

20 4.7 STEEL TRUSSES AND RIGID FRAMES
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.7 STEEL TRUSSES AND RIGID FRAMES 4.7.1 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. 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. 4.7

21 The portion of the roof between two adjacent trusses is called a bay.
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 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. 4.7

22 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.7

23 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 TYPES OF TRUSSES 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 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. 4.7

24 B. RELATIVE TO FORM 1. Triangular 2. Quadrangular 3. Crescent
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 B. RELATIVE TO FORM 1. Triangular 2. Quadrangular 3. Crescent 4. Scissors 5. Arched 4.7

25 C. RELATIVE TO METHOD OF SUPPORT
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 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 Truss Plate Peak Top Chord Heel Overhang Bottom Chord Length Cantilever Span (Out to Out of Bearings) Web Bottom Chord Bearing Point Panel Point Splice Wedge Block Continuous Lateral Brace Slope Pitch 4.7

26 SAWTOOTH WARREN PETTIT
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 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 SAWTOOTH FINK 4.7 HOWE WARREN PRATT SCISSORS PETTIT

27 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.7

28 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.6.3 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. 4.7

29 4.8 STRUCTURAL STEEL FRAMING SYSTEMS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.8 STRUCTURAL STEEL FRAMING SYSTEMS 4.8.1 ARRANGEMENT OF VERTICAL COMPONENTS 4.8

30 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.8

31 4.8.2 STRENGTHENING THE FRAMING SYSTEM
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.8.2 STRENGTHENING THE FRAMING SYSTEM The framing system can be stiffened against horizontal forces in the following three (3) methods: The structure is composed of rigid frames which may comprise some hinged joints but there must be sufficient rigid joints to ensure that none of the nodes of the frame is free to move sideways. The members may be straight or curved and a variety of shapes may be chosen for such framed structure. 4.8

32 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 A bracing system which consists of a triangulated framework of rolled sections will hold the joints together and further strengthen the framework against lateral loads. The center lines of members converging at a joint should intersect at one point. The joints themselves are conventionally assumed to be hinged, so that the members are either ties or struts, loaded purely in tension or compression, respectively. However, the overall bracing effect of a lattice system can be enhances by constructing it with tiff members and rigid joints. 4.8

33 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 Finally, shear walls in the form of more or less solid diaphragms, usually of reinforced concrete, transmit the wind and earthquake forces by shear and bending. 4.8

34 THE TUBULAR FRAME 4.8.3 The Ultimate Structures for Skyscrapers –
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.8.3 The Ultimate Structures for Skyscrapers – THE TUBULAR FRAME The high-rise building conceived as a rigid tube --- If a high-rise building is of suitably compact shape on plan (circular, square, not too narrow a rectangle), the external columns can be structurally merged with the external lattice bracing or with spandrel girders so as to form a vast rigid tube. This stiffening system is particularly effective and economical. This is due not only to the optimum distribution of the bracing, but also more particularly to the co-operation of all the columns and bracing or spandrel girders in the external walls. 4.8

35 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 The John Hancock Center, Chicago (architects: Graham and Skidmore, Owings and Merrill) employs the tube in its framing system. In this 335 m high 100-story building, all the horizontal forces are transmitted through external bracing, whereby a substantial saving has been achieved in comparison with a bracing system located in the interior. The external lattice members form a distinctive architectural feature. 4.8

36 4.9 JOINING OF STEEL MEMBERS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.9 JOINING OF STEEL MEMBERS Steel shapes can be joined in the building frame using any of the following fastening methods: 4.9.1 RIVETING A rivet is a short pin, of malleable metal such as iron, steel, or copper, with a head at one end; used to unite two metal plates by passing it through a hole in both plates and then hammering down the point to for a second head. In structural riveting, a hot steel rivet with a formed head is inserted in holes through two members to be joined; its head is then held with a hand hammer with a cup shaped depression, while a pneumatic hammer drives a rivet set repeatedly against the other end to form a second head. The rivet shrinks as it cools, drawing members tightly together. 4.9 Rivet set, rivet snap, settoing punch, snap – a tool for shaping the head of a rivet.

37 4.9.2 BOLTING The types of rivet heads are: Countersunk, raised
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 The types of rivet heads are: Countersunk, raised Countersunk, flat Button, coned neck Button, straight neck Pan, coned neck Pan, straight neck 4.9.2 BOLTING The bolts commonly used in steel frame construction falls into two general categories: Carbon-steel bolts – or common bolts; are similar to the ordinary machine bolts. Carbon steel is steel having no specified minimum content of alloying elements; minimum copper content not exceeding 0.40%. High-strength bolts – are bolts made of either high-strength carbon steel or quenched and tempered alloy steel; tempered meaning, heat treated during manufacture to develop the necessary strength. It is usually tightened using pneumatic or electric impact wrench. 4.9

38 There are several ways to achieve proper tightening:
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 A major problem in high strength bolting or friction type connections is how to verify the necessary tension has been achieved in all the bolts in a connection. There are several ways to achieve proper tightening: Turn-of-nut method Load indicator washer Tension control bolts 4.9

39 A. DEFINITION OF FUSION WELDING (ELECTRIC ARC WELDING)
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.9.3 WELDING Welding has become fully accepted as a means of joining steel structural members in buildings because it has the inherent advantage of fusing the metals to be joined, thereby simplifying connections and fabricating operations. A. DEFINITION OF FUSION WELDING (ELECTRIC ARC WELDING) The fusion welding process employs an electric arc, wherein energy in the form of heat is supplied by establishing an arc between the base or parent metal (the parts to be joined) and a metal electrode. As the arc is formed, tremendous heat is concentrated at the point of welding. Instantly, the materials are at melting-point temperature. The parent metal melts in a small pool and additional metal supplied by the electrode is transferred through the arc an deposited in the pool. As the electrode continues along the joint, the molten metal left behind solidifies to form the weld. 4.9

40 The size and strength of weld is determined by the length of its leg.
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.8.2 COATED ELECTRODES Most welding is done with coated electrodes. The function of the coating is to form a gaseous shield, which protects the arc and molten metal from contact with the air. Oxides and nitrides resulting from contact with the air tend to produce brittle welds. The coating also forms a slag-fuse shield, which floats above the molten metal, protecting it from the atmosphere. The slag is easily removed after the weld has cooled. The size and strength of weld is determined by the length of its leg. For an E60 electrode on A36 steel, the allowable stress may be computed on the basis of 800 pounds per linear inch per 1/16 inch of leg size. For A36 steel or higher-strength steels up to Fy = 60 ksi, an E70 electrode should be used and the the allowable stress may be computed on the basis of 930 pounds per linear inch per 1/16 inch of leg size. 4.9

41 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.9

42 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 C. TYPES OF WELD FILLET WELD – is of approximately triangular section joining two surfaces approximately at right angles to each other. The fillet weld is the most common type of weld used in structural work. GROOVE WELD – is made by depositing filler material in a groove between two members to be joined. The standard types of grooves are square, V, bevel-U, and J. With the exception of the square groove, all grooves may be either single or double. PLUG or SLOT WELD – is made of a circular hole (plug) or an elongated hole (slot) in one member of a lap joint, joining that member to the portion of the surface of the other member that is exposed through the hole. 4.9

43 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 4.9

44 Structural Steel Construction
Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members D. WELD POSITIONS There are four positions in welding. In order of economy, they are the flat, horizontal, vertical, and overhead positions. Overhead welds, which is the most difficult, should be avoided whenever possible. E. WELD JOINTS The three most common joints used in structural work are the butt, T, and lap joints. Other types are the edge and corner joints. Fillet welds are applicable to T, lap, and corner joints; groove welds are applicable to all joints with the exception of lap joints. 4.0 4.9

45 STANDARD WELDING SYMBOLS
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 STANDARD WELDING SYMBOLS 4.9

46 WELDING SYMBOLS – Examples of use
Structural Steel Construction Structural Steel Shapes Structural Steel Framing Steel Columns & Connections Steel Beams & Connection Open-Web Steel Joists Metal Decking Steel Trusses and Rigid Frames Structural Steel Framing Systems Joining of Steel Members 4.0 WELDING SYMBOLS – Examples of use 4.9

47 BUILDING CONSTRUCTION 4
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