Building Construction (Chapter 8, 9, and 10) PDF

BUILDING CONSTRUCTION (CHAPTER 8, 9, AND 10) From: Max Fajardo Presentors: ADRIOSULA, ANICO, ARTATES, GIRON, ISADA, PAPA TABLE OF CONTENTS CHAPTER 8 - Post and 01 Column Chapter 9 - Platform– Floor 02 Structure 03 Chapter 10 - Steel Framing CHAPTER 8 POST AND COLUMNS Definitio...

BUILDING CONSTRUCTION (CHAPTER 8, 9, AND 10) From: Max Fajardo Presentors: ADRIOSULA, ANICO, ARTATES, GIRON, ISADA, PAPA TABLE OF CONTENTS CHAPTER 8 - Post and 01 Column Chapter 9 - Platform– Floor 02 Structure 03 Chapter 10 - Steel Framing CHAPTER 8 POST AND COLUMNS Definitions Post - Refers to a piece of timber or metal of either cylindrical, square or other geometrical cross section placed vertically to support a building; a compression vertical member not continuous from story to story is also called post. Column - Refers to a vertical structure used to support a building made of stone, concrete, steel or the combination of the above materials. Storey - Is the space in a building between floor levels or between a floor and a roof above 8.2 Wooden Post Wooden posts are structural components traditionally made from high-quality lumber. They should be selected from the first or second group of lumber for strength and durability. Treated lumber is also used as wooden post in the absence of hardwood lumber. Bent posts can be corrected during construction but require proper bracing and support to avoid damaging the foundation pedestal. Wooden posts have several drawbacks, including: 1. Inferior quality due to the use of younger trees in commercial lumber. 2. Hardwood scarcity, making it difficult to find durable materials. 3. Susceptibility to decay caused by moisture, insects, worms, and termites. 4. Prominent cracks between wooden posts and concrete walls. 8.2 Wooden Post Erecting wooden posts requires precision and proper techniques to ensure structural stability and durability. Steps in Erecting Wooden Posts 1. Dress the wood post and cut the bottom evenly using a steel square. 2. Mark a reference line with charcoal or chalk along the post’s length to check vertical alignment. 3. Measure and mark where girders and girts will attach. Create necessary daps before erection. 4. Erect the post manually with 2x3 braces or use a rope and pulley anchored to a jump-pole. 5. Check vertical alignment with a plumb-bob, brace the post on four sides, and nail it to the post strap. 6. Drill holes across the straps with boring tools and bolt the post into its permanent position. 8.3 Reinforced Concrete Column Reinforced concrete is at present the most popular and widely used materials for column of buildings instead of wooden post regardless of its size or height. Materials: Concrete, Steel Reinforcement (Rebars), Binding Wire, Formwork, and/ or Admixtures. o Reinforced concrete columns are classified as: ▪ Short Column = When the unsupported height is not greater than ten times the shortest lateral dimension of the cross section. ▪ Long Column = When the unsupported height is more than ten times the shortest lateral dimension of the cross section. 8.3 Reinforced Concrete Column Columns are classified according to the types of reinforcement used: 1. Tied Column 2. Spiral Column 3. Composite Column 4. Combined Column 5. Lally Column 8.4 Tied Column A tied column consists of vertical (longitudinal) bars held in position by lateral reinforcement known as lateral ties. Lateral ties are essential for securing the vertical bars and ensuring column stability. The vertical reinforcement must have at least four bars with a minimum diameter of No. 5 (16 mm). o Lateral ties for a tied column must meet certain specifications. The tie size should be No. 3 for longitudinal bars of No. 10 or smaller, and No. 4 for No. 11, 14, 18, or bundled longitudinal bars. The spacing of the lateral ties must not exceed three limits: 16 times the diameter of the longitudinal bars, 48 times the diameter of the lateral ties, or the shortest dimension of the column. 8.4 Tied Column The size and number of steel bars in a tied column are determined by the reinforcement ratio, which is the proportion of the cross-sectional area of the vertical reinforcement to the gross area of the column. The cross-sectional area of the vertical reinforcement in a tied column should be no less than 0.01 and no more than 0.08 times the gross area of the column section. This ensures proper strength and stability of the column. Bundled bars are used in tied columns to address the difficulties of concrete placement in forms congested with steel bars. When a column is heavily loaded with reinforcement, placing concrete can be challenging due to the large number of individual bars held by lateral ties. Bundled bars, consisting of two to four bars tied together in direct contact, are placed as one unit reinforcement. These bundled bars are positioned at the corners of the lateral ties, improving concrete flow and reducing congestion during construction. 8.4 Tied Column Tables 8-2 and 8-3 from the ACI Reinforced Concrete Design Handbook use the old English measurement system. *shown in previous slides* These values can be easily converted to the SI (Metric) system using the provided conversion factors. The transition to the Metric system was gradual to allow users to adjust, as abruptly changing to unfamiliar units would have been difficult. 8.4 Tied Column The design of a tied column must be strong enough to carry the superimposed load, referred to as the allowable load. Tied columns can be under-designed, over-designed, or correctly designed. Under-designed columns are unsafe, while over-designed columns are costly. A standard design ensures safety. Failure of a tied column occurs by crushing and shearing outward along an inclined plane, where vertical bars buckle outward between lateral ties. The failure of a tied column is abrupt and can be more disastrous than the failure of a single beam or girder. 8.4 Tied Column Tied columns are an essential part of reinforced concrete construction, requiring specific methods to ensure their stability and strength. There are three main methods for constructing tied columns in small and medium reinforced concrete buildings: 1. Block laying after concreting of columns 2. Concreting columns before block laying walls 3. Simultaneous concreting of columns and walls 8.4 Tied Column First method: block laying after concreting of columns Step 1: Construct scaffolding to support the column reinforcement in its vertical position. Vertical lumber pieces are installed around the column with horizontal braces spaced at 1-meter elevations. Step 2: Transfer the building markings and reference line from the batter board to the scaffolding, ensuring vertical alignment with a plumb bob. Step 3: Install a temporary horizontal wood brace to hold the bars in place and allow the installation of the column forms. Step 4: Check the vertical position of reinforcement in the column and install the small sides of the column forms in the opposite direction, ensuring proper alignment. Step 5: Verify the installation of accessories (downspouts, conduits, plumbing, etc.) before closing the column forms. Step 6: Ensure the wider form cover is installed with charcoal marks and nails as a guide for the column size and form alignment. Step 7: Check that the column forms are securely set and supported, avoiding potential bulging failures. Step 8: Inspect the work before concreting to ensure proper alignment and reinforcement installation. 8.4 Tied Column Second method: concreting columns before block laying walls Step 1: Begin by constructing the wall footing and install the vertical reinforcement for the walls. Block laying follows immediately after concreting the wall footing to optimize the use of cement mortar. Step 2: Leave the space for the column reinforcement vacant during the block laying process. Step 3: Install necessary pipes for various accessories in the designated column space. Step 4: Clear the column space of sawdust, earth, dirt, and debris, then wash thoroughly before installing the column forms. Step 5: Install the forms around the column reinforcement, ensuring proper alignment and vertical positioning. Brace the forms securely with galvanized wire or machine bolts before pouring the concrete mixture. 8.4 Tied Column Third method: simultaneous concreting of columns and walls Requires only two pieces of formwork to cover each column, with the column reinforcement flanked by hollow block walls on both sides, improving structural bonding. Horizontal bars in block laying are continuous across the column reinforcement, eliminating the need for horizontal dowels that would otherwise be necessary if the column was poured before the walls. The column is laterally supported by the hollow block walls, making the work easier, faster, and more economical by reducing the destruction of formwork and braces. This method may not be suitable for independent columns. If concrete mixes for the columns and walls differ, the column should be poured first.  8.5 Spiral Column A spiral column consists of a circular concrete core enclosed by spirals and vertical bars, held in place by at least three spacers. A monolithic concrete cover protects the reinforcement. This design is stronger than tied columns and is preferred for slender columns bearing heavy loads. When a cylindrical column bears a load, lateral pressure induces hoop tension in the spiral. The closely spaced spiral resists lateral expansion, enhancing the core concrete's load capacity. Spiral columns fail gradually and ductilely, marked by spalling of the outer shell and eventual yielding or bursting of the spiral, unlike the abrupt failure of tied columns.  8.5 Spiral Column Spiral Reinforcement Limitation and Spacing o For cast in place construction, spiral reinforcement shall have a minimum diameter of 10 mm, and that the clear spacing between the spirals shall not be more than 7.5 cm. or less than 2.5 cm. The longitudinal reinforcement area to the gross column area shall not be less than.01 nor more than.08 and that the minimum number of vertical bars shall not be less than 6 pcs. of 16 mm bar diameter. o Section 7.12.2 of the ACI Building Code specifies "Spiral reinforcement for compression members shall consist of evenly spaced continuous spiral held firmly in place and true to line by vertical spacers. ▪ At least two spacers shall be used for spirals less than.50 m. diameter, ▪ Three for spirals.50 to.75 meter in diameter. ▪ Four spirals for more than.75 m diameter. o When bigger size of steel bar is used for spiral such as 16 mm or larger, ▪ Three spacers shall be used for a spiral having.60 m or less in diameter. ▪ Four spacers to a spiral having more than 60 m diameter.  8.5 Spiral Column Spiral Anchorage and Splicing o The anchorage of spiral reinforcement shall be provided by one and a half extra turn of spiral bar or wire at each end of the spiral unit. When splicers are necessary for special bars it shall be tension lap splices with 48 bar diameters as minimum but in no case shall be less than 30 cm. or weld. o The reinforcing spiral shall extend from the floor level in any story or from the top of the footing to the level of the lowest horizontal reinforcement in the slab, drop panel or beam above. Where beams or brackets are not present on all sides of the column, ties shall extend above the terminal of the spiral to the bottom of the slab or drop panel. 8.6 Composite Column A composite column combines a structural steel column embedded within the concrete core of a spiral column. The construction work is similar to that of a spiral column, with the addition of setting the structural steel into its designated position within the concrete core. 8.7 Combined Column - A column with structural steel encased in concrete of at least 7 cm. thick reinforced with wire mesh surrounding the column at a distance of 3 centimeters inside the outer surface of the concrete covering. - The construction processes of a combined column calls for the installation of the structural steel as the main reinforcement, followed by the attachment of the wire mesh covering. - Usually used to support heavier loads, to resist buckling in tall structures, and space optimization. 8.6 Lally Column A Lally column is a fabricated steel pipe column, typically used to support a girder, girts, or beam. The steel pipe is sometimes filled with grout or concretefor additional strength and protection from rust or corrosion. CHAPTER 9 PLATFORM – FLOOR STRUCTURE  PLATFORM – FLOOR STRUCTURE 9.1 WOOD FLOOR SYSTEM Floor framing – platform structure of the building suspended by posts, columns and beams. The development of machinery and sawmills has significantly advanced construction techniques. This progress introduced the skeleton frame type, which utilizes the versatility of lumber in various sizes for interchangeable framing purposes The design of a platform – floor system depends upon the following considerations 1. Live load – movable loads imposed on the floor (e.g. people, furniture) 2. Dead load – static load (e.g. weight of the construction materials carrying the live load 3. Types of Materials to be used – The choice from the various construction materials available (e.g. lumber, concrete, steel, etc.) 4. Sizes and spacing of the structural members – depends on its strength and capability to carry the load at a certain spacing. 5. Span of the supports – distances between the post, columns, or supporting walls.  9.1 WOOD FLOOR SYSTEM Classification of P-F Framing Structure a.) Plank and beam floor type - This system uses large wooden planks placed on top of beams. It's commonly used for creating a rustic or traditional aesthetic, offering both strength and natural beauty. b.) Panelized – floor system - This method involves the use of prefabricated panels that are manufactured off-site. The panels are then transported and assembled on-site, offering faster construction times and increased efficiency. c.) The conventional floor framing system - This traditional method utilizes individual pieces of lumber (joists) that are spaced evenly and run parallel to each other, supported by beams. It's widely used in residential construction for its flexibility and cost-effectiveness. Among the three, the conventional type is the most popular and widely used because of economy, simplicity, and ease of work  9.1 WOOD FLOOR SYSTEM Parts of a Platform-Floor System Sill – part of the side of a house that rests Girder – principal beam extending from wall to wall of a building horizontally upon the foundation supporting the floor joints or floor beams. - Wood members fastened with anchor bolts to the - The major horizontal support members upon which the floor foundation walls system is laid - May either be: a.) Solid b.) Built-up Floor Joists - parts of the floor system placed on the girders where the floor boards are fastened. - Usually nailed on the girders at a distance from 30 to 25 cm, on center rigidly secured by bridging to prevent from wagging sideways  9.1 WOOD FLOOR SYSTEM Parts of a Platform-Floor System Header and Trimmer Tail beam, Ledger Strip, Draftstop Plate Header - a short transverse joist that supports the end of the cut- off joist at a stairwell hole. Trimmer – supporting joist which carries an end portion of a header. Flooring – The Tongue and Groove (T & G) is generally specified for wood flooring. The board thickness is either 2 cm or 2.5 cm (¾ or 1 inch). With varying width that ranges from 7cm to 15 cm (3-6") and the length from (8 – 20') 2.50 to 6 m. long3 REINFORCED CONCRETE FLOOR SYSTEM 9.2 Beam Beam – a structural member that supports the transverse load which usually rest on supports at its end. Girder – term applied to a beam that supports one or more smaller beam Classification of Beams Simple Beam – beam having a single span supported at its end without a restraint at the support - Simply supported beam Restraint – a rigid connection or anchorage at the support Continuous Beam – beam that rest on more than two supports Semi – Continuous Beam - Beam with two spans with or without restraint at the two extreme ends. 9.2 Beam Classification of Beams Cantilever Beam – supported on one end and the other end projecting beyond the support or wall T – Beam - When floor slabs and beams. are poured simultaneously producing a monolithic structure where the portion of the slab at both sides of the beam serves as flanges of the T-Beam. - The beam below the slab serves as the web member and is sometimes called stem. REINFORCED CONCRETE FLOOR SYSTEM Shear – effect of external forces that acts upon the structure causing the adjacent sections of a member to slip at each other. Strength – cohesive power of the materials that resist an attempt to pull it apart in the direction of its fiber. Ultimate Strength – maximum unit of stress developed at any time before rupture Moment – tendency of a force to cause rotations about a certain point or axis. Strain – a kind of alteration or deformation produced by the stresses. Stress – an internal action set up between the adjacent molecule of the body when acted upon by forced, or combination of forces, which produces strain, - Refers to the pressure of load, weight, and some other adverse forces on influences 9.3 RELATION BETWEEN THE MATERIALS AND STRUCTURE A building structure is distinct from building materials. When different materials are combined to create a building part, it forms the building structure. Raw building materials do not contribute to strength or load resistance until they are incorporated into the structure. Each material in the structure serves a specific purpose in counteracting forces. Design determines the size, quantity, quality, spacing, proportions, and mixture of these materials. While the details of stresses, moments, and compression are beyond the scope, a basic understanding of these concepts is important for beginner builders. The behavior of a structure under various forces is crucial knowledge in building construction. Different kinds of Stresses that may act on the structure are: 1. Compressive stresses 2. Tension (Tensile) Stress 3. Shear Stress and Strain 4. Torsional Stress and Strain 9.3 RELATION BETWEEN THE MATERIALS AND STRUCTURE Stresses on structures are usually brought about by load which are classified into; Dead Load - loads that are distributed or concentrated, which are fixed in position throughout the lifetime of the structure such as the weight of the structure itself. The dead load on a beam are also categorized into two: 1. Concentrated Load 2. Distributed Load Live Load - Occupancy load which is either partially or fully in place or may not be present at all. Environmental Load - Consists of wind pressure and suctions, earthquake loads rainwater on flat roof, snow and forces caused by temperature differentials 9.4 BEHAVIOR OF BEAM UNDER THE INFLUENCE OF LOAD A homogeneous concrete beam even if free from carrying live or concentrated loads has to carry its own weight classified as a distributed load. The gravitational effects of its own weight will cause the structure to sag or bend downward between its support as shown on the following illustration; 9.4 BEHAVIOR OF BEAM UNDER THE INFLUENCE OF LOAD Bending Moment - A moment is the force's tendency to cause rotation about a specific point or axis. Bending moments come in two types: positive and negative. Positive bending occurs when a beam bends downward between supports, compressing the upper portion above the neutral axis and stretching the lower portion. Negative bending happens when a beam bends upward at the supports, compressing the lower portion below the neutral axis and stretching the upper portion 9.5 REINFORCEMENT OF CONCRETE BEAM Concrete beams under load react to forces such as positive and negative bending, which can lead to failure or collapse. To prevent this, reinforcement is required to avoid rupture under stress. Concrete is strong in compression but weak in tension, while steel can resist both. Combining concrete and steel allows the structure to handle both compression and tension forces. A balanced reinforcement or Balance Beam design ensures that the concrete and steel areas are sufficient to carry these forces simultaneously. According to building codes, the steel reinforcement area should be 0.005 times the product of the beam's width and depth. Thus, "Find the cross sectional area of steel bars required for a beam having a cross sectional dimension of 25 x 40 cm concrete beam to be considered as a balanced beam, As =.005 * 25 *40 = 5 sq, cm This is the minimum required area of steel bars in a 25 x 40 concrete beam to be considered as "Balanced Beam" 9.6 THE COMPRESSION AND TENSION IN A BEAM In the figure, the beam's depth is divided by a Neutral Axis (NA). Above the axis at supports, the beam is under tension, and below, it's under compression. Between supports, the lower portion is under tension, and the upper part is under compression. Concrete carries compression loads, while steel resists tension forces. Steel bars are placed where tension stresses develop: at the lower portion for positive bending and the upper portion for negative bending. There are two methods to do the reinforcement: Bent Reinforcing Bars and No Bent Bars  9.6 THE COMPRESSION AND TENSION IN A BEAM Bent Reinforcing Bars - Reinforcing bars are bent up on or near the inflection points and are extended at the top of the beam across the support towards the adjacent span. - Inflection points – portion of a beam where bending moment changes from positive to negative. - Usually located at a distance of about 1/5 to ¼ length of beam from the face of the support. No Bent Bars - When bars are not bent, an additional straight reinforcing bars are placed on the top of the beam across the supports extended to the required length usually a distance about 1/3 the beam span length from the face of the support, other straight additional bars are also placed at the bottom center of the beam span where positive moment develops. The first method uses bend bars to resist diagonal tension and shear, usually counteracted by stirrups or web reinforcement. The second method, although less effective in tension and shear resistance, offers easier fabrication and installation of reinforcing bars, avoiding the difficulties encountered with bent bars and their repair. 9.7 SPACING OF REINFORCING BARS IN BEAM Reinforcing bars are accurately placed and secured using concrete or metal chairs, spacers, or bolsters. When bent-up bars are needed in the beam design, an even number of bars is preferred for main reinforcement. Some bars are bent at inflection points, leaving straight bars at the bottom at the supports, where stirrups are tied. The minimum clear distance between main reinforcing bars should be at least 2.5 cm or 1 1/3 times the maximum gravel size. The measurements in the table include a 4 cm (1 ½ ") protective covering for steel bars on both sides of the beam and an allowance for 10 mm (3/8) stirrups. The table also indicates the maximum bar sizes for a given beam width. When multiple layers of bars are required, the clear distance between layers should be at least 3 cm, with the upper layer placed directly above the bottom layer. 9.8 SPLICING HOOKS AND BENDS Splicing of Reinforcement The ACI Code provides essential guidelines on the proper handling of splicing, hooks, and bends in reinforcement bars to maintain structural integrity and safety. It emphasizes that splicing should only be done as specified in the design plans or with the approval of the engineer. Lap splices are not allowed for bars larger than No. 11 or 35 mm in diameter, and bundled bars must be spliced individually with non- overlapping lap lengths. In cases where splices are unavoidable in high-stress areas, they must be staggered to ensure even load distribution. Hooks and Bends in Reinforcement The Code also outlines specific requirements for hooks and bends to secure bars effectively in concrete. A standard hook consists of a semicircular bend with an extension of at least four bar diameters or 6.5 cm. Alternatively, a 90-degree hook must have a 12-bar diameter extension. The minimum bend diameters for stirrups and tie hooks vary by bar size, ranging from 4 cm to 6.5 cm. Furthermore, bars must be bent cold unless otherwise permitted by the engineer, and partially embedded bars should not be field bent unless specified in the design. These provisions are critical to ensuring strong, reliable reinforcement connections that reduce the risk of structural failure. 9.9 STEEL BARS CUT OFF AND BEND POINT In reinforced concrete construction, it is a common practice to cut or bend bars where they are no longer needed to resist tension stresses. For continuous beams, bottom steel bars are often bent at a 45-degree angle to serve as top reinforcement over the supports. According to the ACI Code, bars must extend beyond the point where they are no longer required by at least the effective depth of the beam or 12 times the bar diameter, whichever is greater. The Code also mandates that at least one positive moment bar in continuous spans must extend uninterrupted by at least 15 cm into the supports. Additionally, at least one bar used for negative moment reinforcement must extend beyond the inflection point by a distance not less than half the clear span, the beam’s depth, or 12 bar diameters. These guidelines ensure that reinforcement provides adequate tension resistance and prevents potential structural failures. 9.10 BEAMS REINFORCED FOR COMPRESSION When architectural conditions limit a beam's cross-sectional dimension, the concrete area may become insufficient to resist compression loads. In such cases, steel reinforcement is used to supplement the concrete and counteract compression stresses. This type of beam is called a "Double Reinforced Beam," where stirrups or ties hold the reinforcement in position, spaced no further apart than 16 times the bar diameter or 48 diameters. When using compression bars in a flexural member, it's crucial to prevent them from buckling and spalling off the outer concrete under load. Proper anchoring of these bars is essential, similar to how compressive bars in columns are anchored using lateral ties. These ties should be used throughout the length where compression reinforcement is needed. 9.11 WEB REINFORCEMENT Web reinforcement, similar to stirrups, holds the beam's reinforcement in its designed position and provides lateral support. It also resists diagonal tension and counters shear action. Vertical stirrups should encircle the main reinforcement, with hook bends at the ends at least 5 times the stirrup's diameter, and be securely tied to prevent the main reinforcement from slipping in the concrete. 9.12 TORSION IN REINFORCED CONCRETE MEMBER To resist torsion, structures need longitudinal reinforcing bars with closely spaced stirrups. U-stirrups, used for transverse shear reinforcement, aren't suitable for torsional reinforcement. Instead, lateral ties, like those used in columns, are effective in counteracting torsional stresses. Good anchorage involves hooking the stirrup ends around the longitudinal or main reinforcement. When including T-Beam flanges in torsional strength calculations, supplementary slab reinforcement is needed. Main reinforcement should be well-distributed around the cross-section perimeter to control cracking, with spacing not exceeding 30 cm (12"). Bars should be at least No. 3 in size, with one bar placed in each corner of the stirrups. 9.13 T-BEAM DESIGN AND LIMITATION What is a T-Beam? A T-beam combines a slab and a beam to reduce slab thickness and save materials. The flange (top slab portion) resists compression, while the web resists shear and tension. ACI Code on T-Beams: Specifies the effective flange width based on beam spacing. Reinforcement must be properly placed in both the web and flange. Limitations: Requires accurate design to prevent cracking in the flange. Beam spacing must follow ACI standards to ensure the slab contributes effectively to load distribution. 9.14 Other Causes of Beam Failure Common Causes of Beam Failure: 1. Inadequate Reinforcement: Insufficient reinforcement can lead to collapse under load. 2. Improper Splicing: Incorrect splicing can reduce the beam’s load-bearing capacity. 3. Insufficient Anchorage: Lack of hooks or proper bends can cause reinforcement to slip. 4. Poor Construction Practices: Errors during construction, such as inadequate curing or improper mixing of concrete. 9.15 REINFORCED CONCRETE SLAB Definition: A reinforced concrete slab is a horizontal structural element that distributes loads to supporting beams or columns. Types of Slabs: 1. One-Way Slab: Supported on two opposite sides, load transfers in one direction. 2. Two-Way Slab: Supported on all four sides, load transfers in two directions. 3. Flat Slab: A slab without beams, supported directly by columns. 4. Ribbed Slab: Consists of ribs for strength and a thinner top slab. Reinforcement Requirements: Proper reinforcement spacing and support during casting is essential. Control and expansion joints must be considered to prevent cracking. 9.16 RIBBED FLOOR SLAB What is a Ribbed Floor Slab? Ribbed slabs have a series of ribs (beams) running underneath a thin slab. Ribs reduce the dead load of the slab while maintaining strength. Advantages: Saves material costs by reducing concrete volume. Provides better load distribution compared to traditional slabs. Considerations: Rib spacing and depth must follow ACI guidelines to ensure strength. Requires careful formwork to achieve the desired shape. 9.17 THE ACI ON CONCRETE JOIST FLOOR CONSTRUCTION The ACI provides rules for concrete joist floor construction to ensure strength and safety. Joist ribs must be at least 10 cm wide, spaced no more than 75 cm apart, and their depth should not exceed three times their width. Ribbed slabs must follow these spacing and thickness rules or be designed as slabs and beams. If strong permanent fillers are used, only the vertical parts touching the joists can be included in strength calculations. The concrete slab over fillers must be at least 4 cm thick, with reinforcement placed across the joists. For removable forms, slabs must be at least 5 cm thick and reinforced to handle bending forces. If the slab has pipes or conduits, it must be 2.5 cm thicker than the depth of those items to maintain strength. These rules ensure joist floors are durable and safe. CHAPTER 10 STEEL FRAMING 10.1 INTRODUCTION Roots of Steel Framing Prefabrication of construction parts and the methods of erect- ing and assembling to their designed form is not new in the field of construction. Prefabrication of parts has originated as early as the time of Greek and Egyptian Architecture manifested in the remains of the famous Parthenon of Greece and the Pyramid of Egypt. Fabricate – means to put together. The combination of pre to fabricate simply means that the parts of the structure are assembled or put together before the erection. The recent pre-fabricated construction of experimental houses sponsored by the National Association of Home Builders include: 1. Pre·cut steel post, beam and foundation system. 2. Combination of sheating and siding finished with poly- vinyl flouride film. 3. Vinyl finished interior wallboard 4. Combination of sub-flooring completely finished at the factory. 5. Reinforced plastic shower stalls and roofing coated with hypalan that are fastened to rafters by a concealed nailing strip.  10.2 STRUCTURAL SHAPES The most common shapes of structural steel used in building construction are the American Standard forms such as: 1. Square Bars 2. Round Bars 3. Plate Bars 4. Angle Bars 5. Channels 6. I-Beam 7. Tee Beam 8. H-Column 9. Wide Flanges 10. Zee 10.3 STRUCTURAL STEEL The early structural steel grade was mostly focused on the ASTM A7 which concurrently is no longer considered as the basic structural steel after the introduction of new types of structural grade such as ASTM A36. However, the Code so provides that structural steel to be used in the construction shall conform to any of the following specifications: 1. For steel bridges and buildings ASTM A7 2. Structural steel for welding ASTM A373 · 3. Structural steel ASTM A36 4. High-strength structural steel ASTM A440 5. High strength low alloy structural manganese vanadium steel ASTM A441. 6. High strength low alloy structural steel ASTM A242 The ASTM A36 is stronger with higher yielding point than the ASTM A7. The carbon content of ASTM A36 had been reduced to improve weldabiljty, although it could be connected by means of bolts and rivets. 10.4 HIGH STRENGTH STEEL The early structural steel grade was mostly focused on the ASTM A7 which concurrently is no longer considered as the basic structural steel after the introduction of new types of structural grade such as ASTM A36. However, the Code so provides that structural steel to be used in the construction shall conform to any of the following specifications: 1. For steel bridges and buildings ASTM A7 2. Structural steel for welding ASTM A373 · 3. Structural steel ASTM A36 4. High-strength structural steel ASTM A440 5. High strength low alloy structural manganese vanadium steel ASTM A441. 6. High strength low alloy structural steel ASTM A242 The ASTM A36 is stronger with higher yielding point than the ASTM A7. The carbon content of ASTM A36 had been reduced to improve weldabiljty, although it could be connected by means of bolts and rivets. 10.5 RIVETS AND BOLTS The rivets and bolts used in building construction are of three grades: 1. ASTM A141 structural rivet steel 2. ASTM Al95 high strength structural rivet steel 3. ASTM A406 high strength structural alloy rivet steel Fasteners is the term used for both rivets and bolts. The three methods adopted in connecting structural steels are rivets, bolts and welds. The choice of any of the above methods depends upon the condition of fabrication and erection, detail of arrangement and condition of service 10.6 PROCEDURES OF INSTALLING RIVETS 1. The steel metal to be connected are drilled and Since the rivets are heated when inserted into the hole, securely held in such a manner that their holes are shrinkage will occur on cooling that the two connected perfectly aligned. 2. Heated rivets are inserted into the holes and a plates will bedrawn tightly together by the rivets. The size buckin-up tool is pressed against the rivet head. of the rivets depends upon the types of work, the 3. The projecting shank is then covered by the power thickness of the materials to be connected and the riveter which delivers rapid blows fill the hole, deforming the shank and forming the head. strength to be transmitted across the joints. The most commonly used rivets are ( ¾)19 mm diameter and (3/4) 22 mm. However, It is suggested that only one size of rivet should be used. TABLE 10-1 CONVENTIONAL SIGNS FOR RIVETS 10.7 CONDITIONS FOR PUNCHING AND DRILLING RIIVETS 1. 3. If the thickness of the plate is not The materials adjacent to the holes are bigger than the diameter of the usually damaged by the punching of the rivets plus (1/8) 3 mm, the hole may structural steel. Therefore, it is necessary be punch. that the hole of the punch plate should be 3 Failure of Rivets: mm greater than the diameter of the rivet or bolt, thus punching 22 mm hole for a 19 mm 1. By shearing of the rivets rivet or 25 mm for a 19 mm rivets are 2. By crushing of the rivet or recommended. metal on which it bear. 3. By tension in the sections of the connected members 2. 4. 4. By tearing at the edge. The hole should be ( 1/16 ) 3 mm All rivets shall be hot power-driven, bigger than the diameter of the heated to a temperature not more rivets or the bolts for ease in than 1065C and in no case shall be inserting the bolts and driven below 537C to avoid damages of the threads. CONDITIONS FOR PUNCHING AND DRILLING RIIVETS 5. GAGE LINE Is the line parallel with the length of a member wherein the rivets are placed, or the· normal distance between the gage line and the edge of a member CONDITIONS FOR PUNCHING AND DRILLING RIIVETS 6. PITCH OF RIVETS The Pitch of rivet is the center to center distance between ad- jacent rivets whether they fall on the same different Iines. The accepted minimum pitch between the center of rivet holes shall not be less than 9 cm. for ( 1 ") 25 mm rivets; 7 cm. for 22 mm; 6 cm for 19 mm rivets; and 5 cm. for 16 rivets. Pitch should not be less than 3 times the diameter of the rivets. CONDITIONS FOR PUNCHING AND DRILLING RIIVETS 7. STITCH RIVETS Truss members are usually built up of two angles provided with gusset plate that separate the two angles. These angles act as ·one unit by the use of rivets connecting the members placed at intervals between the ends of the members. This is called sti1Ch · rivets. CONDITIONS FOR PUNCHING AND DRILLING RIIVETS 8. EDGE DISTANCE OF RIVETS Rivets or bolts placed so close to the edge of the pJate have the tendency to tear the adjacent thin metal. A standard' specification requires a minimum edge distance of holes as shown on the following Table 10-4. The maximum distance from the center of any rivet or bolt to the nearest edge shall be 12 times the thickness of the plate but shall not exceed 15 cm. 10.8 BOLTS Bolts used to connect structur.al steel are either common bolts or high strength bolts. ‘ Common bolts are not permitted in some Codes for building construction for more than a prescribed height but rather limited to field connections or to work of less importance not subject to shock or vibration and those buildings containing machineries or rolling loads that will cause loosening of the nuts which will subs- tantially reduce the strength of the connections. 10.8 BOLTS High Strength Bolts: - Are usually made of ASTM A325 steel which have been used for years in building construction. High-strength bolts provide a resisting force. by friction between the contacting surfaces of the plates, eliminating bending, shearing or bearing stresses on the bolts. Bolts and rivets are called "fasteners’. Bolts are called "threaded fatteners". Bearing Type Connection: - Where the end of the plates are in bearing against rivets and the shank of the rivets that resist shear. Friction Type Connection: When high-strength bolts are used, tensile stresses are set up in the shank of the bolts and the friction between the plates which resist the tension and compression load. 10.9 CONNECTIONS OF STRUCTURAL MEMBERS 1. THE COLUMN BASE PLATE Spreads the column load over the foundation in various sizes where the length in meter and thickness of 2 mm increments. Rolled steel gearing plates should be in absolute contact for proper 'distribution of load. Plates of more than 5 mm to 10 mm thick maybe straightened by pressing or planning. Steel column should be properly anchored to the foundation by steel bolts which passes through the plates and angles riveted or welded to the flange of the column. Angles are sometimes omitted for light columns, instead, the base plate is secured to the column by means of fillet weld. 10.9 CONNECTIONS OF STRUCTURAL MEMBERS 2. COLUMN SPLICES Are usually made at 60 Cm. or more above the floor levels. Splices are generally made by riveting or welding splice plates of 10 to 12 mm thickness to the flanges of the columns. The splice plates does not resist compression load but only serves to hold the column sections in the right position. Where the upper column is smaller in width than the supporting column, filler plates are used. If the difference in width is so great, a horizontal plate is used instead. · FIGURE OF COLUMN SPLICES 10.9 CONNECTIONS OF STRUCTURAL MEMBERS 3. BEAM BEARING PLATES Beams to rest on masonry walls or pier usually are provided with bearing plates to provide an angle bearing area and to attain a uniform distribution of the beam load. The bearing plates are usually not riveted nor welded to the beam flange. 10.9 CONNECTIONS OF STRUCTURAL MEMBERS 4. BEAM CONNECTIONS TO COLUMNS Beams connected to columns has a great variety of conditions using rivets or weld anchorage. For large beams, seat connections with stiffeners are commonly employed which usually consists of shelf angle and single or double angles. The filler should be the same in thickness as the shelf angle. The top angle, or clip angle is used only to hold the beam in its right position but not to assist in transferring the beam load to the column. FIGURE OF BEAM CONNECTION TO COLUMNS 10.9 CONNECTIONS OF STRUCTURAL MEMBERS 5. SEAT CONNECTION - without stiffeners maybe used for beam with smaller reactions. 10.9 CONNECTIONS OF STRUCTURAL MEMBERS 6. BEAM TO GIRDER CONENCTIONS -The methods commonly adopted in connecting beams to girders is by attaching two angles to the web of the beam connected either by rivets, bolts or weld. 10.10 PLATE GIRDERS When a rolled steel sections are inadequate to meet the span requirements built-up section plate or box girder is the solution. A plate girder is a beam made up of steel plates and angles either riveted or welded together forming an 1-section. When the web of I-section consists of two separated steel plates, the structure is called box girder. 10.10 PLATE GIRDERS The axial vertical plate is called the "web plate". Flange angles are placed at the top and at the bottom of the web plate secured by rivets. One or more plates are riveted to the outstanding legs of the flange angle called cover plates and a stiffener made of angle section riveted to its side to prevent buckling of the web plates. In welded plate girders, the flange angles are omitted since the cover plate could be connected directly to the vertical plate. The three principles involved In making built-up plates are: 1. Web plate is to resist shearing stresses 2. The flange made-up angles cover plates and 1/8 of the web area, will resist tension and compression stresses due to bending. 3. The stiffeners serves to prevent buck ling of the web plates.  10.11 WEB PLATES AND INTERMEDIATE STIFFENERS The Code specifies a minimum thickness of web plate to be 10 mm for interior and 6 mm for exterior locations. In addition, plate girder web's thickness should not be less than 1/320 of the unsupported distance between the flange angles. If full allowance bending stress in the flange is used, the web plate thickness should not be less than ~ of the unsupported distance: This requirement applies to ASTM A36 steel. The intermediate stiffness prevent buckling is usually 6 x 6 cm x 6 mm angles placed in pairs at each end of the girder then at a distance not to exceed, 85 cm as the first pair of intermediate stiffness then at 2.25 m. there- after. 10.11 WEB PLATES AND INTERMEDIATE STIFFENERS  10.11 WEB PLATES AND INTERMEDIATE STIFFENERS An Open web Steel Joist is considered lightweight structure to support floor and panels between main supports. 10.11 SUPPLEMENTARY JOISTS EXAMPLES 10.11 SUPPLEMENTARY JOISTS EXAMPLES 10.11 ROOF TRUSSES Roof trusses is the most economical structure to cover a building having a wide span of supporting columns or walls. A truss is a structural frame generally supported only at both ends by columns, beams, or walls. Different Types of trusses are: 1. King post truss 2. Simple Fink truss 3. Fink truss 4. Howe Truss 5. Pratt Truss 6. Fan Truss 7. Single-span fink truss 8. Clipped Truss 9. Rigid frame open-web clear span truss 10. Rigid frame clear span 11. Single span slope beam 12. Continuous Beam 10.11 ROOF TRUSSES PURLINS Purlins is a beam placed on top of the rafters or top chord that extends from truss to truss which carry and transfer the roof load to the truss at the panel points. Roof Panel: - Refers to the roof portion that lies between two adjacent joints of the upper chord, in short, roof panel is that portion of the roof supported by each purlins. Sag rods: - Refers to a steel bar usually of 16 mm or 19 mm diameter rod attached at the center or endpoints of the span of the purlins. The Sag rod is secured to the purl ins over the line of the ridge truss usually placed at 7 cm. below the top flange of the purlins. 10.12 CHANNEL PURLINS 10.13 WELDED CONNECTIONS In a typical construction setting, welded connections are classified namely: Arc Welding:- Although arc and gas welding are permitted in the connection of structural steel members, arc welding is the one most preferred. Penetration: - Is the term used to indicate the depth from the original surface of the base metal to the point at which fusion ceases. Partial penetration: - is the failure of the weld metal and base metal to fuse at the root of the weld. Welded Joints:- Are classified into three: 1. Butt joint 2. Tee Joint 3. Lap Joint End of Presentation CREDITS: This presentation template was Slidesgo created by Slidesgo, including icons by Flaticon Flaticon, and infographics & images by Freepik Freepik