2STEEL GeneralSteel is a structural material which consists mostly of iron and carbon. It can, however, contain other additives which might change the steel's properties. Steel can be hot rolled or cold formed into structural shapes, such as the familiar "I" beam known today as a wide flange. Steel has the same strength in tension as it has in compression, unlike concrete.
3STEELGeneral There are some tests for steel must be applied as : Tension test: this test used to measure the material properties of a steel (or really any material, for that matter),Beam bending test: this test used to measure the material properties of a specimen and the effectiveness of the orientation of the beam.
4STEELGeneralSome types of steel are specifically for use in fabricating large structures. They are called ‘high-strength low alloy’ or HSLA steels. These steels are:much stronger and tougher than ordinary carbon steelsductilehighly formableweld ableHighly resistant to corrosion - which is important since the structure may be in place for a long time.
5STEEL Why HSLA Steels are Strong:- The starting point in achieving the desirable properties of structural steels is to get the composition of the alloy right. The extra strength can be achieved through various combinations of alloying elements which means that there can be some choice in the other properties that the steel will have.A typical HSLA steel will contain about 0.15% carbon, 1.65% manganese and low levels (under 0.035%) of phosphorous and sulphur and additions of other elements:
6Advantages of steel as a construction material High load resistingHigh ductilityEasy control for steel structureNo formed as in a concrete structureElastic properties
7Disadvantages of steel as a construction material No ability to resist the fireNo ability to resist the corrosionHigh costEngineering properties of steel
8STEEL Microstructure of HSLA steels The strength of all steels, including HSLA steels, comes from their microstructure. Strength is increased by:increasing the amount of pearliteincreasing the fineness of the grains structureincreasing the amount of hard precipitate.
9STEEL Chemical Composition of Structural Steels The primary types of structural steel are usually classified according to the following chemical composition categories:Carbon-manganese steelsHigh-strength, low-alloy (HSLA) steelsHigh-strength quenched and tempered alloy steels
10STEEL whose primary chemical components are carbon and Carbon manganese Steelswhose primary chemical components are carbon andmanganese in addition to iron, are referred to as carbon steels or mild structural steels. The materials of this type are generally least expensive; they have quite adequate strength and ductility characteristics, and are therefore by far the most widely used grades. One of the most prominent of these steels are ASTM grade A36, with a specified minimum yield stress of36 ksi.
11STEEL High-strength, low-alloy (HSLA) steels represent a relatively recent development in steelmaking. The higher strength (42 to 65 ksi) is achieved by adding small amounts of additional chemical elements. Two of the most common HSLA steels are ASTM grade A572 and A588.High-strength quenched and tempered alloy steels:-used for structural purposes are essentially available only as grade A514 today. With a yield stress level of 90 to 100 ksi, the increase in strength is achieved through heat treatment. A514 is available only in plate form, up to 6 inches thick.
12STEEL some elements used in structural steels: Carbon (C)Manganese (Mn)Aluminum (Al)Chromium (Cr)Columbium (Cb)Copper (Cu)Molybdenum (Mo)Nickel (Ni)Phosphorus (P) and Sulfur (S)Silicon (Si)Vanadium (V)Other chemical elements
13STEELSteel AlloysSteel Alloys can be divided into five groupsCarbon SteelsHigh Strength Low Alloy Steels Quenched and Tempered SteelsHeat Treatable Low Alloy SteelsChromium-Molybdenum SteelsCarbon steels are normally classified as shown below.
14STEEL classification of Carbon steel Low-carbon steels:-contain up to 0.30 weight percent C. The largest category of this class of steel is flat-rolled products (sheet or strip) usually in the cold-rolled and annealed condition. The carbon content for these high-formability steels is very low, less than 0.10 weight percent C, with up to 0.4 weight percent Mn. For rolled steel structural plates and sections, the carbon content may be increased to approximately 0.30 weight percent, with higher manganese up to 1.5 weight percent.
15STEEL classifications of Carbon steel Medium-carbon steels:-are similar to low-carbon steels except that the carbon ranges from 0.30 to 0.60 weight percent and the manganese from 0.60 to 1.65 weight percent. Increasing the carbon content to approximately 0.5 weight percent with an accompanying increase in manganese allows medium-carbon steels to be used in the quenched and tempered condition.
16STEEL classifications of Carbon steel High-carbon steels:-contain from 0.60 to 1.00 weight percent C with manganese contents ranging from 0.30 to 0.90weight percent.
17STEEL classifications of Carbon steel High-strength low-alloy (HSLA) steels,or micro alloyed steels, are designed to provide better mechanical properties than conventional carbon steels. They are designed to meet specific mechanical properties rather than a chemical composition. The chemical composition of a specific HSLA steel may vary for different product thickness to meet mechanical property
18STEEL classifications of Carbon steel Requirements. The HSLA steels have low carbon contents (0.50 to ~0.25 weight percent C) in order to produce adequate formability and weld ability, and they have manganese contents up to 2.0 weight percent. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium, and zirconium are used in various combinations.
19STEEL Structural Steel Sections Steel Material with Large Cross-sectionSteel material with large cross-section
25STEEL Market forms of Steel Bar Size ShapesStructural-Size Shapes"W" Shapes"HP" Shapes"L" Shapes"S" Shapes"C" Shapes"M" Shapes"MC" Shapes
26Introduction -Steel Design Standard cross-sectional shapesCross-sections of some of the more commonly used hot-rolled shapes :W- shape OR Wide –flange Shape.For example :(w 18×50)W-type of shape.18 section depth in inches .50 section weight in pounds per foot .
27Introduction -Steel Design Standard cross-sectional shapesS- shape OR American standard SFor example :(S 18×70)S-type of shape18 -section depth in inches .70 section weightin pounds per foot .
28Introduction -Steel Design Standard cross-sectional shapesL- shape OR Angle shape .For example :(L6× L6× ¾’’)(L6× L3× 5/8’’)SEE FIGURE
29Introduction -Steel Design Standard cross-sectional shapesC- shape .For example :(C18× 70)SEE FIGURE
30Introduction -Steel Design Standard cross-sectional shapesC- shape OR-American standard channel.For example :(C9× 20)SEE FIGUREC9×20
31Introduction -Steel Design Standard cross-sectional shapesT- shape OR- standard Tee .For example :(WT18× 115)SEE FIGURENoteThis section produced by cuttingan I-shape member at middepth(WT18× 115) (W36× 230)
32STEEL Basic Definitions The nominal loads and load combinations shall be as stipulated by the applicable code under which the structure is designed or dictated by the conditions involved. In the absence of a code, the loads, including impact and crane loads, and load combinations, shall be those stipulated in ASCE 7. For design purposes, the loads stipulated by the applicable code or ASCE 7 shall be taken as nominal loads.