Presentation on theme: "1 BUILDING MATERIAL PALESTINE UNIVERSITY chapter No.#5 Steel."— Presentation transcript:
1 BUILDING MATERIAL PALESTINE UNIVERSITY chapter No.#5 Steel
2 STEEL General Steel 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.
3 STEEL General 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.
4 STEEL General Some 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 steels –ductile –highly formable –weld able –Highly resistant to corrosion - which is important since the structure may be in place for a long time.
5 STEEL 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:
6 Advantages of steel as a construction material High load resisting High ductility Easy control for steel structure No formed as in a concrete structure Elastic properties
7 Disadvantages of steel as a construction material 1.No ability to resist the fire 2.No ability to resist the corrosion 3.High cost 4.Engineering properties of steel
8 STEEL Microstructure of HSLA steels The strength of all steels, including HSLA steels, comes from their microstructure. Strength is increased by: increasing the amount of pearlite increasing the fineness of the grains structure increasing the amount of hard precipitate.
9 STEEL Chemical Composition of Structural Steels The primary types of structural steel are usually classified according to the following chemical composition categories: Carbon-manganese steels High-strength, low-alloy (HSLA) steels High-strength quenched and tempered alloy steels
10 STEEL Carbon manganese Steels whose primary chemical components are carbon and manganese 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.
11 STEEL 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.
12 STEEL 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
13 STEEL Steel Alloys Steel Alloys can be divided into five groups Carbon Steels High Strength Low Alloy Steels Quenched and Tempered Steels Heat Treatable Low Alloy Steels Chromium-Molybdenum Steels Carbon steels are normally classified as shown below.
14 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. STEEL classification of Carbon steel
15 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. STEEL classifications of Carbon steel
16 High-carbon steels:- contain from 0.60 to 1.00 weight percent C with manganese contents ranging from 0.30 to 0.90weight percent. STEEL classifications of Carbon steel
17 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 STEEL classifications of Carbon steel
18 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. STEEL classifications of Carbon steel
19 Steel Material with Large Cross-section STEEL Structural Steel Sections Steel material with large cross-section
26 Introduction -Steel Design Standard cross-sectional shapes Cross-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.
27 Introduction -Steel Design Standard cross-sectional shapes S- shape OR American standard S For example :(S 18×70) S-type of shape 18 -section depth in inches. 70 section weight in pounds per foot.
28 Introduction -Steel Design Standard cross-sectional shapes L- shape OR Angle shape. For example : (L 6 × L 6 × ¾) (L 6 × L 3 × 5/8) SEE FIGURE
29 Introduction -Steel Design Standard cross-sectional shapes C- shape. For example : (C 18 × 70) SEE FIGURE
30 Introduction -Steel Design Standard cross-sectional shapes C- shape OR-American standard channel. For example : (C 9 × 20) SEE FIGURE C9×20
31 Introduction -Steel Design Standard cross-sectional shapes T- shape OR- standard Tee. For example : (WT 18 × 115) SEE FIGURE Note This section produced by cutting an I-shape member at middepth (WT 18 × 115) (W 36 × 230)
32 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. STEEL Basic Definitions
33 STEEL Loads
34 Trusses are structures composed entirely of two force members. They consists generally of triangular sub-element and are constructed and supported so as to prevent any motion. STEEL Trusses