Lecture Civil Engineering Materials PDF

CVE236 CIVIL ENGINEERING MATERIALS Steel bars and structural steel Ekkachai Yooprasertchai  Mechanics Mechanics Rigid Bodies Deformable Bodies Fluids (Things that do no...

CVE236 CIVIL ENGINEERING MATERIALS Steel bars and structural steel Ekkachai Yooprasertchai  Mechanics Mechanics Rigid Bodies Deformable Bodies Fluids (Things that do not change shape) (Things that do change shape) Statics Dynamics Incompressible Compressible  STRESS-STRAIN DIAGRAM  The diagram representing the relation between stress and strain in a given material is an important characteristic of the material. Plastic behavior d M 11 - O 2 Stress = σ = force per unit area = (N/mm ) E Stress at rupture= strength (compression or tensile strength according to the direction of F) Strain = ε = specific deformation = (mm/mm) Plastic behavior: the material deforms under compression or tension without stress increment  Concept of normal stress Both the analysis and design of a given structure F involve the determination of stresses and deformations. Conditions for static equilibrium: ↑  M C  0  Ax 0.6 m   30 kN 0.8 m  Ax  40 kN  Fx  0 Ax  C x C x   Ax  40 kN  Fy  0  Ay  C y  30 kN  0 Ay  C y  30 kN Concept of normal stress Consider a free-body diagram for the boom:  M B  0   Ay 0.8 m  Ay  0 substitute into the structure equilibrium equation C y  30 kN Results: A  40 kN C x  40 kN  C y  30 kN  Reaction forces are directed along boom and rod Concept of normal stress Joints must satisfy the conditions for static equilibrium which may be expressed in the form of a force triangle:   FB  0 FAB FBC 30 kN   4 5 3 FAB  40 kN FBC  50 kN  Concept of normal stress Can the structure safely support the 30 kN load? From a statics analysis FAB = 40 kN (compression) FBC = 50 kN (tension) At any section through member BC, the internal force is 50 kN with a force intensity or stress of dBC = 20 mm P 50 103 N  BC    159 MPa A 314  10-6 m 2 From the material properties for steel, the allowable stress is  all  165 MPa Conclusion: the strength of member BC is adequate  Concept of normal stress Can the structure safely support the 30 kN load? From a statics analysis FAB = 40 kN (compression) FBC = 50 kN (tension) At any section through member BC, the internal force is 50 kN with a force intensity or stress of dBC = 20 mm P 50 103 N  BC    159 MPa A 314  10-6 m 2 From the material properties for steel, the allowable stress is  all  165 MPa Conclusion: the strength of member BC is adequate  Normal Strain P 2P P   stress   A 2A A     normal strain  L L P  A 2    2L L  Type of loading Flexure Tensile Compressive  Depending on the arrangement and direction of external loads, the stress produced in the body may be:  Direct stress (direct tensile Torsion stress or direct compressive stress) Shear  Bending stress (bending tensile stress or bending compressive stress),  Shearing stress,  Torsional stress, or  A combination of the different stresses. Materials standards  Materials standards are specific sets of requirements that define the performance of a material for engineering design.  These characteristic allow engineers to size engineered members, avoid environmental hazards and ultimately design long-lasting systems.  Testing standards are also included.  They specific guidelines and procedures for performing test on materials.  Introduction  The properties of steels which make them unique among constructional materials are high stiffness and a resist shape tensile strength, the ability to be formed into plate, sections and wire, and the weldability or ease of welding of those metals commonly used for constructional purposes. 141 Elastic initiv  Civil and construction engineers rarely have the opportunity to formulate steel with specific properties. Rather, they must select existing products from suppliers.  Introduction Construction steels refer to various materials used in construction projects  Reinforcing steels  Structural steels  Hot rolled structural steels High strength steels  Cold form structural steels  Built-up structural steels  Prestressing steels  Fastening products  Introduction Structural Steel Low Carbon Steel c  0.15% Mild Steel c = 0.15%  0.29% Medium Carbon Steel c = 0.30%  0.59% High Carbon Steel c = 0.60%  1.70% ductile =>  Average E value = 200GPa in use design2  Unit Weight Steel = 7,850 kg/m3 (Conc = 2,400 kg/m3) Most of Structural Steel falls in Mild Steel (MS)  Advantages of steels En Dus o :  High strength M  Uniformity  Elasticity Ey En  Permanence > - the state of lasting remaining unchanged  Ductility Elongation -  Toughness Energy that material absorb Disadvantages of steels  Corrosion  Fireproofing costs  Corrosion in steels  Electrochemical process  The iron is oxidized (Anodic process)  Electrons react with water and oxygen to produce hydroxyl 4OH- (Cathodic process)  At the anode, ferrous hydroxide occurs Disadvantages of steels I  Susceptibility to buckling  Steel production  This process consists of the following three phases:  reducing iron ore to pig iron  refining pig iron (and scrap steel from recycling) to steel  forming the steel into products h Iron ore Pig iron melt make it pure & alloy Source: Siam Yamato  Steel alloys  Alloy metals can be used to alter the characteristics of steel.  Alloy agents are added to improve one or more of the following properties:  hardenability  corrosion resistance  machinability  ductility  strength Source: MAMLOUK and ZANIEWSKI, (2011)  Structural steels TIS 1227-2539 Grade Maximum Composition (% by weight) Carbon Silicon Manganese Phosphorus Sulfur SM 400 0.20 0.35 0.60 to 1.40 0.035 0.035 SM 490 0.18 0.55 1.60 0.035 0.035 SM 520 0.20 0.55 1.60 0.035 0.035 SM 570 0.18 0.55 1.60 0.035 0.035 SS 400 - - - 0.050 0.050 SS 490 - - - 0.050 0.050 SS 540 0.30 - 1.60 0.040 0.040  Structural steels  Steel structures are assembly of structural steel shapes joined together by means of connections (such as riveted / bolted or welded ) according to specification/standard. Bolted connection Welded connection  Structural steels Source: aisc.org  Structural steel TIS 1227-2539 m Grade Min. yield strength (MPa) Tensile Elongation strength (%) t < 16 mm t 16 mm. (MPa) t < 5 mm. t = 5 - 16 t 16 mm. mm. SM 400 245 235 400-510 23 18 22 SM 490 325 315 490-610 22 17 21 SM 520 365 355 520-640 19 15 19 SM 570 460 450 570-720 19 19 26 SS 400 245 235 400-510 21 17 21 SS 490 285 275 490-610 19 15 19 SS 540 400 390 Min. 540 16 13 17 & steel of structure  Structural steels ASTM A36 ASTM A572 ASTM A992  Structural steels X -X  ASTM A6 Standard Shapes TIS 1227-2539  Sectional Shapes Pipes Flat bars Angles C Channel Light lip channel SQ. Tubes  Sectional Shapes Rectangular Tubes Wide Flange/H Beam Steel plates d A  d Source: Siam Yamato Steel O CTep N A. O G: By ; c : nimum diea from centroid. Guy ASTM Standard A6 https://www.aisc.org/publications/detailing-resources2/dimensioningtool/  Reinforcing steels  Grade ASTM A615  No. 3 to No. 18 (10 mm to 57 mm) Grade Yield Tensile Elongation strength strength % MPa MPa 300 300 500 11-12 420 420 620 7-9 520 520 690 6-7 Reinforcing steels  Grade (TIS)  TIS 24-2548 (Deform bar)  TIS 20-2543 (Round bar) Grade Yield strength Tensile strength Elongation MPa (kg/cm2) MPa (kg/cm2) % SR24 235 (2,400) 385 (3,900) 21 SD30 295 (3,000) 480 (4,900) 17 SD40 390 (4,000) 560 (5,700) 15 SD50 490 (5,000) 620 (6,300) 13 Physical properties of reinforcing bars grade SD40 Measured behavior Stress (ksc) Design (4000 ksc) Es=2.04x106 ksc 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 Strain (mm/mm) Stress-strain diagrams with different steel grades Reinforcing steels  Stress-strain relation of concrete 400 360 320 280 1. Initial tangent modulus 3. Tangent modulus 240 Stress (ksc) 200 160 120 80 2. Secant modulus 40 0 0 0.001 0.002 0.003 0.004 Strain (mm/mm) Concrete and reinforcing steels 4000 ksc 280 ksc Reinforced concrete structures  Cold-formed steels  Cold-formed steel is used for structural framing of floors, walls and roofs as well as interior partitions and exterior curtain wall applications. The thickness of cold- formed steel framing members ranges from 0.455 mm to 3.000 mm.  The changes of mechanical properties due to cold work are caused mainly by strain hardening and strain ageing. Source: Chajes et al., 1963 Cold-formed steels  Cold-formed steels Source: Crisinel and Marimon Source: AISC Problem Discussion Problem Discussion