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Elevated Temperatures & Materials.pptx
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PR-2Elevated Temperatures
& High Strength Materials
____Design Excellence
Temperature Behaviour
____Design Excellence
L = L0 ( 1+α ΔT ) where
α = Coefficient of Expansion = 1 X 10-5 / oC for Steel = 1 X 10-5 / oC for Concrete
ΔT = Difference in Temperature ΔL/ L0 = α ΔT ( Strain ) Example : Ideally,100 oC change in Steel Section gives
0.12% Strain.
Material Behaviour - STEEL
____Design Excellence
Stress Strain Curve for Mild Steel
Yield Point & Plastic Range
Material Behaviour - STEEL
____Design Excellence
Stress Strain Curves of Steel & Mild Steel
Hooke’s Law
Stress Associated with 0.2 percent Strain is yield Stress
Temperature Behaviour - STEEL
____Design Excellence
Proportional Limit
Temperature Behaviour - ANALYSIS
____Design Excellence
P – M Relation with Temperature P= Stress X Area = (E x Strain ) X Area
= EA α ΔT M = K E I δ /L2
Where K varies with B.Cs & Joint Stiffness
P & Counteract Each Other With for Temperature Stress
Temperature Behaviour & Codes
____Design Excellence
Maximum & Minimum Temperatures are defined as per Region in IS 875 Part V .
Temperature Variation is taken from Mean Temperature to Extremity.(Except Desert Conditions)
Codal Provisions preclude temperature design with Guidelines for Geometry and detailing.
IS 800 Section 3.10.4 Indicates Stress Analysis of Structure for Temperature need not be done if provisions of code are met
Design Excellence
Temperature Behaviour & Codes
IS456 :2000 Section 27 ,45 m Maximum Length for Expansion Joint,Else refer IS 3414
Strength Variation & alloys Enhanced Physical Properties are achieved
mainly by Heat Treatment Process Addition of Elements to steel
What are the physical Properties ? 1) Strength2) Ductility3) Toughness
____Design Excellence
Metallurgic processTemperatures o C Lattice Structure Identified As
< 910 BCC ferrite
910 -1400 FCC austenite
1400-1539 BCC δ - ferrite
Body Centred Cubic
Face Centred Cubic
____Design Excellence
Crystalline Structural Variation Ferrite Pearlite Austenite
Martensite
Pearlite-Ferrite
Pearlite : Laminated mixture of Ferrite & Cementite
is hard and has low ductility Martensite : Extremely Hard & Brittle
____Design Excellence
Cooled RapidlyCooled Slowly
Heating Treatment process
Annealing Normalizing
Quenching & Tempering
____Design Excellence
Heat Treatment Process
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Heat Treatment of Steel :
1) Annealing : Steel is Heated above 910 C , held at that temperature ,
slowly Cooled in the Furnace.
2) Normalizing : Like Annealing,but Steel is Cooled at a fast rate in ambient
air temperature.
3) Quenching & Tempering
Quenching ( Oil) : Steel is water quenched at higher cooling rate
Quenching ( Water) : Steel is water quenched at even higher cooling
rate and
When Martensite is Heated to a temperature of 600 C , it results in steel
with superior strength & ductility . Therefore High Strength steels
obtained with same material
Strength Variation Grain Size & Yield Strength
Fy = Fo + K/√d
Strength is Achieved by additives to Steel1. Carbon Content
2. Micro Alloy ( Carbon Manganese Steels) with Al,V,Mo etc
3. Chromium
Examples FE490 , SAILMA. Carbon Equivalent ( CE ) :
CE of 0.43 & Above May require Preheating in the HAZ( Heat Affected Zone ) for Welds (IIW,1967)
____Design Excellence
Structural SteelsType of Steel Carbon Content Uses
Mild Steel Up to 0.1% Steel Sections in buildings , bridges etc
Medium - Carbon Steel
Up to 0.25% Boiler Plates, Structural Steel
High Carbon Steel Up to 1% Sledgehammers,mason tools,Drills,Axes etc
IS 2062 : Structural Steel Specification for Fabrication
IS 8500 : Structural Steel – MicroAlloyed( Medium and High Strength quality)
____Design Excellence
Analysis & Design Input IS 800 :2007 Section 16 :Fire Resistance , Young’s Modulus relation with
Temperature. Coefficient of Expansion for Steel above 100 oC Increases to 1.4 X 10-5 / oC
(AISC 360) IS 6533 (Part 2) : 1989 Chimneys – Fy for IS2062 Steel in relation with
temperature, till 400 oC
Example, Yield Strength at 400 oC is considered 0.5X Fy for structural Steel(fy = 250 ) EN 13084 :7 Design of Chimneys – ELEVATED temperature steel properties
If Temperature Resistant Alloy Steels are Used for Elevated temperatures then the mechanical properties are obtained from , A387 Or Equivalent
ASME Boiler & Pressure Code : 2004 part II Section D TABLE Y-1
____Design Excellence
BOLTS
For Example : A194M , Nuts are specified For High Temperature Service as :
M72 Grade 2H Heavy Hex nut shall be reheated above critical Range
Quenched in a suitable Medium ,
And then tempering at a temperature not less than 455 oC .____Design Excellence
BOLT ASSEMBLY
High Temperatu
re
A193M
BOLTS
A194M
NUTS
F436MWASH
ER
BOLT ASSEMBL
YHigh
Strength
A490M
BOLTS
A563M
NUTS
F436MWASH
ER
Structural Steel Bolts , NUTS & WASHERS for HIGH STRENGTH & HIGH TEMPERATURES
A193M - Specification for Alloy-Steel and Stainless Steel Bolting Materials for High-Temperature Service
A194M - Specification for Carbon and Alloy Steel Nuts for Bolts for High Pressure or High Temperature Service, or Both
A320M - Specification for Alloy-Steel and Stainless Steel Bolting Materials for Low-Temperature Service
A325M - Specification for Structural Bolts, Steel, Heat Treated 830 MPa Minimum Tensile Strength
A490M - Specification for High-Strength Steel Bolts, Classes 10.9 and 10.9.3, for Structural Steel Joints
A563M - Specification for Carbon and Alloy Steel Nuts F436M - Specification for Hardened Steel Washers
____Design Excellence
Codal References
Design Excellence
References AISC 360 -10 :Specification for Structural Steel Buildings
Appendix 4 BS 5950 : PART 8 Fire Resistance for structural steelwork EN 1993-1-2:2005 : Structural Fire Design Behaviour of High Strength Structural Steel at Elevated
Temperatures: Ju Chen & Ben Young ;Brian Uy, Journal of Structural Engineering,ASCE,2006
Thank You
____Design Excellence