1. Introduction to Steel Design
ECIV 325
Introduction to Steel Design
Instructor
Dr. Dimitris C. Rizos

2. Steel Structures

3. Steel Structures

4. Steel Structures

6. Steel Structures

7. Steel Structures

8. Steel Structures

10. GENERAL DESIGN PROCEDURES
Problem Definition
Service Functions
Location
Surface & Subsurface Conditions
Infrastructure
Environmental Impact etc
Constraints
Material Availability
Zoning Requirements
Construction Expertise ...

11. General Design Procedures
Geometric/Architectural Design
Altern. 1
Altern. 2
Altern. 3
……….
Altern. n
Final Layout
Floorplans
Elevations etc

12. General Design Procedures
Preliminary Structural Design
Altern. 1
Altern. 2
Altern. 3
……….
Altern. n
Prliminary Design: Location and arrangement of load bearing elements, columns, beams, footings etc., Sizing of structural elements for safety and serviceability
Architectural Constraints - Simplicity & Duplication - Fabrication & Construction Procedures
Economy: Add preliminary $ value to each design
Select Alternative for Final Design

13. General Design Procedures
FINAL DESIGN
Sizing of Members
Design of Details
Design Drawings* (Blueprints)
Bill of Materials
Total Cost
*Design Drawings Complete and Easy to Read
AISC: Detailing for Steel Construction
Engineering for Steel Construction

14. Preliminary/Final Design
Define External Loads
Safe
Functional
Economic
Select New Sizes NO
Estimate/Assume Initial Size of Structural Elements
Calculate Self Weigth
Structural Analysis
Check Design (Codes & Specs)
YES
O.K.

15. Structural Design
Safety
Seviceability
Economy
Practicality

16. ECIV 325 OBJECTIVE FOCUS ON DESIGN OF COMPONENTS
Steel Structural Members
Tension Members
Compression Members (Columns)
Beams
Beam-Columns
Connections

17. Sructural Steel – Typical Composition
Element
Composition %
HPS
50W and 70W
100W
Mild Steel A36
Carbon (C)
0.11 max
0.08 max
Manganese (Mn)
1.20 max
Phosphorus (P)
0.020 max
0.015 max
0.04 max
Sulfur (S)
0.006 max
0.005 max
0.05 max
Silicon (Si)
0.40 max
Copper (Cu)
0.20 min (when specified)
Nickel (Ni) -
Chromium (Cr)
Vanadium (V)
Molybdenum (Mo)
Aluminum (Al)
Nitrogen (N)

18. Structural Steel - Properties
Elastic Limit:
Transition from elastic to inelastic behavior
Yield Point:
Stress Fy at the elastic limit
Elastic Modulus:
Slope of elastic part of curve E~29,000 ksi (200,000 Mpa)

19. Structural Steel - Properties
Yield Point:
Stress Fy at the elastic limit
Ult. Tens. Str:
Fu is the maximum stress developed in the inelastic zone

20. Structural Steel - Properties
Residual Strain:
Permanent deformation after unloading

21. Structural Steel - Properties
If Yield Point not Clearly Defined
0.2% Method
Draw line parallel to elastic part
0.2% Strain

22. Structural Steel - Characteristics
Elasticity: Ability of metal to return to its original shape after loading and subsequent unloading
Fatigue: Cycling loading and unloading stresses material above its endurance limit and leads to failure
Ductility: Deformation without fracture beyond the elastic limit (ineleastic behavior)
High Ductility
Toughness: Combination of strength and ductility
High toughness

23. Structural Steel - Characteristics
Maintenance: Susceptible to Corrosion when exposed to air and water
Use paints, or weathering steels
Fireproofing: Strength reduces with increased temperature - Fireproofing required

24. Structural Steel - Sections
Typical Hot Rolled Steel Shapes
See AISC Manual PART 1 Section Properties and other shapes

25. Structural Steel - Sections
Typical Cold-Formed Light Gage Steel Shapes
See LRFD Manual for other sections

26. Structural Steel - Sections
Built-Up Members

27. Structural Steel - Characteristics
Buckling: Instability due to slenderness

28. DESIGN MUST ADDRESS UNDERSTRENGTH
Structural Steel
Idealized Case: Material Properties - Uniaxial Cases
Real Life: Multiaxial scenarios determine material strength
UNCERTAINTIES
DESIGN MUST ADDRESS UNDERSTRENGTH

29. Design Loads
Most important and difficult task is the accurate estimation of loads applied to a structure over its life
Second most difficult is to determine load combinations

30. Design Loads - Types Dead Loads Live Loads Self Weight
Loads Permanantly Attached
Walls
Floor
Roof
Plumbing
Fixtures etc
Easier to determine but are not known a priori
Live Loads
Occupancy - Floor Loads
Snow & Ice
Rain
Traffic Loads for Bridges
Impact Loads
Lateral Loads
Wind
Earthquakes
Other

31. Occupancy - Floor Loads
Specified by building codes
Check Local (state) specs and requirements
In the absence of any available codes refer to:
ASCE Standard 7 Minimum Design Loads for Buildings and Other Structures SEI/ASCE 7-05
Typical Variation
psf

32. Snow & Ice Depend On Typical Variation Account for Location
Slope of Roofs
Typical Variation
10 psf (45o slope) psf (North Main)
Account for
Snow Drift
Increased wind loads due to increased surface area of ice coated members

33. Rain Loads More sever on flat roofs Geometric Design for Draining
ponding
Geometric Design for Draining
Allow for 0.25 in/ft slope with good drainage facilities

34. Bridges - Traffic Loads
American Association of Highway and Transportation Officials
AASHTO
American Railway Engineering Association
AREA
Truck and Lane Load
Impact
Longitudinal

35. Lateral Loads - Wind Depend On Effects Reference geographic location
height above ground
types of terrain including surrounding buildings
percentage of openings
Effects
Severe Effects on tall buildings & long flexible structures
Reference
ASCE Wind Forces on Structures, Transactions ASCE 126
Uniform Building Code

36. Lateral Loads - Earthquakes
Depend On
geographic location - area seismicity
soil conditions
dynamic properties and characteristics of structure
Analysis & Design
Dynamic
Equiv. Static :Horizontal Loads associated to the mass of the structure
Bracing, Special Connections, Design for Shear etc.

37. Other Loads
Soil Pressures
Hydrostatic Pressures
Blast
Thermal Forces
Centrifugal Forces (trucks on curved bridges)

38. Specifications for Steel Railway Bridges (AREA 1980)
Loads - References
ASCE Minimum design loads for buildings and other structures SEI/ASCE 7-05 NY
Specifications for Steel Railway Bridges (AREA 1980)
Standard Specifications for Highway Bridges (AASHTO)
ICC IBC International Building Code International Code Council (formerly BOCA, ICBO, and SBCCI)

39. DESIGN MUST ADDRESS OVERLOAD
Design Loads
Real Life: Design loads difficult to predict
UNCERTAINTIES
DESIGN MUST ADDRESS OVERLOAD

40. ASSIGNEMENT
READING
Chapter 1
Homework
1.5-3, 1.5-6