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## ECIV 325

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**ECIV 325**Introduction to Steel Design Instructor Dr. Dimitris C. Rizos rizos@engr.sc.edu**GENERAL DESIGN PROCEDURES**Problem Definition Service Functions Location Surface & Subsurface Conditions Infrastructure Environmental Impact etc • Constraints • Material Availability • Zoning Requirements • Construction Expertise ...**General Design Procedures**Geometric/Architectural Design ………. Altern. 1 Altern. 2 Altern. 3 Altern. n Final Layout Floorplans Elevations etc**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**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**Define External Loads**Estimate/Assume Initial Size of Structural Elements Calculate Self Weigth Structural Analysis Select New Sizes Check Design (Codes & Specs) Safe Functional Economic NO YES O.K. Preliminary/Final Design**Structural Design**Safety Seviceability Economy Practicality**ECIV 325 OBJECTIVE**FOCUS ON DESIGN OF COMPONENTS Steel Structural Members Tension Members Compression Members (Columns) Beams Beam-Columns Connections**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)**Structural Steel - Properties**Yield Point: Stress Fy at the elastic limit Ult. Tens. Str: Fu is the maximum stress developed in the inelastic zone**Structural Steel - Properties**Residual Strain: Permanent deformation after unloading**Structural Steel - Properties**If Yield Point not Clearly Defined 0.2% Method Draw line parallel to elastic part 0.2% Strain**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**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**Structural Steel - Sections**Typical Hot Rolled Steel Shapes See AISC Manual PART 1 Section Properties and other shapes**Structural Steel - Sections**Typical Cold-Formed Light Gage Steel Shapes See LRFD Manual for other sections**Structural Steel - Sections**Built-Up Members**Structural Steel - Characteristics**Buckling: Instability due to slenderness**Structural Steel**Idealized Case: Material Properties - Uniaxial Cases Real Life: Multiaxial scenarios determine material strength UNCERTAINTIES DESIGN MUST ADDRESS UNDERSTRENGTH**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**Design Loads - Types**• Dead 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**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 40-250 psf**Snow & Ice**• Depend On • Location • Slope of Roofs Typical Variation 10 psf (45o slope) - 100 psf (North Main) • Account for • Snow Drift • Increased wind loads due to increased surface area of ice coated members**Rain Loads**More sever on flat roofs ponding Geometric Design for Draining Allow for 0.25 in/ft slope with good drainage facilities**Bridges - Traffic Loads**American Association of Highway and Transportation Officials AASHTO American Railway Engineering Association AREA • Truck and Lane Load • Impact • Longitudinal**Lateral Loads - Wind**• Depend On • 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**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.**Other Loads**Soil Pressures Hydrostatic Pressures Blast Thermal Forces Centrifugal Forces (trucks on curved bridges)**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-2006 2006 International Building Code International Code Council (formerly BOCA, ICBO, and SBCCI)**Design Loads**Real Life: Design loads difficult to predict UNCERTAINTIES DESIGN MUST ADDRESS OVERLOAD**ASSIGNEMENT**• READING • Chapter 1 • Homework • 1.5-3, 1.5-6