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Structural Design- Steel
SDS443
Topic 1: Structural Design Basics
Prepared by Maura Lecce
Fall 2016
Structural Steel Design
• Brief Overview of:
– Design Process
– Construction Process
Design Process - Overview
• Structural designer endeavors to provide a
structure that is:
– Safe, reliable and satisfactorily performs the
function for which it was intended
– Economical to build and maintain
– Aesthetically pleasing
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Design Process - Overview
• Owner identifies a need for a structure and
arranges financing
• Architect/Engineer becomes familiar with
building by-laws, building codes to ensure
health and safety requirements are met
• Geological/geotechnical investigations to
determine foundation type appropriate for
site and structure
Design Process - Overview
• Structural designer investigates the site
conditions
• Form, shape, size of structure is determined
Design Process - Overview
• Probable loads (wind, earthquake, occupancy,
etc) must be estimated
• Suitable structural material is selected
(consider required performance, life-cycle
cost, supply, transportation construction).
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Design Process - Overview
• Various structural systems are compared
• Structural analysis is performed to determine
forces on structural members
• Drawings and specifications
Construction Process - Overview
• Fabrication
– Interpretation of structural drawings and
preparation of shop fabrication and field erection
drawings (sequence of placing steel)
Construction Process - Overview
http://www.daysteel.co.uk
www.waltersinc.com
– Procuring material/cutting (flame-cut, saw-cut,
cut by heavy shears, drilled or punched holes
/assembling/fastening (bolting, welding) /shipping
material
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Construction Process - Overview
• Delivery of steel assemblies (in stages)
• Steel is organized on site
Construction Process - Overview
• Erection of Structural Steel
– Often requires further calculations to ensure adequate
safety during erection of the steel
– Strength/stability of structures must be considered during
the construction phase.
Construction Process - Overview
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Construction Process - Overview
• Inspection
– Fabricators have quality control programs to inspect the
steel before shipment
– Designer will inspect the structure to ensure it has been
fabricated and erected in accordance to specifications and
drawings.
Codes, Specifications and Standards
• Ontario Building Code (OBC)/National Building
Code of Canada (NBCC)
– Contains loading information
• wind load, snow load, earthquake load for a particular
locality
• Occupancy loads, minimum specified live loads (area
loads and point loads)
– Rules for applying loads to buildings for analysis
– Division B – Part 4 is used for structural design
Codes, Specifications and Standards
• Specifications
– Project specifications and drawings
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Materials to be used
Structural steel members to be used
Methods of joining members
General instructions for construction
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Codes, Specifications and Standards
• Standards
– Governs quality of steel
– Dimensions (eg. Size of beam, dimension of
threads on bolts)
– Canadian Standards Association (CSA)
– American Society for Testing and Materials (ASTM)
– American Welding Society (AWS)
Codes, Specifications and Standards
• Canadian Standards Association
– Buildings: CSA S16 – 14 “Design of Steel
Structures”
– Welded Structures: CSA – W59 “Welded Steel
Construction (Metal Arc Welding)
– Steel: CSA-G40.20/G40.21-04 “General
Requirements for Rolled or Welded Structural
Quality Steel / Structural Quality Steel”
– Cold-formed steel: CSA-S136 “Cold Formed Steel
Structural Members
Handbook of Steel Construction
• Published by the Canadian Institute of Steel
Construction (Required for this course)
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Handbook of Steel Construction
– Part 1: Standard CSA – S16 – 14 “Design of Steel
Structures”
– Part 2: Commentary – provides interpretation of CSA
– S16 - 14
– Part 3: Connections and Tension Members - Design
examples, tables, dimensions for connections and
tension members.
– Part 4: Compression Members - Design examples,
tables, for compression members (columns and beam
columns)
– Part 5: Flexural Members - Design examples, tables for
flexural members (beams), beam diagrams and
formulae
Handbook of Steel Construction
– Part 6: Properties and Dimensions - Structural
steel material standard, composition, standard
mill practice, properties and dimensions of
structural steel shapes, detailing data, design dead
loads of materials
– Part 7: Miscellaneous - CISC Code of Standard
Practice for structural steel, Sheet products, Loads
for materials, conversion factors, geometric
properties, and more...
– Part 8: Index
Loads on a Structure
• What are the loads (and potential loads) on a
structure?
– Basic load categories are listed in the NBCC/OBC
• How are the Loads Combined?
– Rules for combining loads are given in the
NBCC/OBC
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Loads on a Structure
• The Ontario Building Code (OBC) specifies the
types of loads to be considered on a structure
– D - Dead Load – self-weight of all structural
material, cladding, roofing material, mechanical
ducts, electrical etc. Permanent loads of all
building components
• Dead Loads for various materials are provided in the
Steel Handbook – pg. 7-69
Loads on a Structure
– L - Live Load – occupancy (ex. people), cranes,
variable loads
• OBC specifies minimum values of live load (see handout
for examples)
Loads on a Structure
– S - Snow Load – variable load due to snow
including ice and rain, variable load due to rain
• OBC has climatic data (see handout for examples). OBC
rules for calculating S.
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Loads on a Structure
– W - Wind Load– variable load due to wind
• OBC rules for calculating W
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www.payhembury-weather.co.uk/
Loads on a Structure
– E – Earthquake Load
• Depends on site conditions, structure type - OBC rules
for calculating E
– T – effects due to contraction expansion due to
temperature changes, moisture changes, creep
etc.
– P – permanent effects caused by prestress
– H – permanent load due to lateral earth pressure
(incl. Groundwater).
– Other loads
Loads on a Structure
• In this course, we will typically consider:
– Dead Loads
Loads act downwards (gravity
– Snow Loads
loads)
– Live Loads
– Wind Loads (acting perpendicular to a surface)
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Limit States Design
Limit States Design – Definition
• Def’n ”Those conditions of a building structure that
result in the building ceasing to fulfill the function for
which it was designed.”
• ULTIMATE LIMIT STATES – safety
• SERVICEABILITY LIMIT STATES - serviceability
• FATIGUE LIMIT STATES - fatigue
• All limit states must be satisfied.
Limit States Design
• Ultimate Limit States (concerning safety)
– Loads are factored and combined according to
OBC.
• Check for Strength (also overturning, sliding, fracture)
Limit States Design
• Ultimate Limit States (concerning safety)
Check that:
Factored Resistance ≥ Effect of Factored Loads
For example: consider the design for a steel bar subject to
tension:
Tr = Factored tensile resistance = φs AFy
Resistance factor for steel = φs = 0.9
Tf = Factored tensile load due to applied factored loads
Tr ≥ Tf
φs AFy ≥ Tf
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Limit States Design
• Ultimate Limit States (concerning safety)
(for some steel deck and joists we will be using tabulated
technical data)
Limit States Design
• Serviceability Limit States (concerning
serviceability)
– Check under unfactored loads
• Check deflections (also vibration, permanent
deformations)
• In this course, check that:
Max. Actual vertical deflection ≤ Max. allowable vertical
deflections
• Page1-184 Table D.1 information on the Deflection
Criteria for steel structures
• (use technical data for steel deck and joists)
Limit States Design
• Importance Category applied to Snow,
Wind (and Earthquake Loads) per
NBCC/OBC
– Calculations for S, W, (and E) will be influenced
by the Importance of the building.
– Greater safety factor applied to calculation of S,
W and E for strength and stability
considerations (High/Post-disaster category).
– See also Clause 6.2.2 p. 1-39 of S16-14 (Part 1
of the Handbook)
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