Lecture 5 Steel Construction (Latest)(2)

8/18/2019 Lecture 5 Steel Construction (Latest)(2)

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Title Slide

Structural Steel

Members and Systems Assoc. Prof. Dr. Fadzil Hassan


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Overview of

Structural Steel Members and Systems

A x i a l l y L o a d e d

S p a n n i n

g M e m b e r s

Steel Piles

Lintels

Steel Trusses

Steel Beams / Girders

Open Web Joists / Girders

Linear Configurations

Space Frames

Decking / Diaphragms

Planar Members and Configurations

Steel Bracing

Steel Columns

CONTENTS

CONTENTSStructural Steel Members and Systems |


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CHOICE OFCONSTRUCTION

MATERIAL

• Steel

• Reinforced concrete

• Timber (domestic)

• Aluminum alloy

The choice:

• Availability of material

• Cost

• Speed of erection

• Possibility of standardizing the

sizes of the structural

members

• Size and nature of site

• Fire resistance required

Steel Structures | Overview


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Comparison/similarities:

Steel Concrete

Site

consideration

Made under factory

condition – BS

Fabricate “off-site”

Strict supervision on

site

Manufacturing on

site

Cost and

speed of

erection

Erection by skilled-

labour, quickly &

accurately

Early completion but

may be limited due to the

large number of

complicated connections.

Combination or

skilled & unskilled

Site space required

for storage & mixing

Cheaper in cost but

longer in construction



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Comparison/similarities:

Steel Concrete

Designconsideration

Extension – need to

expose by the removal

of any fire-resisting

casing

Flexibility in design-monolithic in nature &not confine to standard

sections but limit to the

cost of formwork



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Manufacturing: Hot Rolled & Cold Rolled Steel Sections


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Steel as a material:- High strength: weight ratio- Hot rolled and cold rolled sections- Loses strength rapidly in fires- Liable to corrosion- Carbon steel (common strength grade 36,000psi)- High strength steel (50,000 psi)

• Alloys:- Aluminum: improve surface hardening- Chromium: Increase hardness and corrosion resistant- Copper: Increase hardness and corrosion resistant- Manganese: Promotes hardness and wear resistance- Molybdenum: Increase strength and corrosion resistance- Nickel : Increase tensile strength and corrosion resistance

- Tungsten : Improve strength retention at high temperatures



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Hot Rolled Steel Sections


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Hot Rolled Steel Sections:

•Process where large pieces of metal, are heated

and then deformed between rollers to form thinner

cross sections.

•Shapes: Universal Columns, Universal Beams,

Tees, Channels, Angles, Pound, Rectangular, Boxed,

Plates.

• Mainly used for heavy construction – primary

elements of large buildings (heavy loading)

http://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Metal


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Universal BeamUniversal Beam & Column Shapes

Angles U Channels


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Cold-Rolled Steel Section Shapes


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Steel Structures are skeletal frame systems.

Steel frames can handle heavy loadsand long spans.

Steel is an ideal material for tension applications.

Steel is also very strong in shear.

Field welding is more costly than shop welding.

Field welding is more costly than field bolting.

Steel is fabricated in the shop and assembledon the site (not a wet trade).

Special attention is required to protect steelstructures against fire and corrosion.

Accuracy, precision and tolerancesare very high in steel construction.

OVERVIEW


Structural Steel Members and Systems |


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Joints and connections are particularly vulnerable and must be designed carefully.

Rigidity of the frame must be secured against buckling (unlike wood and concrete,steel members are typically slender).

Lateral loads must be resisted through the use of diaphragms, rigid connections,bracing or shear walls.

Gravitational loads are resisted in roof / floor decking, joists, beams, girders,columns and walls.

OVERVIEWStructural Steel Members and Systems |


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Steel Welding


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Bolts


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STRUCTURAL STEEL CONNECTORS

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There are four basic connectors used in making structural steel connections.

They are:

- bolts,

- welds,

- pins,and

-rivets.


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Rivets


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Long span system

Light / uniform roof loads

Works best for square bays, but canaccommodate highly irregular configurations

Visually rich, uniform in all directions

Usually left exposed to express visual richness

Linear members - all same size

Essentially a space frame is a 3-dimensional truss,in other words, two triangulated grids

Depth is constant and equals plan cell dimensions

Cross-Sectional shape : Tubular (Pipe) in shape

Space frames are visually rich, light,and span great distances.

SPACE FRAMES

Steel Structures | Space Frames

Structural Steel Members and Systems | 19


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Cell configuration: tetrahedral, pyramidal

Typical modules: 4’, 5’, 8’, 12’

Overhang: 1/4 span

Joints: balls / socket - all the samemechanically fastened - bolted / welded / screwed

Different support conditions affect the depth

Column support - single-point- multi-point.

Perimeter support - beam / girder- wall.

Multi-point column support Perimeter SupportMulti-point column support

Space frame assembly (courtesy of Douglas Steel)

20SPACE FRAMESStructural Steel Members and Systems |


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SPACE FRAMESStructural Steel Members and Systems | 21


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Fabricated from copper-alloy steel.

Deck is galvanized or painted againstmoisture and condensation.

May be corrugated or cellular.

Addition of a straight piece of sheet metalat the bottom can turn corrugations intoelectric / information raceways.

Serves as a platform during construction.

Deck transfers a uniform load to the beam

Shear studs make the concrete deck and the steel beamact together. This is called composite action

Steel | Decking and Diaphragms

DECKING AND DIAPHRAGMSStructural Steel Members and Systems |


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Serves as formwork and reinforcing for concrete.

Composite construction with concrete.

Welded Wire Mesh / Fabric used in composite construction for

moederating temperature and shrinkage steel.

Deformations on the surface of the metal deck allow the concrete

to bond to the decking.

Perforations in roof deck allow steam of hydration to escape.



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Shear Studs fastened to the top flange of thesupporting beam or girder will create a lockbetween the concrete and the top flange.

This creates a composite action in which theconcrete deck and the supporting member actas a unit.

When concrete is poured in a metal deck,it is forms a rigid composite structure (diaphragm)

and is enables the floor to lateral loads.

Pouring concrete on deck gives a rigid diaphragm.



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Flexible diaphragms are metal decks that do NOT

have concrete poured in them.

Roof diaphragms are often constructed as flexible

diaphragms (rigid insulation, water-proof

membrane, ballast, etc…without concrete).

As long as a roof is constructed of panels andis not “monolithic”, then the diaphragm is

considered flexible.

DECKING AND DIAPHRAGMS

Flexible diaphragms


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Lightweight structure, capable of long spans.

Repetitive members that are closely spacedand that support uniform loads.

Support members may be beams,girders, or load-bearing walls.

Shop fabricated, welded very quickly.

Bar joists have standardized span, depth,member size, dead and live load capacity.

Span of bar joists depends on: depth, topand bottom chord areas, web areas,configuration, and deck load.

Spacing of bar joists depends on the

span capability of the deck (gauge of deck,spacing, and depth of corrugations).

Ceiling may be hung from bottom chord.

Integration with HVAC - could run parallel,in between, or perpendicular to bar joists.

Bar joists support uniform loads.

OPEN WEB JOISTS / GIRDERS

The depth of the bearing seat is variable and depends

on the joist configuration and type of support

Steel Structures | Open Web Joists / Girders


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Closer spacing allows shallower floor / roof thickness

Fire rating depends on floor / ceiling material.

Bearing length varies with type and size of openweb joist

Horizontal or diagonal bridging to prevent lateralmovement of top and bottom chords.

Joist span and chord size determine

bridging requirements (10’

-15’

c/c. max).

Horizontal bridging must be top and bottom.

Top chord overhangs are possible.

Horizontal bridging of top and bottom chords.

Diagonal bridging between top and bottom

chords.

OPEN WEB JOISTS / GIRDERSStructural Steel Members and Systems |

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Top and bottom chords for all bar joists in all series are a pair of angles.

8 - 24 Deep 32 - 36 Deep

Typical Web

a Round Bar (Rod)

may also be Crimped Angle

LH - Series DLH - Series

LH & DLH SERIESK -SERIES

Shortspans Longspans

Typical Web

Crimped Angle / Lighter loads

Double Angle / Heavier loads

G - SERIES

Supports other joists

Typical Web

Double Crimped Angles

K-Series G - Series

OPEN WEB JOISTS / GIRDERSStructural Steel Members and Systems |

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29OPEN WEB JOISTS / GIRDERSStructural Steel Members and Systems |

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Standard depth ranges from 4” - 44”.

Steel beams and girders may receive uniformlydistributed or concentrated loads.

A steel girder is a large member that supportsother beams, joists or decking.

Increasing the depth of a beam, increases

its section modulus which improves its abilityto withstand bending moments.

Bar joists receive a uniform load from the deck. Beamreceives a uniform load from the bar joists and deliversa concentrated load to the column.

Girder supports loads from decking , bar joists or otherbeams.

Coped Flanges Coped Flanges

Steel Structures | Beams / Girders

BEAMS / GIRDERSStructural Steel Members and Systems |

W Sections S Sections

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All physical dimensions andproperties of steel shapes are

listedin tables in the SteelManufacturersManual.

The further the flanges are

from each other (deeperbeam), the larger the bendingmoment capacity of thesection.

Beams that have a thin web or

a narrow flange aresusceptible to lateral buckling.


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In a wide flange beam or girdersubjected to downward gravitationalloads, the top flange is in compressionwhile the bottom flange is in tension.

The thicker and deeper the web,the larger the shear capacity of theshape.

If the web of a member is slender for theconcentrated load it supports, stiffeners

are added to prevent the web fromcrippling.Stiffeners prevent buckling of the web


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The wider and / or thicker theflanges, the larger the abilityof the structure to

withstanding bendingmoment forces.

When deck is parallel to beam compression flange, no lateralsupport is provided.


When the deck is perpendicular to the beam flange, lateral support is provided.

Since the beam is perpendicular to the girder flange, they provide lateral support.

BEAMGIRDER

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Steel Fireproofing

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Fireproofing Materials

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http://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpghttp://upload.wikimedia.org/wikipedia/en/f/f4/Unitherm2.jpghttp://upload.wikimedia.org/wikipedia/en/a/a0/Unitherm1.jpg


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Fire Protection for Steel

•

Fire protection in a building, offshore facility or a ship, is asystem with equally important components, including:

• Active fire protection, which is detection and suppressionby automatic or manual means

• Passive fire protection, which is compartmentalisation ofthe fire through the use of walls and floors, and theircomponents

- proven to bear a prescribed fire-resistance rating onthe basis of fire testing and product certification,

- organised into fire compartments, which may consist ofone or more rooms or floors,

- allowing emergency evacuations and protection ofcritical building components, such as an area of refuge

Y

http://en.wikipedia.org/wiki/Compartmentalisationhttp://en.wikipedia.org/wiki/Compartmentalisation


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Fire Rating

• A fire-resistance rating typically meansthe duration for which a passive fire

protection system can withstand a standard

fire resistance test.

• This can be quantified simply as a measure

of time, or it may entail a host of other

criteria, involving other evidence offunctionality or fitness for purpose.

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http://en.wikipedia.org/wiki/Passive_fire_protectionhttp://en.wikipedia.org/wiki/Passive_fire_protectionhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Fire_testhttp://en.wikipedia.org/wiki/Fire_testhttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Passive_fire_protectionhttp://en.wikipedia.org/wiki/Passive_fire_protection


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Fireproofing structural steel

• In order for a fireproofing product to qualify for a

certification listing of structural steel, through a fire

test, the critical temperature is set by the national

standard, which governs the test.

• In Japan, this is below 400°C. In China, Europe

and North America, it is set at ca. 540°C. The time

it takes for the steel element that is being tested to

reach the temperature set by the national standarddetermines the duration of the fire-resistance rating.

Y

http://en.wikipedia.org/wiki/Japanhttp://en.wikipedia.org/wiki/Chinahttp://en.wikipedia.org/wiki/Europehttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/North_Americahttp://en.wikipedia.org/wiki/Europehttp://en.wikipedia.org/wiki/Chinahttp://en.wikipedia.org/wiki/Japan


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Fireproofing structural steel

•

Care must be taken to ensure that thermalexpansion of structural elements does notdamage fire-resistance rated wall and floorassemblies.

• Penetrants in a firewalls and ferrous cabletrays in organic firestops should be installedin accordance with an appropriate

certification listing that complies with thelocal building code.

Y

http://en.wikipedia.org/wiki/Thermal_expansionhttp://en.wikipedia.org/wiki/Thermal_expansionhttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Penetranthttp://en.wikipedia.org/wiki/Firewall_(construction)http://en.wikipedia.org/wiki/Cable_trayhttp://en.wikipedia.org/wiki/Cable_trayhttp://en.wikipedia.org/wiki/Firestophttp://en.wikipedia.org/wiki/Certification_listinghttp://en.wikipedia.org/wiki/Building_codehttp://en.wikipedia.org/wiki/Building_codehttp://en.wikipedia.org/wiki/Building_codehttp://en.wikipedia.org/wiki/Building_codehttp://en.wikipedia.org/wiki/Certification_listinghttp://en.wikipedia.org/wiki/Certification_listinghttp://en.wikipedia.org/wiki/Certification_listinghttp://en.wikipedia.org/wiki/Firestophttp://en.wikipedia.org/wiki/Cable_trayhttp://en.wikipedia.org/wiki/Cable_trayhttp://en.wikipedia.org/wiki/Cable_trayhttp://en.wikipedia.org/wiki/Firewall_(construction)http://en.wikipedia.org/wiki/Penetranthttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Fire-resistance_ratinghttp://en.wikipedia.org/wiki/Thermal_expansionhttp://en.wikipedia.org/wiki/Thermal_expansionhttp://en.wikipedia.org/wiki/Thermal_expansion


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Fireproofing structural steel• Structural steel requires external insulation

(fireproofing) in order to prevent the steel fromweakening in the event of a fire.

• When heated, steel expands and softens,eventually losing its structural integrity. Given

enough energy, it can also melt.

• Heat transfer to the steel can be slowed by the useof fireproofing materials. While concrete structures

that comprise buildings are able to achieve fire-resistance ratings with out additional fireproofing,concrete can be subject to severe spalling,particularly if it has an elevated moisture content.

AY


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Thank you

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