Steel Construction Overview

1-A
STEEL CONSTRUCTION
• Plane products
• Long products
Prof. CLAUDIO BERNUZZI. / STEEL / POLITECNICO DI MILANO
Traslated by Manuel Andrés Rubiano Martin

2-A
STEEL CONSTRUCTION
• Components:
PLANE PRODUCTS

3-A
STEEL CONSTRUCTION
• Steel-concrete composite slab
• DETAIL
• Tipical synergy element • Example of curved metal deck

4-A METAL DECK
SHEET
Thickness
Distance between suports (Meters)

5-A STEEL SHEET
SHEET
Statics Features
Thickness
SHEET

6-A
STEEL-CONCRETE COMPOSITE
SLAB
Static Features of sheet

7-A
GEOMETRICAL PROPERTIES
Static Features

8-A SLAB PERFORMANCE
Useful Overload - uniformely distributed Kg/m2

9-A Long Products

10-A Long products

1-B
Breve Cenno Storico
Short historical review
Iron extraction was made for millenniums
inside partially linked-land ovens, and was
fed with bellows, (Catalan method). The
result was a doughy, fluffy, full of impurity
iron-mass. This impurity was eliminated
just by means of a patient work of cocky
(forging).
The product achieved, called forged iron is
characterized by modest mechanics
properties and it’s possible to weld it by
boiling, that means heating up the pieces
to join, and then link those ones
vigorously, by mean of hammer beating

2-B
Breve Cenno Storico
•A major boost of metallic construction sector,
was developed during the industrial revolution
from the lasts decades of 18th century.
•In 1874 in England, Henry Coart introduced a
different kind of oven (reflective oven) inside
which the uncarburation of cast-iron is made by
mean of a manual and constant mixing, aimed to
favor the contact between the fused material
with an air current. The achieved product was
doughy (puddled iron) So then, it was forged by
hand aimed to clean impurities. The quality was
improved subsequently in the lamination
process, obtained with cylinders without
channels to achieve sheets and products of
hollow or I-Shaped section.
Prof. Ing.Claudio BERNUZZI. / STEEL / POLITECNICO DI MILANO

3-B
Breve Cenno Storico
•Others improvements on the iron and steel
industry were introduced from the second half of
the 19th century. In 1856, on the occasion of the
British Society Congress to the Science
Progress, the official new of a complete system
of fast cast-iron - Steel transformation was
confirmed. (Work of the English man Henry
Bessmer). The idea was very innovative: To
blow up air directly into the fused cast iron ,
aimed to the oxygen contained on the air
could be mixed with a great part of the
present carbon on the fused material,
eliminating under the form of oxide of
carbon gaseous

4-B
Breve Cenno Storico
•The first important and documented
use of structural’s elements of cast-iron
can be found from the lasts decades of
18th century in bridges and buildings. A
relevant example is the cast-iron
bridge over the Severn river (30 Km
to Birmingham, Uk), with an arc
typology, building during 1775 and
1779. The structure is made up of 5
sharp arcs, in 30 meters span, each of
one compounded by two parts of 21
meters long and joined in keystone
without any specific joint mechanism,
exactly at the half of the arc.
Detail
Bridge over the
Severn river-
General view

5-B
Breve Cenno Storico
The Britannia Bridge
General View
Project by:Stephenson jr,Fairbairn and Hodgkinson
•Because of the
development in railway
sector there was a major
boost for the bridges
area. During 1844 and
1855 a majestic work was
made: The Britannia
Bridge over Menai River
(UK). This bridge was a
significant example of a
continuum beams
structure over 5 supports,
with the centrals spans
142 meters length
SECTION

6-B
Breve Cenno Storico
•As to the buildings sector,
the use of metallic
materials has contributed
to the diffusion of a
typological idea: the
skeletal structure. Toward
the end of 18th century
were made having
columns of cast-iron
square section, or
circulars. The made up by
fusion helped to model the
outside form of the column
and capital.
St George’s Church U.K.
Building during 1812-14
National library of Paris
Building during 1858-68

9-B Short historical review
•The first important example of a structure with
mono-dimensional elements in cast-iron(Beams
and columns) is represented by an industrial
building of seven floors in Manchester (U.K.)
built in 1807.
•At the end of the first half of 18th century, the
widespread use of cast-iron in the civil buildings
resulted not convenient resulted because of the
new age of steel. Sheets and channels in
puddled iron were available in 1820-21, and
since 1836 began the production of double T
profiles.

10-B “LA TOUR EIFFEL”
•Height: 321 meters (With antenna)
•Construction period date: During January
1887 to 15 My 1889
•1700 global technical figures
•3629 detailed technical figures
•18,038 structural elements

14-B
HOME INSURANCE BUILDING
•Built in 1883 with steel
structure on 10 floors.
• Frame with rigid beam-to-
column joints.
•Brick walls used as bracing
systems to reinforce the
structure to horizontal forces.

15-B
Mohawok Indians : Ironworkers

16-B Woolworth Building
Finished in 1913 was
the highest building on
the World, with 241
meters height

17-B Chrysler Building
1930
240 meters

18-B Empire State Building
1930
381 meters

1-C Steel as a building material
Iron-carbon alloy
1. Cast-Iron: Quantity of Carbon not greater than 1,7% (In some books
one can find as the limit value 2%)
2. Steel: Quantity of Carbon is less than 1,7%
• Very low carbon steel: (C<0,15% is also called Iron)
• Low carbon Steel: (C=0,15% - 0,25%)
• Carbon Steel (C=0,25% - 0,50%)
• High strength carbon steel (C=0,50% - 0,75%)
• Very hard strength carbon steel (C>0,75)
3.Structural steel: Quantity of Carbon 0,1% - 0,2%

Carbon increases resistance but reduces appreciably weld-ability and
ductility.
Among the elements which are not eliminated in the production process,
one can cite:
The Phosphorus and the sulfur, which are generally negative because of
increasing the fragility of steel and reducing weld -ability. (The quantity
of these ones must be not upper than 0,05%) .
Other elements generally negative because of increase the fragile-fracture
tendency are the Oxygen and the Hydrogen
Manganese and Silicon can be used to increase weld-ability and to
improve the mechanical features; Nevertheless, the carbon quantities
must be low.
Chrome increases mechanical performances and in a suitable proportion
also increases chemical features (stainless steel)
Nickel Increases mechanicals performances and decreases the
lengthening. (INVAR Steel, with a expansion coefficient extremely low)

1. ELASTC PHASE:
E,Between 190,000
N/mm2 and 210,000
N/mm2
2. PLASTIC PHASE: Final
strain between 6 and 16
times the elastic strain
limit
1. STRAIN HERDENING
PHASE: Reduced
eleastic modulus
between 4000 and
6000

4-C
Steel in accordance with
DM 9/11/1996

5-C
Steel in accordance with NTC and EC3-part1-1
Norme Tecniche per le costruzioni (1/2)

6-C
Steel in accordance with NTC and EC3-part1-1
Norme Tecniche per le costruzioni (1/2)

7-C STEEL DENOMINATION
With regard to the symbols, used to distinguish steels types, the term S indicates
structural steel, whereas numerical value represents the minimum value of
yielding tension expressed in N/mm2. Sometimes the alphanumeric figure is
complemented with followings terms:
•The letter N and M define the supplier’s features.
•The letter L is associate to minimum value of impact energy on temperatures no
lowers than -50°C
•The W letter is associate to an elevated corrosion resistance
•The Q letter and the abbreviations QL and QL1 are associates to minimum value
of impact energy on different temperatures (-20°C,-40°C,-60°C)
•The H print shows profiles with hollow section.
1.3 The Calculus method and loads combinations
According with the semi-probabilistic method, the design of structures on limited
state must be done with ultimate Limited States (SLU) as well as with service
ability (SLS) Limited States (EN 1990 – Basis of structural Design,2002).

8-C OTHER STEEL CLASSES?
Other steels classes on construction can be used if a security level can be
guaranteed with suitable theoretical and experimental information, never lower
than existing laws.
Steels products must to qualify its production following these 3 parameters:
1. Demonstration of quality in production process.
2. Internal control of quality production process trough probabilism bases.
3. Periodic checking of quality trough officials laboratories according to the Law
No 1086 of 1971

9-C STEEL PROPERTIES
DM 9/1/96
Elastic modulus: E=206000
Tangential modulus: E=78400
EC3 And NTC (§ 11.3.4.1)
Density: = ρ 7850/ kg/
Poisson Coefficient= V=0,3
Elastic modulus E= 210000
Tangential modulus= G=E
2(1+V)
Termal coefficient : α=12 x 10-6 per °C

10-C PROCESS PRODUCTION
Steel:
Steel is obtained by fusion, is found in his
basic state on ingot form; needs
particular production process to obtain
an elaborate product.
Thermal treatment: The aim is to obtain
metallurgic structures that give material
suitable mechanical features to the
foresee use.
The product can be achieved with
diversity:
1. Technique of production with traction or
compression forces: (Lamination,
Extrusion)
2. Technique of production with bending
or cut forces.

11-C LAMINATION

20-C FORMING PRODUCTION

1-D IMPERFECTIONS
The performance of steel structures and its elements depend on the
imperfections of these elements.
This term covers two kinds of imperfections:
1. Mechanical.
1. Geometrical:
• Section imperfections
• Element imperfection
• Frame imperfection

2-D Geometrical imperfections:

1. Tolerances:
• Dimensional tolerances:
The tolerances in the
dimensions of parallels
and narrows-flanged on
IPE sections profiles are
indicated in standards.

Tolerances in the dimensions of parallels and narrows flanged on IPE sections profiles are
indicated on the following table:
Before request order, Asymmetric tolerances can be agreed as far as the thickness is concerned and,
eventually also one-side tolerance, as long as tolerances don’t vary.

The length tolerances (See picture) of the IPE profile (with standard length) are
indicated on the following prospectus:
On the case of common limit displacement, the
length L corresponds to maximum use length
on the beams end (square cut)
On the case of reduced tolerances, the two
lengths L and the L maximum must be both
within the standards tolerances.
The request order must be filled with the length
tolerance demanded; in the absence of this
precision will be applied on the beams
standard length, the common limit
displacements +-100mm.
Before request order, Asymmetric tolerances can
be agreed as far as the thickness is
concerned and, eventually also one-side
tolerance, as long as tolerances don’t vary.

Shapes and positions tolerances
Vertical position tolerance:
The vertical position tolerance t (See picture) must be satisfied with the
following restrictions:

Symmetry tolerances:
The symmetry tolerance S=(b1-b2)/ 2 (see picture) must be satisfied with
the following restrictions:

Vertical position tolerance:
The vertical position tolerance t (See picture) must be satisfied with the

Tolerance of Longitudinal linearity in the beam plane:
Tolerance Longitudinal linearity in the beam plane q (See picture) and the
longitudinal linearity tolerance on the beam axis in the beam plane
must be measure on this plane and in the L length of the profile.
Tolerance of Longitudinal linearity in the strut beam must be satisfied the

Tolerance of Longitudinal linearity out of the beam plane:
The tolerance of longitudinal linearity out of the beam plane u (See
picture) and the tolerance of longitudinal linearity out of the beam plane
must be measure on the wing plane and in the length of the profile.
Tolerance of Longitudinal linearity in the strut beam must be satisfied with
the following restrictions:

12-D Frame imperfections:
• Out-of-plumb of columns
• Different column base levels
• Different member sizes
• Column out-of-plumb Equivalent
horizontal forces.

13-D General idea:
• Replacment of initial imperfactions by
equivalent horizontal forces

14-D General idea:

15-D General idea:

16-D General idea:

17-D General idea:

18-D General idea:

19-D General idea:

20-D Mechanical imperfections:
Residual stresses and non homogeneity-distributions of the
mechanical features on the transversal sections of the
product, it means a stress-state self-balanced closely linked
to industrial production process

21-D Mechanical imperfections:

22-D Cold rolled profiles

1-E Test of Features material
National and international normative regulations give by:
• UNI (Ente Nazionale Italiano di Unificazione)
• CEN (Comitato Europeo di Normazione)
• ISO (International Organization for Standardization).
1. Chemical analysis: Made on the tapping, aim to determine the carbon
percentage and the impurities of the iron-carbon alloy.
2. Macro graphic analysis: To determinate the Steel deoxidizing
percentage, that’s means, to know the weld-ability
3. Micrographic analysis: To analyze crystalline structure and grain
dimensions (Creates a relation between the material micrographic
structure with some of its mechanical features and the influence that is
been exerted by some thermal treatments on this material micrographic
structure)

2-E Normative references:

3-E Example of CE label
• CE approval mark, made with “CE”
symbol.
• Identification number of
certification organism
• Trademark and distributor address.
• Last two figures of
trademark year
• Certificate number.
• Number of European normative.
• Product description.
• Information of regulated features.

4-E Chemical analysis:
Chemical composition determined by ladle analysis must be done
satisfying EN 10025-2 to EN 10025-6 normative.

The applicable limits to the product analysis are reported on the
pertinent prospect of the normative EN 10025-2 to EN10025-6

8-E Traction test
The yielding and ultimate stress value, and
elongation percentage values , are
determinated by the stress deformation (σ-ε)
relation

9-E Traction test
Typical stress-deformation (σ-
ε) relation to construction
steels.
Ld: Distance between the fixed references
Upper and lower yielding
values

10-E Influence of the test speed

11-E
Influence of the test temperature
Influence of temperature on relation with steel type

12-E
Influence of the test temperature

13-E Compression test:
Global (Stub column test): assessment of
the relation σ-ε for the whole transversal
section. Mechanicals features of standard
material respect to profile structural’s
imperfections, that’s means the residuals
imperfections and non-homogeneity
distributions of yielding stresses of the
profile component.
Industrial shelves System: upright= profile
with thin walls, this one presents a regular
hole system to hook the beam

14-E Charpy pendular test:
Steel resilience: resistance to fragile
rupture.
The associate parameters to tenacity and
resilience are determinate by means of
pendulum machine. (Charpy pendulum)
Ep = G x (h-ho)
G=hummer weight
The resilience value depends on the relation
of Ep with machine’s test section area
The resilience value depends on machine’s
test form, and specially the type of
patterned. (Unified patterned type KV, KCU,
KEYHOLE, MESSENGER Y DVM)

15-E Bending test:
It serves to value the material capacity to
tolerate significant plastic deformations
without breaking.

16-E Hardness test:
Hardness: resistance to
mass penetration.
Hardness test: Energy
assimilation capacity to
obtain an approximate
value of the material’s
resistance.
There are different kinds
of hardness tests due to
the incisive instrument
shape (Brinell, Vickers e
Rockwell tests)
Hardness test: a)
hardness meter b) conic
penetrating instrument c)
steel-sphere penetrating
instrument

16-E Hardness test:

17-E
relationship between hardness and
traction resistance.

18-E
relationship between hardness and
traction resistance.

19-E A history case

20-E A history case

21-E A history case

22-E STEEL OR IRON?

23-E Another history case

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