Session T02 2/22

Design of Structures 2020/2021José Oliveira Pedro

Session T02 1/22PROPERTIES OF STRUCTURAL MATERIALS

• STRUCTURAL STEEL

• CONCRETE

• REINFORCING STEEL

• PRESTRESSING STEEL

• STONE AND MASONRY

• TIMBER

• COMPOSITES ‐ GFRP, CFRP

• GLASS

• ALUMINUM ...


Session T02 2/22PROPERTIES OF STRUCTURAL STEEL

Steel gradeYield strength [MPa]

Ultimate tensile strength [MPa]

𝑡 16𝑡 16

40𝑡 40

63𝑡 63

80𝑡 80

100𝑡 100

150𝑡 3

𝑡 3100

S235 𝟐𝟑𝟓 225 215 215 215 195 360 360

S275 𝟐𝟕𝟓 265 255 245 235 225 430 410

S355 𝟑𝟓𝟓 345 335 325 315 295 510 470

S420 𝟒𝟐𝟎 400 390 370 360 340 520 520

S460 𝟒𝟔𝟎 440 430 410 400 380 540 540

Nota : Values depending on thickness (t ) in [mm], according to the NP EN 10025‐2(for grades S235, S275 and S355) and NP EN 10025‐3 (for grades S420 and S460).

Nota : Tubular profiles can be:Hot rolled – Norma NP EN 10210Cold‐formed – Norma NP EN 10219


Steel gradeYield strength [MPa]

Ultimate tensile strength [MPa]

𝑡 16𝑡 16

40𝑡 40

63𝑡 63

80𝑡 80

100𝑡 100

150𝑡 3

𝑡 3100

S235 𝟐𝟑𝟓 225 215 215 215 195 360 360

S275 𝟐𝟕𝟓 265 255 245 235 225 430 410

S355 𝟑𝟓𝟓 345 335 325 315 295 510 470

S420 𝟒𝟐𝟎 400 390 370 360 340 520 520

S460 𝟒𝟔𝟎 440 430 410 400 380 540 540


Density ρ 7700 a 7850 kg/m3

Modulus of elasticity 𝐸 210 GPa

Poisson coefficient 𝜈 0,3

Distortional modulus 𝐺 81 GPa

Linear thermal coefficient 𝛼 12 10 °C

γM,s =1,00Nota : Values depending on thickness (t ) in [mm], according to the NP EN 10025‐2(for grades S235, S275 and S355) and NP EN 10025‐3 (for grades S420 and S460).



Properties of hot‐rolled and cold‐formed profiles, plates and tubes – prEN 1993‐1‐1:2019



MATERIAL TOUGHNESS – Carbon steels exhibit arelatively ductile behaviour in tensile tests performed at"normal" temperature, being also noted that ductility ishigher the lower the steel grade.

However, the same steel material may show a fragilebehaviour in conditions of low ambient temperature andhigher deformation speed (e.g. due to intense impact actions)or in situations with a significant stress concentration (e.g.welded connections, due to the effect of residual stressesinstalled after welding).


Session T02 6/22

Charpy impact testaccording to NP EN 10045‐1

MATERIAL TOUGHNESS –The tenacity of a steel corresponds to its ability to resist to crack propagation.

Tenacity is generally assessed through the "Charpy impact test", in which a standard test prototype, with a V notch in the mid‐span section, is subject to the impact of a pendulum hammer.

PROPERTIES OF STRUCTURAL STEEL


Session T02 7/22

MATERIAL TOUGHNESS –The recorded value of the deformation energy of the specimen, 𝐾𝑉, at a certain temperature at which the test is carried out, shall be taken as a measure of the tenacity of the steel.

In steels covered by NP EN 10025‐2, the tenacity quality is expressed by the designations "JR", "J0", "J2" and "K2", inwhich the letters "J" and "K" indicate 𝐾𝑉 ≥ 27 J and 𝐾𝑉 ≥ 40 J, respectively, and "R", "0" and "2" refer to atemperature of +20 °C (Room temperature), 0°C and – 20°C, respectively.

Ex: "J2" steel, must have a deformation energy of at least 27 J in the Charpy impact test carried out with a roomtemperature of 𝑇 = –20 °C.

Aço “J2”

= –20°C

For fine‐grained steels (“N”, “NL”, standard NP EN 10025‐3), and the steels with thermomechanical rolling (“M”,“ML”, standard NP EN 10025 4), due to its microscopy and manufacturing process, show greater ductility, tenacity andweldability.



Session T02 8/22

Complete designation of structural steelsaccording to the standard ‐EN 10027‐1:2005



Session T02 9/22

FATIGUE – Deterioration process characterized by the formation and propagation of cracks as a result of installed stressranges. In most cases, the problems in the performance of older steel structures are due to insufficient fatigueresistance, as is the case with several bridge decks. There are also numerous reported cases of fatigue problems incranes, lift suspension cables, …

The experience of fatigue problems usually results from the combination of several factors, especially if the followingaspects occur:

• construction details or joints that promote the concentration of stresses,• cycle loads of high magnitude during a long period of time that result in a high number of stress ranges withsignificant amplitudes, i.e. ∆𝜎 = 𝜎max – 𝜎min.


∆𝜎


Session T02 10/22

C

2x106 5x106

R

1m=3

N 2x106 5x106

1m=3

N100x106

1m=5

Constant amplitude Variable amplitude

Cut of limit

R

C

D

L

D

“FATIGUE CURVES “ – The performance of the steel detail in terms of fatigue is usually characterized by resistance curves called Wöhler curves (S‐N curves), which provide, for calculation purposes, the maximum amplitude of the stress ranges (in the case of normal stresses, indicated by ∆𝜎R) which can be applied, depending on the number of cycles (𝑁), without the event of fatigue damage in the steel detail.

These curves, usually represented in the form (log ∆𝜎R)‒(log 𝑁), result from test specimen tests in which the number of cycles is recorded until the failure (𝑁) for constant‐amplitude stress ranges.

𝑁Ri



Session T02 11/22

Fatigue Category details and fatigue resistance curves



C

2x106 5x106

R

1m=3

N 2x106 5x106

1m=3

N100x106

1m=5

Constant amplitude Variable amplitude

Cut of limit

R

C

D

L

D

Session T02 12/22

“FATIGUE CURVES“ – Although simplified fatigue safety verification can be done by assuming cyclic stresses of constantamplitude. In fact, in a steel structure details will generally be subject to stress ranges with variable amplitude.

In this situation, the verification becomes more complex, and it is necessary to evaluate the number of times 𝑁Ei overthe design life of the structure that a certain stress range occurs ∆𝜎i , and using to the fatigue curve to know themaximum number of times that this stress range would cause the structure collapse 𝑁Ri by fatigue. Using the Palmgren‐Miner rule as the Damage Law, there will be an accumulated damage 𝐷 given by:

𝐷 𝑁 𝑁

1,0

Damage Law ‐ Palmgren‐Miner rule

∆𝜎i

𝑁Ei 𝑁Ri

𝑁Ri



Session T02 13/22CONCRETE PROPERTIES

Density ‐ normal concreteρ 2400 kg/m3 simple concreteρ 2500 kg/m3 reinforced concrete (1 a 2% reinforcement)

Modulus of elasticity 𝐸 variable ("function of the concrete strength class")

Poisson coefficient 𝜈 0,2 (uncracked concrete) 𝜈 0 (cracked concrete)

Distortional modulus 𝐺 Variable [ 𝐺 = 𝐸 /2 (1+𝜈) ]

Linear thermal coefficient 𝛼 10 10 °C

Pier and Wall

Beams and slabs


Session T02 14/22

Compressive strength

Concrete class C20/25 C25/30 C30/37 C35/45 C40/50 C45/55 C50/60

𝑓 [MPa] 20 25 30 35 40 45 50

𝑓 [MPa] 28 33 38 43 48 53 58

𝑓 [MPa] 2,2 2,6 2,9 3,2 3,5 3,8 4,1

𝐸 [GPa] 30 31 33 34 35 36 37

𝜀 (‰) 2,0 2,1 2,2 2,25 2,3 2,4 2,45

𝜀 (‰) 3,5 3,5 3,5 3,5 3,5 3,5 3,5

at 28 days

𝑓cd 𝑓ck 𝛾M,c

γM,c =1,50

CONCRETE PROPERTIES

Pier and Wall

Beams and slabs


c1 cu1

fcm

0,4 fcm

Ec = tan( )

fctm

Session T02 15/22

Tensile strength

at 28 day

Concrete class C20/25 C25/30 C30/37 C35/45 C40/50 C45/55 C50/60

𝑓 [MPa] 20 25 30 35 40 45 50

𝑓 [MPa] 28 33 38 43 48 53 58

𝑓 [MPa] 2,2 2,6 2,9 3,2 3,5 3,8 4,1

𝐸 [GPa] 30 31 33 34 35 36 37

𝜀 (‰) 2,0 2,1 2,2 2,25 2,3 2,4 2,45

𝜀 (‰) 3,5 3,5 3,5 3,5 3,5 3,5 3,5

𝑓 , max 1,6 ℎ ; 1,0 · 𝑓(ℎ in [m])

CONCRETE PROPERTIES

Pier and Wall

Beams and slabs


Session T02 16/22

Regarding the conditions of exposure to environmental actions, NP EN 206‐1 defines the following types of exposure classes:

• X0 class relating to the absence of risk of corrosion or attack,

• XC (1 a 4) classes for the risk of carbonation‐induced corrosion,

• XD (1 a 3) classes for the risk of chloride‐induced corrosion not from seawater,

• XS (1 a 3) classes for the risk of chloride‐induced corrosion of seawater,

• XF (1 a 4) classes related to ice/defrost attack,

• XA (1 a 3) classes related to chemical attack.

CONCRETE PROPERTIES

Pier and Wall

Beams and slabs


Session T02 17/22

Evolution of concrete properties during time

𝑓 𝑡 𝛽 𝑡 · 𝑓

if t 28 days 𝑓 𝑡 𝛽 𝑡 · 𝑓

if t 28 days 𝑓 𝑡 𝛽 𝑡 / · 𝑓

𝐸 𝑡 𝛽 𝑡 , · 𝐸

Age [days] 3 7 14 28 365 18250

Type of

Cement

42,5R , 52,5R ou 52,5N 0,66 0,82 0,92 1,00 1,16 1,21

32,5R ou 42,5N 0,60 0,78 0,90 1,00 1,20 1,27

32,5N 0,46 0,68 0,85 1,00 1,32 1,44

𝛽 𝑡 Hardening coefficient

Creep and Shrinkage of the concrete during time

𝜀 𝑡, 𝑡 𝜑 𝑡, 𝑡 ·𝜎𝐸

𝐶𝑟𝑒𝑒𝑝 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡𝑡 ≫ 𝜑 𝑡, 𝑡 = 1.5 to 3.0𝑆𝑟𝑖𝑛𝑘𝑎𝑔𝑒 𝑠𝑡𝑟𝑎𝑖𝑛 ≫ 𝜀 𝑡 = -20 to -40 x 10-5

Shrinkage of concrete corresponds to the decrease in the

dimensions of concrete parts, in the absence of

temperature variations and applied stresses, as a result

essentially of the migration of the water through the

hardened concrete.𝑖𝑛𝑠𝑡𝑎𝑛𝑡𝑑𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛

𝑐𝑟𝑒𝑒𝑝 𝑑𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛

CONCRETE PROPERTIES


Session T02 18/22PROPERTIES OF STEEL BARS FOR REINFORCED CONCRETE ELEMENTS

Mechanical properties of reinforcing steels

aço laminado a quente

yd s

s

fyd

s Es s

a) bilinear model with hardening

b) elastic‐perfectly plastic model

Es 200 GPa

Es 200 GPa

γM,sc =1,15

𝑓 𝑓

γM,sc

Parameter Ductility class𝑓 [MPa]

A B C

𝑓/𝑓 1,05 1,081,151,35

B400 ⇒ 400 MPa

𝜀 % 2,5 5,0 7,5 B500 ⇒ 500 MPa

Types of reinforcements

A500 ERA400 NRA500 NR

A400 NR SDA500 NR SD

<= Portuguese designation


Session T02 19/22PROPERTIES OF PRESTRESSING STEELS

Type Steel 𝑓 [MPa] 𝑓 , [MPa] 𝑓 [MPa] 𝐸 [GPa]𝜀 ,[%]

Wires

Y1860C 1860 1600 1391

205 3,5Y1770C 1770 1520 1322

Y1670C 1670 1440 1252

StandsY1860S 1860 1600 1391

195 3,5Y1770S 1770 1520 1322

BarsY1100H 1100 900 783

205 4,0Y1030H 1030 830 722

Anchorage ‐ cable with 12 strands

Strand with 7 wires

Prestress strand bobine

Mechanical properties of prestressing steels


Session T02 20/22

Type Steel 𝑓 [MPa] 𝑓 , [MPa] 𝑓 [MPa] 𝐸 [GPa]𝜀 ,[%]

WiresY1860C 1860 1600 1391

205 3,5Y1770C 1770 1520 1322

Y1670C 1670 1440 1252

StandsY1860S 1860 1600 1391

195 3,5Y1770S 1770 1520 1322

BarsY1100H 1100 900 783

205 4,0Y1030H 1030 830 722

Anchoring ‐ prestress bar


Prestress bar Coupler

Prestress bar

PROPERTIES OF PRESTRESSING STEELS


Session T02 21/22

Type 𝜙 [mm] 𝐴 [mm2] Steel 𝐹 [kN] 𝐹 , [kN]

Starnds(with

7 wires)

8,0 38

Y1860S7

70,7 60,8

12,5 93 173 149

12,9 100 186 160

15,2 139 259 223

15,7 150 279 240

15,2 139Y1770S7

246 212

15,7 150 266 229

Bars

26,5 552

Y1230H

678 596

32,0 804 989 869

36,0 1018 1252 1099

26,5 552

Y1030H

568 461

32,0 804 828 672

36,0 1018 1048 850

40,0 1257 1294 1049

PROPERTIES OF PRESTRESSING STEELS



Session T02 22/22STEEL PROPERTIES ‐ EXAMPLE OF SPECIFICATION IN A REAL DESIGN

Reinforcement Steel

STEEL

Structural steel (for secondary structures)

Prestressing steel(0,6”N stands)

Prestressing steel bars

Structural steel (profiles and plates)

Session T02 2/22

Documents