Abstract: This is a sample file demonstrating the style for Eurodyn 2011 papers



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Input data


In order to have statistical mechanical data that reflects the actual European steel production, RIVA and ARCELORMITTAL have collected the mechanical properties of structural steel profiles produced in their plants considering various cross sectional geometries and steel manufacturing processes [8].

The statistical characteristics of these data sets have been used by RIVA to define a probabilistic model. Two different situations were identified, i.e. plate thicknesses under 16 mm, and plate thicknesses between 16 and 40 mm. An inter-correlated multi log-normal distribution has been assumed for the yield stress fy, the ultimate stress fu, and the ultimate elongation . Sample sets of mechanical properties have then been generated based on the theoretical statistical model whose parameters have been properly calibrated. All the corresponding input data and generated sample properties are detailed in the final report of the OPUS research program [8].

The mechanical steel properties are defined by three values: the yielding stress fy, the ultimate stress fu and the ultimate deformation A. A simplified bilinear constitutive relationship is adopted, as shown in Figure :

Figure . Simplified - law for steel

Mean values, standard deviations and overstrength factors deduced from statistical analysis of the mechanical properties of steel profiles and rebars obtained from the design of each structure (see section 3) are presented in Table .

These values give a first estimate of the overstrength ov. Following EN1998-1-1 [11], if the statistical distribution of the yielding stress is known, the overstrength factor is computed according to equation ():





()

with fyk,sup being the 95% fractile of the statistical distribution and fy,nominal the nominal yield strength of the steel in dissipative zones. Calculated values of ov,ac are reported in Table .

Some overstrength factors obtained from mechanical characteristics appear quite high. For steel reinforcement, ov values are in line with those given by Eurocode 8. For S355, ov value is slightly larger, while for S235 steel grade the value appears to be very large.

It must be noted that the actual overstrength factor of S235 is nearly equal to the ratio 355/235 = 1.51. The Eurocode 8 proposes to fulfill the strong column - weak beam principle by adopting higher steel grade for columns. In view of the results, this recommendation may look questionable. Nevertheless, the lower 5 % fractile of S355 steel is shifted from 355 MPa to 380 MPa, and the hierarchy of the resistances is preserved.

Table : Mean values, standard deviations and overstrength factors of steel for all case studies.









Mean 

Standard deviation 

ov,ac

Case Study No.

1

2

3

4

1

2

3

4

1

2

3

4

Structural steel grade

S355

S355

S235

S235

S355

S355

S235

S235

S355

S355

S235

S235

Beams

profile

IPE 330

IPE 330

IPE 360

IPE 360

IPE 330

IPE 330

IPE 360

IPE 360

IPE 330

IPE 330

IPE 360

IPE 360

fy (Mpa)

415

415

320

320

23

23

18

18

1.28

1.28

1.49

1.49

fu (Mpa)

565

565

411

410

19

19

15

15

A (%)

25

25

25

25

2

2

2

1

Columns

profile

HEA 360

HEA 320

HEA 450

HEA 400

HEA 360

HEA 320

HEA 450

HEA 400

HEA 360

HEA 320

HEA 450

HEA 400

fy (Mpa)

430

415

320

320

27

22

22

22

1.34

1.27

1.52

1.52

fu (Mpa)

550

565

420

420

25

21

15

15

A (%)

25

25

28

28

2

2

2

2

Rebar grade

BAS 500

BAS 500

BAS 450

BAS 450

BAS 500

BAS 500

BAS 450

BAS 450

BAS 500

BAS 500

BAS 450

BAS 450

Rebars

fy (Mpa)

561

560

525

525

22

22

17

17

1.20

1.19

1.23

1.23

fu (Mpa)

671

670

630

630

20

20

19

19

A (%)

21

21

13

13

1

1

1

1




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