Il nuovo quadro normativo sulla progettazione antincendio delle strutture di calcestruzzo armato

1. Il nuovo quadro normativo sulla progettazioneantincendio delle strutture di calcestruzzo armato Venerdì 8 febbraio 2008 AICAP – Università di Roma Tre Meccanica del danno in caso di incendio

2. Phase Changes with Fire • The hot resistance of concrete depends on the decomposition of: • - Tobermoritic GEL • - Calcium Hydroxide • - a - b quartz • The quenched resistance of the concrete depends on the micro cracks formed by the cement paste around the gravel and sand elements

3. Merloni production plant fire

4. DIAVIA Fire (1995) • La struttura pallettizzata del magazzino ha favorito la propagazione di un incendio a riscaldamento rapido • Le pareti tagliafuoco in cartongesso con camera hanno consentito l’operatività dei locali protetti anche durante l’incendio • Il calcestruzzo prefabbricato ad alta resistenza ha subito un danno consistente principalmente per esfoliazione (ploughing)

5. Damage of Concrete elements of DIAVIA • Tutti gli elementi strutturali sono caratterizzati da perdite di materia per esfoliazione con conseguente esposizione delle armature • La presenza di cloro liberato dalla combustione della plastica ha innescato pesanti effetti di corrosione del ferro • Gli elementi di bassa massività (quali quelli di copertura) presentano ampi squarci e caduta di pezzi

6. Thermal Shock sloughing or cover detachment

7. Laboratory Calibration of the NDT Site Measurements • Core Laboratory characterization • Transversal ultrasound velocity measurements • Cylinder preparation for cutting • Longitudinal velocity measurement in cut samples • Compression test of the cylindrical samples

8. Elastic moduli distribution in fire damaged concrete sections Andrea Benedetti, (1998), “On the ultrasonic pulse propagation into fire damaged concrete”, ACI Structural Journal, vol. 95-3.

9. Path reconstruction by the minimum travelling time concept

10. Crack Density as a measure of Damage

11. Spatial Crack Distributionalong the section thickness

12. Correlation with the concrete disk punch tests

13. Disk SplittingTensile Test • The tensile strength is temperature and thus depth dependent

14. Other Damage Measures (1)Surface Hardness

15. Other Damage Measures (2)Flexural Strength

16. Other Damage Measures (3)Dynamic Modulus

17. Other Damage Measures (4)Ultrasonic Pulse Velocity

18. HotConcreteStrength Schneider U., (1986), “Modeling of concrete behaviour at high temperature”, In: Anchor, Malhotra,Purkiss, Ed.s: Design of structures against fire, New York, Elsevier, p. 53–69.

19. Residual strength after cooling • Residual Strength is dependent on the stress level during the thermal cycling

20. Formulas for tangent modulus and peak strength

21. Time-Temperature-Loadnon Holonomic Processes

22. Evidence of Creep Irreversibility

23. Thermo Plastic Creep of Concrete (LITS)

24. Stress Profiles of heated cylinders under axial load

25. Maximum Restraint Force During Expansion Heating test of a concrete specimen confined by two fixed distance plate. The test shows the features of the thermo plastic viscous behavior

26. Thelandersson Analysis (1) • The standard thermo elastic analysis is not able to capture the essence of the LITS phenomenon

27. Thelandersson Analysis (2) • The LITS effect comes out from coupling of stress and temperature increase

28. Constitutive Models (1) • Anderberg & Thelandersson Anderberg Y., Thelandersson S., (1976), “Stress and deformation characteristics of concrete, experimental investigation and material behaviour model”, Bulletin 54, University of Lund, Sweden

29. Constitutive Models (2) • Schneider Schneider U., (1986), “Modeling of concrete behaviour at high temperature”, In: Anchor, Malhotra, Purkiss, Ed.s: Design of structures against fire, New York, Elsevier, p. 53–69.

30. Constitutive Models (3) • Diederichs Diederichs U., (1987), “Modelle zur Beschreibung der Betonverformung bei instantionaren Temperaturen“. In Abschlubkolloquium Bauwerke unter Brandeinwirkung, TechnischeUniversität, Braunschweig, p. 25–34.

31. Constitutive Models (4) • Khoury and Terro Terro M., (1886), “Numerical modelling of the behaviour of concrete structures”, ACI Structural Journal 95(2), pp. 183–193.

32. Comparison of Models (1) Li L., Purkiss J., (2005), “Stress–strain constitutive equations of concrete material at elevated temperatures”, Fire Safety Journal, 40, pp. 669–686

33. Comparison of Models (2)

34. Comparison of Models (3)

35. Comparison of Models (4)

36. Comparison of Models (5)

37. Biaxial limit surfacefor heated concrete

38. Water moisture migration in concrete during fire

39. FERRARIExperience Centre

40. Fire damages to the Ferrari Experience Centre

41. Two Zone Model of the fire evolution

42. P/C Beam Thermal Analysis Coducibility [W/m2°C] Specific Heat [W/kg°C]

43. T [°C] T [°C] Y [cm] X [cm] Temperature in the Beam Flange Temperature profile in the horizontal direction at a depth of 40 mm Temperature profile in the vertical direction at a depth of 40 mm

44. T [°C] X [cm] Steel wire Temperature Web temperature in the transversal direction Prestressing wire temperature Light gray denotes the section area that rises up to a temperature larger than 500°C

45. Ultrasonic NDT Tests Reduction of the elastic modulus with the temperature increase Paths used for the ultrasonic velocity measurements

46. Elastic Modulus Distribution Elastic modulus distributions along path A Elastic modulus distributions along path B

47. Ultrasonic propagation data

48. Comparison between theory and measurements

49. Comparison of the strength reduction in the main section

50. Calculation of the residual resisting moment