TY - GEN A1 - Korzen, Manfred A1 - Rodrigues, J. P. C. A1 - Correia, A. M. ED - F. Wald, ED - P. Kallerová, ED - J. Chlouba, T1 - Thermal restraint effects on the fire resistance of steel and composite steel and concrete columns T2 - International Conference - Applications of structural fire engineering CY - Prague, Czech Republic DA - 2009-02-19 KW - Fire resistance KW - Thermal restraint KW - Steel columns KW - Steel-concrete columns PY - 2009 SN - 978-80-01-04266-3 SP - 512 EP - 517 CY - Prague, Czech Republic AN - OPUS4-19111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brás, A. R. A1 - Noronha, J. P. A1 - Antunes, A. M. M. A1 - Cardoso, M. M. A1 - Schönhals, Andreas A1 - Affouard, F. A1 - Dionísio, M. A1 - Correia, N.T. T1 - Molecular motions in amorphous Ibuprofen as studied by broadband dielectric spectroscopy N2 - The molecular mobility of amorphous ibuprofen has been investigated by broadband dielectric relaxation spectroscopy (DRS) covering a temperature range of more than 200 K. Four different relaxation processes, labeled as α, β, γ, and D, were detected and characterized, and a complete relaxation map was given for the first time. The γ-process has activation energy Ea = 31 kJ·mol-1, typical for local mobility. The weak β-relaxation, observed in the glassy state as well as in the supercooled state was identified as the genuine Johari-Goldstein process. The temperature dependence of the relaxation time of the α-process (dynamic glass transition) does not obey a single VFTH law. Instead two VFTH regimes are observed separated by a crossover temperature, TB = 265 K. From the low temperature VFTH regime, a Tgdiel(t =100 s) = 226 K was estimated, and a fragility or steepness index m = 93, was calculated showing that ibuprofen is a fragile glass former. The D-process has a Debye-like relaxation function but the temperature dependence of relaxation time also follows the VFTH behavior, with a Vogel temperature and a pre-exponential factor which seem to indicate that its dynamics is governed by the α-process. It has similar features as the Debye-type process observed in a variety of associating liquids, related to hydrogen bonding dynamics. The strong tendency of ibuprofen to form hydrogen bonded aggregates such as dimers and trimers either cyclic or linear which seems to control in particular the molecular mobility of ibuprofen was confirmed by IR spectroscopy, electrospray ionization mass spectrometry, and MD simulations. PY - 2008 DO - https://doi.org/10.1021/jp8040428 SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 112 IS - 35 SP - 11087 EP - 11099 PB - Soc. CY - Washington, DC AN - OPUS4-17866 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fernádez-Canteli, A. A1 - Castillo, E. A1 - Blasón Gonzalez, Sergio A1 - Correia, J. A. F. O. A1 - de Jesus, A. M. P. T1 - Generalization of the Weibull probabilistic compatible model to assess fatigue data into three domains: LCF, HCF and VHCF N2 - n this work, three classes of fatigue models are reviewed according to the fatigue regimes commonly considered in the current components design. Particular attention is devoted to the so-called Class III fatigue models, covering the three fatigue regimes, namely, LCF, HCF and VHCF. The applicability and limitations of the pro-posed analytical sigmoidal solutions are discussed from the viewpoint of practical design. The compatible Weibull S-N model by Castillo and Canteli is revisited and improved by considering a new reference parameter GP = E⋅σM ⋅(dε/dσ)|M as the driving force alternative to the conventional stress range. In this way, the requirement, σM ≤ σu, according to the real experimental conditions, is fulfilled and the parametric limit number of cycles, N0, recovers its meaning. The probabilistic definition of the model on the HCF and VHCF regimes is maintained and extended to the LCF regime. The strain gradients may be calculated from the monotonic or cyclic stress–strain curve of the material although a direct derivation from the hysteresis loop is recommended. Some Class III fatigue models from the literature and another one improved by the authors are applied to the assessment of one experimental campaign under different stress ratios conditions and the results compared accordingly. Finally, the new probabilistic GP-N field is evaluated. The results confirm the practical confluence of the stress- and the strain-based approaches into a single and advantageous unified methodology. KW - LCF region KW - S-N probabilistic field KW - Energetic reference parameter PY - 2022 DO - https://doi.org/10.1016/j.ijfatigue.2022.106771 SN - 0142-1123 VL - 159 SP - 1 EP - 18 PB - Elsevier Ltd. AN - OPUS4-55235 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Korzen, Manfred A1 - Rodrigues, J.P.C. A1 - Correia, A.M. ED - Kodur, V. ED - Franssen, J.-M. T1 - Composite columns made of partially encased steel sections subjected to fire T2 - 6th International conference "Structures in fire" CY - East Lansing, Michigan, USA DA - 2010-06-02 KW - Fire resistance KW - Thermal restraint KW - Composite steel-concrete columns KW - Substructuring method KW - Restraining frame PY - 2010 SN - 978-1-60595-027-3 SP - 341 EP - 348 PB - DEStech Publications, Inc. CY - Lancaster, PA, USA AN - OPUS4-22482 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Correia, A.M. A1 - Rodrigues, J.P.C. A1 - Korzen, Manfred T1 - Experimental research on the load-bearing capacity of partially encased steel columns under fire conditons N2 - The composite steel and concrete columns are known to have enhanced fire behaviour when compared with bare steel columns. However there are still aspects that must be clarified, as the influence of the building surrounding structure on the fire resistance of the columns. In this paper, the results of fire resistance tests on partially encased steel columns carried out with two different experimental systems are compared. In one of the experimental systems, the building surrounding structure is materialised by a steel restraining frame, and in the other is performed by the so-called substructuring method. Due to the concept of hybrid substructuring, the entire building is decomposed in two parts: one is represented by the building element under test, whereas the remaining building is simulated numerically in a computer. The main conclusion drawn from this work was that the surrounding structure has a major influence in the development of axial forces in the test columns. Moreover, it was observed that the higher the non-dimensional axial restraint ratio the lower the critical time of the columns. KW - Fire resistance KW - Thermal restraint KW - Composite steel-concrete columns KW - Substructuring method KW - Restraining frame PY - 2012 DO - https://doi.org/10.1260/2040-2317.3.1.81 SN - 2040-2317 VL - 3 IS - 1 SP - 81 EP - 94 PB - Multi-Science Publ. Co. CY - Brentwood AN - OPUS4-25632 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -