Modelling short-term tension stiffening in tension members

Abstract

Recent research has questioned the validity of bond-slip relationships owing to the 'necessity for the concrete to be able to slip past the ribs on the bar'. Conversely, it is suggested in this paper that bond-slip models are simply a numerical device that relates bond stress to the relative displacements between the concrete, which surrounds the internal cracking zone, and steel. This paper shows that the short-term response of a reinforced concrete tension member with a central reinforcement bar is predicted well by a one-dimensional non-linear finite-element analysis incorporating a trilinear idealisation of the Model Code 1990 bond-slip relationship. The authors' analysis is significant since it is shown to predict many of the trends in behaviour observed in tests associated with tension stiffening and cracking. Different approaches are adopted in Eurocode 2 (EC2) (2004) for modelling tension stiffening in the calculation of crack width and mean axial extension. These approaches are reviewed in the light of the authors' finite-element analysis and existing experimental data. The EC2 models for mean axial strain are shown to be reasonable but the crack spacing formula overestimates crack spacing in the tension members considered in this study.

Crack development in transverse loaded base-restrained reinforced concrete walls

“…This is consistent with Kheder's change of restraint diagrams [5], which indicate a higher change of heights H increase almost proportionally to 0.5 . This is consistent with the experimental observations of Stoffers [2] and Kheder [3][4][5] but contrary to the predictions of BS 8007 [11] and EN 1992 [12,13] which relate crack width to the restraint factor which reduces with height from the base for / < 8 [23] whereas the observed crack widths increase with height (see Figure 13).…”

“…Bond-slip between reinforcement and concrete was modelled using a tri-linear idealisation of the MC 2010 bond-slip relationship. The modelling of bond-slip in conjunction with the very fine adopted mesh (see Figure 7) effectively simulates discrete cracks because cracks are localised in vertical columns of single elements [23]. Consequently, crack widths were calculated directly by subtracting horizontal nodal displacements of cracked elements and correcting for the displacement of uncracked concrete.…”

Cracking in walls with combined base and end restraint

“…Elasto-plastic 2D beamcolumn elements were used for reinforcement bars. Bond-slip between reinforcement and concrete was modelled using a tri-linear idealisation of the Model Code 2010 (MC2010) (fib, 2013) bond-slip relationship which in conjunction with the very fine adopted mesh effectively simulates discrete cracks (Vollum et al, 2008). Cracks localised in vertical columns of single elements.…”

Betono tempiamojo sustandėjimo modelis atitinkantis euronormų nuostatas

“…Todėl tarp plyšių į darbą įsijungia betonas -jame atsiranda tempimo įtempimų. Betono ir armatūros sukibimą tyrė Watstein ir Seese (1945), Watstein (1947), Lutz ir Gergely (1967), Esfahani ir Rangan (1998) Gambarova et al (1989), Kwak ir Song (2002), Ruiz et al (2007), Leutbecher ir Fehlng (2009) Lackner & Mang (2003, Borosnyói & Balázs (2005), Eckfeldt (2005) , Ruiz et al (2007), Vollum et al (2008), Piyasena (2002), Leutbecher & Fehlng (2009).…”