An average stress strain approach to creep analysis of RC uncracked elements

The effect of concrete creep on the long-term tension-stiffening law and prediction of a time-dependent inertia moment of the cracked RC flexural cross-sections

“…Moreover, a separation of equations in the set (1), as a linearization of neutral axis function vs. internal bending moments, is required to obtain a third order polynomial (Balevičius, 2006). Thereby, this solution in terms of an effective moment of inertia (Balevičius, 2006), reflecting four stages of the tension zone behavior under cracking is implemented thereinafter along with the application of an analytical average stress and strain approach for evaluating the effect of creep (Balevičius, 2010). Hence, the solution of Eq.…”

“…The creep data is calculated by the code EC-2 (EN 1992-1-1, 2004). The numerical solution is performed by numerical procedures (Balevičius, 2010) for obtaining exact values of Finally,using Eq. (15), the function   As can be seen in Figure 3, the theoretical deflections match quite well the values obtained during long-term tests of cracked RC beams.…”

“…In the paper, the analytical approach for predicting the long-term stress-strain state of the cracked RC beams under sustained load is developed by combination of the average stress strain approach (Balevičius, 2010) for creep analysis with an effective stiffness model of cracked cross-sections (Balevičius, 2006). The formulae accounting for the tension stiffening decay with time due to time-variable stress are derived and applied in prediction of the inertia moment of the cracked RC flexural members along with the obtained results verification with the experimental data.…”

“…is defined from solution of stress-strain state at t induced by due to M=M cr for the transformed age-adjusted cross-section (Balevičius, 2010);…”

Time-dependent evolution of strand transfer length in pretensioned prestressed concrete members

“…Then the friction mechanism and the mechanical action are activated and frictional bond stresses are developed, which are caused by radial compressive stresses around the prestressing strand. Several effects contribute to radial compressive stresses (den Uijl 1998, FIB 2000, including long-term effects such as shrinkage of concrete (William et al 2008) and creep of concrete (Balevicius 2010). Shrinkage of the concrete surrounding the prestressing strand enhances additional radial compressive strength and bond resistance over time, while creep of concrete and prestressing strand relaxation diminish high local stresses and strains and bond stresses (Weerasekera 1991;Barnes et al 2003;FIB 2010).…”