Hypoelastic modeling of reinforced concrete walls

This paper presents a new hypoelasticity model which was implemented in a nonlinear finite element formulation to analyze reinforced concrete (RC) structures. The model includes a new hypoelasticity constitutive relationship utilizing the rotation of material axis through successive iterations. The model can account for high nonlinearity of the stress-strain behavior of the concrete in the pre-peak regime, the softening behavior of the concrete in the post-peak regime and the irrecoverable volume dilatation at high levels of compressive load. This research introduces the modified version of the common application orthotropic stress-strain relation developed by Darwin and Pecknold. It is endeavored not to violate the principal of “simplicity” by improvement of the “capability”. The results of analyses of experimental reinforced concrete walls are presented to confirm the abilities of the proposed relationships

A new approach for nonlinear finite element analysis of reinforced concrete structures with corroded reinforcements

A new approach for nonlinear finite element analysis of corroded reinforcements in reinforced concrete (RC) structures is elaborated in the article. An algorithmic procedure for producing the tension-stiffening curve of RC elements taking into consideration most of effective parameters, e.g.: the rate of steel bar corrosion, bond-slip behavior, concrete cover and amount of reinforcement, is illustrated. This has been established on both experimental and analytical bases. This algorithm is implemented into a nonlinear finite element analysis program. The abilities of the resulted program have been studied by modeling some experimental specimens showing a reasonable agreement between the analytical and experimental findings

Effect of second order analysis on the drift reliability of steel buildings

Serviceability limit state is an important limit state in the reliability analysis of building structures. One of the serviceability limit states to consider in the design is the lateral displacement or drift check. Due to the uncertainties in the cross-sectional dimensions and the mechanical properties of materials, the lateral drift of structures is a random variable. Second order effects also amplify the lateral displacements and are a function of gravity loads and lateral displacements. In this study, the drift reliability of steel frames and the effects of second order analysis are investigated using geometric nonlinear analysis and Monte Carlo Simulation technique. Results show that for the drift limit state that does not include P-Δ effect, reliability indices do not depend on return period of the load cmbination, the wind to gravity load ratio or the drift limits. On the other hands, for the limit state in which P-Δ effect is incorporated, in low wind to gravity range, the reliability indices are sensitive, and could change dramatically. The limit state that does not have the P-Δ effect is the lower bound of load combination with 50 year return period, but is the upper bound for the other load combination with 20 year return period. Furthermore, the value of drift limit affects the reliability indices for the limit states that include P-Δ effect