finite element modeling

Bond behavior between reinforcement and concrete, due to increasing application of reinforced concrete, is one of the most important issues all over the world. In this research, which has been done experimentally and finite element (FE) modeling (using ABAQUS software), 36 mixtures are deigned considering three cement strength grades and various percentages of polymer fibers, silica fume and nano-silica. The effects of these admixtures on the bond behavior between concrete and reinforcement and also the compressive strength of concrete are investigated. The method of applying nonlinear spring (translator) for finite element modeling is presented and the model is analyzed using nonlinear dynamic analysis. The results yielded acceptable correlation between experimental and FE model. Since there are some translators in model, it can be mentioned that the results of bond slip are not influenced by meshing algorithm. Moreover, comparison of the experimental and FE results showed that while the effect of fiber in bond strength is negligible, it can be so effective in determining the failure shape. The combination of silica fume and nano silica can also improve the bond strength about 20% so that applying equal amount of these two admixtures may leads to the best strength results.

In this paper, chirality effect on the buckling behavior of SWCNTs has been investigated. In order to explore the effect of chiral angle, all structures are used with the same length and diameter but different chiral angles. For modeling of chemical bonds between carbon atoms, potential energy of molecular mechanics theory and strain energies of a 3D beam element have been equalized. After calculating the element properties, the node coordinates have been determined using a computer code developed in MATLAB software. Then, ANSYS software is used to study the chirality effects on axial and torsional buckling load. Results show that the chiral angle has no significant influence on critical axial force. However, chiral angle is an effective parameter in torsional buckling. Chiral angle of 19.11 degree has the maximum critical torsional moment among all structures. In counter-clock-wise loading condition, chiral angle of 9.64 degree has the minimum critical torsional moment. Also, the direction of twisting (cw or ccw) is important and the difference between cw and ccw critical torsional moment reaches its maximum value for chiral angle of 15.48 degree.