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Showing 2 results for Finite Element Technique

H.r. Ghafouri,
Volume 1, Issue 1 (9-2003)

A two-dimensional mathematical model for the prediction of time-variations of river-bend displacements was developed which is particularly applicable to meandering rivers. The computational procedure consists of two stages, that is , in the first stage by utilizing depth-averaged continuity and momentum equations, velocity field as well as water surface profile in a river is determined. The well-known Finite-Element technique was applied to the governing equations. In the second stage the rate of river bank erosion is computed in terms of determined depths and velocities. The model utilizes Odgaards (1989) bank-erosion model in this stage. The procedure is then performed repeatedly over the entire time span in a staggered manner. The developed model was applied to simulate the migration of Qezel Ozan river. The fairly good match obtained indicates the applicability of the model.
Mahnoosh Biglari, Iman Ashayeri, Mohammad Bahirai,
Volume 14, Issue 6 (9-2016)

In this article, general procedures for vulnerability assessment and retrofitting of a generic seismically designed bridge are outlined and the bridge’s damage criteria for blast resistance are explained. The generic concrete bridge is modeled and analyzed with the finite element technique implemented in ANSYS LS-DYNA environment and explosion threats are categorized into three main levels. Uncoupled dynamic technique is adopted to apply the blast loads on the bridge structure, damage and performance levels are resulted based on quantitatively verified damage mechanisms for the bridge members. The results show that, amongst different loading scenarios, the explosions that happen under deck are more critical comparing to blasts initiating from over deck sources. Furthermore, two retrofitting methods 1) concrete filled steel tube (CFST) and 2) concrete jacket are applied on the bridge columns. The program AUTODYN is used with coupled dynamic analysis of a column to compare the effectiveness of each method. Afterward, more efficient method for a column is applied to the whole bridge and its efficiency is revaluated. It is shown that CFST can decrease concrete spall, scabbing, rotation, displacements and shear forces more than the concrete jacket. Considering the proposed damage and performance levels, the bridge retrofitted with CFST reacts with lower damage level and higher performance level to blast loads.

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