Evaluation of Damage Index for RC Frames with Irregular Geometrical Shape Subjected to Blast Loads

The present research focuses on studying the effect of architectural shape of reinforced concrete frames resulting from irregularity of geometrical shape of building frame. The reinforced concrete Frame, consisting of eight storey and three bays, was designed by the American Code ACI-14. SAP2000 (V.20) software was used for the purposes of design, analysis, of the structural response for behavior elasto-plastic under the effect of blast loading, through a number of variables, including the maximum displacement and plastic deformations at the tip of structure, number and status of plastic hinges formed, and damage index. The interaction diagram between axial force and bending moment was adopted as a yield surface to undergo the transition from elastic to plastic behavior for the columns, while the design yield moment was defined as a yield criterion for beams. The accumulated plasticity (Plastic hinge) at the ends of structural element was used to simulate the elasto-plastic behavior . Irregularity and unsymmetrical form of frame structure have a significant effect on increasing the deformations and plastic displacements in the elements more than 40% and increasing the damage index in structure more than 18%, that is calculated on the basis of dissipated energy by plastic deformations. The distance between centers of Mass (C.M.) and Stiffness (C.S.) significantly affects the response of structure, where the plastic deformations of structural elements are in the least damage zone in case of convergence between two centers, compared to other cases of heterogeneity irregularity of geometrical shape of structure that results in diverging of these centers.