The authors regret for the error in this paper. The errors are: 1. This reference [22] is incorrect and the corrected reference which used in our paper is: [22] M. Kh. Kasim, Dynamic analysis of reinforced concrete slabs, PhD Thesis, University of Baghdad, Iraq, 2006.2. In addition in page 706, it was wrote in the last line that “The results match those found by Ayyad [2] who” this is incorrect phrase because we were depended on the reference Kasim [22], thus the correct sentence must be “The results match those found by Kasim [22] who”.3. The reference for Figs. 10 and 11 is [22].And the reference for Figs. 15, 16 and 17 is [17]. We are so sorry for these error; we would like to apologize for that. © 2013