COMPUTATIONAL MECHANICS New Trends and Applications S. Idelsohn, E. Oñate and E. Dvorkin(Eds.) ©CIMNE, Barcelona, Spain 1998 1 ELASTOPLASTIC ANALYSIS OF RC PLATES USING THE REISSNER’S MODEL AND THE BOUNDARY ELEMENT METHOD Gabriel de O. Ribeiro * , Afonso L. Oliveira † * Department of Structural Engineering Federal University of Minas Gerais (UFMG) Av. do Contorno,842 - 30110-060 - Belo Horizonte - MG - Brazil e-mail:gabriel@dees.umfg.br, web page: http://cimne.upc.es/ † Master Course of Structural Engineering of UFMG Federal University of Minas Gerais (UFMG) Av. do Contorno,842 - 30110-060 - Belo Horizonte - MG – Brazil e-mail:aolive@dees.umfg.br Key words: plates, slabs, boundary element method, reinforced concrete plates, Reissner’s theory Abstract. The formulation of the Boundary Element Method applied to the plate bending problem using the Reissner’s hypothesis is developed. This hypothesis makes possible to achieve a more consistent numerical procedure in which three physical conditions along the plate boundary can be enforced. The boundary element approach using this theory is extended to consider initial stress fields over the plate domain, as well as to take into account several kinds of loads. The presence of initial stress fields enables one to analyze shrinkage and temperature effects, and to formulate procedures to deal with physical non-linearities. A procedure to consider elastoplastic behavior of RC plates is implemented using an incremental iterative algorithm based on the modified Newton-Raphson Method, where the plastic solution is obtained by applying initial stress fields. The elastoplastic concrete behavior is modeled based on the Willam-Warnke version of the five parameter failure surface. This surface is taken directly as a fixed yield surface in the stress space and the steel bars are regarded as unidimensional elements of elastic perfectly plastic material under the Von Mises yield criterion. The concrete behaves as a perfect plastic material after the maximum carrying capacity has been reached. An associated flow rule is adopted. There is no need to assume fictitious plate division into layers, in order to take into account of the through-thickness yielding, as usually made for this kind of problem. Stresses are computed at selected control Gauss points defined along the thickness and in each of these points a plane stress state is achieved and analyzed.