A thesis submitted in partial fulfillments of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1974

Finite element method is used to study the stiffness of rectangular infilled frame. Rectangular element with simple displacement function for plane stress problem is used in the formulation of the stiffness matrix of the structure. Experiments were carried out to verify the theoretical results and to study the behaviour and effect of the infill. Concrete frames with mortar infill and without infill were tested for this purpose. The stiffness of the infilled frame obtained from the finite element technique is considerably stiffer than those obtained from the experiments. Parametric study for brick infilled concrete frame was also carried out from which stiffness curves were obtained. A simplified method using these curves is introduced to estimate the lateral deflection of a multistory infilled frame and its result was compared with those obtained from diagonal strut theory and the frame without infill. From the comparison, diagonal strut theory gives a larger deflection than that obtained by the simplified method which indicates that the equivalent strut method may lead to an underestimation of the stiffness.